Signaling multiple predicted BVD / MVD suffix choices

Abstract

To improve the encoding and subsequent decoding of block offset vector differences, of motion vectors for inter-prediction or block vectors for intra-prediction of video sequences, the method of deriv

Description

[0001] SIGNALING MULTIPLE PREDICTED BVD / MVD SUFFIX CHOICES

[0002] FIELD OF THE INVENTION

[0003] The invention relates to reduced amount of bit compression coding of video images, and related decoding, of a type similar to MPEG encoding. In particular it relates to optimal coding of vector differences such as block vector differences for intra-prediction based on a block at a previously decoded position of a current image which is being decoded, or a motion vector for inter-prediction based on a similar block in a previously decoded image corresponding to another presentation time moment in the video.

[0004] BACKGROUND OF THE INVENTION

[0005] Video coding has achieved significant compression ratios, which makes several applications possible, such as the storage of a video in a limited memory, or a communication over a communication mechanism of limited bandwidth.

[0006] One of the principles has been that those properties of the video that can faithfully be predicted at the decoding side, need no or few bits to describe them. E.g., if a block containing a sequence of text characters is already present (correctly decoded) in a previous location, instead of fully coding the block of pixel colors, coding a location where the block can be fetched for copying to the current being decoded position may require less bits. E.g., if there is a panning motion of a background such as houses in a street, one need not communicate a separate motion vector for each block (which, as in the older MPEG codecs would imply a lot of bits being spent for coding the motion vectors), but rather most blocks would be predictable from the global panning motion vector.

[0007] In the later codecs, since processing power of the decoders is increasing (even in small appliances like mobile phones), there is a trend towards researching so that the decoder by itself can establish as much as possible without needing even any indication bits in some situations. E.g., if there is a wallpaper in view with always the same pattern, the decoder would be able to figure out that the coming blocks will also contain that wallpaper pattern, unless it is communicated that something else is in the block, such as a person, in which case the regular more explicit coding formalisms can be used.

[0008] This first part, of prediction and correction, also takes into account that some small errors are probably not so visually important for the viewer of the video (e.g. a movie or television broadcast, or video conference, etc.), ergo, some correction bits can also be saved by not storing or communicating them.

[0009] The last part of the codec makes use of mathematical techniques by transforming the data elements of the first part (e.g. DCT coefficients coding the errors of prediction called residuals) in a manner which doesn’t make approximation errors, yet still saves bits. One can do this by making use of the probabilities of the data elements. E.g., if we know that the character “Q” will not occur as often as an “A”, we can give the “A” a below-average code word length (e.g. “10”) in return for giving the “Q” an above-average length (e.g. “111110000111001”), instead of giving all characters an 8-bit word. For a long sequence of N data elements, such an entropy coding algorithm will need less bits than N*8. Of course one needs to technically well-understand and probability model the various data elements that would occur from the first prediction and correction algorithms.

[0010] As the number of alternative predictions grow, there is a constant desire to invent better algorithms to also save more bits here or there in the representation and entropy coding of data elements, such as specifically vector differences.

[0011] SUMMARY OF THE INVENTION

[0012] To improve the coding of video sequences, the method of deriving a block offset vector difference (1810) for predicting second pixel colors of a second block of a second picture based on first pixel colors of a first block of a first picture at a position which is offset from the second block depending on the block offset vector difference and a block offset vector prediction (1808), comprises: obtaining, based on a first one or more symbols in a bitstream, at least one prefix (3514) of a magnitude of the block offset vector difference; determining at least one suffix of the magnitude based on a flag and a second one or more symbols in the bitstream, wherein the determining the suffix comprises: when a value of the flag is a first value: determining, based on the prefix, one or more candidate values for the suffix; and selecting, using an index value encoded in the second one or more symbols, one of the one or more candidate values for the suffix to use in the determination of the suffix; or when the value of the flag is a second value, determining the suffix based on at least one context-coded symbol of one or more bits of the suffix in the second one or more symbols; wherein the magnitude is based on a concatenation of the prefix and the suffix.

[0013] This method can be used in video decoding, when receiving a compressed e.g. MPEG video, for establishing the vector differences for finding which block should predict a currently being decoded block (either in intra-prediction, or inter-prediction). This principle can mutatis mutandis be used in an encoder, which emulates how the decoder will decode, and use this for coding (the encoder will typically select an optimal block for prediction from the original video data, based typically on rate distortion metrics balancing amount of bits versus reconstruction quality).

[0014] Embodiments of the basic concept may involve inter aha: The method in which the second picture is the same as the first picture (i.e. wherein blocks are predicted intra, from already previously reconstructed blocks higher up in the same image).

[0015] The method wherein, when the value of the flag is the first value: searching in at least one reference area in the first picture for at least one candidate block for prediction of the second block, wherein the at least one reference area is determined according to at least a value of the prefix; if there is more than one candidate block, ordering the candidate blocks according to a degree of match of a first template around the candidate block and a corresponding second template around the second block; selecting one of the at least one candidate block based on the index value; and determining the at least one suffix based on the selected candidate block.

[0016] The method in which at least one of the second one or more symbols coding the suffix in case the flag has the first value is CABAC bypass encoded.

[0017] The method in which at least one of the second one or more symbols coding the suffix in case the flag has the second value is CABAC bypass encoded.

[0018] The method wherein when the flag has the second value the at least one context-coded symbol is an indication of whether a prediction of a symbol matches the corresponding symbol of the block offset vector difference.

[0019] The method wherein at least one of the symbols to be binarized is Golomb -encoded.

[0020] The method comprising at least one flag indicating whether one or more components of the suffix are zero respectively greater than zero.

[0021] A method of video coding, comprising:

[0022] - receiving a video sequence (108);

[0023] - compressing a video sequence by predicting blocks of an image of the video sequence, the compressing comprising the method of deriving a block offset vector difference (1810) as in one of the above embodiments of the method of deriving a block offset vector difference.

[0024] A method of video decoding, comprising:

[0025] - receiving a compressed bitstream (110);

[0026] - decoding the compressed bitstream to obtain a reconstructed video sequence, the decoding comprising one of the embodiments of the method of deriving a block offset vector difference (1810).

[0027] A video encoder (114) comprising a circuit connected to a memory, wherein the circuit is arranged to perform one of the embodiments of the method of deriving a block offset vector difference (1810).

[0028] A video decoder (120) comprising a circuit connected to a memory, wherein the circuit is arranged to perform one of the embodiments of the method of deriving a block offset vector difference (1810). A video signal comprising a data structure comprising: encoded video data which represents a magnitude of a block offset vector difference (1810), which represents a difference between firstly a block offset vector (1802) specifying a position distance of a first block for predicting a second block, and secondly a block offset vector prediction (1808), wherein the magnitude is encoded as first data encoding a prefix part of the magnitude and second data encoding a suffix part; wherein the video signal further comprises a flag, which indicates when having a first value that the second data comprises an index value specifying one of a set of candidate vectors specifying the suffix part, and which indicates when having a first value that the second data comprises at least one context-coded symbol directly encoding one or more bits of the suffix.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Examples of several of the various embodiments of the present disclosure are described herein with reference to the drawings.

[0031] FIG. 1 illustrates an exemplary video coding / decoding system in which embodiments of the present disclosure may be implemented.

[0032] FIG. 2 illustrates an exemplary encoder in which embodiments of the present disclosure may be implemented.

[0033] FIG. 3 illustrates an exemplary decoder in which embodiments of the present disclosure may be implemented.

[0034] FIG. 4 illustrates an example quadtree partitioning of a coding tree block (CTB) in accordance with embodiments of the present disclosure.

[0035] FIG. 5 illustrates a corresponding quadtree of the example quadtree partitioning of the CTB in FIG. 4 in accordance with embodiments of the present disclosure.

[0036] FIG. 6 illustrates example binary and ternary tree partitions in accordance with embodiments of the present disclosure.

[0037] FIG. 7 illustrates an example quadtree + multi-type tree partitioning of a CTB in accordance with embodiments of the present disclosure.

[0038] FIG. 8 illustrates a corresponding quadtree + multi-type tree of the example quadtree + multi-type tree partitioning of the CTB in FIG. 7 in accordance with embodiments of the present disclosure.

[0039] FIG. 9 illustrates an example set of reference samples determined for intra prediction of a current block being encoded or decoded in accordance with embodiments of the present disclosure.

[0040] FIG. 10A illustrates the 35 intra prediction modes supported by HEVC in accordance with embodiments of the present disclosure.

[0041] FIG. 10B illustrates the 67 intra prediction modes supported by HEVC in accordance with embodiments of the present disclosure. FIG. 11 illustrates the current block and reference samples from FIG. 9 in a two- dimensional x, y plane in accordance with embodiments of the present disclosure.

[0042] FIG. 12 illustrates an example angular mode prediction of the current block from FIG. 9 in accordance with embodiments of the present disclosure.

[0043] FIG. 13A illustrates an example of inter prediction performed for a current block in a current picture being encoded in accordance with embodiments of the present disclosure.

[0044] FIG. 13B illustrates an example horizontal component and vertical component of a motion vector in accordance with embodiments of the present disclosure.

[0045] FIG. 14 illustrates an example of bi-prediction, performed for a current block in accordance with embodiments of the present disclosure.

[0046] FIG. 15A illustrates an example location of five spatial candidate neighboring blocks relative to a current block being coded in accordance with embodiments of the present disclosure.

[0047] FIG. 15B illustrates an example location of two temporal, co-located blocks relative to a current block being coded in accordance with embodiments of the present disclosure.

[0048] FIG. 16 illustrates an example of IBC applied for screen content in accordance with embodiments of the present disclosure.

[0049] FIG. 17 illustrates an example implementation of a context-based adaptive binary arithmetic coding (CABAC) encoder in accordance with embodiments of the present disclosure.

[0050] FIG. 18A illustrates an example of IBC in accordance with some embodiments of the present disclosure.

[0051] FIG. 18B illustrates example BVD candidates used to entropy encode a magnitude symbol of a BVD in accordance with some embodiments of the present disclosure.

[0052] FIG. 18C illustrates an example of entropy encoding an indication of whether a value of a magnitude symbol of a BVD matches a value of the magnitude symbol of a BVD candidate used as a predictor of the BVD in accordance with some embodiments of the present disclosure.

[0053] FIG. 18D illustrates an example of entropy decoding an indication of whether a value of a magnitude symbol of a BVD matches a value of the magnitude symbol of a BVD candidate used as a predictor of the BVD and using the indication to determine a magnitude symbol of the BVD in accordance with some embodiments of the present disclosure.

[0054] FIG. 19A illustrates an example where the method for coding a BVD as described in FIG. 18 is applied to a sign symbol of the BVD in accordance with some embodiments of the present disclosure.

[0055] FIG. 19B illustrates an example where the method for coding a BVD as described in FIG. 18 is applied to a sign symbol of the BVD in accordance with some embodiments of the present disclosure. FIG. 19C illustrates an example where the method for coding a BVD as described in FIG.

[0056] 18 is applied to a sign symbol of the BVD in accordance with some embodiments of the present disclosure.

[0057] FIG. 19D illustrates an example of entropy decoding an indication of whether a value of a sign symbol of a BVD matches a value of the sign symbol of a BVD candidate used as a predictor of the BVD and using the indication to determine a sign symbol of the BVD in accordance with some embodiments of the present disclosure.

[0058] FIG. 20A and FIG. 20B illustrate example representations of a BVD.

[0059] FIG. 21 illustrates a representation of a BVD in accordance with some embodiments of this disclosure.

[0060] FIG. 22A illustrates a flowchart for decoding a BVD, such as, for example, the BVD as in FIG. 21, in accordance with some embodiments of this disclosure.

[0061] FIG. 22B illustrates a flowchart for encoding a BVD, such as, for example, the BVD as in FIG. 21, in accordance with some embodiments of this disclosure.

[0062] FIG. 22C illustrates a flowchart of an aspect of the encoding method of FIG. 22B.

[0063] FIG. 22D schematically illustrates a flowchart for determining a search area and a template matching search used in determining the BVD during the decoding or encoding of a BVD as, for example, in FIG. 22A or FIG. 22B.

[0064] FIG. 23A and FIG. 23B illustrate another representation of a BVD in accordance with some embodiments of this disclosure.

[0065] FIG. 24A illustrates a flowchart for decoding a BVD, such as, for example, the BVD as in FIG. 23 A and FIG. 23B, in accordance with some embodiments of this disclosure.

[0066] FIG. 24B illustrates a flowchart for encoding a BVD, such as, for example, the BVD as in FIG. 23 A and FIG. 23B, in accordance with some embodiments of this disclosure.

[0067] FIG. 24C illustrates a flowchart of an aspect of the encoding method of FIG. 24B.

[0068] FIG. 25A and FIG. 25B illustrate another representation of a BVD in accordance with some embodiments of this disclosure.

[0069] FIG. 26A illustrates a flowchart for decoding a BVD, such as, for example, the BVD as in FIG. 25 A and FIG. 25B, in accordance with some embodiments of this disclosure.

[0070] FIG. 26B illustrates a flowchart for encoding a BVD, such as, for example, the BVD as in FIG. 25 A and FIG. 25B, in accordance with some embodiments of this disclosure.

[0071] FIG. 27A illustrates a flowchart of a method of decoding a BVD in accordance with some embodiments of this disclosure.

[0072] FIG. 27B illustrates a flowchart of a method of encoding a BVD in accordance with some embodiments of this disclosure.

[0073] FIG. 28A and FIG. 28B illustrate example representation of suffix information of the magnitude of a BVD in some embodiments of this disclosure. FIG. 29A illustrates a flowchart of a method for decoding a BVD that includes, for example, a representation of suffix information similar to that shown in FIGs. 28A or 28B, in accordance with some embodiments of this disclosure.

[0074] FIG. 29B illustrates a flowchart of a method for encoding a BVD that includes, for example, a representation of suffix information similar to that shown in FIGs. 28A or 28B, in accordance with some embodiments of this disclosure.

[0075] FIG. 30A and FIG. 3 OB illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD in accordance with some embodiments of this disclosure.

[0076] FIG. 30C and FIG. 30D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0077] FIG. 30E is a flowchart for a template matching search performed during the encoding of a BVD in accordance with some embodiments of this disclosure.

[0078] FIG. 3 OF is a flowchart for a template matching search performed during the decoding of a BVD in accordance with some embodiments of this disclosure.

[0079] FIG. 31 illustrates a further representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure.

[0080] FIG. 32A and FIG. 32B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD in accordance with some embodiments of this disclosure.

[0081] FIG. 32C and FIG. 32D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0082] FIG. 33 illustrates a further representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure.

[0083] FIG. 34A and FIG. 34B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD in accordance with some embodiments of this disclosure.

[0084] FIG. 34C and FIG. 34D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0085] FIG. 35 illustrates a further representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure.

[0086] FIG. 36A and FIG. 36B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD in accordance with some embodiments of this disclosure.

[0087] FIG. 36C and FIG. 36D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0088] FIG. 37 illustrates a further representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure.

[0089] FIG. 38A and FIG. 38B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD in accordance with some embodiments of this disclosure. FIG. 38C and FIG. 38D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0090] FIG. 39 illustrates a block diagram of an example computer system in which embodiments of the present disclosure may be implemented.

[0091] DETAILED DESCRIPTION OF THE FIGURES

[0092] References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but not every embodiment must necessarily include the particular feature, structure, or characteristic. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described when the skilled person understand those feature would work mutatis mutandis.

[0093] Also, it is noted that individual embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, sometimes the order of the operations may be rearranged. A process is terminated when its operations are completed, but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function.

[0094] The term “computer-readable medium” includes, but is not limited to, portable or nonportable storage devices, and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. A computer-readable medium may include a non-transitory medium in which data can be stored and that does not include carrier waves and / or transitory electronic signals propagating wirelessly or over wired connections. Examples of a non-transitory medium may include, but are not limited to, a magnetic disk or tape, optical storage media such as compact disk (CD) or digital versatile disk (DVD), flash memory, memory or memory devices. A computer-readable medium may have stored thereon code and / or machine-executable instructions that may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, or the like.

[0095] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks (e.g., a computer-program product) may be stored in a computer-readable or machine- readable medium. A processor(s) may perform the necessary tasks.

[0096] Representing a video sequence in digital form may require a large number of bits. The data size of a video sequence in digital form may be too large for storage and / or transmission in many applications. Video encoding may be used to compress the size of a video sequence to provide for more efficient storage and / or transmission. Video decoding may be used to decompress a compressed video sequence for display and / or other forms of consumption.

[0097] FIG. 1 illustrates an exemplary video coding / decoding system 100 in which embodiments of the present disclosure may be implemented. Video coding / decoding system 100 comprises a source device 102, a transmission medium 104, and a destination device 106. Source device 102 encodes a video sequence 108 into a bitstream 110 for more efficient storage and / or transmission. Source device 102 may store and / or transmit bitstream 110 to destination device 106 via transmission medium 104. Destination device 106 decodes bitstream 110 e.g. typically to display video sequence 108. Destination device 106 may receive bitstream 110 from source device 102 via transmission medium 104. Source device 102 and destination device 106 may be any one of a number of different devices, including a desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, or video streaming device. E.g. the source device may be operated by a consumer, or reside in a professional environment. In the latter case it may e.g. be the play-out towards consumers of a real-time broadcasting of a studio based on a selected capturing of several cameras. The communication may e.g. happen over a television signal cable network, or the internet, etc.

[0098] To encode video sequence 108 into bitstream 110, source device 102 may comprise a video source 112, an encoder 114, and an output interface 116. Video source 112 may provide or generate video sequence 108 from a capture of a natural scene and / or a synthetically generated scene. A synthetically generated scene may be a scene comprising computer generated graphics or screen content. Video source 112 may comprise a video capture device (e.g., a video camera), a video archive comprising previously captured natural scenes and / or synthetically generated scenes, a video feed interface to receive captured natural scenes and / or synthetically generated scenes from a video content provider, and / or a processor to generate synthetic scenes.

[0099] A shown in FIG. 1, a video sequence, such as video sequence 108, may comprise a series of pictures (also referred to as frames). A video sequence may achieve the impression of motion when a constant or variable time is used to successively present pictures of the video sequence. A picture may comprise one or more sample arrays of intensity values. The intensity values may be taken at a series of regularly spaced locations within a picture. A color picture typically comprises a luminance or brightness coding sample array and two chrominance sample arrays, which code the proper color, i.e. hue and color saturation. The luminance sample array may comprise intensity values representing the brightness (or luma component, Y) of a picture. The chrominance sample arrays may comprise intensity values that respectively represent the blue and red excess components of a picture (or chroma components, Cb and Cr) separate from the brightness. Other color picture sample arrays are possible based on different color schemes (e.g., an RGB color scheme, wherein the e.g. 8 bit R value non-linearly codes the amount of red in the additive mix, and G and B the amount of green and blue respectively). For color pictures, a pixel may refer to all three intensity values for a given location in the three sample arrays used to represent color pictures. A monochrome picture comprises a single, luma sample array.

[0100] Encoder 114 may encode video sequence 108 into bitstream 110. To encode video sequence 108, encoder 114 may apply one or more prediction techniques to reduce redundant information in video sequence 108. Redundant information is information that may be predicted at a decoder and therefore may not be needed to be transmitted to the decoder for accurate decoding of the video sequence. For example, encoder 114 may apply spatial prediction (e.g., intra-frame or intra prediction), temporal prediction (e.g., inter-frame prediction or inter prediction), inter-layer prediction, and / or other prediction techniques to reduce redundant information in video sequence 108. So the bitstream contains prediction and correction data, and typically as sets of bits in a manner uniquely decodable by decoders. Before applying the one or more prediction techniques, encoder 114 may partition pictures of video sequence 108 into rectangular regions referred to as blocks (e.g. a block of 64x64 pixels). Encoder 114 may then encode a block using one or more of the prediction techniques.

[0101] For temporal prediction, encoder 114 may search for a block similar to the block being encoded in another picture (also referred to as a reference picture) of video sequence 108. The block determined during the search (also referred to as a prediction block) may then be used to predict the block being encoded. Some encoders may in the data explicitly code the position of the block in a previous image found to best predict a current block, by putting a motion vector in the encoded bitstream. For spatial prediction, encoder 114 may form a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of video sequence 108. A reconstructed sample refers to a sample that was encoded and has been decoded. Encoder 114 may determine a prediction error (also referred to as a residual) based on the difference between a block being encoded and a prediction block. The prediction error may represent non-redundant information that may be transmitted to a decoder for accurate decoding of a video sequence. The decoder can determine for each block, which prediction to best use, how many residual bits to add (e.g. strongly quantized), etc., and then compare the data rate needed versus the reconstruction errors made, i.e. the accuracy of the reconstruction, and based on comparing those two needs determine a best option, and put the data of that option in the bitstream (in case the encoder doesn’t rely on the option that the decoder will by itself find the reconstructed pixel colors from data it already knows, in which case the amount of communicated data may be as small as an indicator to use an implicit coding model).

[0102] Encoder 114 may apply a transform to the prediction error (e.g. a discrete cosine transform (DCT)) to generate transform coefficients. Encoder 114 may form bitstream 110 based on the transform coefficients and other information used to determine prediction blocks (e.g., prediction types, motion vectors, and prediction modes). In some examples, encoder 114 may perform one or more of quantization and entropy coding of the transform coefficients and / or the other information used to determine prediction blocks before forming bitstream 110 to further reduce the number of bits needed to store and / or transmit video sequence 108.

[0103] Output interface 116 may be configured to write and / or store bitstream 110 onto transmission medium 104 for transmission to destination device 106. In addition or alternatively, output interface 116 may be configured to transmit, upload, and / or stream bitstream 110 to destination device 106 via transmission medium 104. Output interface 116 may comprise a wired and / or wireless transmitter configured to transmit, upload, and / or stream bitstream 110 according to one or more proprietary and / or standardized communication protocols, such as Digital Video Broadcasting (DVB) standards, Advanced Television Systems Committee (ATSC) standards, Integrated Services Digital Broadcasting (ISDB) standards, Data Over Cable Service Interface Specification (DOCSIS) standards, 3rd Generation Partnership Project (3GPP) standards, Institute of Electrical and Electronics Engineers (IEEE) standards, Internet Protocol (IP) standards, and Wireless Application Protocol (WAP) standards. Further formatting such as channel coding may be involved, which is usually out of scope of the present techniques which will focus primarily on techniques to optimally encode the visual data of the video images.

[0104] Transmission medium 104 may comprise a wireless, wired, and / or computer readable medium. For example, transmission medium 104 may comprise one or more wires, cables, air interfaces, optical discs, flash memory, and / or magnetic memory. In addition or alternatively, transmission medium 104 may comprise one more networks (e.g., the Internet) or fde servers configured to store and / or transmit encoded video data. E.g., the video may be sent to a content delivery network. The present techniques may be used by an original creator of the video to deliver the video as final product for mere communication by the CDN to end consumers, or, the methods described may be applied on a server of the CDN, e.g. to perform a transcoding of an original video.

[0105] To decode bitstream 110 into video sequence 108 usable for display, destination device 106 may comprise an input interface 118, a decoder 120, and a video display 122. Input interface 118 may be configured to read bitstream 110 stored on transmission medium 104 by source device 102, and apply all necessary deformatting and other retrieval actions, such as e.g. demodulation. In addition or alternatively, input interface 118 may be configured to receive, download, and / or stream bitstream 110 from source device 102 via transmission medium 104. Input interface 118 may comprise a wired and / or wireless receiver configured to receive, download, and / or stream bitstream 110 according to one or more proprietary and / or standardized communication protocols, such as those mentioned above.

[0106] Decoder 120 may decode video sequence 108 from encoded bitstream 110. It may e.g. use one of the MPEG video decoding protocols. To decode video sequence 108, decoder 120 may generate prediction blocks for pictures of video sequence 108 in a similar manner as encoder 114 and determine prediction errors for the blocks from residual data for the block being decoded received in the received stream. Decoder 120 may generate the prediction blocks using prediction types, prediction modes, and / or motion vectors received in bitstream 110 and determine the prediction errors using transform coefficients also received in bitstream 110. Decoder 120 may determine the prediction errors by weighting transform basis functions using the transform coefficients. Decoder 120 may combine the prediction blocks and prediction errors to decode video sequence 108. In some examples, decoder 120 may decode a video sequence that approximates video sequence 108 due to, for example, lossy compression of video sequence 108 by encoder 114 and / or errors introduced into encoded bitstream 110 during transmission to destination device 106.

[0107] Video display 122 (which is not an essential part of every apparatus comprising a decoder according to the present principles) may display video sequence 108 to a user. Video display 122 may comprise a cathode rate tube (CRT) display, liquid crystal display (LCD), a plasma display, light emitting diode (LED) display, or any other display device suitable for displaying video sequence 108.

[0108] It should be noted that video encoding / decoding system 100 is presented by way of example and not limitation. In the example of FIG. 1, video encoding / decoding system 100 may have other components and / or arrangements. For example, video source 112 may be external to source device 102. Similarly, video display 122 may be external to destination device 106 or omitted altogether where video sequence is intended for consumption by a machine and / or storage device. In another example, source device 102 may further comprise a video decoder and destination device 106 may comprise a video encoder. In such an example, source device 102 may be configured to further receive an encoded bit stream from destination device 106 to support two-way video transmission between the devices.

[0109] In the example of FIG. 1, encoder 114 and decoder 120 may operate according to any one of a number of proprietary or industry video coding standards. For example, encoder 114 and decoder 120 may operate according to one or more of International Telecommunications Union Telecommunication Standardization Sector (ITU-T) H.263, ITU-T H.264 and Moving Picture Expert Group (MPEG)-4 Part 10 (also known as Advanced Video Coding (AVC)), ITU-T H.265 and MPEG-H Part 2 (also known as High Efficiency Video Coding (HEVC), ITU-T H.265 and MPEG-I Part 3 (also known as Versatile Video Coding (VVC)), the WebM VP8 and VP9 codecs, and AOMedia Video 1 (AVI), etc.

[0110] FIG. 2 illustrates an exemplary encoder 200 in which embodiments of the present disclosure may be implemented. Note that -as understood by the skilled person- a corresponding video decoder will have some of its electronic circuit blocks being similar as in the encoder, in particular the inter prediction unit 206, and intra prediction unit 208 in which the present innovation’s embodiments may reside (the formatting may also reside after the prediction, e.g. in or before the entropy coding circuit), but it will not start with an original to be coded video sequence as input, but rather the coded and compressed data, which will be reconstructed into a close approximation of the original video sequence at the output of the decoder. Yet the predictions will follow the same process as at the encoder. Physically, the circuit blocks, which are processing blocks connected to permanent and / or temporary data memories, may in some apparatuses typically reside in e.g. hardware -acceleration circuits, such as e.g. an ASIC, but in other apparatuses they may be executed as software running on a CPU, etc. Encoder 200 encodes a video sequence 202 into a bitstream 204 for more efficient storage and / or transmission. Encoder 200 may be implemented in video coding / decoding system 100 in FIG. 1 or in any one of a number of different devices, including a desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, or video streaming device. Encoder 200 comprises an inter prediction unit 206, an intra prediction unit 208, combiners 210 and 212, a transform and quantization unit (TR + Q) unit 214, an inverse transform and quantization unit (iTR + iQ) 216, entropy coding unit 218, one or more filters 220, and a buffer 222.

[0111] Encoder 200 may partition the pictures of video sequence 202 into blocks and encode video sequence 202 on a block-by-block basis. Encoder 200 may perform a prediction technique on a block being encoded using either inter prediction unit 206 or intra prediction unit 208. Inter prediction unit 206 may perform inter prediction by searching for a block similar to the block being encoded in another, reconstructed picture (also referred to as a reference picture) of video sequence 202. A reconstructed picture refers to a picture that was encoded and then decoded. The block determined during the search (also referred to as a prediction block) may then be used to predict the block being encoded to remove redundant information. Inter prediction unit 206 may exploit temporal redundancy or similarities in scene content from picture to picture in video sequence 202 to determine the prediction block. For example, scene content between pictures of video sequence 202 may be similar except for differences due to motion or affine transformation of the screen content over time.

[0112] Intra prediction unit 208 may perform intra prediction by forming a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of video sequence 202. A reconstructed sample refers to a sample that was encoded and then decoded. Intra prediction unit 208 may exploit spatial redundancy or similarities in scene content within a picture of video sequence 202 to determine the prediction block. For example, the texture of a region of scene content in a picture may be similar to the texture in the immediate surrounding area of the region of the scene content in the same picture.

[0113] After prediction, combiner 210 may determine a prediction error (also referred to as a residual) based on the difference between the block being encoded and the prediction block. The prediction error may represent non-redundant information that may be transmitted to a decoder for accurate decoding of a video sequence.

[0114] Transform and quantization unit 214 may transform and quantize the prediction error. Transform and quantization unit 214 may transform the prediction error into transform coefficients by applying, for example, a DCT to reduce correlated information in the prediction error. Transform and quantization unit 214 may quantize the coefficients by mapping data of the transform coefficients to a predefined set of representative values. Transform and quantization unit 214 may quantize the coefficients to reduce irrelevant information in bitstream 204. Irrelevant information is information that may be removed from the coefficients without producing visible and / or perceptible distortion in video sequence 202 after decoding. Entropy coding unit 218 may apply one or more entropy coding methods to the quantized transform coefficients to further reduce the bit rate. For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and syntax-based context-based binary arithmetic coding (SBAC). The entropy coded coefficients are packed to form bitstream 204.

[0115] Inverse transform and quantization unit 216 may inverse quantize and inverse transform the quantized transform coefficients to determine a reconstructed prediction error. Combiner 212 may combine the reconstructed prediction error with the prediction block to form a reconstructed block. Filter(s) 220 may filter the reconstructed block using, for example, a deblocking filter and / or a sample- adaptive offset (SAG) filter. Buffer 222 may store the reconstructed block for prediction of one or more other blocks in the same and / or different picture of video sequence 202.

[0116] Although not shown in FIG. 2, encoder 200 further comprises an encoder control unit configured to control one or more of the units of encoder 200 shown in FIG. 2. The encoder control unit may control the one or more units of encoder 200 such that bitstream 204 is generated in conformance with the requirements of any one of a number of proprietary or industry video coding standards. For example, the encoder control unit may control the one or more units of encoder 200 such that bitstream 204 is generated in conformance with one or more of ITU-T H.263, AVC, HEVC, VVC, VP8, VP9, and AVI video coding standards.

[0117] Within the constraints of a proprietary or industry video coding standard, the encoder control unit may attempt to minimize or reduce the bitrate of bitstream 204 and maximize or increase the reconstructed video quality. For example, the encoder control unit may attempt to minimize or reduce the bitrate of bitstream 204 given a level that the reconstructed video quality may not fall below, or attempt to maximize or increase the reconstructed video quality given a level that the bit rate of bitstream 204 may not exceed. The encoder control unit may determine / control one or more of: partitioning of the pictures of video sequence 202 into blocks, whether a block is inter predicted by inter prediction unit 206 or intra predicted by intra prediction unit 208, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, filtering performed by filter(s) 220, and one or more transform types and / or quantization parameters applied by transform and quantization unit 214. The encoder control unit may determine / control the above based on how the determination / control effects a rate-distortion measure for a block or picture being encoded. The encoder control unit may determine / control the above to reduce the rate-distortion measure for a block or picture being encoded.

[0118] After being determined, the prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and transform and quantization parameters, may be sent to entropy coding unit 218 to be further compressed to reduce the bit rate. For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and syntax-based context-based binary arithmetic coding (SBAC) to compress the prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and transform and quantization parameters. The prediction type, prediction information, and transform and quantization parameters may be packed with the prediction error to form bitstream 204.

[0119] It should be noted that encoder 200 is presented by way of example and not limitation. In other examples, encoder 200 may have other components and / or arrangements. For example, one or more of the components shown in FIG. 2 may be optionally included in encoder 200, such as entropy coding unit 218 and fdters(s) 220.

[0120] FIG. 3 illustrates an exemplary decoder 300 in which embodiments of the present disclosure may be implemented. Decoder 300 decodes an bitstream 302 into a decoded video sequence for display and / or some other form of consumption. Decoder 300 may be implemented in video coding / decoding system 100 in FIG. 1 or in any one of a number of different devices, including a desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, or video streaming device. Decoder 300 comprises an entropy decoding unit 306, an inverse transform and quantization (iTR + iQ) unit 308, a combiner 310, one or more fdters 312, a buffer 314, an inter prediction unit 316, and an intra prediction unit 318.

[0121] Although not shown in FIG. 3, decoder 300 further comprises a decoder control unit configured to control one or more of the units of decoder 300 shown in FIG. 3. The decoder control unit may control the one or more units of decoder 300 such that bitstream 302 is decoded in conformance with the requirements of any one of a number of proprietary or industry video coding standards. For example, the decoder control unit may control the one or more units of decoder 300 such that bitstream 302 is decoded in conformance with one or more of ITU-T H.263, AVC, HEVC, VVC, VP8, VP9, and AVI video coding standards.

[0122] The decoder control unit may determine / control one or more of: whether a block is inter predicted by inter prediction unit 316 or intra predicted by intra prediction unit 318, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, filtering performed by filter(s) 312, and one or more inverse transform types and / or inverse quantization parameters to be applied by inverse transform and quantization unit 308. One or more of the control parameters used by the decoder control unit may be packed in bitstream 302.

[0123] Entropy decoding unit 306 may entropy decode the bitstream 302. For example, entropy decoding unit 306 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and syntax-based context-based binary arithmetic coding (SBAC) to decompress the prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and transform and quantization parameters. Inverse transform and quantization unit 308 may inverse quantize and inverse transform the quantized transform coefficients to determine a decoded prediction error. Combiner 310 may combine the decoded prediction error with a prediction block to form a decoded block. The prediction block may be generated by inter prediction unit 318 or inter prediction unit 316 as described above with respect to encoder 200 in FIG 2. Filter(s) 312 may fdter the decoded block using, for example, a deblocking fdter and / or a sample -adaptive offset (SAG) filter. Buffer 314 may store the decoded block for prediction of one or more other blocks in the same and / or different picture of the video sequence in bitstream 302. Decoded video sequence 304 may be output from filter(s) 312 as shown in FIG. 3.

[0124] It should be noted that decoder 300 is presented by way of example and not limitation. In other examples, decoder 300 may have other components and / or arrangements. For example, one or more of the components shown in FIG. 3 may be optionally included in decoder 300, such as entropy decoding unit 306 and filters(s) 312.

[0125] It should be further noted that, although not shown in FIGS. 2 and 3, each of encoder 200 and decoder 300 may further comprise an intra block copy unit in addition to inter prediction and intra prediction units. The intra block copy unit may perform similar to an inter prediction unit but predict blocks within the same picture. For example, the intra block copy unit may exploit repeated patterns that appear in screen content. Screen content may include, for example, computer generated text, graphics, and animation.

[0126] As mentioned above, video encoding and decoding may be performed on a block-by- block basis. The process of partitioning a picture into blocks may be adaptive based on the content of the picture. For example, larger block partitions may be used in areas of a picture with higher levels of homogeneity to improve coding efficiency.

[0127] In HEVC, a picture may be partitioned into non-overlapping square blocks, referred to as coding tree blocks (CTBs), comprising samples of a sample array. A CTB may have a size of 2nx2nsamples, where n may be specified by a parameter of the encoding system. For example, n may be 4, 5, or 6. A CTB may be further partitioned by a recursive quadtree partitioning into coding blocks (CBs) of half vertical and half horizontal size. The CTB forms the root of the quadtree. A CB that is not split further as part of the recursive quadtree partitioning may be referred to as a leaf-CB of the quadtree and otherwise as a non-leaf CB of the quadtree. A CB may have a minimum size specified by a parameter of the encoding system. For example, a CB may have a minimum size of 4x4, 8x8, 16x16, 32x32, or 64x64 samples. For inter and intra prediction, a CB may be further partitioned into one or more prediction blocks (PBs) for performing inter and intra prediction. A PB may be a rectangular block of samples on which the same prediction type / mode may be applied. For transformations, a CB may be partitioned into one or more transform blocks (TBs). A TB may be a rectangular block of samples that may determine an applied transform size.

[0128] FIG. 4 illustrates an example quadtree partitioning of a CTB 400. This is just for elucidation purposes, since not all codecs need to employ such a coding structure, and it is not essential for the techniques of the present innovation. What will typically be similar, is that there will be a part covering one or typically more regions that have already been reconstructed in an image, and a remainder part that still has to be reconstructed, and is being reconstructed as the decoding of the received bitstream moves forward. Typically the image is being reconstructed from the left to the right and from top to bottom. FIG. 5 illustrates a corresponding quadtree 500 of the example quadtree partitioning of CTB 400 in FIG. 4. As shown in FIGS. 4 and 5, CTB 400 is first partitioned into four CBs of half vertical and half horizontal size. Three of the resulting CBs of the first level partitioning of CTB 400 are leaf-CBs. The three leaf CBs of the first level partitioning of CTB 400 are respectively labeled 7, 8, and 9 in FIGS. 4 and 5. The non-leaf CB of the first level partitioning of CTB 400 is partitioned into four sub-CBs of half vertical and half horizontal size. Three of the resulting sub-CBs of the second level partitioning of CTB 400 are leaf CBs. The three leaf CBs of the second level partitioning of CTB 400 are respectively labeled 0, 5, and 6 in FIGS. 4 and 5. Finally, the non-leaf CB of the second level partitioning of CTB 400 is partitioned into four leaf CBs of half vertical and half horizontal size. The four leaf CBs are respectively labeled 1, 2, 3, and 4 in FIGS. 4 and 5.

[0129] Altogether, CTB 400 is partitioned into 10 leaf CBs respectively labeled 0-9. The resulting quadtree partitioning of CTB 400 may be scanned using a z-scan (left-to-right, top-to-bottom) to form the sequence order for encoding / decoding the CB leaf nodes. The numeric label of each CB leaf node in FIGS. 4 and 5 may correspond to the sequence order for encoding / decoding, with CB leaf node 0 encoded / decoded first and CB leaf node 9 encoded / decoded last. Although not shown in FIGS. 4 and 5, it should be noted that each CB leaf node may comprise one or more PBs and TBs.

[0130] In VVC, a picture may be partitioned in a similar manner as in HEVC. A picture may be first partitioned into non-overlapping square CTBs. The CTBs may then be partitioned by a recursive quadtree partitioning into CBs of half vertical and half horizontal size. In VVC, a quadtree leaf node may be further partitioned by a binary tree or ternary tree partitioning into CBs of unequal sizes. FIG. 6 illustrates example binary and ternary tree partitions. A binary tree partition may divide a parent block in half in either the vertical direction 602 or horizontal direction 604. The resulting partitions may be half in size as compared to the parent block. A ternary tree partition may divide a parent block into three parts in either the vertical direction 606 or horizontal direction 608. The middle partition may be twice as large as the other two end partitions in a ternary tree partition.

[0131] Because of the addition of binary and ternary tree partitioning, in VVC the block partitioning strategy may be referred to as quadtree + multi-type tree partitioning. FIG. 7 illustrates an example quadtree + multi-type tree partitioning of a CTB 700. FIG. 8 illustrates a corresponding quadtree + multi -type tree 800 of the example quadtree + multi -type tree partitioning of CTB 700 in FIG. 7. In both FIGS. 7 and 8, quadtree splits are shown in solid lines and multi -type tree splits are shown in dashed lines. For ease of explanation, CTB 700 is shown with the same quadtree partitioning as CTB 400 described in FIG. 4. Therefore, description of the quadtree partitioning of CTB 700 is omitted. The description of the additional multi-type tree partitions of CTB 700 is made relative to three leaf-CBs shown in FIG. 4 that have been further partitioned using one or more binary and ternary tree partitions. The three leaf-CBs in FIG. 4 that are shown in FIG. 7 as being further partitioned are leaf-CBs 5, 8, and 9.

[0132] Starting with leaf-CB 5 in FIG. 4, FIG. 7 shows this leaf-CB partitioned into two CBs based on a vertical binary tree partitioning. The two resulting CBs are leaf-CBs respectively labeled 5 and 6 in FIGS. 7 and 8. With respect to leaf-CB 8 in FIG. 4, FIG. 7 shows this leaf-CB partitioned into three CBs based on a vertical ternary tree partition. Two of the three resulting CBs are leaf-CBs respectively labeled 9 and 14 in FIGS. 7 and 8. The remaining, non-leaf CB is partitioned first into two CBs based on a horizontal binary tree partition, one of which is a leaf-CB labeled 10 and the other of which is further partitioned into three CBs based on a vertical ternary tree partition. The resulting three CBs are leaf-CBs respectively labeled 11, 12, and 13 in FIGS. 7 and 8. Finally, with respect to leaf-CB 9 in FIG. 4, FIG. 7 shows this leaf-CB partitioned into three CBs based on a horizontal ternary tree partition. Two of the three CBs are leaf-CBs respectively labeled 15 and 19 in FIGS. 7 and 8. The remaining, non-leaf CB is partitioned into three CBs based on another horizontal ternary tree partition. The resulting three CBs are all leaf-CBs respectively labeled 16, 17, and 18 in FIGS. 7 and 8.

[0133] Altogether, CTB 700 is partitioned into 20 leaf CBs respectively labeled 0-19. The resulting quadtree + multi -type tree partitioning of CTB 700 may be scanned using a z-scan (left-to-right, top-to-bottom) to form the sequence order for encoding / decoding the CB leaf nodes. The numeric label of each CB leaf node in FIGS. 7 and 8 may correspond to the sequence order for encoding / decoding, with CB leaf node 0 encoded / decoded first and CB leaf node 19 encoded / decoded last. Although not shown in FIGS. 7 and 8, it should be noted that each CB leaf node may comprise one or more PBs and TBs.

[0134] In addition to specifying various blocks (e.g., CTB, CB, PB, TB), HEVC and VVC further define various units. While blocks may comprise a rectangular area of samples in a sample array, units may comprise the collocated blocks of samples from the different sample arrays (e.g., luma and chroma sample arrays) that form a picture as well as syntax elements and prediction data of the blocks. A coding tree unit (CTU) may comprise the collocated CTBs of the different sample arrays and may form a complete entity in an encoded bit stream. A coding unit (CU) may comprise the collocated CBs of the different sample arrays and syntax structures used to code the samples of the CBs. A prediction unit (PU) may comprise the collocated PBs of the different sample arrays and syntax elements used to predict the PBs. A transform unit (TU) may comprise TBs of the different samples arrays and syntax elements used to transform the TBs.

[0135] It should be noted that the term block may be used to refer to any of a CTB, CB, PB, TB, CTU, CU, PU, or TU in the context of HEVC and VVC. It should be further noted that the term block may be used to refer to similar data structures in the context of other video coding standards. For example, the term block may refer to a macroblock in AVC, a macroblock or sub-block in VP8, a superblock or sub-block in VP9, or a superblock or sub-block in AV 1.

[0136] In intra prediction, samples of a block to be encoded (also referred to as the current block) may be predicted from samples of the column immediately adjacent to the left-most column of the current block and samples of the row immediately adjacent to the top-most row of the current block. The samples from the immediately adjacent column and row may be jointly referred to as reference samples. Each sample of the current block may be predicted by projecting the position of the sample in the current block in a given direction (also referred to as an intra prediction mode) to a point along the reference samples. The sample may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. A prediction error (also referred to as a residual) may be determined for the current block based on differences between the predicted sample values and the original sample values of the current block.

[0137] At an encoder, this process of predicting samples and determining a prediction error based on a difference between the predicted samples and original samples may be performed for a plurality of different intra prediction modes, including non-directional intra prediction modes. The encoder may select one of the plurality of intra prediction modes and its corresponding prediction error to encode the current block. The encoder may send an indication of the selected prediction mode and its corresponding prediction error to a decoder for decoding of the current block. The decoder may decode the current block by predicting the samples of the current block using the intra prediction mode indicated by the encoder and combining the predicted samples with the prediction error.

[0138] FIG. 9 illustrates an example set of reference samples 902 determined for intra prediction of a current block 904 being encoded or decoded. In FIG. 9, current block 904 corresponds to block 3 of partitioned CTB 700 in FIG. 7. As explained above, the numeric labels 0-19 of the blocks of partitioned CTB 700 may correspond to the sequence order for encoding / decoding the blocks and are used as such in the example of FIG. 9.

[0139] Given current block 904 is of w x h samples in size, reference samples 902 may extend over 2w samples of the row immediately adjacent to the top-most row of current block 904, 2h samples of the column immediately adjacent to the left-most column of current block 904, and the top left neighboring comer sample to current block 904. In the example of FIG. 9, current block 904 is square, so w = h = s. For constructing the set of reference samples 902, available (i.e. already reconstructed by the decoder) samples from neighboring blocks of current block 904 may be used. Samples may not be available for constructing the set of reference samples 902 if, for example, the samples would lie outside the picture of the current block, the samples are part of a different slice of the current block (where the concept of slices are used), and / or the samples belong to blocks that have been inter coded and constrained intra prediction is indicated. When constrained intra prediction is indicated, intra prediction may not be dependent on inter predicted blocks.

[0140] In addition to the above, samples that may not be available for constructing the set of reference samples 902 include samples in blocks that have not already been encoded and reconstructed at an encoder or decoded at a decoder based on the sequence order for encoding / decoding. This restriction may allow identical prediction results to be determined at both the encoder and decoder. In FIG. 9, samples from neighboring blocks 0, 1, and 2 may be available to construct reference samples 902 given that these blocks are encoded and reconstructed at an encoder and decoded at a decoder prior to coding of current block 904. This assumes there are no other issues, such as those mentioned above, preventing the availability of samples from neighboring blocks 0, 1, and 2. However, the portion of reference samples 902 from neighboring block 6 may not be available due to the sequence order for encoding / decoding.

[0141] Unavailable ones of reference samples 902 may be fdled with available ones of reference samples 902. For example, an unavailable reference sample may be fdled with a nearest available reference sample determined by moving in a clock-wise direction through reference samples 902 from the position of the unavailable reference. If no reference samples are available, reference samples 902 may be fdled with the mid-value of the dynamic range of the picture being coded (e.g. the luma value 128 for 8 bit luma).

[0142] It should be noted that reference samples 902 may be fdtered based on the size of current block 904 being coded and an applied intra prediction mode. In such a case the value of a luma may be replaced by a weighted combination of the values of luma of adjacent pixels. It should be further noted that FIG. 9 illustrates only one exemplary determination of reference samples for intra prediction of a block. In some proprietary and industry video coding standards, reference samples may be determined in a different manner than discussed above. For example, multiple reference lines may be used in other instances, such as used in VVC.

[0143] After reference samples 902 are determined and optionally filtered, samples of current block 904 may be intra predicted based on reference samples 902. Most encoders / decoders support a plurality of intra prediction modes in accordance with one or more video coding standards. One or more of those predictions may be selected as found to be predicting well (whereas the others may be discarded as not prediction well for the current block being reconstructed). For example, HEVC supports 35 intra prediction modes, including a planar mode, a DC mode, and 33 angular modes (the technical definition and word meaning of an angular mode is fetching a pixel from the reference samples from the current being reconstructed pixel position by following the (single) one of the 33 angles as specified). VVC supports 67 intra prediction modes, including a planar mode, a DC mode, and 65 angular modes. Planar and DC modes (which are not angular modes) may be used to predict smooth and gradually changing regions of a picture. E.g. the DC mode calculates an average of reference sample lumas. Angular modes may be used to predict directional structures in regions of a picture. E.g. if a pixel block of a skyscraper in the image needs to be predicted, the windows and wall between the windows may form nice vertical structures, for which the straight downwards angular prediction copying a value from above will be a good predictor for a lower value along the same vertical line. Even if changes compared to the predictor do occur (e.g. due to local illumination differences, or an unexpected added structure, or another object in front), such changes are typically expected to be of smaller magnitude and / or infrequent, hence making the prediction worthwhile.

[0144] FIG. 10A illustrates the 35 intra prediction modes supported by HEVC. The 35 intra prediction modes are identified by indices 0 to 34. Prediction mode 0 corresponds to planar mode. Prediction mode 1 corresponds to DC mode. Prediction modes 2-34 correspond to angular modes. Prediction modes 2-18 may be referred to as (essentially) horizontal prediction modes (not strictly horizontal, which would be the predictor 10) because the principal source of prediction is in the horizontal direction. Prediction modes 19-34 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction.

[0145] FIG. 10B illustrates the 67 intra prediction modes supported by VVC. The 67 intra prediction modes are identified by indices 0 to 66. Prediction mode 0 corresponds to planar mode. Prediction mode 1 corresponds to DC mode. Prediction modes 2-66 correspond to angular modes. Prediction modes 2-34 may be referred to as horizontal prediction modes because the principal source of prediction is in the horizontal direction. Prediction modes 35-66 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction. Because blocks in VVC may be non-square, some of the intra prediction modes illustrated in FIG. 10B may be adaptively replaced by wide-angle directions.

[0146] To further describe the application of intra prediction modes to determine a prediction of a current block, reference is made to FIGS. 11 and 12. In FIG. 11, current block 904 and reference samples 902 from FIG. 9 are shown in a two-dimensional x, y plane, where a sample may be referenced as p[x] [y] . In order to simplify the prediction process, reference samples 902 may be placed in two, onedimensional arrays. Reference samples 902 above current block 904 may be placed in the onedimensional array ref, [x] : refjx] = p[-l + x][— 1], (x > 0) (1)

[0147] Reference samples 902 to the left of current block 904 may be placed in the one -dimensional array ref2[x]: ref2[y] = p[— 1] [— 1 + y], (y > 0) (2)

[0148] For planar mode a sample at location [x] [y] in current block 904 may be predicted by calculating the mean of two interpolated values. The first of the two interpolated values may be based on a horizontal linear interpolation at location [x] [y] in current block 904. The second of the two interpolated values may be based on a vertical linear interpolation at location [x] [y] in current block 904. The predicted sample p[x] [y] in current block 904 may be calculated as where h[x][y] = (s — x — 1) ■ ref2[y] + (x + 1) ■ ref- s] (4) may be the horizonal linear interpolation at location [x] [y] in current block 904 and v[x][y] = (s - y - 1) - ref x] + (y + 1) ■ ref2[s] (5) may be the vertical linear interpolation at location [x] [y] in current block 904. For DC mode, a sample at location [x] [y] in current block 904 may be predicted by the mean of the reference samples 902. The predicted value sample p[x] [y] in current block 904 may be calculated as s-1 \ ref x] + ^ ref2[y] j (6) y=0 )

[0149] For angular modes, a sample at location [x] [y] in current block 904 may be predicted by projecting the location [x] [y] in a direction specified by a given angular mode to a point on the horizontal or vertical line of samples comprising reference samples 902. The sample at location [x] [y] may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. The direction specified by the angular mode may be given by an angle cp defined relative to the y-axis for vertical prediction modes (e.g., modes 19-34 in HEVC and modes 35-66 in VVC) and relative to the x-axis for horizontal prediction modes (e.g., modes 2-18 in HEVC and modes 2-34 in VVC).

[0150] FIG. 12 illustrates a prediction of a sample at location [x] [y] in current block 904 for a vertical prediction mode 906 given by an angle cp. For vertical prediction modes, the location [x] [y] in current block 904 is projected to a point (referred to herein as the “projection point”) on the horizontal line of reference samples ref) [x]. Reference samples 902 are only partially shown in FIG. 12 for ease of illustration. Because the projection point falls at a fractional sample position between two reference samples in the example of FIG. 12, the predicted sample p[x] [y] in current block 904 may be calculated by linearly interpolating between the two reference samples as follows

[0151] P[x][y] = (1 - if) - ref x + ii + 1] + if■ ref x + i, + 2] (7) where ij is the integer part of the horizontal displacement of the projection point relative to the location [x] [y] and may calculated as a function of the tangent of the angle cp of the vertical prediction mode 906 as follows ii = L(y + 1) ■ tan cpj, (8) and if is the fractional part of the horizontal displacement of the projection point relative to the location [x] [y] and may be calculated as if= ((y + 1) - tan ip) - L(y + 1) - tan ipj. (9) where [ ■ J is the integer floor.

[0152] For horizontal prediction modes, the position [x][y] of a sample in current block 904 may be projected onto the vertical line of reference samples ref2[y] . Sample prediction for horizontal prediction modes is given by:

[0153] P[x][y] = (1 — if) ’ ref2[y + ij + 1] + if■ ref2[y + i, + 2] (10) where ij is the integer part of the vertical displacement of the projection point relative to the location [x] [y] and may be calculated as a function of the tangent of the angle cp of the horizontal prediction mode as follows ii = L(x + 1) ■ tan cpj, (11) and if is the fractional part of the vertical displacement of the projection point relative to the location [x] [y] and may be calculated as if = ((x + 1) ■ tamp) — [(x + 1) ■ tan cpj . (12) where [ ■ ] is the integer floor.

[0154] The interpolation functions of (7) and (10) may be implemented by an encoder or decoder, such as encoder 200 in FIG. 2 or decoder 300 in FIG. 3, as a set of two-tap finite impulse response (FIR) filters. The coefficients of the two-tap FIR filters may be respectively given by ( 1 -if) and if. In the above angular intra prediction examples, the predicted sample p[x] [y] may be calculated with some predefined level of sample accuracy, such as 1 / 32 sample accuracy. For 1 / 32 sample accuracy, the set of two-tap FIR interpolation filters may comprise up to 32 different two-tap FIR interpolation filters — one for each of the 32 possible values of the fractional part of the projected displacement if. In other examples, different levels of sample accuracy may be used.

[0155] In an embodiment, the two-tap interpolation FIR filter may be used for predicting chroma samples. For luma samples, a different interpolation technique may be used. For example, for luma samples a four-tap FIR filter may be used to determine a predicted value of a luma sample. For example, the four tap FIR filter may have coefficients determined based on if, similar to the two-tap FIR filter. For 1 / 32 sample accuracy, a set of 32 different four-tap FIR filters may comprise up to 32 different four-tap FIR filters — one for each of the 32 possible values of the fractional part of the projected displacement if. In other examples, different levels of sample accuracy may be used. The set of four-tap FIR filters may be stored in a look-up table (LUT) and referenced based on if. The value of the predicted sample p[x][y], for vertical prediction modes, may be determined based on the four-tap FIR filter as follows: p [ x ][ y ] = Xi?=o fT[ i ] * ref[ x + ildx + i ] (13) where ft[i], i = 0. . .3, are the filter coefficients. The value of the predicted sample p[x][y], for horizontal prediction modes, may be determined based on the four-tap FIR filter as follows:

[0156] P [ x ][ y ] = Ef=ofT[ i ] * ref[ y + ildx + i ]. (14)

[0157] It should be noted that supplementary reference samples may be constructed for the case where the position [x][y] of a sample in current block 904 to be predicted is projected to a negative x coordinate, which happens with negative vertical prediction angles cp. The supplementary reference samples may be constructed by projecting the reference samples in ref2[y] in the vertical line of reference samples 902 to the horizontal line of reference samples 902 using the negative vertical prediction angle cp. Supplemental reference samples may be similarly for the case where the position [x][y] of a sample in current block 904 to be predicted is projected to a negative y coordinate, which happens with negative horizontal prediction angles cp. The supplementary reference samples may be constructed by projecting the reference samples in ref) [x] on the horizontal line of reference samples 902 to the vertical line of reference samples 902 using the negative horizontal prediction angle cp. An encoder may predict the samples of a current block being encoded, such as current block 904, for a plurality of intra prediction modes as explained above. For example, the encoder may predict the samples of the current block for each of the 35 intra prediction modes in HEVC or 67 intra prediction modes in VVC. For each intra prediction mode applied, the encoder may determine a prediction error for the current block based on a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), or sum of absolute transformed differences (SATD)) between the prediction samples determined for the intra prediction mode and the original samples of the current block. The encoder may select one of the intra prediction modes to encode the current block based on the determined prediction errors. For example, the encoder may select an intra prediction mode that results in the smallest prediction error for the current block. In another example, the encoder may select the intra prediction mode to encode the current block based on a rate-distortion measure (e.g., Lagrangian ratedistortion cost) determined using the prediction errors. The encoder may send an indication of the selected intra prediction mode and its corresponding prediction error to a decoder for decoding of the current block.

[0158] Similar to an encoder, a decoder may predict the samples of a current block being decoded, such as current block 904, for an intra prediction modes as explained above. For example, the decoder may receive an indication of an angular intra prediction mode from an encoder for a block. The decoder may construct a set of reference samples and perform intra prediction based on the angular intra prediction mode indicated by the encoder for the block in a similar manner as discussed above for the encoder. The decoder would add the predicted values of the samples of the block to a residual of the block to reconstruct the block. In another embodiment, the decoder may not receive an indication of an angular intra prediction mode from an encoder for a block. Instead, the decoder may determine an intra prediction mode through other, decoder-side means.

[0159] Although the description above was primarily made with respect to intra prediction modes in HEVC and VVC, it will be understood that the techniques of the present disclosure described above and further below may be applied to other intra prediction modes, including those of other video coding standards like VP8, VP9, AVI, and the like.

[0160] As explained above, intra prediction may exploit correlations between spatially neighboring samples in the same picture of a video sequence to perform video compression. Inter prediction is another coding tool that may be used to exploit correlations in the time domain between blocks of samples in different pictures of the video sequence to perform video compression. In general, an object may be seen across multiple pictures of a video sequence. The object may move (e.g., by some translation and / or affine motion) or remain stationary across the multiple pictures. A current block of samples in a current picture being encoded may therefore have a corresponding block of samples in a previously decoded picture that accurately predicts the current block of samples. The corresponding block of samples may be displaced from the current block of samples due to movement of an object, represented in both blocks, across the respective pictures of the blocks. The previously decoded picture may be referred to as a reference picture and the corresponding block of samples in the reference picture may be referred to as a reference block or motion compensated prediction. An encoder may use a block matching technique to estimate the displacement (or motion) and determine the reference block in the reference picture.

[0161] Similar to intra prediction, once a prediction for a current block is determined and / or generated using inter prediction, an encoder may determine a difference between the current block and the prediction. The difference may be referred to as a prediction error or residual. The encoder may then store and / or signal in a bitstream the prediction error and other related prediction information for decoding or other forms of consumption. A decoder may decode the current block by predicting the samples of the current block using the prediction information and combining the predicted samples with the prediction error.

[0162] FIG. 13A illustrates an example of inter prediction performed for a current block 1300 in a current picture 1302 being encoded. An encoder, such as encoder 200 in FIG. 2, may perform inter prediction to determine and / or generate a reference block 1304 in a reference picture 1306 to predict current block 1300. Reference pictures, like reference picture 1306, are prior decoded pictures available at the encoder and decoder. Availability of a prior decoded picture may depend on whether the prior decoded picture is available in a decoded picture buffer at the time current block 1300 is being encoded or decoded. The encoder may, for example, search one or more reference pictures for a reference block that is similar to current block 1300. The encoder may determine a “best matching” reference block from the blocks tested during the searching process as reference block 1304. The encoder may determine that reference block 1304 is the best matching reference block based on one or more cost criterion, such as a rate-distortion criterion (e.g., Lagrangian rate-distortion cost). The one or more cost criterion may be based on, for example, a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), or sum of absolute transformed differences (SATD)) between the prediction samples of reference block 1304 and the original samples of current block 1300.

[0163] The encoder may search for reference block 1304 within a search range 1308. Search range 1308 may be positioned around the collocated position (or block) 1310 of current block 1300 in reference picture 1306. In some instances, search range 1308 may at least partially extend outside of reference picture 1306. When extending outside of reference picture 1306, constant boundary extension may be used such that the values of the samples in the row or column of reference picture 1306, immediately adjacent to the portion of search range 1308 extending outside of reference picture 1306, are used for the “sample” locations outside of reference picture 1306. All or a subset of potential positions within search range 1308 may be searched for reference block 1304. The encoder may utilize any one of a number of different search implementations to determine and / or generate reference block 1304. For example, the encoder may determine a set of a candidate search positions based on motion information of neighboring blocks to current block 1300. One or more reference pictures may be searched by the encoder during inter prediction to determine and / or generate the best matching reference block. The reference pictures searched by the encoder may be included in one or more reference picture lists. For example, in HEVC and VVC, two reference picture lists may be used, a reference picture list 0 and a reference picture list 1. A reference picture list may include one or more pictures. Reference picture 1306 of reference block 1304 may be indicated by a reference index pointing into a reference picture list comprising reference picture 1306.

[0164] The displacement between reference block 1304 and current block 1300 may be interpreted as an estimate of the motion between reference block 1304 and current block 1300 across their respective pictures. The displacement may be represented by a motion vector 1312. For example, motion vector 1312 may be indicated by a horizontal component (MVX) and a vertical component (MVy) relative to the position of current block 1300. FIG. 13B illustrates the horizontal component and vertical component of motion vector 1312. A motion vector, such as motion vector 1312, may have fractional or integer resolution. A motion vector with fractional resolution may point between two samples in a reference picture to provide a better estimation of the motion of current block 1300. For example, a motion vector may have 1 / 2, 1 / 4, 1 / 8, 1 / 16, or 1 / 32 fractional sample resolution. When a motion vector points to a non-integer sample value in the reference picture, interpolation between samples at integer positions may be used to generate the reference block and its corresponding samples at fractional positions. The interpolation may be performed by a fdter with two or more taps.

[0165] Once reference block 1304 is determined and / or generated for current block 1300 using inter prediction, the encoder may determine a difference (e.g., a corresponding sample -by-sample difference) between reference block 1304 and current block 1300. The difference may be referred to as a prediction error or residual. The encoder may then store and / or signal in a bitstream the prediction error and the related motion information for decoding or other forms of consumption. The motion information may include motion vector 1312 and a reference index pointing into a reference picture list comprising reference picture 1306. In other instances, the motion information may include an indication of motion vector 1312 and an indication of the reference index pointing into the reference picture list comprising reference picture 1306. A decoder may decode current block 1300 by determining and / or generating reference block 1304, which forms the prediction of current block 1300, using the motion information and combining the prediction with the prediction error.

[0166] In FIG. 13 A, inter prediction is performed using one reference picture 1306 as the source of the prediction for current block 1300. Because the prediction for current block 1300 comes from a single picture, this type of inter prediction is referred to as uni-prediction. FIG. 14 illustrates another type of inter prediction, referred to as bi-prediction, performed for a current block 1400. In bi-prediction, the source of the prediction for a current block 1400 comes from two pictures. Bi-prediction may be useful, for example, where the video sequence comprises fast motion, camera panning or zooming, or scene changes. Bi-prediction may also be useful to capture fade outs of one scene or fade outs from one scene to another, where two pictures are effectively displayed simultaneously with different levels of intensity. Whether uni-prediction or both uni-prediction and bi-prediction are available for performing inter prediction may depend on a slice type of current block 1400. For P slices, only uniprediction may be available for performing inter prediction. For B slices, either uni-prediction or biprediction may be used. When uni-prediction is performed, an encoder may determine and / or generate a reference block for predicting current block 1400 from reference picture list 0. When bi-prediction is performed, an encoder may determine and / or generate a first reference block for predicting current block 1400 from reference picture list 0 and determine and / or generate a second reference block for predicting current block 1400 from reference picture list 1.

[0167] In FIG. 14, inter-prediction is performed using bi-prediction, where two reference blocks 1402 and 1404 are used to predict current block 1400. Reference block 1402 may be in a reference picture of one of reference picture list 0 or 1, and reference block 1404 may be in a reference picture of the other one of reference picture list 0 or 1. As shown in FIG. 14, reference block 1402 is in a picture that precedes the current picture of current block 1400 in terms of picture order count (POC), and reference block 1402 is in a picture that proceeds the current picture of current block 1400 in terms of POC. In other examples, the reference pictures may both precede or proceed the current picture in terms of POC. POC is the order in which pictures are output from, for example, a decoded picture buffer and is the order in which pictures are generally intended to be displayed. However, it should be noted that pictures that are output are not necessarily displayed but may undergo different processing or consumption, such as transcoding. In other examples, the two reference blocks determined and / or generated using bi -prediction may come from the same reference picture. In such an instance, the reference picture may be included in both reference picture list 0 and reference picture list 1.

[0168] A configurable weight and offset value may be applied to the one or more inter prediction reference blocks. An encoder may enable the use of weighted prediction using a flag in a picture parameter set (PPS) and signal the weighting and offset parameters in the slice segment header for the current block. Different weight and offset parameters may be signaled for luma and chroma components.

[0169] Once reference blocks 1402 and 1404 are determined and / or generated for current block 1400 using inter prediction, the encoder may determine a difference between current block 1400 and each of reference blocks 1402 and 1404. The differences may be referred to as prediction errors or residuals. The encoder may then store and / or signal in a bitstream the prediction errors and their respective related motion information for decoding or other forms of consumption. The motion information for reference block 1402 may include motion vector 1406 and the reference index pointing to a reference picture, of the reference picture list, comprising reference block 1402. In other instances, the motion information for reference block 1402 may include an indication of motion vector 1406 and an indication of the reference index pointing to a reference picture, of the reference picture list, comprising reference block 1402. The motion information for reference block 1404 may include motion vector 1408 and the reference index pointing to a reference picture, of the reference picture list, comprising the reference picture comprising reference block 1404. In other instances, the motion information for reference block 1404 may include an indication of motion vector 1408 and an indication of the reference index pointing to a reference picture, of the reference picture list, comprising the reference picture comprising reference block 1404. A decoder may decode current block 1400 by determining and / or generating reference blocks 1402 and 1404, which together form the prediction of current block 1400, using their respective motion information and combining the predictions with the prediction errors.

[0170] In HEVC, VVC, and other video compression schemes, motion information may be predictively coded before being stored or signaled in a bit stream. The motion information for a current block may be predictively coded based on the motion information of neighboring blocks of the current block. In general, the motion information of the neighboring blocks is often correlated with the motion information of the current block because the motion of an object represented in the current block is often the same or similar to the motion of objects in the neighboring blocks. Two of the motion information prediction techniques in HEVC and VVC include advanced motion vector prediction (AMVP) and inter prediction block merging.

[0171] An encoder, such as encoder 200 in FIG. 2, may code a motion vector using the AMVP tool as a difference between the motion vector of a current block being coded and a motion vector predictor (MVP). An encoder may select the MVP from a list of candidate MVPs. The candidate MVPs may come from previously decoded motion vectors of neighboring blocks in the current picture of the current block or blocks at or near the collocated position of the current block in other reference pictures. Both the encoder and decoder may generate or determine the list of candidate MVPs.

[0172] After the encoder selects an MVP from the list of candidate MVPs, the encoder may signal, in a bitstream, an indication of the selected MVP and a motion vector difference (MVD). The encoder may indicate the selected MVP in the bitstream by an index pointing into the list of candidate MVPs. The MVD may be calculated based on the difference between the motion vector of the current block and the selected MVP. For example, for a motion vector represented by a horizontal component (MVX) and a vertical displacement (MVy) relative to the position of the current block being coded, the MVD may be represented by two components calculated as follows:

[0173] MVDX= MVX- MVPX(15)

[0174] MVDy = MVy - MVPy (16) where MVDXand MVDyrespectively represent the horizontal and vertical components of the MVD, and MVPx and MVPyrespectively represent the horizontal and vertical components of the MVP. A decoder, such as decoder 300 in FIG. 3, may decode the motion vector by adding the MVD to the MVP indicated in the bitstream. The decoder may then decode the current block by determining and / or generating the reference block, which forms the prediction of the current block, using the decoded motion vector and combining the prediction with the prediction error.

[0175] In HEVC and VVC, the list of candidate MVPs for AMVP may comprise two candidates referred to as candidates A and B. Candidates A and B may include up to two spatial candidate MVPs derived from five spatial neighboring blocks of the current block being coded, one temporal candidate MVP derived from two temporal, co-located blocks when both spatial candidate MVPs are not available or are identical, or zero motion vectors when the spatial, temporal, or both candidates are not available. FIG. 15A illustrates the location of the five spatial candidate neighboring blocks relative to a current block 1500 being encoded. The five spatial candidate neighboring blocks are respectively denoted Ao, Ai, Bo, Bi, and B2. FIG. 15B illustrates the location of the two temporal, co-located blocks relative to current block 1500 being coded. The two temporal, co-located blocks are denoted Co and Ci and are included in a reference picture that is different from the current picture of current block 1500.

[0176] An encoder, such as encoder 200 in FIG. 2, may code a motion vector using the inter prediction block merging tool also referred to as merge mode. Using merge mode, the encoder may reuse the same motion information of a neighboring block for inter prediction of a current block. Because the same motion information of a neighboring block is used, no MVD needs to be signaled and the signaling overhead for signaling the motion information of the current block may be small in size. Similar to AMVP, both the encoder and decoder may generate a candidate list of motion information from neighboring blocks of the current block. The encoder may then determine to use (or inherit) the motion information of one neighboring block’s motion information in the candidate list for predicting the motion information of the current block being coded. The encoder may signal, in the bit stream, an indication of the determined motion information from the candidate list. For example, the encoder may signal an index pointing into the list of candidate motion information to indicate the determined motion information.

[0177] In HEVC and VVC, the list of candidate motion information for merge mode may comprise up to four spatial merge candidates that are derived from the five spatial neighboring blocks used in AMVP as shown in FIG. 15A, one temporal merge candidate derived from two temporal, colocated blocks used in AMVP as shown in FIG. 15B, and additional merge candidates including bi- predictive candidates and zero motion vector candidates.

[0178] It should be noted that inter prediction may be performed in other ways and variants than those described above. For example, motion information prediction techniques other than AMVP and merge mode are possible. In addition, although the description above was primarily made with respect to inter prediction modes in HEVC and VVC, it will be understood that the techniques of the present disclosure described above and further below may be applied to other inter prediction modes, including those of other video coding standards like VP8, VP9, AVI, and the like. In addition, history based motion vector prediction (HMVP), combined intra / inter prediction mode (CIIP), and merge mode with motion vector difference (MMVD) as described in VVC may also be performed and are within the scope of the present disclosure.

[0179] In inter prediction, a block matching technique may be applied to determine a reference block in a different picture than the current block being encoded. Block matching techniques have also been applied to determine a reference block in the same picture as a current block being encoded. However, it has been determined that for camera-captured videos, a reference block in the same picture as the current block determined using block matching may often not accurately predict the current block. For screen content video this is generally not the case. Screen content video may include, for example, computer generated text, graphics, and animation. Within screen content, there is often repeated patterns (e.g., repeated patterns of text and graphics) within the same picture. Therefore, a block matching technique applied to determine a reference block in the same picture as a current block being encoded may provide efficient compression for screen content video.

[0180] HEVC and VVC both include a prediction technique to exploit the correlation between blocks of samples within the same picture of screen content video. This technique is referred to as intra block (IBC) or current picture referencing (CPR). Similar to inter prediction, an encoder may apply a block matching technique to determine a displacement vector (referred to as a block vector (BV)) that indicates the relative displacement from the current block to a reference block (or intra block compensated prediction) that “best matches” the current block. The encoder may determine the best matching reference block from blocks tested during a searching process similar to inter prediction. The encoder may determine that a reference block is the best matching reference block based on one or more cost criterion. The one or more cost criterion may be, for example, a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), sum of absolute transformed differences (SATD), or difference determined based on a hash function) between the prediction samples of the reference block and the original samples of the current block. A reference block may correspond to prior decoded blocks of samples of the current picture. The reference block may comprise decoded blocks of samples of the current picture prior to being processed by in-loop filtering operations, like deblocking or SAG filtering. FIG. 16 illustrates an example of IBC applied for screen content. The rectangular portions with arrows beginning at their boundaries are current blocks being encoded and the rectangular portions that the arrows point to are the reference blocks for predicting the current blocks.

[0181] Once a reference block is determined and / or generated for a current block using IBC, the encoder may determine a difference (e.g., a corresponding sample-by-sample difference) between the reference block and the current block. The difference may be referred to as a prediction error or residual. The encoder may then store and / or signal in a bitstream the prediction error and the related prediction information for decoding or other forms of consumption. The prediction information may include a BV. In other instances, the prediction information may include an indication of the BV. A decoder, such as decoder 300 in FIG. 3, may decode the current block by determining and / or generating the reference block, which forms the prediction of the current block, using the prediction information and combining the prediction with the prediction error.

[0182] In HEVC, VVC, and other video compression schemes, a BV may be predictively coded before being stored or signaled in a bit stream. The BV for a current block may be predictively coded based on the BV of neighboring blocks of the current block. For example, an encoder may predictively code a BV using the merge mode as explained above for inter prediction or a similar technique as AMVP also explained above for inter prediction. The technique similar to AMVP may be referred to as BV prediction and difference coding.

[0183] For BV prediction and difference coding, an encoder, such as encoder 200 in FIG. 2, may code a BV as a difference between the BV of a current block being coded and a BV predictor (BVP). An encoder may select the BVP from a list of candidate BVPs. The candidate BVPs may come from previously decoded BVs of neighboring blocks of the current block in the current picture. Both the encoder and decoder may generate or determine the list of candidate BVPs.

[0184] After the encoder selects a BVP from the list of candidate BVPs, the encoder may signal, in a bitstream, an indication of the selected BVP and a BV difference (BVD). The encoder may indicate the selected BVP in the bitstream by an index pointing into the list of candidate BVPs. The BVD may be calculated based on the difference between the BV of the current block and the selected BVP. For example, for a BV represented by a horizontal component (BVX) and a vertical component (BVy) relative to the position of the current block being coded, the BVD may represented by two components calculated as follows:

[0185] BVDX= BVX- BVPX(17)

[0186] BVDy= BVy— BVPy(18) where BVDXand BVDyrespectively represent the horizontal and vertical components of the BVD, and BVPXand BVPyrespectively represent the horizontal and vertical components of the BVP. A decoder, such as decoder 300 in FIG. 3, may decode the BV by adding the BVD to the BVP indicated in the bitstream. The decoder may then decode the current block by determining and / or generating the reference block, which forms the prediction of the current block, using the decoded BV and combining the prediction with the prediction error.

[0187] In HEVC and VVC, the list of candidate BVPs may comprise two candidates referred to as candidates A and B. Candidates A and B may include up to two spatial candidate BVPs derived from five spatial neighboring blocks of the current block being encoded, or one or more of the last two coded BVs when spatial neighboring candidates are not available (e.g., because they are coded in intra or inter mode). The location of the five spatial candidate neighboring blocks relative to a current block being encoded using IBC are the same as those shown in FIG. 15A for inter prediction. The five spatial candidate neighboring blocks are respectively denoted Ao, Ai, Bo, Bi, and B2.

[0188] As explained above with respect to FIGS. 2 and 3, entropy coding may be performed at the end of the video encoding process and at the beginning of the video decoding process. Entropy coding is a technique for compressing a sequence of symbols by representing symbols with greater probability of occurring using fewer bits than symbols with less probability of occurring. When the compressed sequence of symbols is represented in bits {0, 1}, Shannon’s information theory provides that the optimal average code length for a symbol with probability p is -log2p. Arithmetic coding is one method of entropy coding. Arithmetic coding is based on recursive interval subdivision. To arithmetically encode a symbol that takes a value from an m-ary source alphabet, an initial coding interval may be divided into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol having a different one of the values in the m-ary source alphabet. The probabilities of the symbol having the different values in the m- ary source alphabet may be referred to as a probability model for the symbol. The symbol is arithmetically encoded by choosing the subinterval corresponding to the actual value of the symbol as the new coding interval. By recursively applying this interval-subdivision scheme to each symbol Si of a given sequence s = {si, S2, . . SN), the encoder may determine a value in the range of the final coding interval, after the Nth interval subdivision, as the arithmetic code word for the sequence s. Each successive symbol of the sequence s that is encoded reduces the size of the coding interval in accordance with the probability model of the symbol. The more likely symbol values reduce the size of the coding interval by less than the unlikely symbol values and hence add fewer bits to the arithmetic code word for the sequence s in accordance with the general principle of entropy coding.

[0189] Arithmetic decoding is based on the same recursive interval subdivision. To arithmetically decode a symbol that takes a value from an m-ary source alphabet, an initial coding interval may be divided into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol having a different one of the values in the m-ary source alphabet. The probabilities of the symbol having the different values in the m-ary source alphabet may be referred to as a probability model for the symbol as mentioned above. The symbol is arithmetically decoded from an arithmetic code word by determining the symbol value corresponding to the subinterval in which the arithmetic code word falls within. This subinterval then becomes the new coding interval. The decoder may sequentially decode each symbol Si of a sequence s = {si, S2, . . ., SN) by recursively applying this interval-subdivision scheme N times and determining which subinterval the arithmetic code word falls within during each iteration.

[0190] For each symbol arithmetically coded, a different probability model may be used to subdivide the coding interval. For example, the probability model for a symbol may be determined by a fixed selection (e.g., based on a position of the symbol in a sequence of symbols) or by an adaptive selection from among two or more probability models (e.g., based on information related to the symbol). It is also possible for two or more symbols in a sequence of symbols to use a joint probability model. Selection of a probability model for a symbol is referred to as context modeling. Arithmetic coding that employs context modeling may be referred to more specifically as context-based arithmetic coding. In addition to probability model selection for a symbol, the selected probability model may be updated based on the actual coded value of the symbol. For example, the probability of the actual coded value of the symbol may be increased in the probability model while the probability of all other values may be decreased. Arithmetic coding that employs both context modeling and probability model adaptation may be referred to more specifically as context-based adaptive arithmetic coding. The above description provides only one example of arithmetic coding. Other variations of arithmetic coding may be possible as would be appreciated by a person of ordinary skill in the art. For example, during arithmetic coding, a renormalization operation may be performed to ensure that the precision needed to represent the range and lower bound of a subinterval does not exceed the finite precision of registers used to store these values. In addition, other simplifications to the coding process may be made to decrease complexity, increase speed, and / or reduce power requirements of the implementation of the coding process in either hardware, software, or some combination of the two. For example, probabilities of symbols and lower bounds and ranges of subintervals may be approximated or quantized in such implementations.

[0191] FIG. 17 illustrates an example implementation of a context-based adaptive binary arithmetic coding (CABAC) encoder 1700 in accordance with embodiments of the present disclosure. CABAC encoder 1700 may be implemented in a video encoder, such as video encoder 200 in FIG. 2, for entropy encoding syntax elements of a video sequence. As illustrated in FIG. 17, CABAC encoder 1700 includes a binarizer 1702, an arithmetic encoder 1704, and a context modeler 1706.

[0192] CABAC encoder 1700 may receive a syntax element 1708 for arithmetic encoding. Syntax elements, such as syntax element 1708, may be generated at a video encoder and may describe how a video signal may be reconstructed at a video decoder. For a coding unit (CU), the syntax elements may comprise an intra prediction mode based on the CU being intra predicted, motion data (e.g., MVD and MVP related data) based on the CU being inter predicted, or displacement data (e.g., BVD and BVP related data) based on the CU being predicted using IBC.

[0193] Binarizer 1702 may first map the value of syntax element 1708 to a sequence of binary symbols (also referred to as bins). Binarizer 1702 may define a unique mapping of values of syntax element 1708 to sequences of binary symbols. Binarization of syntax elements may help to improve probability modeling and implementation of arithmetic encoding. Binarizer 1702 may implement one or more binarization processes, such as unary, truncated unary, k-th order truncated Rice, k-th order exponential -Golomb (EGk), fixed-length, or some combination of two or more of these binarization processes. Binarizer 1702 may select a binarization process based on a type of syntax element 1708 and / or one or more syntax elements processed by CABAC encoder 1700 before syntax element 1708. Based on syntax element 1708 already being represented by a sequence of one or more binary symbols, binarizer 1702 may not process syntax element 1708. In another example, binarizer 1702 may not be used and syntax element 1708 represented by a sequence of one or more non-binary symbols may be directly encoded by CABAC encoder 1700.

[0194] After binarizer 1702 optionally maps the value of syntax element 1708 to a sequence of binary symbols, one or more of the binary symbols (bins) may be processed by arithmetic encoder 1704. Arithmetic encoder 1704 may process each of the one or more binary symbols in one of at least two modes: regular arithmetic encoding mode or bypass arithmetic encoding mode. Arithmetic encoder 1704 may process binary symbols that do not have a uniform (or approximately uniform) probability distribution in regular arithmetic encoding mode (e.g., binary symbols that do not have a probability distribution of 0.5 for each of their two possible values). In regular arithmetic encoding mode, arithmetic encoder 1704 may perform arithmetic encoding as described above. For example, arithmetic encoder 1704 may subdivide a current coding interval into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the binary symbol having a different one of the values in an m-ary source alphabet. In the case of a binary symbol, m is equal to two and the current coding interval may be subdivided into two disjoint intervals that each have a width proportional to the probability of a different one of the two possible values {0, 1 } for the binary symbol being encoded. The probabilities of the two possible values for the binary symbol may be indicated by a probability model 1710 for the binary symbol. Arithmetic encoder 1704 may then encode the binary symbol by choosing the subinterval corresponding to the actual value of the binary symbol as the new coding interval for the next binary symbol to be encoded.

[0195] Arithmetic encoder 1704 may receive probability model 1710 from context modeler 1706. Context modeler 1706 may determine probability model 1710 for the binary symbol by a fixed selection (e.g., based on a position of the binary symbol in the sequence of binary symbols representing syntax element 1708) or by an adaptive selection from among two or more probability models (e.g., based on information related to the binary symbol). As shown in FIG. 17, probability model 1710 may comprise two parameters: the probability PLPS of the least probable symbol (LPS) and the value V PS of the most probable symbol (MPS). In other examples, probability model 1710 may comprise the probability P PS of the MPS in addition or alternatively to the probability PLPS of the LPS. Similarly, in other examples, probability model 1710 may comprise the value VLPS of the LPS in addition or alternatively to the value VMPS of the MPS. After arithmetic encoder 1704 encodes the binary symbol, arithmetic encoder 1704 may provide one or more probability model update parameters 1712 to context modeler 1706. Context modeler 1706 may adapt probability model 1710 based on the one or more probability model update parameters 1712. For example, the one or more probability model update parameters 1712 may comprise the actual coded value of the binary symbol. Context modeler 1706 may update probability model 1710 by increasing PLPS if the actual coded value of the binary symbol is not equal to V PS and by decreasing PLPS otherwise.

[0196] Arithmetic encoder 1704 may process binary symbols that have (or are assumed to have) a uniform (or approximately uniform) probability distribution in bypass arithmetic encoding mode. Because binary symbols processed by arithmetic encoder 1704 in bypass arithmetic encoding mode have (or are assumed to have) a uniform (or approximately uniform) probability distribution, arithmetic encoder 1704 may bypass probability model determination and adaptation performed in regular arithmetic encoding mode when encoding these binary symbols to speed up the encoding process. In addition, subdivision of the current coding interval may be simplified given the uniform (or assumed uniform) probability distribution. For example, the current coding interval may be partitioned into two disjoint subintervals of equal width, which may be realized using a simple implementation that may further speed up the encoding process. Arithmetic encoder 1704 encodes the binary symbol by choosing the subinterval corresponding to the value of the binary symbol as the new coding interval for the next binary symbol to be encoded. The resulting increase in encoding speed for binary symbols encoded by arithmetic encoder 1704 in bypass arithmetic encoding mode is often important because CABAC encoding may have throughput limitations.

[0197] After processing a number of binary symbols (e.g., corresponding to one or more syntax elements), arithmetic encoder 1704 may determine a value in the range of the final coding interval as an arithmetic code word 1714 for the binary symbols. Arithmetic encoder 1704 may then output arithmetic code word 1714. For example, arithmetic encoder 1704 may output arithmetic code word 1714 to a bitstream that may be received and processed by a video decoder.

[0198] As explained above, HEVC and VVC both include a prediction technique to exploit the correlation between blocks of samples within the same picture. This technique is referred to as intra block (IBC). IBC is also included in the Enhanced Compression Model (ECM) software algorithm that is currently under coordinated exploration study by the Joint Video Exploration Team (JVET) of ITU-T Video Coding Experts Group (VCEG) and ISO / IEC MPEG as a potential enhanced video coding technology beyond the capabilities of VVC.

[0199] FIG. 18A illustrates an example of IBC in accordance with embodiments of the present disclosure. During IBC, an encoder may determine a block vector (BV) 1802 that indicates the displacement from a current block 1804 to a reference block (or intra block compensated prediction) 1806. The encoder may determine reference block 1806 from among one or more reference blocks tested during a searching process. For example, for each of the one or more reference blocks tested during a searching process, the encoder may determine a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), sum of absolute transformed differences (SATD), or difference determined based on a hash function) between the samples of the reference block and the samples of current block 1804. The encoder may determine reference block 1806 from among the one or more reference blocks based on reference block 1806 having the smallest difference from current block 1804 among the one or more reference blocks or based on some other criteria. Reference block 1806 and the one or more other reference blocks tested during the searching process may comprise decoded (or reconstructed) samples. The decoded (or reconstructed) samples may not have been processed by in-loop filtering operations, like deblocking or SAG filtering.

[0200] Once reference block 1806 is determined for current block 1804, the encoder may use reference block 1806 to predict current block 1804. For example, the encoder may determine or use a difference (e.g., a corresponding sample-by-sample difference) between reference block 1806 and current block 1804. The difference may be referred to as a prediction error or residual. The encoder may then signal the prediction error and the related prediction information in a bitstream. The prediction information may include BV 1802. In other instances, the prediction information may include an indication of BV 1802. A decoder, such as decoder 300 in FIG. 3, may receive the bitstream and decode current block 1804 by determining reference block 1806, which forms the prediction of current block 1804, using the prediction information and combining the prediction with the prediction error.

[0201] BV 1802 may be predictively encoded before being signaled in a bit stream. BV 1802 may be predictively encoded based on the BVs of neighboring blocks of current block 1804 or BVs of other blocks. For example, the encoder may predictively encode BV 1802 using the merge mode or AMVP as explained above. For AMVP, the encoder may encode BV 1802 as a difference between BV 1802 and a BV predictor (BVP) 1808 as shown in FIG. 18A. The encoder may select BVP 1808 from a list of candidate BVPs. The candidate BVPs may come from previously decoded BVs of neighboring blocks of current block 1804 or other sources. Both the encoder and decoder may generate or determine the list of candidate BVPs.

[0202] After the encoder selects BVP 1808 from the list of candidate BVPs, the encoder may signal, in a bitstream, an indication of BVP 1808 and a BV difference (BVD) 1810. The encoder may indicate BVP 1808 in the bitstream by an index, pointing into the list of candidate BVPs, or one or more flags. BVD 1810 may be calculated based on the difference between BV 1802 and BVP 1808. BVD 1810 may comprise a horizontal component (BVDX) 1812 and a vertical component (BVDy) 1814 that may be respectively determined in accordance with (17) and (18) above. The two components BVDX1812 and BVDy 1814 each comprise a magnitude and sign. As shown in FIG. 18A, BVDX1812 has a magnitude of 10011 in fixed length binary (or 19 in base 10) and a negative sign (the positive horizontal direction points to the right in the example of FIG. 18A). As further shown in FIG. 18 A, BVDy1814 has a magnitude of 01011 in fixed length binary (or 11 in base 10) and a positive sign (the positive vertical direction points down in the example of FIG. 18A). The encoder may indicate BVD 1810 in the bitstream via its two components BVDX1812 and BVDy1814.

[0203] The decoder may decode BV 1802 by adding BVD 1810 to BVP 1808. The decoder may then decode current block 1804 by determining reference block 1806, which forms the prediction of current block 1804, using BV 1802 and combining the prediction with the prediction error. The decoder may determine reference block 1806 by adding BV 1802 to the location of current block 1804, which may give the location of reference block 1806.

[0204] As explained above, the magnitude of BVD 1810 is encoded in bypass arithmetic encoding mode in existing technologies. Although the bypass arithmetic encoding mode may be used to speed up the arithmetic encoding process, compression of the magnitude symbols of BVD 1810 encoded in bypass arithmetic encoding mode is limited because their probability distributions are uniformly distributed (or at least assumed to be uniformly distributed). From information theory, a symbol cannot be compressed at a rate less than its entropy without loss of information, and a symbol with uniform probability distribution has maximum entropy. Thus, symbols encoded using the bypass arithmetic encoding mode generally require more bits to encode than symbols encoded using the regular arithmetic encoding mode. Embodiments of the present disclosure may improve the compression efficiency of one or more magnitude symbols of BVD 1810 compared to existing technologies. For example, instead of directly entropy encoding a magnitude symbol of BVD 1810, the encoder may entropy encode an indication of whether a value of the magnitude symbol of BVD 1810 matches a value of the same magnitude symbol of a BVD candidate used as a predictor of BVD 1810. The indication of whether the value of the magnitude symbol of BVD 1810 matches the value of the magnitude symbol of the BVD predictor may have a non-uniform probability distribution and therefore provide improved compression efficiency. The encoder may select the BVD predictor from among a plurality of BVD candidates based on costs of the plurality of the BVD candidates. The BVD candidates may include a BVD candidate for each possible value of the magnitude symbol of BVD 1810. For example, a magnitude symbol of BVD 1810 represented in binary form has only two possible values. Therefore, the BVD candidates may include two BVD candidates for this representation (one for each possible value of the magnitude symbol in BVD 1810 being encoded): a first BVD candidate equal to BVD 1810 itself and a second BVD candidate equal to BVD 1810 but with the opposite (or other) value of the magnitude symbol of BVD 1810. The cost for each BVD candidate in the plurality of BVD candidates may be calculated based on a difference between a template of current block 1804 and a template of a candidate reference block. The candidate reference block may be displaced relative to the current block by a sum of the BVD candidate and BVP 1808.

[0205] To provide a more specific example, FIG. 18A indicates an example magnitude symbol 1816 of BVD 1810 to be entropy encoded. Magnitude symbol 1816 of BVD 1810 is the second most significant bit in the fixed length binary representation of horizontal component BVDX1812 of BVD 1810 and has a binary value of “0”. As explained above, instead of directly entropy encoding magnitude symbol 1816 of BVD 1810, the encoder may entropy encode an indication of whether the value of magnitude symbol 1816 of BVD 1810 matches the value of the same magnitude symbol of a BVD candidate used as a predictor of BVD 1810. The encoder may select the BVD predictor from among a plurality of BVD candidates based on costs of the plurality of BVD candidates. The BVD candidates may include a BVD candidate for each of the two possible values {0, 1} of magnitude symbol 1816 of BVD 1810: a first BVD candidate 1818 equal to BVD 1810 itself and a second BVD candidate 1820 equal to BVD 1810 but with the opposite (or other) value of magnitude symbol 1816 of BVD 1810.

[0206] FIG. 18B illustrates both BVD candidates used to entropy encode magnitude symbol 1816 of BVD 1810. More specifically, FIG. 18B illustrates BVD candidate 1818 equal to BVD 1810 itself and BVD candidate 1820 equal to BVD 1810 but with the opposite (or other) value of magnitude symbol 1816 of BVD 1810. With the opposite (or other) value of magnitude symbol 1816 of BVD candidate 1818, BVD candidate 1820 has a horizontal component BVDX1822 with a magnitude of 11011 in fixed length binary (or 27 in base 10) and a negative sign. The vertical component BVDy1824 of BVD candidate 1820 has the same magnitude of 01011 in fixed length binary (or 11 in base 10) and positive sign as vertical component BVDy1814 of BVD candidate 1818 (or BVD 1810). The cost for each BVD candidate in the plurality of BVD candidates may be calculated based on a difference between a template of current block 1804 and a template of a candidate reference block displaced relative to current block 1804 by a sum of the BVD candidate and BVP 1808. For example, the encoder may determine a cost for BVD candidate 1818 based on a difference between a template 1826 of current block 1804 and a template 1828 of a candidate reference block 1830 displaced relative to current block 1804 by a sum of BVD candidate 1818 and BVP 1808. The encoder may determine the difference between template 1826 and template 1828 based on a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), sum of absolute transformed differences (SATD), mean removal SAD, or mean removal SSD) between samples of template 1826 and samples of template 1828. The encoder may similarly determine a cost for BVD candidate 1820 based on a difference between template 1826 of current block 1804 and a template 1832 of a candidate reference block 1834 displaced relative to current block 1804 by a sum of BVD candidate 1820 and BVP 1808. The encoder may determine the difference between template 1826 and template 1832 based on a difference (e.g., SSD, SAD, SATD, mean removal SAD, or mean removal SSD) between samples of template 1826 and samples of template 1828. Templates 1826, 1828, and 1832 may comprise one or more samples to the left and / or above their respective blocks. For example, templates 1826, 1828, and 1832 may comprise samples from one or more columns to left of their respective block and / or from one or more rows above their respective block. FIG. 18B illustrates one example position and shape (L-shape rotated clockwise 90 degrees) of templates 1826, 1828, and 1832.

[0207] After determining the costs of each of the plurality of BVD candidates, the encoder may select one of the plurality of BVD candidates as a BVD predictor. For example, the encoder may select the BVD candidate with the smallest cost among the plurality of BVD candidates as the BVD predictor. FIG. 18C illustrates a table with the components (horizontal and vertical) and costs of each BVD candidate 1818 and 1820 in respective rows. In this example, BVD candidates 1818 and 1820 are assumed to be the only BVD candidates. In other example, more BVD candidates may be used. The rows of the table are sorted by the costs of BVD candidates 1818 and 1820, with the BVD candidate with the smallest cost on top. In this example, BVD candidate 1818 has the smallest cost among BVD candidates 1818 and 1820. The encoder may therefore select BVD candidate 1818 as the BVD predictor 1836 for BVD 1810.

[0208] After selecting BVD candidate 1818 as BVD predictor 1836, the encoder may entropy encode an indication 1838 of whether the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 in BVD predictor 1836. Magnitude symbol 1816 of BVD predictor 1836 has a value of “0”, which matches the value of magnitude symbol 1816 of BVD 1810. In this example, indication 1838 would indicate that the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 of BVD predictor 1836. In one example, indication 1838 may be a single bit that has the value: “0” when the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 of BVD predictor 1836; and “1” when the value of magnitude symbol 1816 of BVD 1810 does not match the value of magnitude symbol 1816 of BVD predictor 1836. Logic 1840 may be used to determine indication 1838. In one example, logic 1840 may implement a logical exclusive or (XOR) function. It should be noted that in other examples where magnitude symbol 1816 is non-binary, indication 1838 may indicate the first candidate among the plurality of candidates (e.g., as sorted based on their respective costs) that has a value of magnitude symbol 1816 that matches the value of magnitude symbols 1816 in BVD 1810.

[0209] In the example of FIG. 18C, the encoder may entropy encode indication 1838 using arithmetic encoder 1842. Based on the method of determining indication 1838 as described above, indication 1838 may have a non-uniform probability distribution. Therefore, arithmetic encoder 1842 may process indication 1838 in regular arithmetic encoding mode as described above. For example, arithmetic encoder 1842 may subdivide a current coding interval into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol being encoded having a different one of the values in an m-ary source alphabet. In the case of indication 1838, which is binary, m is equal to two and the current coding interval may be subdivided into two disjoint intervals that each have a width proportional to the probability of a different one of the two possible values {0, 1 } for indication 1838 being encoded. The probabilities of the two possible values for indication 1838 may be indicated by a probability model 1844 for indication 1838. Arithmetic encoder 1842 may then encode indication 1838 by choosing the subinterval corresponding to the actual value of indication 1838 as the new coding interval for the next binary symbol to be encoded.

[0210] Arithmetic encoder 1842 may receive probability model 1844 from context modeler 1846. Context modeler 1846 may determine probability model 1844 for indication 1838 by a fixed selection or an adaptive selection from among two or more probability models. For example, context modeler 1846 may determine probability model 1844 by a fixed selection or an adaptive selection from among two or more probability models based on a position of magnitude symbol 1816 in B VDX1812 of BVD 1810 or an index of (e.g., a value indicating) the position of magnitude symbol 1816 in BVDX1812 of BVD 1810. The position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 provides an indication of the distance 1864 (illustrated in FIG. 18B) between the two candidate BVDs. The likelihood of the value of magnitude symbol 1816 of BVD predictor 1836 matching the value of magnitude symbol 1816 of BVD 1810 may be proportional to distance 1864. Thus, the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 may be helpful in selecting probability model 1844 for indication 1838.

[0211] For adaptive selection from among two or more probability models, context modeler 1846 may compare the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 to one or more thresholds. For example, context modeler 1846 may compare the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 to a first threshold. Based on the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 being less than the threshold, context modeler 1846 may select a first probability model for indication 1838. Based on the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 being greater than the threshold, context modeler 1846 may select a second probability model for indication 1838. In another example, based on the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 being greater than the threshold, context modeler 1846 may compare the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 to a second threshold. Based on the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 being less than the second threshold, context modeler 1846 may select a second probability model for indication 1838. Based on the position (or index of the position) of magnitude symbol 1816 in BVDX1812 of BVD 1810 being greater than the second threshold, context modeler 1846 may select a third probability model for indication 1838.

[0212] In another example, context modeler 1846 may determine probability model 1844 by a fixed selection or an adaptive selection from among two or more probability models based on the change in value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810. The change in value of BVD 1810 (or BVDx1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 may be determined as 2(n l), where n is the bit position of magnitude symbol 1816 in BVDX1812 of BVD 1810. In the example of FIG. 18, n=4 and therefore the change in value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 may be determined as 2(4 1)or 8. The change in value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 provides an indication of the distance 1864 (illustrated in FIG. 18B) between the two candidate BVDs. As mentioned above, the likelihood of the value of magnitude symbol 1816 of BVD predictor 1836 matching the value of magnitude symbol 1816 of BVD 1810 may be proportional to distance 1864. Thus, the change in value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 may be helpful in selecting probability model 1844 for indication 1838.

[0213] For adaptive selection from among two or more probability models, context modeler 1846 may compare the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 to one or more thresholds. For example, context modeler 1846 may compare the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 to a first threshold. Based on the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 being less than the threshold, context modeler 1846 may select a first probability model for indication 1838. Based on the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 being greater than the threshold, context modeler 1846 may select a second probability model for indication 1838. In another example, based on the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 being greater than the threshold, context modeler 1846 may compare the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 to a second threshold. Based on the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 being less than the second threshold, context modeler 1846 may select a second probability model for indication 1838. Based on the value of BVD 1810 (or BVDX1812 of BVD 1810) for an incremental change in value of magnitude symbol 1816 of BVD 1810 being greater than the second threshold, context modeler 1846 may select a third probability model for indication 1838.

[0214] As shown in FIG. 18C, probability model 1844 may comprise two parameters: the probability PLPS of the least probable symbol (LPS) for indication 1838 and the value VMPS of the most probable symbol (MPS) for indication 1838. In other examples, probability model 1844 may comprise the probability PMPS of the MPS for indication 1838 in addition or alternatively to the probability PLPS of the LPS for indication 1838. Similarly, in other examples, probability model 1844 may comprise the value VLPS of the LPS for indication 1838 in addition or alternatively to the value VMPS of the MPS for indication 1838. After arithmetic encoder 1842 encodes indication 1838, arithmetic encoder 1842 may provide one or more probability model update parameters 1850 to context modeler 1846. Context modeler 1846 may adapt probability model 1844 based on the one or more probability model update parameters 1850. For example, the one or more probability model update parameters 1850 may comprise the actual coded value of indication 1838. Context modeler 1846 may update probability model 1844 by increasing PLPS for indication 1838 if the actual coded value of indication 1838 is not equal to VMPS and by decreasing PLPS for indication 1838 otherwise.

[0215] After processing a number of binary symbols (e.g., corresponding to one or more syntax elements), arithmetic encoder 1842 may determine a value in the range of the final coding interval as an arithmetic code word 1852 for the binary symbols. Arithmetic encoder 1842 may then output arithmetic code word 1852. For example, arithmetic encoder 1842 may output arithmetic code word 1852 to a bitstream that may be received and processed by a video decoder.

[0216] FIG. 18D illustrates an example of a decoder (e.g., decoder 300 in FIG. 3) that may receive arithmetic code word 1852, arithmetically decode indication 1838 from arithmetic code word 1852, and use indication 1838 to determine magnitude symbol 1816 of BVD 1810 in accordance with embodiments of the present disclosure.

[0217] The decoder may receive arithmetic code word 1852 in a bitstream. The decoder may provide arithmetic code word 1852 to an arithmetic decoder 1854. Based on the method of determining indication 1838 as described above, indication 1838 may have a non-uniform probability distribution. Therefore, arithmetic decoder 1854 may process indication 1838 in regular arithmetic decoding mode. For example, arithmetic decoder 1854 may perform recursive interval subdivision as explained above to decode symbols encoded by arithmetic code word 1852. For example, arithmetic decoder 1854 may arithmetically decode a symbol that takes a value from an m-ary source alphabet by dividing an initial coding interval into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol having a different one of the values in the m-ary source alphabet. In the case of binary symbols like indication 1838, m is equal to two and the initial coding interval may be subdivided into two disjoint intervals that each have a width proportional to the probability of a different one of the two possible values {0, 1 } . The probabilities of the symbol having the different values in the m-ary source alphabet may be referred to as a probability model for the symbol as mentioned above. The symbol is arithmetically decoded from arithmetic code word 1852 by determining the symbol value corresponding to the subinterval in which the arithmetic code word falls within. The decoder may sequentially decode each symbol Si of a sequence s = {si, S2, . . SN) encoded by arithmetic code word 1852 by recursively applying this interval-subdivision scheme N times and determining which subinterval arithmetic code word 1852 falls within during each iteration.

[0218] When decoding the symbol corresponding to indication 1838, arithmetic decoder 1854 may receive probability model 1844 for indication 1838 from context modeler 1846. Context modeler 1856 may determine probability model 1844 for indication 1838 by a fixed selection or by an adaptive selection from among two or more probability models in the same manner as described above for context modeler 1846 in FIG. 18C.

[0219] As shown in FIG. 18D, after arithmetic decoder 1854 decodes indication 1838, arithmetic decoder 1854 may provide one or more probability model update parameters 1850 to context modeler 1856. Context modeler 1856 may adapt probability model 1844 based on the one or more probability model update parameters 1850. For example, the one or more probability model update parameters 1850 may comprise the actual decoded value of indication 1838. Context modeler 1856 may update probability model 1844 by increasing PLPS for indication 1838 if the actual decoded value of indication 1838 is not equal to VMPS and by decreasing PLPS for indication 1838 otherwise.

[0220] After entropy decoding indication 1838, the decoder may determine the value of magnitude symbol 1816 of BVD 1810 based on the value of magnitude symbol 1816 of BVD predictor 1836 and the value of indication 1838. For example, the decoder may determine the value of magnitude symbol 1816 of BVD 1810 as being equal to the magnitude symbol of BVD predictor 1836 based on indication 1838 indicating that the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 of BVD predictor 1836. Conversely, the decoder may determine the value of magnitude symbol 1816 of BVD 1810 as being not equal to (or equal to the opposite value of) magnitude symbol 1816 of BVD predictor 1836 based on indication 1838 indicating that the value of magnitude symbol 1816 of BVD 1810 does not match the value of magnitude symbol 1816 of BVD predictor 1836. Magnitude symbol 1816 of BVD predictor 1836 has a value of “0”, which matches the value of magnitude symbol 1816 of BVD 1810. In this example, indication 1838 would indicate that the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 of BVD predictor 1836. In one example, indication 1838 may be a single bit that has the value: “0” when the value of magnitude symbol 1816 of BVD 1810 matches the value of magnitude symbol 1816 of BVD predictor 1836; and “1” when the value of magnitude symbol 1816 of BVD 1810 does not match the value of magnitude symbol 1816 of BVD predictor 1836. Logic 1858 may be used to determine magnitude symbol 1816 of BVD 1810. In one example, logic 1858 may implement a logical XOR function. It should be noted that in other examples where magnitude symbol 1816 is non-binary, indication 1838 may indicate the first candidate among the plurality of candidates (e.g., as sorted based on their respective costs) that has a value of magnitude symbol 1816 that matches the value of magnitude symbols 1816 in BVD 1810.

[0221] The decoder may determine the value of magnitude symbol 1816 of BVD predictor 1836 in the same manner as the encoder described above. More specifically, the decoder may select BVD predictor 1836 from among a plurality of BVD candidates based on costs of the plurality of the BVD candidates. The BVD candidates may include a BVD candidate for each possible value of the magnitude symbol of BVD 1810. For example, a magnitude symbol of BVD 1810 represented in binary form has only two possible values. Therefore, the BVD candidates may include at least two BVD candidates for this representation (one for each possible value of the magnitude symbol in BVD 1810 being encoded): a first BVD candidate equal to BVD 1810 itself and a second BVD candidate equal to BVD 1810 but with the opposite (or other) value of the magnitude symbol of BVD 1810. The cost for each BVD candidate in the plurality of BVD candidates may be calculated as described above with respect to the encoder based on a difference between a template of current block 1804 and a template of a candidate reference block. The candidate reference block may be displaced relative to the current block by a sum of the BVD candidate and BVP 1808. The decoder may select the BVD candidate with the lowest cost as BVD predictor 1836.

[0222] It should be noted that the approach discussed above with respect to FIG. 18 to entropy code an indication of whether a value of a magnitude symbol of a BVD matches a value of the magnitude symbol of a BVD candidate used as a predictor of the BVD may be applied to multiple magnitude symbols of the BVD. For example, the above approach may be further applied to one or more magnitude symbols of BVDX1812 other than magnitude symbol 1816 and / or to one or more magnitude symbols of BVDy1814. For each additional magnitude symbol of BVDX1812 and / or BVDy1814 that the approach discussed above with respect to FIG. 18 is applied, additional candidate BVPs may be determined. For example, applying the approach discussed above with respect to FIG. 18 to N magnitude symbols of BVDX1812 and / or BVDy1814 (where N is an integer value), different BVP candidates may be determined - one for each possible combination of values for the N magnitude symbols of BVDX1812 and / or BVDy1814. Cost values may be further determined for each of the BVP candidates and sorted to determine a BVD predictor for encoding each of the N magnitude symbols of BVDX1812 and / or BVDy1814.

[0223] It should be further noted that the approach discussed above with respect to FIG. 18 to entropy code an indication of whether a value of a magnitude symbol of a BVD matches a value of the magnitude symbol of a BVD candidate used as a predictor of the BVD may be applied not only to one or more magnitude symbols of the BVD, but also to one or more sign symbols (e.g., the sign of the horizontal component and / or the sign of the vertical component) of the BVD. For example, the above approach may be further applied to one or more magnitude symbols of BVD 1810 and to one or more sign symbols of BVD 1810.

[0224] To provide a more specific example, FIG. 19A continues with and reproduces the example in FIG. 18A except that FIG. 19A further indicates an example sign symbol 1916 of BVD 1810 to be entropy encoded according to the approach discussed above with respect to FIG. 18. Sign symbol 1916 of BVD 1810 indicates the sign of horizontal component BVDX1812 of BVD 1810. In the example of FIG. 19A, the sign of BVDX1812 is negative (-). Sign symbol 1916 may indicate the sign of BVDX1812 using a binary symbol. For example, sign symbol 1916 may have a value of either binary “0” or “1” to indicate that the sign of BVDX1812 is negative (-) (a positive (+) sign may be indicated using the other binary symbol value not used to indicate the negative (-) sign).

[0225] Instead of directly entropy encoding sign symbol 1916 of BVD 1810, the encoder may entropy encode an indication of whether the value of sign symbol 1916 of BVD 1810 matches the value of the same sign symbol of a BVD candidate used as a predictor of BVD 1810. The encoder may select the BVD predictor from among a plurality of BVD candidates based on costs of the plurality of BVD candidates. The BVD candidates may at least include a BVD candidate for each of the two possible values of sign symbol 1916 of BVD 1810: a first BVD candidate 1918 equal to BVD 1810 itself and a second BVD candidate 1920 equal to BVD 1810 but with the opposite (or other) value of sign symbol 1916 of BVD 1810.

[0226] FIG. 19B illustrates both BVD candidates used to entropy encode sign symbol 1916 of BVD 1810. More specifically, FIG. 19B illustrates BVD candidate 1918 equal to BVD 1810 itself and BVD candidate 1920 equal to BVD 1810 but with the opposite (or other) value of sign symbol 1916 of BVD 1810. With the opposite (or other) value of sign symbol 1916 of BVD candidate 1918, BVD candidate 1920 has a horizontal component BVDX1922 with a magnitude of 10011 in fixed length binary (or 19 in base 10) and a positive (+) sign. The vertical component BVDy1924 of BVD candidate 1920 has the same magnitude of 01011 in fixed length binary (or 11 in base 10) and positive sign as vertical component BVDy1814 of BVD candidate 1918 (or BVD 1810).

[0227] The cost for each BVD candidate in the plurality of BVD candidates may be calculated based on a difference between a template of current block 1804 and a template of a candidate reference block displaced relative to current block 1804 by a sum of the BVD candidate and BVP 1808. For example, the encoder may determine a cost for BVD candidate 1918 based on a difference between a template 1926 of current block 1804 and a template 1928 of a candidate reference block 1930 displaced relative to current block 1804 by a sum of BVD candidate 1918 and BVP 1808. The encoder may determine the difference between template 1926 and template 1928 based on a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), sum of absolute transformed differences (SATD), mean removal SAD, or mean removal SSD) between samples of template 1926 and samples of template 1928. The encoder may similarly determine a cost for BVD candidate 1920 based on a difference between template 1926 of current block 1804 and a template 1932 of a candidate reference block 1934 displaced relative to current block 1804 by a sum of BVD candidate 1920 and BVP 1808. The encoder may determine the difference between template 1926 and template 1932 based on a difference (e.g., SSD, SAD, SATD, mean removal SAD, or mean removal SSD) between samples of template 1926 and samples of template 1928. Templates 1926, 1928, and 1932 may comprise one or more samples to the left and / or above their respective blocks. For example, templates 1926, 1928, and 1932 may comprise samples from one or more columns to left of their respective block and / or from one or more rows above their respective block. FIG. 19B illustrates one example position and shape (L-shape rotated clockwise 90 degrees) of templates 1926, 1928, and 1932.

[0228] After determining the costs of each of the plurality of BVD candidates, the encoder may select one of the plurality of BVD candidates as a BVD predictor. For example, the encoder may select the BVD candidate with the smallest cost among the plurality of BVD candidates as the BVD predictor. FIG. 19C illustrates a table with the components (horizontal and vertical) and cost of each BVD candidate 1918 and 1920 in respective rows. In this example, BVD candidates 1918 and 1920 are assumed to be the only BVD candidates. In other examples, more BVD candidates may be used (e.g., BVD candidate 1820 from FIG. 18 may be further included in the plurality of BVD candidates where magnitude symbol 1816 is further being entropy encoded according to the method discussed in FIG. 18). The rows of the table are sorted by the costs of BVD candidates 1918 and 1920, with the BVD candidate with the smallest cost on top. In this example, BVD candidate 1918 has the smallest cost among BVD candidates 1918 and 1920. The encoder may therefore select BVD candidate 1918 as the BVD predictor 1936 for BVD 1810.

[0229] After selecting BVD candidate 1918 as BVD predictor 1936, the encoder may entropy encode an indication 1938 of whether the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936. Sign symbol 1916 of BVD predictor 1936 has a value that indicates a negative sign, which matches the value of sign symbol 1916 of BVD 1810 that also indicates a negative sign. In this example, indication 1938 would indicate that the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936. In one example, indication 1938 may be a single bit that has the value : “0” when the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936; and “1” when the value of sign symbol 1916 of BVD 1810 does not match the value of sign symbol 1916 of BVD predictor 1936. Logic 1940 may be used to determine indication 1938. In one example, logic 1940 may implement a logical exclusive or (XOR) function.

[0230] In the example of FIG. 19C, the encoder may entropy encode indication 1938 using arithmetic encoder 1942. Based on the method of determining indication 1938 as described above, indication 1938 may have a non-uniform probability distribution. Therefore, arithmetic encoder 1942 may process indication 1938 in regular arithmetic encoding mode as described above. For example, arithmetic encoder 1942 may subdivide a current coding interval into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol being encoded having a different one of the values in an m-ary source alphabet. In the case of indication 1938, which is binary, m is equal to two and the current coding interval may be subdivided into two disjoint intervals that each have a width proportional to the probability of a different one of the two possible values {0, 1 } for indication 1938 being encoded. The probabilities of the two possible values for indication 1938 may be indicated by a probability model 1944 for indication 1938. Arithmetic encoder 1942 may then encode indication 1938 by choosing the subinterval corresponding to the actual value of indication 1938 as the new coding interval for the next binary symbol to be encoded.

[0231] Arithmetic encoder 1942 may receive probability model 1944 from context modeler 1946. Context modeler 1946 may determine probability model 1944 for indication 1938 by a fixed selection or an adaptive selection from among two or more probability models. For example, context modeler 1946 may determine probability model 1944 by a fixed selection or an adaptive selection from among two or more probability models based on the magnitude of the component of BVD 1810 to which sign symbol 1916 corresponds, which in the example of FIG. 19 is horizontal component BVDX1812 of BVD 1810. The magnitude of horizontal component BVDX1812 of BVD 1810 provides an indication of the distance 1964 (illustrated in FIG. 19B) between candidate reference blocks 1930 and 1934. Distance 1964 is specifically equal to two times the magnitude of horizontal component BVDX1812 of BVD 1810. The likelihood of the value of sign symbol 1916 of BVD 1810 matching the value of sign symbol 1916 of BVD predictor 1936 may be generally related to distance 1964. More specifically, the greater distance 1964 between candidate reference blocks 1930 and 1934 (and between their respective templates 1928 and 1932), the more likely it may be that the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936. Thus, the magnitude of horizontal component BVDX1812 of BVD 1810 may be helpful in selecting probability model 1844 for indication 1838.

[0232] A problem may arise, however, if context modeler 1946 relies on the magnitude of horizontal component BVDX1812 of BVD 1810 to determine probability model 1944 for indication 1938. As discussed above, one or more of the magnitude symbols ofhorizontal component BVDX1812 of BVD 1810 may be entropy encoded according to the method of FIG. 18. For example, magnitude symbol 1816 ofhorizontal component BVDX1812 of BVD 1810 may be entropy encoded according to the method of FIG. 18 as discussed above. As a result, the value of magnitude symbol 1816 may not be available at the decoder after the arithmetic decoder parses the information related to magnitude symbol 1816 from the bitstream . Rather, only the indication 1838 indicating whether the value of magnitude symbol 1816 of horizontal component BVDX1812 of BVD 1810 matches the value of the same magnitude symbol of the horizontal component of the selected BVD predictor may be available after the arithmetic decoder parses the related information. The decoder may have to further perform the decoding process to determine the actual value of magnitude symbol 1816. For example, the decoder may have to determine the costs, using templates, of the plurality of BVD candidates for magnitude symbol 1816 as discussed above with respect to FIG. 18. This may create a parsing dependency or, in other words, a dependency between parsing of the bitstream (e.g., as performed by the arithmetic decoder) and the decoding process. The arithmetic decoder cannot parse indication 1938 for sign symbol 1916 from the bitstream until magnitude symbol 1816 (or any other magnitude symbol of horizontal component BVDX1812 of BVD 1810 entropy encoded according to the method of FIG. 18) is decoded. This may result in the arithmetic decoder, which is often a throughput bottleneck, to stall until the magnitude is decoded.

[0233] The parsing dependency may be resolved by binarizing the magnitude (e.g., horizontal and / or vertical component magnitude) of a BVD using a binarization scheme or code that includes a first part that indicates a range of values that the magnitude of the BVD falls within and a second part that indicates a precise value, within the range of values, of the magnitude of the BVD. There are a wide class of codes that include a first part that indicates a range of values and a second part that indicates a precise value within the range of values, such as Rice codes, Golomb codes (e.g., Golomb-Rice codes or Exponential Golomb codes), and fixed length codes. The encoder and decoder may respectively entropy encode and decode the first part that indicates the range of values that the magnitude of the BVD falls within in such a manner that does not require the decoding process (e.g., in bypass arithmetic coding mode) to determine the first part that indicates the range of values that the magnitude of the BVD falls within. Although not the precise value of the magnitude of the BVD, the first part that indicates the range of values that the magnitude of the BVD falls within may then be used to determine a probability model for entropy encoding an indication (e.g., indication 1938) of whether the value of a sign symbol of the BVD matches the value of a sign symbol of a BVD predictor. Because selection of the probability model does not use the second part that indicates a precise value, within the range of values, of the magnitude of the BVD, magnitude symbols of the second part may still be entropy encoded according to the method of FIG. 18 without creating a parsing dependency as described above.

[0234] For example, referring back to FIG. 19, the magnitude of horizontal component BVDX1812 of BVD 1810 may be binarized using a Golomb-Rice code. Golomb-Rice codes have the structure discussed above, with a first part that that indicates a range of values and a second part that indicates a precise value within the range of values. In Golomb-Rice codes, the first part is referred to as the “prefix” and the second part is referred to as the “suffix”. A Golomb-Rice code Cgrk(v) of order k includes a unary coded prefix, i.e. the first (rough) part obtained by division by a divisor consists of a set of ones and one zero (or vice versa). The remainder will be coded as k suffix bits. The k suffix bits are a binary representation of an integer 0 < i < 2k. An example of a Golomb-Rice code for k = 4 is given in Table 1 below. In the table and the following explanation, xo, xi, . . . , xndenote bits of the code word (namely the accurate remainder after the division) with xn{0, 1 } . TABLE 1

[0235] The number of prefix bits is denoted by np, the number of suffix bits is denoted by ns. For the Golomb-Rice code, the number of suffix bits is ns= k. When encoding a value v, the number of prefix bits is determined by:

[0236] [xj is the integer part of x. The suffix is the ns-bit representation of: vs= v - 2k(np- 1). (20)

[0237] The Golomb-Rice codes discussed above use a suffix of fixed length. The length of the suffix may also be determined by the length of the prefix. Exponential Golomb codes (Exp-Golomb) use this approach and can further be used to binarize the magnitude of horizontal component BVDX1812 of BVD 1810. A kth-order Exp-Golomb code Cegk(v) includes a unary prefix code and a suffix of variable length. The number of bits in the suffix nsis determined by the value npas follows: ns= k + np- 1. (21)

[0238] The number of prefix bits npof Cegk(v) is determined from the value v by:

[0239] 2k(2np-1- 1) < v < 2k(2nP - 1). (22)

[0240] The suffix is then the ns-bit representation of: vs= v - 2k(2nP - 1). (23)

[0241] An example of Exp-Golomb codes for k = 1 is given in Table 2 below. TABLE 2 In the example of FIG. 19, the magnitude of horizontal component BVDX1812 of BVD 1810 has a value of 19 in base 10, which may be represented by a Golomb-Rice code or an Exp-Golomb code. For example, the magnitude of horizontal component BVDX1812 of BVD 1810 may be represented by the Exp-Golomb code of order k = 4 with a prefix of “0001” and a suffix of “0101”. The prefix “0001” indicates that the magnitude of the horizontal component BVDX1812 of BVD 1810 falls within the range of values 14 - 29, and the suffix “0101” indicates that the magnitude of the horizontal component BVDX1812 of BVD 1810 has the precise value of 19 within the range of values of 14 - 29. One or more of the magnitude bits of the suffix may be entropy encoded and decoded according to the method of FIG. 18 (e.g., similar to magnitude symbol 1816), while one or more of the bits of the prefix may be entropy encoded and decoded in such a manner that does not require the arithmetic decoding process (e.g., in bypass arithmetic coding mode) to determine the value of the prefix. Because the prefix is entropy encoded and decoded in such a manner that does not require the decoding process, context modeler 1946 may determine probability model 1944 for indication 1938 based on the prefix (or range of values that the magnitude of horizontal component BVDX1812 falls within) without resulting in a parsing dependency. It is understood that context modeler 1946 may determine probability model 1944 for indication 1938 based on the prefix without resulting in a parsing dependency because context modeler 1946 makes such a determination without the suffix (or precise value within the range of values indicated by the prefix).

[0242] For adaptive selection from among two or more probability models, context modeler 1946 may compare a value in the range of values indicated by the prefix of the code used to represent the magnitude of horizontal component B VDX1812 (or value in the range of value s that the magnitude of horizontal component BVDX1812 falls within) to a first threshold. Based on the value in the range of values indicated by the prefix being less than the first threshold, context modeler 1946 may select a first probability model for indication 1938. Based on the value in the range of values indicated by the prefix being greater than the first threshold, context modeler 1946 may select a second probability model for indication 1938. In another example, based on the value in the range of values indicated by the prefix being greater than the first threshold, context modeler 1946 may compare the value in the range of values indicated by the prefix to a second threshold. Based on the value in the range of values indicated by the prefix being less than the second threshold, context modeler 1946 may select a second probability model for indication 1938. Based on the value in the range of values indicated by the prefix being greater than the second threshold, context modeler 1946 may select a third probability model for indication 1938. The value in the range of values indicated by the prefix may be the lower bound of the range of values, the upper bound of the range of values, or a value that is greater than the lower bound of the range of values and less than an upper bound of the range of values. In another example, instead of using a value in the range of values indicated by the prefix directly in the above threshold comparison(s), another value determined based on the value in the range of values indicated by the prefix may be compared to the threshold(s). In another example, instead of using a value in the range of values indicated by the prefix in the above threshold comparison(s), the range of values itself may be used in the above threshold comparison(s).

[0243] As shown in FIG. 19C, probability model 1944 may comprise two parameters: the probability PLPS of the least probable symbol (LPS) for indication 1938 and the value VMPS of the most probable symbol (MPS) for indication 1938. In other examples, probability model 1944 may comprise the probability PMPS of the MPS for indication 1938 in addition or alternatively to the probability PLPS of the LPS for indication 1938. Similarly, in other examples, probability model 1944 may comprise the value VLPS of the LPS for indication 1938 in addition or alternatively to the value VMPS of the MPS for indication 1938. After arithmetic encoder 1942 encodes indication 1938, arithmetic encoder 1942 may provide one or more probability model update parameters 1950 to context modeler 1946. Context modeler 1946 may adapt probability model 1944 based on the one or more probability model update parameters 1950. For example, the one or more probability model update parameters 1950 may comprise the actual coded value of indication 1938. Context modeler 1946 may update probability model 1944 by increasing PLPS for indication 1938 if the actual coded value of indication 1938 is not equal to VMPS and by decreasing PLPS for indication 1938 otherwise.

[0244] After processing a number of binary symbols (e.g., corresponding to one or more syntax elements), arithmetic encoder 1942 may determine a value in the range of the final coding interval as an arithmetic code word 1952 for the binary symbols. Arithmetic encoder 1942 may then output arithmetic code word 1952. For example, arithmetic encoder 1942 may output arithmetic code word 1952 to a bitstream that may be received and processed by a video decoder.

[0245] FIG. 19D illustrates an example of a decoder (e.g., decoder 300 in FIG. 3) that may receive arithmetic code word 1952, arithmetically decode indication 1938 from arithmetic code word 1952, and use indication 1938 to determine sign symbol 1916 of BVD 1810 in accordance with embodiments of the present disclosure.

[0246] The decoder may receive arithmetic code word 1952 in a bitstream. The decoder may provide arithmetic code word 1952 to an arithmetic decoder 1954. Based on the method of determining indication 1938 as described above, indication 1938 may have a non-uniform probability distribution. Therefore, arithmetic decoder 1954 may process indication 1938 in regular arithmetic decoding mode. For example, arithmetic decoder 1954 may perform recursive interval subdivision as explained above to decode symbols encoded by arithmetic code word 1952. For example, arithmetic decoder 1954 may arithmetically decode a symbol that takes a value from an m-ary source alphabet by dividing an initial coding interval into m disjoint subintervals. Each of the m disjoint subintervals may have a width proportional to the probability of the symbol having a different one of the values in the m-ary source alphabet. In the case of binary symbols like indication 1938, m is equal to two and the initial coding interval may be subdivided into two disjoint intervals that each have a width proportional to the probability of a different one of the two possible values {0, 1 } . The probabilities of the symbol having the different values in the m-ary source alphabet may be referred to as a probability model for the symbol as mentioned above. The symbol is arithmetically decoded from arithmetic code word 1952 by determining the symbol value corresponding to the subinterval in which the arithmetic code word falls within. The decoder may sequentially decode each symbol Si of a sequence s = {si, S2, . . SN) encoded by arithmetic code word 1952 by recursively applying this interval-subdivision scheme N times and determining which subinterval arithmetic code word 1952 falls within during each iteration.

[0247] When decoding the symbol corresponding to indication 1938, arithmetic decoder 1954 may receive probability model 1944 for indication 1938 from context modeler 1956. Context modeler 1956 may determine probability model 1944 for indication 1938 by a fixed selection or by an adaptive selection from among two or more probability models in the same manner as described above for context modeler 1946 in FIG. 19C.

[0248] As shown in FIG. 19D, after arithmetic decoder 1954 decodes indication 1938, arithmetic decoder 1954 may provide one or more probability model update parameters 1950 to context modeler 1956. Context modeler 1956 may adapt probability model 1944 based on the one or more probability model update parameters 1950. For example, the one or more probability model update parameters 1950 may comprise the actual decoded value of indication 1938. Context modeler 1956 may update probability model 1944 by increasing PLPS for indication 1938 if the actual decoded value of indication 1938 is not equal to VMPS and by decreasing PLPS for indication 1938 otherwise.

[0249] After entropy decoding indication 1938, the decoder may determine the value of sign symbol 1916 of BVD 1810 based on the value of sign symbol 1916 of BVD predictor 1936 and the value of indication 1938. For example, the decoder may determine the value of sign symbol 1916 of BVD 1810 as being equal to the sign symbol of BVD predictor 1936 based on indication 1938 indicating that the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936. Conversely, the decoder may determine the value of sign symbol 1916 of BVD 1810 as being not equal to (or equal to the opposite value of) sign symbol 1916 of BVD predictor 1936 based on indication 1938 indicating that the value of sign symbol 1916 of BVD 1810 does not match the value of sign symbol 1916 of BVD predictor 1936. Sign symbol 1916 of BVD predictor 1936 has a value that matches the value of sign symbol 1916 of BVD 1810. In this example, indication 1938 would indicate that the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936. In one example, indication 1938 may be a single bit that has the value: “0” when the value of sign symbol 1916 of BVD 1810 matches the value of sign symbol 1916 of BVD predictor 1936; and “1” when the value of sign symbol 1916 of BVD 1810 does not match the value of sign symbol 1916 of BVD predictor 1936. Logic 1958 may be used to determine sign symbol 1916 of BVD 1810. In one example, logic 1958 may implement a logical XOR function.

[0250] The decoder may determine the value of sign symbol 1916 of BVD predictor 1936 in the same manner as the encoder described above. More specifically, the decoder may select BVD predictor 1936 from among a plurality of BVD candidates based on costs of the plurality of the BVD candidates. The BVD candidates may include a BVD candidate for each possible value of the sign symbol of BVD 1810. For example, a sign symbol of BVD 1810 represented in binary form has only two possible values. Therefore, the BVD candidates may include at least two BVD candidates for this representation (one for each possible value of the sign symbol in BVD 1810 being encoded): a first BVD candidate equal to BVD 1810 itself and a second BVD candidate equal to BVD 1810 but with the opposite (or other) value of the sign symbol of BVD 1810. The cost for each BVD candidate in the plurality of BVD candidates may be calculated as described above with respect to the encoder based on a difference between a template of current block 1804 and a template of a candidate reference block. The candidate reference block may be displaced relative to the current block by a sum of the BVD candidate and BVP 1808. The decoder may select the BVD candidate with the lost cost as BVD predictor 1936.

[0251] It should be noted that the approach discussed above with respect to FIG. 18 and FIG. 19 may be further applied to one or more magnitude symbols of an MVD used in inter prediction in addition or alternatively to one or more magnitude symbols of a BVD used in IBC. For inter prediction, the terms BV, BVP, BVD, and BVD candidate used in FIG. 18 and FIG. 19 may be replaced by the terms MV, MVP, MVD, and MVD as would be appreciated by a person of ordinary skill in the art based on the present disclosure.

[0252] It should be further noted that the approach discussed above with respect to FIG. 18 and FIG. 19 is applied to IBC and inter prediction based on a translational motion model for the prediction block. In other examples, the approach discussed above with respect to FIG. 18 and FIG. 19 may be applied to IBC and inter prediction based on an affine motion model for the prediction block.

[0253] It should be further noted that the prefix of a code representing the magnitude of a component of a BVD may further be used to select the context (or probability model) for one or more symbols of the suffix of the code. It should be further noted that one or more of the symbols in the suffix of a code representing the magnitude of a component of a BVD, that are not entropy encoded and decoded according to the method discussed above with respect to FIG. 18, may be used in conjunction with the prefix of the code to select the context (or probability model) for one or more symbols of the suffix of the code.

[0254] For adaptive selection from among two or more probability models, context modeler 1946 may compare a value in the range of values indicated by the prefix of the code used to represent the magnitude of horizontal component B VDX1812 (or value in the range of value s that the magnitude of horizontal component BVDX1812 falls within) to a first threshold.

[0255] FIG. 20A illustrates an example representation of a BVD, more specifically, a magnitude and a sign of a BVD, according to some known video coding implementations. The BVD 2000 comprises, for example, in the bitstream from an encoder to a decoder, values representing its magnitude 2004 and sign 2010. As described above in relation to encoding of a BVD, the magnitude may be represented as an Exponential -Golomb code, and the prefix 2006 of the magnitude can be context-coded using a regular mode of a CABAC coder or the like to gain compression efficiencies in storing or transmitting the BVD. The following table illustrates how, for a given BVD value (i.e., for a given BVD magnitude), the corresponding prefix and suffix values can be specified in accordance with the Exponential -Golomb code.

[0256] TABLE 3

[0257] In the known implementations mentioned above in relation to FIG. 20A, the suffix 2008 of the magnitude and the sign 2010 are encoded in the bypass-mode of the CABAC encoder and thus may not provide the compression efficiencies obtained for context-coded prefix 2006. A flag 2002 indicating whether the magnitude is greater than 0 (sometimes referred to herein as the “magnitude greater than 0 flag”) is included in the BVD 2000. The decoder can use the magnitude greater than 0 flag to more efficiently parse the bit stream.

[0258] The description above in relation to FIG. 18 (FIGs. 18A-18D) and FIG. 19 (FIGs. 19A- 19D) shows how, in some embodiments of this disclosure, the suffix, or both the suffix and the sign, of a BVD can be predictively encoded so that the suffix, or both the suffix and the sign, of the BVD can be entropy encoded using the regular mode of a CABAC coder, thereby improving compression efficiencies for BVD.

[0259] Some other encoding technologies propose to gain compression efficiencies when transmitting the BVD by not signaling the suffix to the decoder when the encoder determines that certain conditions are satisfied for the BVD. The basic idea behind some such proposed technologies is similar to the technology used in IBC Merge Mode with Block Vector Differences (MBVD). In one example of such proposed technology, when the encoder can determine that the BVD corresponds exactly to, or in some instances to a predetermined high degree, with a “best” BVD that can be found at the decoder by a searching a reference area, the encoder selects not to signal the suffix to the decoder. When the encoder determines not to signal the suffix to the decoder, the encoded BVD that is transmitted to the decoder in a bit stream includes the prefix and a suffix indication flag explicitly indicating to the decoder that the suffix is not included in the encoded BVD. The decoder is expected to derive the suffix by itself finding the same “best” BVD and determining the suffix based on that “best” BVD.

[0260] FIG. 20B illustrates an example BVD 2020 that includes a suffix indication flag 2027 that indicates whether or not the encoded BVD 2020 includes the suffix. In the illustrated BVD 2020, the suffix 2028 is included and the value of the suffix indication flag 2027 may be set to a predetermined value that indicates the presence of the suffix. When the suffix 2028 is not included, then what is included in the encoded BVD 2020 would be the magnitude greater than 0 flag 2022 that indicates whether the magnitude is greater than 0, the prefix 2026, and the suffix indication flag 2027 set to a predetermined value that indicates that the suffix is not being signaled. Whereas in the encoding technology described in relation to FIG. 20A, the BVD prefix and suffix, which are part of Exponential -Golomb code, are signaled in the bit stream and the symbols of the prefix are context-coded, in the technology that relates to FIG. 20B, the BVD prefix is signaled in a similar manner as in the technology of FIG. 20A, and then a flag (e.g., the suffix indication flag or more generally “suffix flag”, as referred to in this disclosure) is signaled indicating whether BVD suffix is present or is equal to zero. When the suffix indication flag 2027 indicates that the suffix is included in the encoded BVD, the suffix is bypass-encoded.

[0261] In some embodiments of this disclosure methods and systems for harmonizing techniques that selectively do not signal the suffix of the magnitude of a BVD, such as that, for example, described above in relation to FIG. 20B, with techniques, such as, for example, techniques described above in relation to FIGs. 18A-18D and FIGs. 19A-19D, that predictively encode at least some magnitude symbols of a BVD are described.

[0262] These and other features of the present disclosure are described further below.

[0263] In a first implementation of the mentioned harmonization according to embodiments of this disclosure, a suffix flag is included with all encoded BVD. FIG. 21 illustrates a representation of a BVD 2100 in accordance with some embodiments of this disclosure. When the suffix is not present (i.e., not being signaled), the suffix indication flag 2107 is set to a first value that indicates that the suffix is not included. When the suffix 2108 is included (i.e., is being signaled) in the BVD 2100, the suffix indication flag 2107 is set to a second value indicating that the suffix is present. The suffix 2108 of the BVD 2100, as shown, has one or more of the magnitude symbols that are context-coded. The context-coded magnitude symbols 2109 are also referred to as predictively encoded symbols because, in some embodiments, as described above in relation to FIGs. 18 and 19, each of the context-coded symbols of the suffix contains an indication that indicates whether a prediction is correct.

[0264] The suffix 2108 of BVD 2100 comprises two magnitude symbols 2109 that are context- coded and two magnitude symbols 2110 that are bypass-coded. Embodiments of this disclosure do not limit the number of context-coded symbols or the number of bypass-coded symbols in a suffix 2108. The BVD 2100, when encoded, will include magnitude greater than 0 flag 2102, prefix 2106, suffix indication flag 2107, and suffix 2108.

[0265] FIG. 22A illustrates a flowchart of a method 2200 for decoding a BVD in accordance with some embodiments of the present disclosure. The method 2200 may be implemented by a decoder, such as decoder 300 in FIG.3.

[0266] The method 2200 begins at 2202 (the oval shape represents the start of the method). At 2202, the decoder receives an encoded BVD in a received bit stream. For example, BVD 2100 may be received in a bit stream at the decoder.

[0267] At 2204, it is determined whether the suffix flag (e.g., suffix indication flag 2107) is present in the bit stream for the BVD and has a first value. The diamond shape represents a conditionbased change of flow, with Y indicating that the tested condition is true, and N that it is false. When the value of the suffix flag is a first value, it indicates that the suffix of the magnitude is not included in the encoded BVD. Alternatively, the suffix flag has a second value. The suffix flag having the second value indicates that the suffix is included in the encoded BVD. The values may be zero and one.

[0268] If, at 2204, it is determined that the suffix flag has the first value, then the method proceeds to 2206 indicating that the suffix is not included in the encoded BVD and that the decoder is required to derive the suffix without it being signaled from the encoder (i.e. according to the locally best matching block surrounding template in the limited higher precision region corresponding to various suffix values of the BVD or MVD). (Conversely, if it is detected that the flag is present i.e. has the corresponding indicative value, then entropy decoding of the suffix data will happen).

[0269] In some embodiments, the suffix is determined by the decoder based at least on the value of the prefix that is included in the signaled BVD. The reference area in which to search can be determined based on the prefix. It should be noted that the BVD is specified in two components BVDXand BVDy, corresponding to the magnitude in the x direction and in the y direction, respectively. Accordingly, the prefix specifies an x coordinate and a y coordinate for the reference area to be searched at the decoder. As shown in TABLE 3 above that illustrates how, for a given BVD value (i.e., for a given BVD magnitude), the corresponding prefix and suffix values can be specified in accordance with the Exponential-Golomb code, each prefix value has a corresponding range of suffix values. Thus, the reference area in which to search for a “best” BVD, or more specifically the “best” BVD suffix, can be determined based on the x, y position specified by the prefix (i.e., by the x and y components of the prefix) and a range according to the range of the suffix for that prefix. In some embodiments, the decoder may use template matching search (e.g., based on the SAD cost (or other cost) between the template (one row above and one column left to the block) of each the current block and a reference block in the reference search area) in a range depending on the BVD prefix from the current prefix to the next prefix value. For example, if the BVD prefix is equal to 6, then the next prefix value is 14 (see TABLE 3 above that illustrates how, for a given BVD value (i.e., for a given BVD magnitude), the corresponding prefix and suffix values can be specified in accordance with the Exponential-Golomb code that is used for binarization), so the search range is from 6 to 14. FIG. 22D describes an example process for finding the “best” BVD suffix using a template matching search based at least on the BVD prefix in more detail, according to some embodiments.

[0270] If, at 2204, it is determined that the suffix flag has a second value, then the method proceeds to 2208 indicating that the suffix is included in the BVD. The suffix may have at least one magnitude symbol that is predictively encoded. Each predictively encoded symbol encodes an indication of whether a value of the magnitude symbol of the BVD matches a value of the same magnitude symbol of a BVD candidate used as a predictor of the BVD. The suffix is determined in accordance with the predictively encoded one or more magnitude symbols and one or more bypass-coded magnitude symbols, if any. An example of decoding a predictively encoded suffix is described in relation to FIG. 18D above. FIG. 22B illustrates a flowchart of a method 2210 for encoding a BVD in accordance with some embodiments of the present disclosure. The method 2210 may be implemented by an encoder, such as encoder 200 in FIG.2.

[0271] The method 2210 begins at 2212. At 2212, the encoder determines an encoding mode that it is operating in, and sets the suffix flag according to the determined mode. In an embodiment, at 2212, the encoder may receive a BVD to be transmitted to a decoder, and the encoder may determine, for example, whether the BVD can be transmitted without signaling the suffix. In an example, the encoder may determine that the BVD exactly matches, or matches to a predetermined degree, a BVD that can be found by searching a reference area. In order to determine this, the encoder may perform a search process similar to that would be performed at the decoder for the current BVD. An example search process based on at least the prefix value was described above in relation to the decoder process of FIG. 22A and below in relation to FIG. 22D.

[0272] If it is determined that the BVD can be transmitted without transmitting the suffix, then the suffix flag (e.g., suffix flag 2107) may be set to a first value (e.g., 1). Otherwise, the suffix flag is set to a second value (e.g., 0).

[0273] At 2214, according to the selected setting in the suffix flag, the method proceeds to either 2216 where encoding of the BVD is performed without signaling the suffix, or 2218 where encoding the BVD includes the suffix.

[0274] At 2216, encoding of the magnitude is performed without including, in the encoded BVD, a representation of the suffix. For example, the encoded BVD includes the magnitude flag 2102, the prefix 2104, and the suffix flag set to a first value.

[0275] At 2218, the encoded BVD includes the suffix and the suffix may include at least one context-coded symbol. Encoding of suffixes with context-coded symbols can be performed as described in relation to FIG. 18 and FIG. 19.

[0276] FIG. 22C illustrates a flowchart of an aspect of the encoding method 2210. The method 2220 may be implemented by an encoder, such as encoder 200 in FIG.2.

[0277] The method 2220 begins at 2222, when the encoder receives a BVD to be transmitted and it is determined, for example, at 2214, that the suffix flag is set to the second value that indicates that the suffix is being transmitted.

[0278] At 2224, it is determined whether at least one magnitude symbol of the suffix will be context-coded (i.e. predictive ly encoded). This can be determined, for example, based on a predetermined context-coding budget. Some embodiments may require that the context-coding is limited to a specified maximum number of symbols in order control computational costs. Conversely, if the test of 2224 yields “N”, the prefix, flag and sign will be encoded, and specifically the suffix may be encoded without indication of a prediction, i.e. directly.

[0279] If it is determined that one or more magnitude symbols are to be context-coded, at step 2226, one or more magnitude symbols from the most significant bins are encoded with an indication of whether a prediction is correct (a.k.a. matches). The suffix is determined according to the context-coded magnitude symbols and the bypass-coded magnitude symbols (i.e. those aspects determine the probabilities for the arithmetic coding).

[0280] At 2228, the BVD is encoded, with the encoded BVD having a suffix comprising at least one context-coded magnitude symbol and possibly one or more bypass-coded magnitude symbols, the prefix, the suffix flag, and the magnitude greater than 0 flag.

[0281] If, at 2224, it is determined that no magnitude symbols are to be context-coded, at 2230, the BVD is encoded with the encoded BVD having the prefix and suffix of the magnitude value, the suffix flag, and magnitude greater than 0 flag. All suffix symbols are bypass-coded (i.e. directly coded as their sequence of bins becoming the same sequence of coded bits out).

[0282] FIG. 22D schematically illustrates a technique for defining, based at least on a BVD magnitude prefix, a search area in which to search for a corresponding BVD suffix. If the value of suffix flag 2107 is set to the first value, a search process based on template matching (TM) costs is used. FIG. 22D illustrates a process of defining the search area (also referred to as the reference area) 2244 for this search process. The location of the BVD suffix search area within an IBC reference area depends on the BVP 2236, and the BVD suffix search area size is defined by the BVD prefix value (shown as x, y components Prefix BVDx and Prefix BVDy). TABLE 3 above identifies a range of suffix values for a given prefix value. Accordingly, as illustrated, the bottom right of the search area 2244 is determined based on the BVP 2236 and the prefix value, and size of the search area is determined based on the suffix value range specified in TABLE 3 for the prefix value. In the illustration of FIG. 22D, the reference block 2234 is found within the search area 2244 to have the template that has the smallest template matching cost difference with the template of the current block 2232. As described above, in example embodiments, a block’s template includes pixels outside its left edge and top edge. The template costs may be calculated as the difference between the template of a reference block and the template of the current block based on a difference (e.g., SSD, SAD, SATD, mean removal SAD, or mean removal SSD) between samples of the two templates. The suffix (shown as x, y components Suffix Dx and Suffix Dy) can be determined based on the distance from the bottom right edge of the search area 2244, which is determined by the prefix, to the top left edge of the reference block. This provides for determining the BVD 2240 and BV 2242. In some embodiments, a plurality of reference blocks may be identified based on template matching costs from within the search area, and, for determining the suffix, one of the candidate blocks may be selected as the reference block based upon considering the rate distortion optimization (RD optimization) scores of the plurality of candidate reference blocks in addition to their template matching costs. Considering the RD optimization scores in addition to the template matching costs enables accounting for the estimated signaling overhead associated with each candidate reference block.

[0283] If, according to the determined size, a part of the BVD suffix search area extends beyond the IBC reference area, the template matching-based search is performed within the that part of the BVD suffix search area that is located within the IBC reference area. If the BVD suffix search area is entirely within the IBC reference area, it has a rectangular shape as shown in FIG. 22D. If only the BVD suffix is to be predicted, then the template matching search is performed in a single search area. This scenario is illustrated in FIG. 22D. If, in addition to the BVD suffix, the BVD sign is also predicted, then the search area can be composed of two or more non-contiguous search subareas that are defined by the hypotheses on BVD signs. For example, the size of each of the search subareas are determined based on the range of suffix values as described above, but the respective locations of each search subarea can be determined in accordance with the BVP, the prefix and a respective sign hypothesis.

[0284] The first implementation of harmonization described above in relation to FIG. 21 and FIG. 22 incurs an overhead in including the suffix flag with each BVD. In a second implementation of harmonization, the suffix flag is not included when certain conditions are met. More specifically, whereas the suffix flag is included in the encoded BVD when the suffix is not being included in the encoded BVD, the suffix flag is excluded when a BVD’s suffix includes no, or some number less than a predetermined threshold, of bypass-coded symbols. Thus, in this technique, the suffix flag may be present with a first value indicating that the suffix is not being signaled in the BVD, may be present with a second value indicating that the suffix is being signaled in the BVD, or may be absent indicating that the suffix is present in the BVD and a number of bypass-coded suffix symbols are less than (or less than or equal) to a predefined threshold. FIG. 23A and FIG. 23B illustrate a representation of a BVD in accordance with embodiments of this disclosure.

[0285] FIG. 23A illustrates a BVD 2300 that includes the suffix flag 2307 (referred to in the figure as “suffix derivation flag”). The suffix 2308 is an illustration of a suffix coding example which has multiple context-coded magnitude symbols 2309 and also multiple bypass-coded magnitude symbols 2310. The encoded BVD 2300 includes magnitude greater than 0 flag 2302 for the magnitude, the prefix 2304, the suffix 2308. So the suffix derivation flag indicates (i.e. is included in the signal) that (when) there are some bypass encoded bins representing a part of the suffix of the BVD or MVD data element, i.e. which bins will get bypass coded into an encoded part of the bits in the coded bitstream, by the bypass part of the CABAC encoder.

[0286] FIG. 23B illustrates BVD 2320 that does not include a suffix flag 2307 because there are no bypass coded magnitude symbols in 2320. In the illustrated example, the suffix flag is excluded from the BVD when the BVD does not include any suffix magnitude symbols that are bypass-coded. However, in some embodiments, the suffix flag may be included or excluded based on whether the number of bypass-coded magnitude symbols in the suffix is less than (or less than or equal to) a predetermined threshold value.

[0287] FIG. 24A illustrates a flowchart of a method 2400 for decoding a BVD, such as, for example, the BVD as in FIG. 23 A and FIG. 23B, in accordance with embodiments of this disclosure. The method 2400 may be implemented by a decoder, such as decoder 300 in FIG.3. The method 2400 begins at 2402. At 2402, the decoder receives an encoded BVD in a received bit stream. For example, BVD 2300 may be received in a bit stream at the decoder.

[0288] At 2404, it is determined whether the suffix flag (e.g., suffix indication flag 2307) is present in the bit stream for the BVD. If present, the method proceeds to 2406. If the suffix flag is not present, the method proceeds to 2412 (entropy decoding at least one context-coded symbol to determine the suffix).

[0289] At 2406, it is determined whether the suffix flag has a first value (e.g., 1). When the value of the suffix flag is the first value, it indicates that the suffix of the magnitude is not included in the encoded BVD. Alternatively, the suffix flag has a second value (e.g., 0). The suffix flag having the second value indicates that the suffix is included in the encoded BVD.

[0290] If, at 2406, it is determined that the suffix flag has the first value, then the method proceeds to 2408 indicating that the suffix is not included in the encoded BVD and that the decoder is required to derive the suffix without it being signaled from the encoder. In some embodiments, the suffix is determined by the decoder based at least on the value of the prefix that is included in the BVD. The decoder may use a search process such as that described above (e.g., in relation to 2206 and also in relation to FIGs. 22D) to determine the suffix.

[0291] If, at 2406, it is determined that the suffix flag has the second value, then the method proceeds to 2410 indicating that the suffix is included in the BVD (but now coded in a different manner, comprising at least some bins being bypass encoded). The suffix has at least one magnitude symbol that is predictively encoded. Each predictively encoded symbol encodes an indication of whether a value of the magnitude symbol of the BVD matches a value of the same magnitude symbol of a BVD candidate used as a predictor of the BVD. The suffix is determined in accordance with the predictively encoded one or more magnitude symbols and one or more bypass-coded magnitude symbols. Decoding a suffix that includes one or more context-coded symbols is described above, for example, in relation to FIG. 18 and FIG. 19.

[0292] If at 2404, it is determined that the suffix flag is not included, the method proceeds to 2412. At 2412, the suffix is included in the BVD and includes only context-coded magnitude symbols. In an embodiment each magnitude symbol encodes an indication of whether a value of the magnitude symbol of the BVD matches a value of the same magnitude symbol of a BVD candidate used as a predictor of the BVD. The suffix is determined in accordance with the predictively encoded one or more magnitude symbols.

[0293] FIG. 24B illustrates a flowchart of a method 2420 for encoding a BVD, such as, for example, the BVD as in FIG. 23A and FIG. 23B, in accordance with embodiments of the present disclosure. The method 2420 may be implemented by an encoder, such as encoder 200 in FIG.2.

[0294] The method 2420 begins at 2422. At 2422, the encoder determines an encoding mode that it is operating in, and sets the suffix flag according to the determined mode. In an embodiment, at 2422, the encoder may receive a BVD to be transmitted, for example, to a decoder, and the encoder may determine, for example, whether the BVD can be transmitted without signaling the suffix.

[0295] If it is determined that the BVD can be transmitted without transmitting the suffix, then the suffix flag may be set to a first value (e.g., 1). Otherwise, the suffix flag is set to a second value (e.g., 0). The determination may be made as described, for example, in relation to 2212 above.

[0296] At 2424, in accordance with the status of the suffix flag, the method proceeds to 2426 is the suffix flag is to be included in the bit stream, or to 2432 if the suffix flag is not to be included in the bit stream.

[0297] At 2426, when the suffix flag is set to the first value the method proceeds to 2428, or to 2430 when the suffix flag is set to the second value. At 2428, the suffix flag has the first value and the encoding of the BVD is performed without signaling the suffix in a manner similar to that described in relation to operation 2206 and also in relation to FIGs 22D. At 2430, the suffix flag has the second value and the encoding the BVD includes the suffix in the encoded BVD. The suffix includes at least one context coded symbol.

[0298] FIG. 24C illustrates a flowchart of a method 2450 for an aspect of the encoding method of FIG. 24B. For example, method 2450 can be used to predictively encode magnitude symbols of the suffix in accordance with a predefined threshold.

[0299] Method 2450 begins at 2452. At 2452, it is determined whether any suffix symbols will be context-coded. This decision may be based on a predetermined budget the encoder has allocated for context-encoding symbols. If any symbols are to be context-coded, the method proceeds to 2454. Otherwise, the method proceeds to 2466.

[0300] At 2454, it is determined whether the bypass coded symbols would exceed a predefined threshold. This may be determined based on the context-coding budget and the number of symbols in the suffix and a predefined threshold. If the threshold is exceeded, the method proceeds to 2456. Otherwise, the method proceeds to 2462.

[0301] The threshold helps in preventing the signaling overhead incurred by always including the suffix flag as described in relation to FIGs. 21 and 22A-22C. The threshold enables conditionally signaling the suffix flag.

[0302] The threshold is intended so that the suffix flag is signaled when the number (NBPCB) of bypass-coded symbols for the BVD magnitude suffix symbol prediction method exceeds a threshold (NTHRB):

[0303] NBPCB > NTHRB, where NTHRB can take, for example, the following integer values: 1, 2, 3, 4, etc. Thus, when this condition is met, the suffix flag is omitted. Otherwise, this flag is signaled in the bit stream.

[0304] Another embodiment provides a conditional mechanism to signal the suffix flag in the bitstream using the length (LPREF) of the BVD prefix. In this embodiment, the suffix flag is signaled when the length (LPREF) of the BVD prefix exceeds a threshold (NTHRL): LPREF > NTHRL, where NTHRL can take, for example, the following integer values: 2, 3, 4, etc. Thus, when this condition is met, the suffix flag is signaled in the bit stream. Otherwise, this flag is omitted.

[0305] At 2456, the suffix flag is set to the second value indicating that the BVD includes the suffix (i.e., the suffix is being signaled). At 2458, the suffix is generated with at least one symbol being predictively encoded, and at least one symbol being bypass-coded. In some embodiments, a determined number of most significant bins, starting from the most significant bin, are context-coded. At 2460, the BVD is encoded including the magnitude greater than 0 flag, the prefix, the suffix flag, and the suffix. The suffix includes both context-coded symbols and bypass-coded symbols.

[0306] If, from 2454, the method proceeded to 2462, the method generates the suffix with at least one context-coded symbol. If the threshold is 0, then no bypass-coded symbols exist. Otherwise, some number less than or equal to the threshold is bypass-coded.

[0307] After the suffix is generated at 2462, at 2464, the encoded BVD is generated with the BVD including the magnitude greater than 0 flag, the prefix, and the suffix. Note that the suffix flag is not being signaled. The suffix includes either 0 or a number less than the threshold of bypass-coded symbols (and some predicted symbols). Finally there may be sign symbols.

[0308] If, from 2452, the method proceeds to 2466, the suffix flag is set to the second value indicating that the suffix is being included in the BVD (i.e. directly, without prediction). Then, at 2468, the BVD is generated with the magnitude greater than 0 flag, the prefix, the suffix flag, and the suffix. Note that all suffix symbols are bypass-coded.

[0309] Another implementation of harmonization according to example embodiments is shown in FIGs. 25A-25B. This implementation is similar to that shown in relation to FIG. 23A and FIG. 23B, but illustrates another representation of a BVD in accordance with some embodiments of this disclosure. A suffix flag 2507 (referred to as suffix derivation flag in the figure) is included, as in the example of FIG. 23 A, when the number of bypass-coded magnitude symbols are below a predefined threshold. The suffix flag 2507 is included in BVD 2500 because BVD 2500 includes a number of bypass-coded magnitude symbols 2510 that is greater than the threshold (e.g., threshold = 0), whereas the suffix flag 2507 is not included in BVD 2520 in which the suffix 2508 does not include any bypass-coded symbols.

[0310] BVD 2500 and BVD 2520 (i.e. the coding of the block vector difference) also include their sign 2512. Thus, BVD 2500 includes the magnitude greater than 0 flag 2502, prefix 2504, sign 2512, and suffix. The suffix flag 2507 is included when either there are no suffix symbols included (e.g., suffix flag is set to the first predefined value), or the bypass-coded suffix symbols exceed a predefined threshold (e.g., suffix flag is set to the second predefined value). The suffix flag is not included (not signaled) in the BVD when the number of bypass-coded symbols in the suffix is equal to or less than the predefined threshold.

[0311] Embodiments using the BVD representations 2500 and 2520 may be used for two different uses of the status flag being set to the first value. As noted above, the status flag being equal to the first value (e.g., 0) indicates that the suffix is not being signaled in the encoded BVD. In some example embodiments, when the status flag is set to the first value, both a sign and a suffix value are derived as the result of searching within the search range with the template matching cost. Such a search was described above in relation to FIGs. 21, and 22A-22B. In this case in association with BVD 2500 or 2520, the search range is composed of, at least, 2 subranges defined by

[0312] - a prefix value as shown in TABLE 3 and

[0313] - a sign value that can take values of “+” and which determines the positions of the at least 2 search subranges.

[0314] Alternatively, when the suffix flag value equals the first value, a suffix value is derived as the result of searching within the search range with the minimal template matching cost, whereas a sign symbol is either bypass coded or predicted.

[0315] FIG. 26A illustrates a flowchart of a method 2600 for decoding a BVD, such as, for example, the BVD as in FIG. 25A and FIG. 25B, in accordance with embodiments of the present disclosure. The method 2600 may be implemented by a decoder, such as decoder 300 in FIG.3.

[0316] The method 2600 begins at 2602. At 2602, the decoder receives an encoded BVD in a received bit stream. For example, BVD 2500 may be received in a bit stream at the decoder.

[0317] At 2604, it is determined whether the suffix flag 2507 (e.g., suffix derivation flag in the drawing) is present in the bit stream for the BVD. If present, the method proceeds to 2606. If the suffix flag is not present, the method proceeds to 2612.

[0318] At 2606, it is determined whether the suffix flag has a first value. When the value of the suffix flag is the first value, it indicates that the suffix of the magnitude is not included in the encoded BVD. Alternatively, the suffix flag has a second value. The suffix flag having the second value indicates that the suffix is included in the encoded BVD.

[0319] If, at 2606, it is determined that the suffix flag has the first value, then the method proceeds to 2608 indicating that the suffix is not included in the encoded BVD and that the decoder is required to derive the suffix without it being signaled from the encoder.

[0320] In some embodiments, the suffix is determined by the decoder based at least on the value of the prefix that is included in the BVD. The decoder may use a search process such as that described above (e.g., in relation to 2206 and in FIG. 22D) to determine the suffix. Alternatively, in another embodiment, the search is intended to determine the suffix and also the sign. In this alternative embodiment, instead searching for the best template match in one reference area determined in accordance with the prefix (as described in relation to 2206), at least two disjoint reference areas are determined by considering the prefix value and the “+” or sign values and the search is performed in all the at least two disjoint reference areas for the best matching template. When the search is performed in this manner, the best matching BVD determined will also identify the sign of the BVD in addition to its magnitude. Thus, in this alternative embodiment, when the suffix is not signaled, the sign may also may not be separately signaled. Both the suffix and the sign can be derived by the decoder based on the prefix of the BVD magnitude. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD suffix, or the suffix and sign, based on a candidate reference block are described in more detail in relation to FIGs. 22D.

[0321] If, at 2606, it is determined that the suffix flag has a second value, then the method proceeds to 2610 indicating that the suffix is included in the BVD. The suffix has at least one magnitude symbol that is predictively encoded. Each predictively encoded symbol encodes an indication of whether a value of the magnitude symbol of the BVD matches a value of the same magnitude symbol of a BVD candidate used as a predictor of the BVD. The suffix is determined in accordance with the predictively encoded one or more magnitude symbols and one or more bypass-coded magnitude symbols.

[0322] If at 2604, it is determined that the suffix flag is not included, the method proceeds to 2612. At 2612, the suffix is included in the BVD and includes only context-coded magnitude symbols. In an embodiment each magnitude symbol encodes an indication of whether a value of the magnitude symbol of the BVD matches a value of the same magnitude symbol of a BVD candidate used as a predictor of the BVD. The suffix is determined in accordance with the predictively encoded one or more magnitude symbols.

[0323] FIG. 26B illustrates a flowchart of a method 2620 for encoding a BVD, such as, for example, the BVD as in FIG. 25A and FIG. 25B, in accordance with some embodiments of the present disclosure. The method 2620 may be implemented by an encoder, such as encoder 200 in FIG.2.

[0324] The method 2620 begins at 2622. At 2622, the encoder determines an encoding mode that it is operating in, and sets the suffix flag according to the determined mode. In an embodiment, at 2622, the encoder may receive a BVD to be transmitted to a decoder, and the encoder may determine, for example, whether the BVD can be transmitted without signaling the suffix. The determination may be made as described, for example, in relation to FIG. 26A above. If it is determined that the BVD can be transmitted without transmitting the suffix, then the suffix flag may be set to a first value (e.g., 0). Otherwise, the suffix flag is set to a second value (e.g., 1). If the suffix is to be transmitted, the encoder further determines whether, based on whether the number of bypass-coded symbols exceeds a predefined threshold, whether or not to transmit the suffix flag. The suffix flag is transmitted when the number of bypass-coded suffix symbols exceeds the predefined threshold, and is not transmitted otherwise.

[0325] At 2624, in accordance with the status of the suffix flag, the method proceeds to 2626 when the suffix flag is present in the bit stream, and to 2632 when the suffix flag is not included in the bit stream.

[0326] At 2626, when the suffix flag is set to a first value the method proceeds to 2628 or to 2630 when the suffix flag is set to the second value. Thus, according to the selected setting in the suffix flag, the method proceeds to either 2626 where encoding of the BVD is performed without signaling the suffix, or 2628 where encoding the BVD includes the suffix.

[0327] At 2628, the BVD is encoded without including, in the encoded BVD, a representation of the suffix in a manner similar to that described in relation to operation 2206 and also in relation to FIGs 22D. In some embodiments, as described above, in addition to the suffix, the sign of the BVD too can be derived by the decoder. In such embodiments, the encoded BVD may not include either of the sign or the suffix. Thus, the encoded BVD may have either the magnitude flag, the prefix, and the suffix flag set to the first value, or the magnitude flag, the prefix, the suffix flag and the sign.

[0328] FIG. 27A illustrates a flowchart of a method 2700 of decoding a BVD in accordance with embodiments of this disclosure. Method 2700 can be performed by a decoder such as decoder 300 in FIG. 3.

[0329] Method 2700 starts at 2702 when the decoder has received a bit stream of an encoded BVD from an encoder, and the decoder has decoded the portions of the BVD. As described above, the BVD magnitude comprises a prefix and suffix determined in accordance with an Exponential -Golomb code. At 2702, the value of the prefix is determined based on a first one or more symbols of the BVD.

[0330] At 2704, based on a status of a suffix flag in the BVD, it is determined whether or not the received bit stream includes a second one or more symbols of a suffix of the BVD. When it is determined that the bit stream includes the second one or more symbols of the suffix, the encoder may further determine whether the second one or more symbols include at least one context-coded symbol. The status of the suffix flag may include its presence or absence in the bit stream and / or its value. As noted above, the suffix flag indicates the presence or absence of the suffix (i.e., whether the suffix is being signaled from the encoder to the decoder) and also indicates, at least in some embodiments, the presence of bypass-coded BVD symbols. That is, when the suffix flag indicates that the suffix is not being signaled, in some embodiments, neither the suffix value (e.g., magnitude) nor any representation of the suffix value is included in the encoded BVD on the bit stream. The suffix flag may be 1 or more bits.

[0331] At 2706, in accordance with the determination made at 2704, the suffix of the BVD is obtained. For example, one or the methods 2200, 2400 or 2600 can be used to determine the suffix.

[0332] In some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is a first value, the suffix is determined based at least on the prefix, and when the suffix flag is present in the received bit stream and the value of the suffix flag is a second value, at least one context-coded suffix symbol is entropy decoded in order to obtain the suffix.

[0333] In some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is the first value, the suffix is determined based at least on the prefix by searching in an area within a picture in which a current block is located for another block corresponding to the current block, where the area is determined according to at least a value of the prefix and a possible value of the suffix determined in accordance with the value of the prefix. The other block is selected based on a difference between the other block and the current block, and the suffix is determined based on the selected another block. The difference may be determined based on templates of the current block and another block.

[0334] In some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is a first value, the suffix is determined based at least on the prefix, and when the suffix flag is present in the received bit stream and the value of the suffix flag is a second value, or when the suffix flag is absent in the received bit stream, at least one context-coded suffix symbol is entropy decoded in order to obtain the suffix.

[0335] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the first value, the status of the suffix flag may be determined based on whether or not a value of the suffix is represented in the bit stream to be transmitted by searching in an area within a picture in which a current block is located for another block corresponding to the current block, wherein the area is determined according to at least a value of the prefix and a possible value of the suffix determined in accordance with the value of the prefix. Another block is elected based on a difference between the another block and the current block, and, based at least on the selected another block, whether or not the value of the suffix is represented in the bit stream is determined. The difference may be determined based on respective templates of the current block and the another block.

[0336] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols include at least one context-coded symbol and at least one bypass-coded symbol, and each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction. Each indication may indicate whether a corresponding respective prediction is correct.

[0337] In some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is the second value, decoding of the second one or more symbols, including the at least one context-coded symbol and at least one bypass-coded symbol, is performed to obtain the suffix. When the suffix flag is absent in the received bit stream, decoding of the second one or more symbols is performed to obtain the suffix, where either the second one or more symbols include at least one context- coded symbol and a number of bypass-coded symbols is less than a predefined threshold or a number of symbols in the second one or more symbols is less than the predefined threshold.

[0338] In some embodiments, the suffix and the sign are determined. For example, in some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is the first value, a sign of the BVD and the suffix are determined based at least on the prefix. When the suffix flag is present in the received bit stream and the value of the suffix flag is the second value, or when the suffix flag is absent in the received bit stream, the second one or more symbols including at least one context-coded symbol are decoded to obtain the suffix and another context-coded symbol in the received bit stream is decoded to obtain the sign.

[0339] In some embodiments, when the suffix flag is present in the received bit stream and the value of the suffix flag is a first value, the suffix is determined based at least on the prefix, another symbol in the received bit stream is decoded to obtain a sign of the BVD vector. When the suffix flag is present in the received bit stream and the value of the suffix flag is a second value, or when the suffix flag is absent in the received bit stream, at least one context-coded symbol to is decoded to obtain the suffix and another context-coded symbol in the received bit stream is decoded to obtain a sign of the BVD. At 2708, the BVD is decoded.

[0340] FIG. 27B illustrates a flowchart of a method of encoding a BVD in accordance with some embodiments of this disclosure. Method 2710 can be performed by encoder such as encoder 200 in FIG. 2.

[0341] Method 2710 begins at 2712. At 2712, a BVD is determined based on a BV and a BVP.

[0342] At 2714, the magnitude of the BVD and the sign of the BVD are determined. The magnitude may be determined as a prefix and a suffix. As shown in TABLE 3, a range of values is indicated by the prefix representing the magnitude of the BVD, and the suffix indicates the precise value within the range of values of the magnitude of the BVD.

[0343] At 2716, it is determined how the suffix, or the sign and the suffix, is to be signaled to the decoder, and accordingly a status of a suffix flag is determined for the BVD. For example, one of methods 2210 (FIG. 22B), 2420 (FIG. 24B) and 2620 (FIG. 26B) may be used to make this determination.

[0344] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is a first value, the magnitude is encoded without representing the value of the suffix in the encoded magnitude. When the suffix flag is present in the bit stream and the value of the suffix flag is a second value, the second one or more symbols including the at least one context-coded symbol are encoded to obtain the suffix.

[0345] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the first value, the status of the suffix flag is determined based on whether or not a value of the suffix is represented in the bit stream to be transmitted by searching an area within a picture in which a current block is located for another block corresponding to the current block, where the area is determined according to at least a value of the prefix and a possible value of the suffix determined in accordance with the value of the prefix. Another block is selected based on a difference between the other block and the current block, and based at least on the selected another block, it is determined whether or not the value of the suffix is represented in the bit stream. The difference may be determined based on respective templates of the current block and the other block.

[0346] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols include at least one context-coded symbol and at least one bypass-coded symbol, and each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction. Each indication may indicate whether a corresponding respective prediction is correct.

[0347] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is a first value, the magnitude is encoded without representing a value of the suffix in the encoded magnitude. When the suffix flag is present in the bit stream and the value of the suffix flag is a second value, or when the suffix flag is absent in the bit stream, the second one or more symbols including the at least one context-coded symbol are encoded to determine the suffix. In some embodiments, the suffix flag is present in the bit stream and the value of the suffix flag is the first value, and the status of the suffix flag is determined based on whether or not a value of the suffix is represented in the bit stream to be transmitted by a process including searching in an area within a picture in which a current block is located for another block corresponding to the current block, where the area is determined according to at least a value of the prefix and a possible value of the suffix determined in accordance with the value of the prefix. Another block is searched based on a difference between the other block and the current block, and, based at least on the selected another block, it is determined whether or not the value of the suffix is represented in the bit stream. The difference may be determined based on respective templates of the current block and the other block.

[0348] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols, including the at least one context- coded symbol and at least one bypass-coded symbol, are encoded to determine the suffix. When the suffix flag is absent in the bit stream, the second one or more symbols of the suffix is entropy encoded to obtain the suffix, where either the second one or more symbols include at least one context-coded symbol and a number of bypass-coded symbols is less than a predefined threshold or a number of symbols in the second one or more symbols is less than the predefined threshold.

[0349] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols include at least one context-coded symbol and at least one bypass-coded symbol, each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction. When the suffix flag is absent in the received bit stream, the second one or more symbols include at least one context-coded symbol, each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction. Each indication may indicate whether a corresponding respective prediction is correct.

[0350] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the number of bypass-coded symbols in the second one or more symbols exceeds the predefined threshold. When the suffix flag is absent in the bit stream, the number of bypass-coded symbols in the second one or more symbols is less than or equal to the predefined threshold.

[0351] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, a length of the prefix exceeds the predefined threshold. When the suffix flag is absent in the bit stream, the length of the prefix is less than or equal to the predefined threshold.

[0352] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is a first value, a sign of the BVD and the magnitude are encoded without representing a value of the suffix and the sign in the bit stream. When the suffix flag is present in the bit stream and the value of the suffix flag is a second value, or when the suffix flag is absent in the bit stream, the second one or more symbols including the at least one context-coded symbol and another context-coded symbol representing the sign are encoded.

[0353] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the first value, the status of the suffix flag is determined based on whether or not a value of the suffix is represented in the bit stream to be transmitted by a process that includes searching in a plurality of areas within a picture in which a current block is located for another block corresponding to the current block, where the plurality of areas are determined according to at least a value of the prefix, a possible value of the suffix determined in accordance with the value of the prefix, and possible values of the sign. The other block is selected based on a difference between the other block and the current block, and based at least on the selected another block, it is determined whether or not the value of the suffix is represented in the bit stream. The difference may be determined based on respective templates of the current block and the other block.

[0354] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols, including the at least one context- coded symbol and at least one bypass-coded symbol are encoded to obtain the suffix. When the suffix flag is absent in the bit stream, the second one or more symbols are encoded to obtain the suffix, where either the second one or more symbols include at least one context-coded symbol and a number of bypass-coded symbols is less than a predefined threshold or a number of symbols in the second one or more symbols is less than the predefined threshold.

[0355] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, the second one or more symbols include at least one context-coded symbol and at least one bypass-coded symbol, each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction, and the bit stream includes another context-coded symbol representing the sign. When the suffix flag is absent in the bit stream, the second one or more symbols include at least one context-coded symbol, each context-coded symbol in the second one or more symbols corresponds to an indication of a prediction, and the bit stream includes another context-coded symbol representing the sign. Each indication may indicate whether a corresponding respective prediction is correct.

[0356] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is the second value, a number of bypass-coded symbols in the second one or more symbols exceeds the predefined threshold, and, when the suffix flag is absent in the bit stream, the number of bypass-coded symbols in the second one or more symbols is less than the predefined threshold. When the suffix flag is present in the bit stream and the value of the suffix flag is the second value, a length of the prefix exceeds the predefined threshold, and, when the suffix flag is absent in the bit stream, the length of the prefix is less than the predefined threshold.

[0357] In some embodiments, when the suffix flag is present in the bit stream and the value of the suffix flag is a first value, the magnitude is encoded without representing the suffix in the encoded magnitude, and another symbol in the bit stream is encoded to represent the sign, where the other symbol corresponds to the sign of the BVD. When the suffix flag is present in the bit stream and the value of the suffix flag is a first value, or when the suffix flag is absent in the bit stream, the second one or more symbols including the at least one context-coded symbol and another context-coded symbol representing the sign are encoded.

[0358] At 2718, the BVD is encoded based on the determination at 2716.

[0359] As described below in relation to FIGs. 28A-38D, some embodiments of this disclosure comprise a mechanism to extend the number of suffix candidates that can be indicated in the bit stream for a BVD. In these embodiments, when the suffix flag (derivation flag) value equals a first value (e.g., 1), the decoder selects one of the multiple candidates with, for example, a minimal template matching cost in accordance with a signaled derivation index value. A code such as, for example, truncated unary code, binary code, truncated binary code, etc. can be used as the binarizer for the derivation index. Some symbols of the derivation index can be bypass-coded in a manner similar to the signaling mechanism used for suffixes in embodiments. In general, example embodiments provide for the number of symbols used to signal the derivation index and the suffix bins predicted or bypass-coded to be the same or different.

[0360] In the examples shown in FIGs. 31, 33 and 35, the suffix flag (referred to as the “derivation flag” in FIGs. 28, 31, 33, 35, and 37) indicates a presence of either a derivation index or suffix symbols (for more explicit communication) for horizontal and vertical components of a BVD. Some of these suffix symbols may be predictively encoded (e.g., context-coded) using, for example, the technique described in above embodiments to transmit an indication of the correctness of a hypothesis on the symbol value instead of the symbol value, and the other suffix symbols may be bypass-coded. The hypothesis can be a candidate vector, and whether there is a match (which can include also a hypothesis of the sign).

[0361] FIG. 28A and FIG. 28B illustrate example representations of suffix information of the magnitude of a BVD according to some embodiments of this disclosure. The representations shown in FIGs. 28A and 28B can be used to signal to a decoder either that the suffix of the BVD is not being signaled and is to be derived using a derived candidate indicated by a derivation index encoded in the bit stream, or that the suffix is encoded in the bit stream. When the suffix flag 2802 has a first value (e.g., 1) it indicates that the suffix of the BVD is to be derived using a derived candidate indicated by the derivation index 2804 encoded in the bit stream. When the suffix flag 2802 has a second value (e.g., 0), it indicates that the bit stream includes the encoded suffix 2806. The description herein of embodiments based on the BVD representations shown in any of FIGs. 28A, 28B, 31, 33, 35 and 37, uses the terms first value and second value for 1 and 0, respectively, but example embodiments are not limited to any specific values for the first value and the second value.

[0362] FIG. 28A illustrates an embodiment in which the derivation index 2804 and the encoded suffix 2806 have a different number (amount) of symbols. FIG. 28B illustrates an embodiment in which the derivation index 2808 has the same number of symbols as the encoded suffix 2806. In example embodiments, the derivation index (e.g., 2804, 2808) and / or the encoded suffix 2806 may include one or more context-coded symbols. In example embodiments, the suffix (e.g., 2806) may be separately encoded in the bit stream as the horizontal component of the suffix and the vertical component of the suffix.

[0363] The suffix flag is described in this disclosure as a flag that can take one of two values. However, embodiments do not limit the size or the range of values that can be taken by the suffix flag.

[0364] FIG. 29A illustrates a flowchart of a method 2900 for decoding a BVD that includes, for example, a representation of suffix information that includes a suffix flag and a derivation index, similar to the representations shown in any of FIGs. 28A, 28B, 31, 33, 35 or 37, in accordance with some embodiments of this disclosure. Method 2900 can be performed by a decoder such as decoder 300 shown in FIG. 3.

[0365] Method 2900 may start at 2902 when the decoder has received a bit stream of an encoded BVD, for example, from an encoder. As described above, the BVD magnitude comprises a prefix and suffix determined e.g. in accordance with an Exponential-Golomb code. At 2902, the value of the prefix is determined based on a first one or more symbols of the BVD in the received bit stream.

[0366] As noted above, the suffix flag (e.g., 2802) indicates the presence or absence of the suffix (i.e., whether the suffix is being signaled from the encoder to the decoder). In the embodiments described in relation to FIGs. 29A-29B, the bit stream includes a suffix flag (e.g., flag 2802, referred to as “derivation flag” or “suffix derivation flag”) that indicates to the decoder whether the suffix of the BVD is to be derived using a derived candidate indicated by the derivation index (e.g., 2804, 2808) encoded in the bit stream, or whether the suffix is encoded in the bit stream (e.g., 2806). Accordingly, based on a value of the suffix flag and a second one or more symbols in the received bit stream, the suffix is determined at 2904 and one of 2906 or 2908.

[0367] When the suffix flag (e.g., 2802) has a first value (e.g., 1) indicating that the suffix is to be derived using a derived candidate indicated by the derivation index (e.g., 2804, 2808, etc.), at 2906 the decoder determines one or more reference areas in the picture (which as explained above, inter aha with Fig. 19A and 19B, correspond to reference values of the suffix). The reference areas are determined in accordance with at least the value of the prefix. The one or more reference areas are searched to identify one or more candidate blocks and a difference between each of the one or more candidate blocks and the current block is determined. An example search of one or more reference areas to identify candidate BVD is described in relation to 2202 of FIG. 22A. In contrast to the embodiment described in relation to FIG. 22A, in the present embodiment more than one candidate block may be identified and arranged in an ordered collection that can be accessed based on an index value (e.g., derivation index 2804 or 2808). The derivation index encoded in the second one or more symbols is used to select one of the identified one or more candidate blocks in the ordered collection, and the suffix is calculated based on the selected candidate block. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD suffix by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 3 OF. When the suffix flag has a second value (e.g., 0) indicating that the suffix is encoded in the bit stream, at 2908 the decoder decodes the second one or more symbols to obtain the suffix (i.e. although it may still involve arithmetic coding, it is a more explicit manner of coding that the candidate coding). The suffix may include one or more context-coded symbols. An example of decoding a suffix when the suffix is encoded in the bit stream is described above in relation to 2204 of FIG, 22A.

[0368] At 2910, the magnitude is determined based on the prefix obtained at 2902 and the suffix obtained at 2906 or 2908, by concatenation. In some embodiments, the sign of the magnitude is determined based on a third one or more symbols in the received bit stream to determine the BVD.

[0369] FIG. 29B illustrates a flowchart of a method 2920 for encoding a BVD that includes, for example, a representation of suffix information similar to the representations shown in any of FIGs. 28A, 28B, 31, 33, 35 or 37, in accordance with some embodiments of this disclosure. Method 2920 can be performed by an encoder such as encoder 200 in FIG. 2.

[0370] The method 2920 begins at 2922. At 2922, the encoder determines an encoding mode that it is operating in and sets the suffix flag according to the determined mode. In an embodiment, at 2922, the encoder may receive a BVD that is to be transmitted, for example, to a decoder, and the encoder may determine, for example, whether the BVD can be conveyed to the decoder without signaling the suffix. In an example, the encoder may determine that the BVD exactly matches, or matches to a predetermined degree, a candidate BVD that can be found by searching at least one reference area for one or more BVD candidate blocks. In order for the encoder to determine whether the encoder and the decoder each acting separately and at different times find the same candidate BVD, the encoder may perform the search process that would be performed at a decoder for the BVD to be transmitted. An example search process based on at least the prefix value was described above in relation to the decoder process of FIG. 22A.

[0371] At 2922, a prefix and a suffix of the magnitude of the BVD to be transmitted are determined, and the prefix is encoded in a first one or more symbols of a bit stream to be transmitted. TABLE 3 above illustrates prefix and suffix values for BVD magnitudes. The symbols of the prefix may be context-coded for transmission.

[0372] The encoder may convey the suffix to the decoder either by encoding only an index value in the bit stream (without encoding the suffix value in the bit stream), or by encoding the suffix value in the bit stream. Thus, when a second one or more symbols in the bit stream to be transmitted is to comprise an index value, the method proceeds to 2924, or when the second one or more symbols in the bit stream to be transmitted is to comprise the suffix the method proceeds to 2926.

[0373] At 2924, when a second one or more symbols in the bit stream to be transmitted is to comprise an index value and the method 2920 proceeds from 2922 to 2924, the suffix flag is set to the first value and the index value is determined as the index value to access the “best” BVD information in an ordered collection of BVD information of one or more BVD candidate blocks. The index value is the position of the BVD information selected from the ordered collection in accordance with a predetermined selection criterion. The ordered collection of BVD information is generated by determining one or more reference areas based on at least the prefix and searching the one or more reference areas for BVD candidate blocks that have a lowest difference with the current block. The difference can be calculated based on a technique such as template matching that was described above in relation to FIGs. 18 and 19. Method 3020 described below provides further details of the searching and the selecting.

[0374] At 2926, when the second one or more symbols in the bit stream to be transmitted is to comprise the suffix and the method 2920 proceeds from 2902 to 2926, the suffix flag is set to the second value. The suffix may be encoded so as to include one or more predictive ly encoded symbols, in a manner as described in relation to FIGs. 18 and 19. In some embodiments, a number (e.g., a maximum number) of symbols to be predictively encoded can be determined using a process such as method 2210 described in relation to FIG. 22C.

[0375] The method 2920 proceeds to 2928 from either 2924 or 2926. When the suffix flag is set to the first value, the index value is encoded in the second one or more symbols in the bit stream to be transmitted, and the suffix value is not included in the bit stream to be transmitted. One or more symbols of the index value may be predictively encoded. Predictively encoding one or more symbols of the index value may be performed in a manner similar to predictively encoding one or more symbols of the suffix value. Predictively encoding a suffix value is described above in relation to FIGs. 18-19 and 22C above.

[0376] When the suffix flag is set to the second value, the suffix is encoded in the bit stream to be transmitted. The suffix is encoded by predictively encoding at least one of the symbols of the suffix. Predictively encoding one or more symbols of the suffix may be performed in a manner described above in relation to FIGs. 18-19 and 22C.

[0377] The suffix flag may or may not be entropy encoded. Entropy encoding of the suffix flag may include predicting a value of the suffix flag, and encoding an indication whether or not the prediction is correct. For example, if the prediction is correct, a value of 0 is encoded as the indication, and if the prediction is incorrect, a value of 1 is encoded as the indication.

[0378] Thus, the bit stream to be transmitted would comprise the prefix and the suffix flag, followed by the suffix (if the suffix flag value is the second value) or the index value (if the suffix flag has the first value). The prefix, the suffix flag, the suffix or the index value, may each have one or more of its symbols entropy encoded.

[0379] The bit stream encoded according to method 2920 may be transmitted to a decoder and / or stored for future use.

[0380] FIG. 30A shows a method 3000 for determining the suffix when the suffix flag (e.g., 2802) has a first value indicating that the suffix is to be derived using a derived candidate indicated by the derivation index (e.g., 2804, 2808, etc.). For example, method 3000 may be performed at 2906 described above in relation to FIG. 29A and / or at 2924 of FIG. 29B.

[0381] Method 3000 may begin (oval symbol) when the decoder determines the suffix flag value is the first value, and the prefix of the magnitude of the BVD has been determined. At 3002, a search is performed in at least one reference area within the current picture in which the current block is located for at least one candidate block corresponding to the current block. The one or more reference areas to be searched are determined according to at least the value of the prefix of the magnitude. For example, a range of possible values for the suffix can be determined based on the value of the prefix. One or more other aspects of the BVD, such as, for example, the sign of the magnitude can also be used to determine the one or more reference areas. Further details of the search are provided in relation to 2206 of FIG. 22A and also in relation to FIGs. 22D and 3 OF described above.

[0382] At 3004, based on the value of the derivation index, one of the one or more candidate blocks are selected. The one or more candidate blocks may be arranged in accordance with a respective difference (e.g., SAD, etc.) with the current block calculated for each. This way the decoder will know the index position as was determined by the encoder. For example, BVD information of a predetermined number of candidate blocks that have the lowest differences may be temporarily stored in memory. They may be stored in a predetermined ordering, such as, for example, from lowest difference to highest or vice versa. Then, the derivation index is used to select the BVD information and / or the candidate block in the ordering (e.g., in the ordered collection) that is at the position corresponding to the value of the derivation index. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD information by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 30F.

[0383] At 3006, the suffix is determined based on the selected BVD information and / or the candidate block. For example, a prefix and a suffix can be calculated for the selected BVD information in accordance with Table 3 above.

[0384] FIG. 30B shows a method 3010 for determining the suffix when the value of the suffix flag (e.g., 2802) is the second value indicating that the suffix is encoded in a second one or more symbols in the received bit stream. For example, method 3010 may be performed at 2908 of FIG. 22A.

[0385] At 3012, decoding of the second one or more symbols, including at least one context- coded symbol and at least one bypass-coded symbol, is initiated.

[0386] At 3014, one or more predicted values corresponding to each context-coded symbol in the second one or more symbols and one or more values corresponding to each bypass-coded symbol in the second one or more symbols are obtained. Then, for each context-coded symbol, based on the value of the indication of the prediction encoded in the received bit stream and the prediction, the value of the predictively encoded symbol is determined. In example embodiments, the sign of the BVD may be context-coded in the received bit stream and may comprise a horizontal component of the sign a vertical component of the sign. The sign components can be decoded similarly to the that manner described in relation to FIG. 19D.

[0387] At 3016, determining the suffix based on the one or more predicted values and the one or more values corresponding to each bypass-coded symbol in the second one or more symbols. An example of determining the suffix based on context-coded symbols and bypass-coded symbols is described above, for example, in relation to 2208 of FIG. 22A and FIG. 18D above. FIG. 30C and FIG. 30D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0388] FIG. 30C illustrates a method 3020 for determining the derivation index value to be encoded when the suffix flag is set to the first value. Method 3020 may be performed, for example, during 2924 described above in relation to FIG. 29B.

[0389] Method 3020 may begin at 3022 when the encoder has received a BVD to be encoded into a second one or more symbols on a bit stream to be transmitted. The sign, prefix and suffix are known by the encoder based on the received BVD. At 3022 the encoder proceeds to simulate a search that would be performed by the decoder in order to find the best matching candidate BVD that can be found by the decoder. At 3022, at least one reference area within the picture in which the current block is located is searched for at least one candidate block corresponding to the current block. The at least one reference area to search is determined according to at least a value of the prefix and all possible values of the suffix determined in accordance with the value of the prefix. The correspondence of each of the candidate blocks to the current block can be determined according to a calculated difference for each candidate block. The difference may be calculated based on, for example, a template matching. An example of determining at least one reference area and searching the at least one reference area is described in relation to 2206 in FIG. 22A and FIG. 22D.

[0390] At 3024, an ordered collection is formed of the at least one candidate blocks. The ordering may be in accordance with the differences, and may include the BVD information for a predetermined number of candidate blocks with the lowest differences with the current block. For example, the ordering may arrange the BVD information according to the respective differences. The BVD information of a candidate block may include one or more of a BVD candidate defined for the candidate block, the calculated difference for the candidate block, a suffix value for the candidate blocks, etc. The ordering may, for example, be from lowest to highest difference or vice versa.

[0391] One of the BVD information is selected from the ordered collection based on which BVD most closely matches the BVD that is to be encoded. In some instances the BVD information with the minimum calculated difference is also the BVD that mostly matches the BVD to be transmitted. In some other instances, a BVD information other than the one with the minimum difference is the BVD is selected, for example, the BVD information may be selected based on the template matching cost and an associated RD optimization score.

[0392] At 3026, the derivation index value is determined based on the ordered collection. The derivation index value identifies the selected suffix or suffix information. For example, the derivation index value may specify the position of the selected suffix or suffix information in the ordered collection. Subsequently, the derivation index value is encoded in the bit stream to be transmitted. In this embodiment, neither the suffix nor other suffix information is encoded in the bit stream to be transmitted. Forming the ordered collection of candidate blocks and determining the derivation index are described in further detail in relation to FIG. 30E. FIG. 30D illustrates a method 3030 for encoding the suffix when the suffix flag is set to the second value. Method 3030 may be performed, for example, during 2928 described above in relation to FIG. 29B.

[0393] Method 3030 may begin at 3032. At 3032, for encoding the suffix in the second one or more symbols in the bit stream to be transmitted, a first set of symbols of the suffix is determined to be context encoded. A process such as that described in relation to FIG. 22C above can be used to determine the number of suffix symbols to be predictively encoded.

[0394] At 3034, a predicted value for each symbol in the first set is determined. In example embodiments, the predicted value for each symbol may be determined separately for a sign component in the horizontal direction of the BVD and for a sign component in the vertical direction of the BVD.

[0395] At 3036, each symbol in the first set is entropy encoded by encoding an indication of whether the prediction is correct (i.e., the predicted value matches the actual value) or incorrect (i.e., the predicted value does not match the actual value). A value of 0 in the symbol may indicate the prediction is correct, and a value of 1 may indicate that the prediction is incorrect. The remainder of the symbols of the suffix are encoded in the bypass mode. Encoding a suffix with at least some context-coded symbols is described in relation to 2208 in FIG. 22B.

[0396] FIGs. 30E and 30F illustrate flowcharts of a process for encoding and a process for decoding, respectively, a BVD suffix when the suffix flag (e.g., 3102) has a first value indicating that the suffix is not to be, or is not, included in the transmitted bit stream.

[0397] FIG. 30E illustrates a process 3040 comprising operations 3041-3045 to be performed to find the rate distortion (RD)-optimal template position for the template matching search process on the encoder such as encoder 200 in FIG. 2 in accordance with some embodiments. An example template matching search, and a technique for determining the search area (reference area) based on the BVP and the BVD prefix, or based on the BVP, BVD prefix and sign hypotheses, was described in relation to FIG. 22D. At operation 3041, template matching cost values for a plurality of candidate reference blocks are obtained by using a template matching search with a search area that is based on the BVD prefix, BVP, and in some embodiments, respective sign hypotheses, as described in relation to FIG. 22D. Candidate reference blocks can be determined within the search area based on a pixel-by-pixel evaluation or according to a predetermined pattern of search. At operation 3042, a predetermined number of candidate reference blocks that have the smallest template matching costs with the current block may be selected from the initially determined set of candidate reference blocks. At operation 3043, the selected predetermined number of candidate reference blocks (or the corresponding template positions) are sorted according to their respective template matching costs. Sorting may be performed to enable the candidate reference blocks (or template positions) with the smallest template matching costs have the smallest index values. Since the smallest cost candidates are more likely to be selected, the smallest indices are more likely to be transmitted and therefore can be more efficiently context-coded. At operation 3044 RD- optimization is performed to select the best candidate reference block (or equivalently, the best template position). RD-optimization allows consideration of the signaling overhead etc., in addition to the template matching costs of the respective options. At operation 3046, an index p that identifies the selected best candidate block (or the best template position) among the sorted candidate reference blocks (or sorted template positions) is transmitted. In example embodiments, one of a plurality of types of codes (e.g., truncated unary code, exponential Golomb code, etc.) can be used to signal the index p. All or some bins of the selected code can be context-coded using CABAC.

[0398] FIG. 3 OF illustrates a process 3050 comprising operations 3051-3055 to be performed to derive a reference block BV on a decoder such as decoder 300 in FIG. 3 in accordance with some embodiments. At operation 3051, the index p, which indicates a position within a ordered list of candidate reference blocks (or corresponding template positions), is parsed from the received bit stream. At operation 3052, template matching cost values for a plurality of candidate reference blocks are obtained by using a template matching search with a search area that is based on the BVD prefix, BVP, and in some embodiments, respective sign hypotheses. Candidate reference blocks can be determined within the search area based on a pixel-by-pixel evaluation or according to a predetermined pattern of search. This search process may be identical or similar to the corresponding search described above in relation to process 3040. At operation 3053, a predetermined number of candidate reference blocks that have the smallest template matching costs with the current block may be selected from the initially determined set of candidate reference blocks. At operation 3054, the selected predetermined number of candidate reference blocks (or the corresponding template positions) are sorted according to their respective template matching costs. As noted above, sorting may be performed to enable the candidate reference blocks (or template positions) with the smallest template matching costs have the smallest index values. Since the smallest cost candidates are more likely to be selected, the smallest indices are more likely to be transmitted and therefore can be more efficiently context-coded. At operation 3055, the index p is used to select the candidate reference block (or equivalently the template position) in the corresponding position in the sorted candidate reference blocks (or sorted template positions) and the BVD suffix and the BV is determined based on the selection. Note that, as described above in relation to process 3040 at the encoder, the index p may indicate the option that is determined to be the best (e.g., most optimal) based on template matching costs and RD-optimization.

[0399] Both FIG. 30E and FIG. 3 OF provide a 2-step technique of obtaining the list of predetermined number, N, of candidates with the lowest template matching costs sorted. Since the overall number M of candidate template positions that are obtained at operations 3041 or 3052 can be significantly greater than N, sorting the overall set that contains template matching costs for all M template positions may incur a high overhead. For example, the complexity of such a sort operation can be estimated as O(M logM). To reduce the worst-case complexity of the sort operation, the process can be split into 2 steps: Selection of N template positions with lowest template matching costs from M candidate positions (this has linear complexity, i.e. O(M)); and Sorting of N template positions with lowest template matching costs (this has complexity of O(N logN)). FIG. 31 illustrates a representation of BVD magnitude that is similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure. In FIG. 31 the suffix flag is preceded by one or more sign or sign hypothesis symbols. A horizontal prefix and hypothesis on horizontal sign are conditionally signaled based on the value of a magnitude greater than 0 flag horizontal component (“context-coded abs hor bvd grcatcrO flag" in FIG. 31). Vertical prefix and hypothesis on vertical sign are conditionally signaled based on the value of magnitude greater than 0 flag vertical component (“context-coded abs vcr bvd grcatcrO flag" in FIG. 31).

[0400] The representation shown in FIG. 31 includes a suffix flag 3102 that has the first value when the suffix is not encoded in the bit stream and instead a derivation index value 3104 is encoded. When the suffix flag 3102 has the second value, the suffix is encoded in two components - a horizontal component 3106 of the suffix and a vertical component 3108 of the suffix.

[0401] A sign for a horizontal component of the suffix (referred to as first sign component) 3110 and a sign for a vertical component of the suffix (referred to as second sign component) 3112 are encoded preceding the suffix flag 3102.

[0402] A horizontal prefix 3114 and a vertical prefix 3116 are encoded preceding the sign components 3110 and 3112 and / or the suffix flag 3102. A magnitude greater than 0 flag horizontal component 3118 and a magnitude greater than flag vertical component 3120 may separately indicate whether the horizontal component of the magnitude and the vertical component of the magnitude are greater than 0.

[0403] On the decoder side, when the suffix flag has the first value, the reference area for BVD candidates is determined by the result of derivation of horizontal and vertical signs, which may be performed by determination of the best-cost sign candidate sign symbols and conditionally negating horizontal or vertical sign symbol when the corresponding signaled value of hypothesis on horizontal sign or hypothesis on vertical sign is nonzero. The sign hypothesis can be any hypothesis regarding the expected value of the sign the decoder can make (and the encoder, when at its end modeling in-loop the decoding behavior), and the encoder can then communicate whether the hypothesis was going to be incorrect (i.e. an a different more atypical situation occurs in the coded video data). E.g., if a number of blocks are taken from corresponding positions of a larger solid region, the vectors for predicting adjacent blocks will be the same, and so will be their signs. A prediction that the sign of the current to be decoded block’s block or motion vector will be the same as that of the previous e.g. 4 blocks is a likely hypothesis, yet, it could be that a different vector and sign needs to be used from now onwards.

[0404] After BVD sign symbols are derived, the value of suffix flag indicates whether the derivation index is used to select one of the BVD candidates that have a lowest template-matching cost, or suffix symbols are restored from the context-coded hypotheses on suffix symbols for horizontal and vertical component. In both cases, the reference area where template cost is estimated for BVD candidates is determined based on the derived sign symbol values. FIG. 32A and FIG. 32B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD that is encoded in a representation such as that shown in FIG. 31 in accordance with some embodiments of this disclosure. For example, the methods of FIG. 32A and FIG. 32B receive and decode an encoded BVD of the form shown in FIG. 31 with the horizontal and vertical components of the sign followed by either the suffix flag 3102 having the first value (e.g., 1) and including a derivation index value 3104 in the second one or more symbols in the bit stream to be transmitted, or the suffix flag 3102 having the second value (e.g., 0) and including the horizontal and vertical components of the suffix in the bit stream to be transmitted.

[0405] In FIG. 32A, a method 3200 for decoding a received bit stream is illustrated for when the suffix flag is set to the first value. According to an embodiment, method 3200 can be performed during 3002 of FIG. 30A.

[0406] Method 3200 begins at 3202 when the decoder has received a BVD of the form shown in FIG. 31 in the received bit stream. At 3202, a sign of the magnitude is decoded from a third one or more symbols in the received bit stream. For example, a horizontal component of a sign and a vertical component of a sign are decoded from a third one or more symbols in the received bit stream. In some embodiments, the received sign components are context-coded. Context encoding and context decoding of sign symbols can be performed in accordance with a technique described above in relation to FIGs. 18 and 19.

[0407] At 3204, at least one reference area is determined according to at least a value of the prefix and the sign, the at least one reference area is searched for one or more candidate blocks that have lowest differences with the current block, the BVD information of the one or more candidate blocks with the lowest differences are arranged in an ordered collection, and the derivation index value from the received bit stream is used to select the BVD information of one of the candidate blocks. In an embodiment, a plurality of reference areas are determined according to at least a value of the prefix and possible value(s) of the sign, the plurality of reference areas are searched for one or more candidate blocks that have lowest differences with the current block, the BVD information of the one or more reference blocks with the lowest differences are arranged in an ordered collection, and the derivation index value from the received bit stream is used to select the BVD information of one of the candidate blocks. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD information by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 30F. The selected BVD information is used to determine the suffix.

[0408] FIG. 32B illustrates a method 3210 for decoding a received bit stream, when the suffix flag is set to the second value. Method 3210 may be performed during method 3010 of FIG. 30B.

[0409] Method 3210 begins at 3212 when the decoder has received a BVD of the form shown in FIG. 31 in the received bit stream. At 3212, the method includes decoding, from a third one or more symbols in the received bit stream, a first sign corresponding to a horizontal direction of the magnitude and a second sign corresponding to a vertical direction of the magnitude. The sign components may be context-coded. Context encoding and context decoding of sign symbols can be performed in accordance with a technique described above in relation to FIGs. 18 and 19.

[0410] At 3214, from a second one or more symbols in the received bit stream, a first component of the suffix and a second component of the suffix are decoded. The second one or more symbols include at least one context-coded symbol.

[0411] At 3216, the suffix is obtained based at least on the first sign, the first component of the suffix, the second sign, and the second component of the suffix.

[0412] FIG. 32C and FIG. 32D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD that is encoded in a representation such as that shown in FIG. 31, according to some embodiments.

[0413] FIG. 32C illustrates a method 3220 for encoding a bit stream to be transmitted, when the suffix flag is set to the first value. Method 3220 may be performed during 3020 of FIG. 30C.

[0414] Method 3220 begins at 3222 when the encoder has received a BVD to be transmitted. The BVD may be transmitted in a form similar to that shown in FIG. 31.

[0415] At 3222, the sign of the magnitude is to be encoded in the third one or more symbols in the bit stream to be transmitted. A first sign corresponding to a horizontal direction of the magnitude and a second sign corresponding to a vertical direction of the magnitude are determined from the received BVD.

[0416] At 3224, the first sign and the second sign are context-coded in a third one or more symbols in the bit stream to be transmitted the sign. Context encoding and context decoding of sign symbols can be performed in accordance with a technique described above in relation to FIGs. 18 and 19.

[0417] FIG. 32D illustrates a method 3230 for encoding a bit stream to be transmitted, when the suffix flag is set to the second value, according to some embodiments. Method 3230 may be performed during 3030 of FIG. 30D.

[0418] Method 3230 begins at 3232 when the encoder has received a BVD to be transmitted. The BVD may be transmitted in a form similar to that shown in FIG. 31.

[0419] At 3232, a horizontal component of the prefix, a vertical component of the prefix, a horizontal component of the suffix, a vertical component of the suffix, a first sign, and a second sign, wherein the first sign is a sign of the horizontal component of the magnitude and the second sign is a sign of the vertical component of the magnitude, are determined based on the received BVD. The prefix components are encoded in a first one or more symbols in the bit stream to be transmitted.

[0420] At 3234 the first component of the suffix and the second component of the suffix are encoded to a second one or more symbols, wherein the second one or more symbols includes the at least one context-coded symbol. In some embodiments, the second one or more symbols also include one or more bypass-coded symbols. At 3236 the first sign and the second sign are encoded in a third one or more symbols in the bit stream to be transmitted. The first sign corresponds to a horizontal direction of the magnitude and the second sign corresponds to a vertical direction of the magnitude. The sign components may be context-coded. Context encoding and context decoding of sign symbols can be performed in accordance with a technique described above in relation to FIGs. 18 and 19.

[0421] Subsequent to method 3220 or 3230, the encoded BVD to be transmitted may be of the form shown in FIG. 31 with the horizontal and vertical components of the sign followed by either the suffix flag 3102 having the first value (e.g., 1) and including a derivation index value 3104 in the second one or more symbols in the bit stream to be transmitted, or the suffix flag 3102 having the second value (e.g., 0) and including the horizontal and vertical components of the suffix.

[0422] FIG. 33 illustrates another representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure. In FIG. 33, hypotheses on horizontal and vertical sign components are conditionally signaled in the bitstream depending on the value of the suffix flag. When the suffix flag is non-zero, the values of signs are not signaled in the bitstream, but are determined from the candidate indicated by the signaled derivation index value. In this case, a search area for BVD candidates comprises 2 or 4 non-adjacent reference areas, each of the reference areas corresponds to a combination of signs of the restored horizontal or vertical BVD. Determining a reference area based on prefix and suffix is described above in relation to FIG. 22A. When the suffix flag is zero, the values of hypotheses on horizontal and vertical signs are signaled in the bitstream. Restoration of the BVD in this case is the same as in embodiment shown in FIG. 31.

[0423] The representation shown in FIG. 33 includes a suffix flag 3302 that has the first value when the suffix is not encoded in the bit stream and instead a derivation index value 3304 is encoded. When the suffix flag 3302 has the second value, the suffix is encoded in two components - a horizontal component 3306 of the suffix and a vertical component 3308 of the suffix.

[0424] A sign for a horizontal component of the suffix (referred to as first sign component) 3310 and a sign for a vertical component of the suffix (referred to as second sign component) 3312 are encoded following the suffix flag 3302.

[0425] A horizontal prefix 3314 and a vertical prefix 3316 are encoded preceding the sign components 3310 and 3312 and / or the suffix flag 3302. A magnitude greater than 0 flag horizontal component 3318 and a magnitude greater than 0 flag vertical component 3320 may separately indicate whether the horizontal component of the magnitude and the vertical component of the magnitude are greater than 0.

[0426] FIG. 34A and FIG. 34B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD that is the form shown in FIG. 33, in accordance with some embodiments of this disclosure.

[0427] FIG. 34A illustrates a method 3400 for determining the suffix when the value of the suffix flag is set to a first value. When, for example, the suffix flag 3302 of the BVD shown in FIG. 33 has the first value of 1, the suffix flag 3302 is followed by the derivation index value 3304 and no sign is signaled. According to some example embodiments, method 3400 can be used performed during 3002 of FIG. 30A.

[0428] Method 3400 begins at 3402 when the decoder has received a BVD in the received bit stream. At 3402, since when the suffix flag value is the first value the derivation index value is signaled without a sign of the magnitude being signaled, the reference areas in which the candidate blocks are searched for are configured based on the prefix and on possible values of sign. In some embodiments, two disjoint reference areas may be determined based on the prefix and positive and negative sign values, and in some embodiments 4 disjoint areas may be identified based on, in addition to the prefix, positive and negative values for each sign component (e.g., horizontal sign component and vertical sign component). The 2 or 4 disjoint reference areas are searched for one or more candidate blocks with the lowest differences. In some embodiments, the differences may be determined based on template matching. The BVD information of one or more candidate blocks with the lowest differences may be arranged in an ordered collection.

[0429] At 3404 the derivation index value from a second one or more symbols in the received bit stream is used to select the BVD information of one of the one or more candidate blocks. The BVD information of the selected candidate block is used to determine the suffix of the received BVD. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD information by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 3 OF. Since the candidate is selected while also taking account of both sign values of the BVD, the sign of the received BVD may also be determined based on the selected candidate block.

[0430] FIG. 34B illustrates a method 3410 for determining the suffix when the value of the suffix flag is set to a second value in a received BVD of the form shown in FIG. 33. When, for example, the suffix flag 3302 of the BVD shown in FIG. 33 has the second value of 0, the suffix flag 3302 is followed by the horizontal and vertical components of the sign (3310 and 3312) and by the horizontal and vertical components of the suffix (3306 and 3308). According to some example embodiments, method 3400 can be used performed during 3002 of FIG. 30A. According to some example embodiments, method 3410 can be used performed during 3012 of FIG. 30B.

[0431] Method 3410 begins at 3412 when the decoder has received a BVD in the received bit stream. At 3412, the suffix flag value is set to the second value and the derivation index value is received in the bit stream preceded by horizontal and vertical components of a sign of the magnitude being signaled in a third one or more symbols. The sign components may be context-coded. At 3412 the sign components are decoded.

[0432] At 3414, the horizontal component of the suffix and the vertical component of the suffix are decoded. Each of the components of the suffix may include one or more context-coded symbols. In some embodiments each of the suffix components may also include one or more bypass-coded symbols. FIG. 34C and FIG. 34D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD to be in the form shown in FIG. 33, in accordance with some embodiments of this disclosure.

[0433] FIG. 34C illustrates a method 3430 for encoding a bit stream to be transmitted, when the suffix flag is set to the first value. Method 3430 may be performed during 3020 of FIG. 30C.

[0434] Method 3430 begins at 3432 when the encoder has received a BVD to be transmitted in the form is shown in FIG. 33. At 3432, when the suffix flag is set to the first value, as seen in FIG. 33, the derivation index is encoded without a sign. Accordingly, the derivation index is encoded in the bit stream to be transmitted. One or more symbols of the derivation index can be context-coded in some embodiments. The symbols that are not context-coded are bypass-coded. Further details of determining a derivation index for determining the suffix where the derivation index is used to indicate a candidate reference block in an ordered set of candidate reference blocks in a reference area are described in relation to FIGs. 22D and 30E.

[0435] FIG. 34D illustrates a method 3440 for encoding a BVD to be transmitted, when the suffix flag is set to the second value. Method 3440 may be performed during 3030 of FIG. 30D.

[0436] Method 3440 begins at 3442 when the encoder has received a BVD to be transmitted. At 3442, a horizontal component of the sign and a vertical component of the sign of the magnitude of the BVD are determined based on the received BVD to be transmitted.

[0437] At 3444, the horizontal component and the vertical component of the sign are encoded as respective context-coded symbols in a third one or more symbols in the bit stream to be transmitted.

[0438] At 3446, the horizontal component of the suffix and the vertical component of the suffix are encoded respectively. Each component of the suffix includes at least one context-coded symbol and may include one or more bypass-coded symbols.

[0439] Methods 3430 and 3440 encode a BVD to be in the form shown in FIG. 33. When, for example, the suffix flag 3302 of the BVD shown in FIG. 33 has the first value of 1, the suffix flag 3302 is followed by the derivation index value 3304 and no sign is signaled. When the suffix flag 3302 of the BVD shown in FIG. 33 has the second value of 0, the suffix flag 3302 is followed by the horizontal and vertical components of the sign (3310 and 3312) and by the horizontal and vertical components of the suffix (3306 and 3308).

[0440] FIG. 35 illustrates another representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure. In FIG. 35, hypotheses on horizontal and vertical signs are indicated together with corresponding horizontal and vertical suffix bins. In this embodiment, as well as in embodiment shown in FIG. 33, depending on horizontal and vertical prefix value, for horizontal or vertical components both sign and suffix symbols may be bypass-coded.

[0441] The representation shown in FIG. 35 (which is similar to Fig. 33, but now the sign is included in the magnitude coding instead of separate) includes a suffix flag 3502 that has a first value when the suffix is not encoded in the bit stream and instead a derivation index value 3504 is encoded. When the suffix flag 3502 has a second value, the suffix is encoded in two components - a horizontal component 3506 of the suffix and a vertical component 3508 of the suffix. A sign for the horizontal component of the suffix (referred to as first sign component) 3510 is encoded with the horizontal component of the suffix 3506, and a sign for the vertical component of the suffix (referred to as second sign component) 3512 is encoded with the vertical component of the suffix 3508.

[0442] A horizontal prefix 3514 and a vertical prefix 3516 are encoded preceding the suffix flag 3502. A magnitude greater than 0 flag horizontal component 3518 and a magnitude greater than 0 flag vertical component 3520 may separately indicate whether the horizontal component of the magnitude and the vertical component of the magnitude are greater than 0.

[0443] FIG. 36A and FIG. 36B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD that in in the form shown in FIG. 35, in accordance with some embodiments of this disclosure.

[0444] FIG. 36A illustrates a method 3600 for determining the suffix when the value of the suffix flag is set to a first value. When, for example, the suffix flag 3502 of the BVD shown in FIG. 35 has the first value of 1, the suffix flag 3502 is followed by the derivation index value 3504 and no sign is signaled. According to some example embodiments, method 3600 can be performed during 3002 of FIG. 30A.

[0445] Method 3600 begins at 3602 when the decoder has received a BVD in the received bit stream. At 3602, since when the suffix flag value is the first value the derivation index value is signaled without a sign of the magnitude being signaled, the reference areas in which the candidate blocks are searched for are configured based on the prefix and on possible values of sign. In some embodiments, two disjoint reference areas may be determined based on the prefix and positive and negative sign values, and in some embodiments 4 disjoint areas may be configured based on, in addition to the prefix, positive and negative values for each sign component (e.g., horizontal sign component and vertical sign component). The 2 or 4 disjoint reference areas are searched for one or more candidate blocks with the lowest differences. In some embodiments, the differences may be determined based on template matching. The BVD information of one or more candidate blocks with the lowest differences may be arranged in an ordered collection.

[0446] At 3604 the derivation index value from a second one or more symbols in the received bit stream is used to select the BVD information of one of the one or more candidate blocks. The BVD information of the selected candidate block is used to determine the suffix of the received BVD. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD information by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 3 OF. Since the candidate is selected while also taking account of both sign values of the BVD, the sign of the received BVD may also be determined based on the selected candidate block. FIG. 36B illustrates a method 3610 for determining the suffix when the value of the suffix flag is set to a second value. When, for example, the suffix flag 3502 of the BVD shown in FIG. 35 has the second value of 0, the suffix flag 3502 is followed by the horizontal component of the sign 3510 and the horizontal component of the suffix 3506 followed by the vertical components of the sign 3512 and the vertical components of the suffix 3508. According to some example embodiments, method 3610 can be used performed during 3012 of FIG. 30B.

[0447] Method 3610 begins at 3612 when the decoder has received a BVD in the received bit stream. At 3612, the suffix flag value is set to the second value and the derivation index value is received in the bit stream with each suffix component also including the corresponding sign component encoded therewith. That is, the horizontal component of the sign is signaled with the horizontal component of the suffix and the vertical component of a sign is signaled with the vertical component of the suffix. In some example embodiments, the sign components and at least some symbols of each of the suffix components may be context-coded. At 3612 the sign components are decoded.

[0448] At 3614, the horizontal component of the suffix and the vertical component of the suffix are decoded. In some embodiments, in addition to the one or more context-coded symbols, each component may have one or more bypass-coded symbols.

[0449] FIG. 36C and FIG. 36D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0450] FIG. 36C illustrates a method 3620 for encoding a bit stream to be transmitted, when the suffix flag is set to the first value. Method 3620 may be performed during 3020 of FIG. 30C.

[0451] Method 3620 begins at 3622 when the encoder has received a BVD to be transmitted. At 3622, when the suffix flag is set to the first value, as seen in FIG. 35, the derivation index is encoded without a sign. Accordingly, the derivation index is encoded in the bit stream to be transmitted. One or more symbols of the derivation index can be context-coded in some embodiments. The symbols that are not context-coded are bypass-coded. Further details of determining the derivation index for determining the suffix where the derivation index is used to indicate a candidate reference block in an ordered set of candidate reference blocks in a reference area are described in relation to FIGs. 22D and 30E.

[0452] FIG. 36D illustrates a method 3630 for encoding a bit stream to be transmitted, when the suffix flag is set to the second value. Method 3630 may be performed during 3030 of FIG. 30D.

[0453] Method 3630 begins at 3632 when the encoder has received a BVD to be transmitted. At 3632, a horizontal component of the sign and a vertical component of the sign of the magnitude of the BVD are determined based on the BVD.

[0454] At 3634, a first set of symbols comprising the first component of the sign and a first component of the suffix and a second set of symbols comprising the second sign and a second component of the suffix are encoded in the second one or more symbols in the bit stream to be transmitted. The first component corresponds to the horizontal direction of the magnitude and the second component corresponds to the vertical direction of the magnitude. The sign may be context-coded in some embodiments. Each component of the suffix includes at least one context-coded symbol and may include one or more bypass-coded symbols.

[0455] Methods 3620 and 3630 encode a BVD to be in the form shown in FIG. 35. When, for example, the suffix flag 3502 of the BVD shown in FIG. 35 has the first value of 1, the suffix flag 3502 is followed by the derivation index value 3504 and no sign is signaled. When the suffix flag 3502 of the BVD shown in FIG. 35 has the second value of 0, the suffix flag 3502 is followed by the horizontal components of the sign and suffix (3510 and 3506) followed by the vertical components of the sign and suffix (3512 and 3508).

[0456] FIG. 37 illustrates a further representation of BVD magnitude similar to FIGs. 29A-29B in accordance with some embodiments of this disclosure. In these embodiments the decoder uses a derivation index that is included in the bit stream to determine for which of the BVD components a suffix is determined, and for which of the components some of the suffix bins are signaled.

[0457] In the representation shown in FIG. 37, the suffix flag 3702 that has a first value when the suffix is not encoded in the bit stream and instead a derivation index value 3704 is encoded. When the suffix flag 3702 has a second value, the suffix is encoded in two components - a horizontal component 3706 of the suffix and a vertical component 3708 of the suffix.

[0458] A sign for a horizontal component of the suffix (referred to as first sign component) 3710 and a sign for a vertical component of the suffix (referred to as second sign component) 3712 are encoded preceding the suffix flag 3702.

[0459] A horizontal prefix 3714 and a vertical prefix 3716 are encoded preceding the sign components 3710 and 3712 and / or the suffix flag 3702. A magnitude greater than 0 flag horizontal component 3718 and a magnitude greater than 0 flag vertical component 3720 may separately indicate whether the horizontal component of the magnitude and the vertical component of the magnitude are greater than 0.

[0460] The representation in FIG. 37 also includes a derivation component selection index 3722 that follows the suffix flag 3702 when the suffix flag has the first value. The derivation component selection index 3722 indicates whether the derivation index value is specified as a single index value 3704 or as two components. When specified as two components, it includes an index value for horizontal 3718 and an index value for vertical 3720. The derivation component selection index 3722 may specify the ordering of the two components 3718 and 3720.

[0461] In the embodiment based on the BVD representation similar to FIG. 37, when suffix flag 3702 has the second value, the suffix symbols of both BVD components are included in the bit stream. When the suffix flag 3702 has the first value, the derivation components selection index 3722 is signaled, for example, using an unary code. This codeword may indicate the following cases: both components’ suffixes are determined using derivation index (codeword “1”); suffix of horizontal component is determined using a derivation index and suffix of vertical component is signaled with suffix bin prediction (codeword “00”); or suffix of vertical component is determined using a derivation index and suffix of horizontal component is signaled with suffix bin prediction (codeword “01”).

[0462] The steps to determine sign symbols depends on the values of the suffix flag 3702 and the derivation components selection index 3722. When the suffix flag has the second value, hypotheses on sign bins are indicated in a bitstream together with suffix symbols. As described above in relation to embodiments of FIGs. 31, 33 and 35, sign symbols can be either bypass-coded in the bit stream or corresponding hypotheses bins can be indicated.

[0463] In an example embodiment, when the derivation components selection index 3722 is equal to “00” or “01”, the derivation index is indicated for one suffix component (e.g., 3718) and is followed by sign and suffix bins for the other suffix component (e.g., 3720). For example, when the derivation components selection index is signaled as “00”, a derivation index for the horizontal component of the suffix is indicated in the bit stream, and after this indication, sign and suffix symbols for the vertical component are signaled. All of these sign and suffix symbols for the vertical component may be included in the bit stream or some of the symbols may be predicted and corresponding hypotheses on the symbol values are signaled instead of the symbol values. In this example, when derivation components selection index 3722 is signaled as “01”, a derivation index for the vertical component is indicated, and after this indication, sign and suffix symbols for the horizontal component are signaled. All of these sign and suffix symbols for the horizontal component can be signaled on the bit stream or some of the symbols may be predicted and corresponding hypotheses on the symbol values can be signaled instead of the symbol values.

[0464] FIG. 38A and FIG. 38B illustrate flowcharts of aspects of the method in FIG. 29A for decoding a BVD that is the form shown in FIG. 37, in accordance with some embodiments of this disclosure.

[0465] FIG. 38A illustrates a method 3800 for determining the suffix when the suffix flag is set to the first value. When the suffix flag is set to a value of 1, the received BVD includes a derivation component selection index 3722 that follows the suffix flag 3702, and depending on the value of the derivation component selection index 3722, either a derivation index 3704 for the suffix or alternatively a derivation index 3718 for one of the horizontal or vertical component of the suffix and symbols of the other component 3720 of the suffix. The method 3800 starts when a BVD has been received in a received bit stream at 3802.

[0466] At 3802, the derivation component selection index is decoded from the second one or more symbols in the received bit stream.

[0467] At 3804, based on the value of the derivation components selection index, either one derivation index or a derivation index and a component of the suffix are decoded from the second one or more symbols. For example, when the derivation components selection index is set to 1, it indicates that the derivation index that follows is the derivation index for the suffix; when the derivation components selection index is set to 00 and 01, it indicates that the derivation index that follows is the derivation index for either the horizontal component or vertical component of the suffix and that it is followed by the other of the horizontal component or vertical component of the suffix together with the corresponding sign component.

[0468] At 3806, one or more candidate blocks are determined by searching one or more reference areas and the one or more candidate blocks are arranged in an ordered collection. The candidate blocks may be arranged in the order of differences with the current block as determined by a technique such as the template matching described in relation to FIGs. 18 and 19 above. The derivation index is used to access the ordered collection to obtain the BVD information of a selected candidate block. When the derivation component selection index has a value of 1 in the above example, then the derivation index is intended to select the BVD information for the entire suffix, and when the derivation component selection index has either 01 or 00 as its value, then the derivation index is intended to select the BVD information for just one component of the suffix.

[0469] In some embodiments, determining the one or more reference areas includes, determining a plurality of reference areas based on the prefix and possible values for the sign (positive and negative, in the horizontal and vertical directions), searching the plurality of reference areas for candidate blocks that have lowest differences with the current block, and arranging the candidate blocks (or corresponding BVD information such as the suffix or suffix information corresponding to the candidate blocks) that have the lowest differences according to an ordering, and selecting a candidate block based on the derivation index value.

[0470] When the derivation index (e.g., 3722) is the derivation index for the entire suffix (e.g., derivation index 3704), as can be seen in FIG. 37, the received bit stream does not include the sign of the BVD. Thus, the searching includes searching a plurality of reference areas that are determined based on the prefix and on all values of the sign. When the derivation index (e.g., 3722) is the derivation index for a component of the suffix (e.g., 3720), the component of the suffix that is included in the received bit stream includes a sign (e.g., 3721) in the direction of that component.

[0471] In these example embodiments, when the suffix flag value is the first value and the derivation component selection index indicates a presence of derivation index either for the horizontal component of the suffix or for the vertical component of the suffix, the reference area to determine candidates for the component indicated with derivation index may be defined as follows: The value of the other component which is not indicated using derivation index is set to a predetermined constant value (e.g., 0), or in another example, the value of the maximum suffix value that could be indicated for the signaled prefix value divided by 2; and a set of candidates is defined in such a way that the set comprises candidates with different combinations of signs for the component indicated using derivation index. The maximum absolute value of this component for a candidate belonging to this set is determined by the indicated value of the prefix for this component. When determining the values of the symbols of the component that is not indicated with derivation index, the search range for suffix and sign symbol prediction is defined in such a way that all candidates have one of the components equal to the component indicated with derivation index.

[0472] At 3808, selecting, using the derivation index value encoded in the second one or more symbols, one of the candidate blocks, and determining the suffix based on the selected candidate block. As noted above, the derivation index identifies one of the candidates which are ordered in accordance with their template matching cost. Further details of an example process for searching one or more reference areas for candidate reference blocks and determining the BVD suffix or suffix component by using the derivation index to select a candidate reference block are described in more detail in relation to FIGs. 22D and 3 OF.

[0473] FIG. 38B illustrates a method 3810 for determining the suffix when the value of the suffix flag is set to the second value. When, for example, the suffix flag 3702 is set to the second value 0, the suffix flag is followed by the one of the horizontal or vertical components of the sign and suffix followed by the other of the horizontal or vertical components of the sign and suffix (e.g., 3710 and 3706 followed by 3712 and 3708). According to some example embodiments, method 3810 can be performed during 3012 of FIG. 30B.

[0474] Method 3810 begins at 3812 when the decoder has received a BVD in the received bit stream. At 3812, the suffix flag value is set to the second value and the derivation index value is received in the bit stream with each suffix component also including the corresponding sign component encoded therewith. That is, the horizontal component of the sign is signaled with the horizontal component of the suffix and the vertical component of a sign is signaled with the vertical component of the suffix. In some example embodiments, the sign components and at least some symbols of each of the suffix components may be context-coded. At 3812 the sign components are decoded.

[0475] At 3814, the horizontal component of the suffix and the vertical component of the suffix are decoded. In some embodiments, in addition to the one or more context-coded symbols, each component may have one or more bypass-coded symbols.

[0476] FIG. 38C and FIG. 38D illustrate flowcharts of aspects of the method in FIG. 29B for encoding a BVD in accordance with some embodiments of this disclosure.

[0477] FIG. 38C illustrates a method 3830 when the suffix flag is set to a first value. The method 3830 starts at 3832. At 3832, when the value of the suffix flag is the first value, a derivation components selection index (e.g., derivation component selection index in FIG. 37) is encoded in a second one or more symbols of in the bit stream to be transmitted.

[0478] The value of the derivation components selection index is set in accordance with whether the second one or more symbols will also include just a derivation index (e.g., the derivation index 3704) for the suffix, or the derivation index (e.g., derivation index for one of horizontal or vertical component 3718 shown in FIG. 37) for one of horizontal or vertical component of the suffix and the suffix for the other of the horizontal or vertical component (e.g., 3720). The suffix component may be encoded with the corresponding sign component. For example, when the derivation components selection index is set to 1, it indicates that the derivation index that follows is the derivation index for the suffix; when the derivation components selection index is set to 00 and 01, it indicates that the derivation index that follows is the derivation index for either the horizontal component or vertical component of the suffix and that it is followed by the other of the horizontal component or vertical component of the suffix together with the corresponding sign component.

[0479] At 3834, in accordance with the value of the derivation components selection index, either the derivation index for the entire suffix, or the derivation index for one of the horizontal component or vertical component of the suffix and the symbols of the other of the horizontal component or vertical component of the suffix are encoded. The component of the suffix may be encoded together with the corresponding sign component (e.g., horizontal component of the sign 3710 with the horizontal component of the suffix 3706, and vertical component of the sign 3712 with the vertical component of the suffix 3708 shown in FIG. 37). Further details of determining the derivation index for determining the suffix where the derivation index is used to indicate a candidate reference block in an ordered set of candidate reference blocks in a reference area are described in relation to FIGs. 22D and 30E.

[0480] FIG. 38D illustrates a method 3840 for encoding a bit stream to be transmitted, when the suffix flag is set to the second value. Method 3840 may be performed during 3030 of FIG. 30D.

[0481] Method 3840 begins at 3842 when the encoder has received a BVD to be transmitted. At 3842, a horizontal component of the sign and a vertical component of the sign of the magnitude of the BVD are determined based on the BVD.

[0482] At 3844, a first set of symbols comprising the first component of the sign and a first component of the suffix and a second set of symbols comprising the second sign and a second component of the suffix are encoded in the second one or more symbols in the bit stream to be transmitted. The first component corresponds to the horizontal direction of the magnitude and the second component corresponds to the vertical direction of the magnitude. The sign may be context-coded in some embodiments. Each component of the suffix includes at least one context-coded symbol and may include one or more bypass-coded symbols.

[0483] Methods 3830 and 3840 encode a BVD to be in the form shown in FIG. 37. When, for example, the suffix flag 3702 of the BVD shown in FIG. 37 has the first value of 1, the suffix flag 3702 is followed by the derivation components selection index 3722, and when the suffix flag 3702 has the second value of 0, the suffix flag 3702 is followed by the horizontal components of the sign and suffix (3710 and 3706) followed by the vertical components of the sign and suffix (3712 and 3708). When the derivation components selection index 3722 has a value of 1, the derivation components selection index 3722 is followed by a derivation index (derivation index for suffix) 3704, and when the derivation components selection index 3722 is followed by a derivation index (derivation index for first component of suffix) 3718 and suffix symbols (second component of sign 3721 and suffix 37120).

[0484] It should be further noted that the methods discussed above with respect to FIGs. 22A-D, 24A-C, 26A-B, 27A-B, 29A-B, 30A-F, 32A-D, 34A-D, 36A-D and 37 may be further applied to one or more magnitude symbols of another difference vector such as an MVD used in inter prediction in addition or alternatively to one or more magnitude symbols of a BVD used in IBC.

[0485] Embodiments of the present disclosure may be implemented in hardware using analog and / or digital circuits, in software, through the execution of instructions by one or more general purpose or special -purpose processors, or as a combination of hardware and software. Consequently, embodiments of the disclosure may be implemented in the environment of a computer system or other processing system. An example of such a computer system 3900 is shown in FIG. 39. Blocks depicted in the figures above, such as the blocks in FIGS. 1, 2, and 3, may execute on one or more computer systems 3900. Furthermore, each of the steps of the flowcharts depicted in this disclosure may be implemented on one or more computer systems 3900.

[0486] Computer system 3900 includes one or more processors, such as processor 3904. Processor 3904 may be, for example, a special purpose processor, general purpose processor, microprocessor, or digital signal processor. Processor 3904 may be connected to a communication infrastructure 3902 (for example, a bus or network). Computer system 3900 may also include a main memory 3906, such as random access memory (RAM), and may also include a secondary memory 3908.

[0487] Secondary memory 3908 may include, for example, a hard disk drive 3910 and / or a removable storage drive 3912, representing a magnetic tape drive, an optical disk drive, or the like. Removable storage drive 3912 may read from and / or write to a removable storage unit 3916 in a well- known manner. Removable storage unit 3916 represents a magnetic tape, optical disk, or the like, which is read by and written to by removable storage drive 3912. As will be appreciated by persons skilled in the relevant art(s), removable storage unit 3916 includes a computer usable storage medium having stored therein computer software and / or data.

[0488] In alternative implementations, secondary memory 3908 may include other similar means for allowing computer programs or other instructions to be loaded into computer system 3900. Such means may include, for example, a removable storage unit 3918 and an interface 3914. Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a thumb drive and USB port, and other removable storage units 3918 and interfaces 3914 which allow software and data to be transferred from removable storage unit 3918 to computer system 3900.

[0489] Computer system 3900 may also include a communications interface 3920. Communications interface 3920 allows software and data to be transferred between computer system 3900 and external devices. Examples of communications interface 3920 may include a modem, a network interface (such as an Ethernet card), a communications port, etc. Software and data transferred via communications interface 3920 are in the form of signals which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface 3920. These signals are provided to communications interface 3920 via a communications path 3922. Communications path 3922 carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link, and other communications channels.

[0490] As used herein, the terms “computer program medium” and “computer readable medium” are used to refer to tangible storage media, such as removable storage units 3916 and 3918 or a hard disk installed in hard disk drive 3910. These computer program products are means for providing software to computer system 3900. Computer programs (also called c...

Claims

CLAIMS:

1. A method of deriving a block offset vector difference ( 1810) for predicting second pixel colors of a second block of a second picture based on first pixel colors of a first block of a first picture at a position which is offset from the second block depending on the block offset vector difference and a block offset vector prediction (1808), comprising: obtaining, based on a first one or more symbols in a bitstream, at least one prefix (3514) of a magnitude of the block offset vector difference; determining at least one suffix of the magnitude based on a flag and a second one or more symbols in the bitstream, wherein the determining the suffix comprises: when a value of the flag is a first value: determining, based on the prefix, one or more candidate values for the suffix; and selecting, using an index value encoded in the second one or more symbols, one of the one or more candidate values for the suffix to use in the determination of the suffix; or when the value of the flag is a second value, determining the suffix based on at least one context-coded symbol of one or more bits of the suffix in the second one or more symbols; wherein the magnitude is based on a concatenation of the prefix and the suffix.

2. The method as claimed in claim 1, in which the second picture is the same as the first picture.

3. The method according to claim 1 or 2, wherein, when the value of the flag is the first value: searching in at least one reference area in the first picture for at least one candidate block for prediction of the second block, wherein the at least one reference area is determined according to at least a value of the prefix; if there is more than one candidate block, ordering the candidate blocks according to a degree of match of a first template around the candidate block and a corresponding second template around the second block; selecting one of the at least one candidate block based on the index value; and determining the at least one suffix based on the selected candidate block.

4. The method according to one of the above claims, in which at least one of the second one or more symbols coding the suffix in case the flag has the first value is CABAC bypass encoded.

5. The method according to one of the above claims, in which at least one of the second one or more symbols coding the suffix in case the flag has the second value is CABAC bypass encoded.

6. The method according to one of the above claims, wherein when the flag has the second value the at least one context-coded symbol is an indication of whether a prediction of a symbol matches the corresponding symbol of the block offset vector difference.

7. The method according to one of the above claims, wherein at least one of the symbols to be binarized is Golomb-encoded.

8. The method according to one of the above claims comprising at least one flag indicating whether one or more components of the suffix are zero respectively greater than zero.

9. A method of video coding, comprising:- receiving a video sequence (108);- compressing a video sequence by predicting blocks of an image of the video sequence, the compressing comprising the method of deriving a block offset vector difference (1810) as claimed in one of the above claims.

10. A method of video decoding, comprising:- receiving a compressed bitstream (110);- decoding the compressed bitstream to obtain a reconstructed video sequence, the decoding comprising the method of deriving a block offset vector difference (1810) as claimed in one of the above claims 1 to 8.

11. A video encoder (114) comprising a circuit connected to a memory, wherein the circuit is arranged to perform the method of deriving a block offset vector difference (1810) as claimed in one of the above claims 1 to 8.

12. A video decoder (120) comprising a circuit connected to a memory, wherein the circuit is arranged to perform the method of deriving a block offset vector difference (1810) as claimed in one of the above claims 1 to 8.

13. A video signal comprising a data structure comprising: encoded video data which represents a magnitude of a block offset vector difference (1810), which represents a difference between firstly a block offset vector (1802) specifying a position distance of a first block for predicting a second block, and secondly a block offset vector prediction (1808), wherein the magnitude is encoded as first data encoding a prefix part of the magnitude and second data encoding a suffix part; wherein the video signal further comprises a flag, which indicates when having a first value that the second data comprises an index value specifying one of a set of candidate vectors specifying the suffix part, and which indicates when having a first value that the second data comprises at least one context-coded symbol directly encoding one or more bits of the suffix.

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