Interpolation filtering method and apparatus for predictive coding

Abstract

To provide an apparatus and methods for encoding and decoding.SOLUTION: This disclosure relates to intra or inter prediction for video encoding and decoding. An apparatus and method obtain reference samples and sub-pixel offset values. A sub-pixel 4-tap interpolation filter is used to filter the reference samples to obtain predicted sample values. The filter coefficients c0, c1, c2, and c3 of the subpixel 4-tap interpolation filter satisfy the following formula, and p is the fractional part of a subpixel offset value.SELECTED DRAWING: Figure 23

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE

[0002] Embodiments of the present application (disclosure) relate generally to the field of picture processing, and more particularly to image and / or video coding and decoding, and in particular to methods and apparatus for intra / inter prediction. [Background technology]

[0002] Video coding (video encoding and video decoding) is used in a wide range of digital video applications, such as broadcast digital TV, video transmission over the Internet and mobile networks, real-time interactive applications such as video chat, video conferencing, DVDs and Blu-ray® discs, video content collection and editing systems, and camcorders for security applications.

[0003] The amount of video data required to render even a relatively short video can be substantial, which can pose difficulties when the data is to be streamed or otherwise communicated across communication networks with limited bandwidth capacity. Thus, video data is generally compressed before being communicated across modern telecommunication networks. The size of the video can also be an issue when the video is stored on a storage device, since memory resources may be limited. Video compression devices often use software and / or hardware at the source to code the video data prior to transmission or storage, thereby reducing the amount of data required to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques are desirable that improve compression ratios with little sacrifice in picture quality. Summary of the Invention [Means for solving the problem]

[0004] Embodiments of the present application provide apparatus and methods for encoding and decoding according to the independent and dependent claims.

[0005] These and other objects are achieved by the subject matter of the independent and dependent claims. Further implementations are evident from the dependent claims, the description and the figures.

[0006] Embodiments of the invention are defined by the features of the independent claims, further advantageous implementations of the embodiments are defined by the features of the dependent claims.

[0007] According to one aspect of the present disclosure, there is provided a method for intra or inter prediction processing of a video frame, the method comprising the steps of obtaining a reference sample; obtaining a value of a sub-pixel offset; and filtering the reference sample using a sub-pixel 4-tap interpolation filter to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are:

[0008]

number

[0009] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are the filter coefficients of the sub-pixel 4-tap interpolation filter.

[0010] In one example implementation, the reference sample may be referred to as ref[x], which corresponds to an array of reference samples, ref[x]=p[-1-refIdx+x][-1-refIdx] (where x=0..nTbW+refIdx+1) where "p" refers to an xy two-dimensional array p[x][y] containing sample values. The number of reference samples used may be at least 1. In another example, the number of reference samples may be 4.

[0011] In one exemplary implementation, the sub-pixel offset values ​​obtained are: (y+1+refIdx)*intraPredAngle and "IntraPredAngle" is the value of the intra prediction angle.

[0012] In one exemplary implementation, the predicted sample values ​​“predSamples[x][y]” are

[0013]

number

[0014] where fT[i] refers to filter coefficients. These coefficients may be luma or chroma filter coefficients for inter prediction, referred to as fG and fC, respectively.

[0015] The choice of whether the filter coefficients are luma or chroma can be determined, for example, by fT[j]=filterFlag ? fG[iFact][j] : fC[iFact][j] This may be implemented by using and setting the flag "filterFlag", such as: iFact=((y+1+refIdx)*intraPredAngle)&31 It is.

[0016] The value "31" refers to the fractional part of the sub-pixel offset value and may take other values ​​different from "31". The values ​​of the filter coefficients fG (luma) and / or fC (chroma) may be obtained analytically on the fly using the above analytical expressions for the filter coefficients of a 4-tap filter. Thus, the filter coefficients are defined according to the sub-pixel offset value.

[0017] Thus, the filter coefficients are obtained without accessing their respective values ​​from the LUT, but rather by calculation.

[0018] Alternatively, the filter coefficients may be calculated using the above equations and the values ​​may be stored in a LUT.

[0019] According to one aspect of the present disclosure, the filter coefficients of the sub-pixel 4-tap interpolation filter are calculated according to the following table:

[0020] [Table 1A]

[0021] [Table 1B]

[0022] It is specified in.

[0023] According to one aspect of the present disclosure, there is provided a method for intra or inter prediction processing of a video frame, the method comprising the steps of obtaining a reference sample, obtaining a value of a sub-pixel offset, and filtering the reference sample using a sub-pixel 4-tap interpolation filter to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are as follows, i.e.

[0024] [Table 2]

[0025] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0026] In one example implementation, the values ​​of the filter coefficients may be stored in a LUT, which means that the respective values ​​of the filter coefficients will be fetched from the LUT for sub-pixel interpolation filtering.

[0027] FIG. 23 shows a flowchart of an intra / inter prediction process. In step 2301, a reference sample is obtained. The reference sample may include one or more reference samples. In step 2302, a sub-pixel offset value is then obtained. In step 2303, the reference sample is then calculated using the filter coefficients {c i}, where i=0,...3. This is called a 4-tap filter and / or a 4-point filter.

[0028] The filter coefficients may be obtained from an analytical expression with a given fractional portion p of the sub-pixel offset value. The filter coefficients may also be obtained from a LUT with reference to the p value.

[0029] According to one aspect of the present disclosure, the bits of p are set to 0.

[0030] According to one aspect of the present disclosure, p is incremented by 1, and then the least significant bit of the incremented p is set to 0 before it is used to obtain the filter coefficients.

[0031] According to one aspect of the present disclosure, obtaining the filter coefficients includes:

[0032]

number

[0033] This includes a step of calculating the filter coefficients according to the previous filter coefficients c i to filter coefficient c i+1This may further reduce the time for calculating the filter coefficients.

[0034] According to one aspect of the present disclosure, a method of video coding is provided, the method comprising intra prediction processing of blocks of a video frame comprising filtering reference samples of the video frame using a sub-pixel 4-tap interpolation filter, the sub-pixel 4-tap interpolation filter being a combination of filters, and filter coefficients of at least one of the filters being:

[0035]

number

[0036] where p is the fractional sample position of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0037] Figure 24 shows a flowchart of video coding. In step 2401, an intra prediction process is performed by filtering the reference samples of a block using a sub-pixel 4-tap interpolation filter.

[0038] According to one aspect of the present disclosure, the sub-pixel 4-tap interpolation filter is a smoothing filter that is a parallel combination of two phase-dependent linear filters and a low-pass filter.

[0039] According to one aspect of the present disclosure, the sub-pixel 4-tap interpolation filter is a sharpening filter that is a parallel combination of one phase-dependent linear filter and an intensity-varying high-pass filter.

[0040] According to one aspect of the present disclosure, the intensity variation high pass filter is a phase independent high pass finite impulse response FIR filter, the output of which is multiplied by a phase dependent intensity parameter.

[0041] According to any one of the previous aspects of this disclosure, the lower bits of p are set to 0.

[0042] According to one aspect of the present disclosure, p is incremented by 1, then the least significant bits of the incremented value are set to 0 before this value is used to derive the interpolation filter coefficients.

[0043] According to one aspect of the present disclosure, a clipping operation is performed on the output of the intensity variation high pass filter.

[0044] According to an aspect of the present disclosure, an apparatus for intra or inter prediction processing of a video frame is provided, the apparatus including: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of a sub-pixel offset; and a sub-pixel 4-tap interpolation filter configured to filter the reference sample to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are:

[0045]

number

[0046] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are the filter coefficients of the sub-pixel 4-tap interpolation filter.

[0047] According to one aspect of the present disclosure, the filter coefficients of the sub-pixel 4-tap interpolation filter are calculated according to the following table:

[0048] [Table 3A]

[0049] [Table 3B]

[0050] It is specified in.

[0051] According to an aspect of the present disclosure, an apparatus for intra or inter prediction processing of a video frame is provided, the apparatus comprising: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of a sub-pixel offset; and a sub-pixel 4-tap interpolation filter configured to filter the reference sample to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are as follows, i.e.

[0052] [Table 4]

[0053] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0054] FIG. 25 shows a schematic diagram of an intra / inter processing module 2500, which includes a reference sample obtaining unit 2510, a sub-pixel offset value obtaining unit 2520, and a sub-pixel interpolation filter 2530.

[0055] According to one aspect of the disclosure, an apparatus for video coding is provided, the apparatus comprising: an intra-prediction processing unit configured to intra-predict a block of a video frame; and a sub-pixel 4-tap interpolation filter configured to filter reference samples of the video frame, the sub-pixel 4-tap interpolation filter being a combination of filters, and at least one filter coefficient of the filters being:

[0056]

number

[0057] where p is the fractional sample position of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0058] FIG. 26 shows a schematic diagram of a video coding module 2600, comprising an intra-prediction processing unit 2610 and a sub-pixel interpolation filter 2620.

[0059] According to one aspect of the present disclosure, there is provided an encoder (20) comprising processing circuitry for performing a method according to any one of the previous aspects of the present disclosure.

[0060] According to one aspect of the present disclosure, there is provided a decoder (30) comprising processing circuitry for performing a method according to any one of the previous aspects of the present disclosure.

[0061] According to an aspect of the present disclosure, there is provided a computer program product comprising a program code for performing a method according to any one of the previous aspects of the present disclosure.

[0062] According to one aspect of the present disclosure, there is provided a decoder comprising one or more processors and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processors, configuring the decoder to perform a method according to any one of the previous aspects of the present disclosure.

[0063] According to one aspect of the present disclosure, an encoder is provided, comprising one or more processors and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processors, configuring the encoder to perform a method according to any one of the previous aspects of the present disclosure.

[0064] The present disclosure according to any of the previous aspects may provide the advantage of performing fast intra / inter prediction of video frames, since the filter coefficients of the interpolation filter are obtained analytically, i.e., the coefficients are calculated on the fly, which avoids storing the coefficients in a look-up table (LUT), which requires access time to read the coefficients from memory.

[0065] Therefore, the prediction becomes more efficient and places less demand on the required memory. This also allows for a low-cost implementation of the prediction. Moreover, the analytical filter coefficients {c i Because {x,y,z} are linear in the fractional sample position p and involve division by two operations, the respective operations can be efficiently performed by employing fast low-level bit operations. The time to perform the bit operations and to calculate the filter coefficients is less than the time to access the stored coefficients from the LUT. Thus, latency is reduced.

[0066] Moreover, the particular analytical structure of the filter coefficients may provide the advantage of low-complexity implementation of the filter unit. In addition, the filter responses (i.e., frequency responses) for different sub-pixel positions are matched in terms of magnitude and phase, avoiding artifacts in the response, especially at high frequencies. The linearity of the filter coefficients may provide the advantage of hardware reuse.

[0067] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims.

[0068] The present invention may be implemented in hardware and / or software.

[0069] For clarity, any one of the above embodiments may be combined with any one or more of the other embodiments described above to create new embodiments within the scope of the present disclosure.

[0070] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

[0071] In the following, embodiments of the invention will be explained in more detail with reference to the accompanying figures and drawings. [Brief description of the drawings]

[0072] [Figure 1A] 1 is a block diagram illustrating an example of a video coding system configured to implement embodiments of the present invention. [Figure 1B] 2 is a block diagram illustrating another example of a video coding system configured to implement embodiments of the present invention. [Diagram 2] FIG. 1 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the present invention. [Diagram 3] 2 is a block diagram illustrating an exemplary structure of a video decoder configured to implement embodiments of the present invention. [Figure 4] FIG. 1 is a block diagram showing an example of an encoding device or a decoding device. [Diagram 5] FIG. 13 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] FIG. 2 illustrates angular intra-prediction directions and associated intra-prediction modes in HEVC. [Figure 7] FIG. 13 is a diagram illustrating angular intra-prediction directions and associated intra-prediction modes in JEM. [Figure 8] FIG. 1 illustrates angular intra-prediction directions and associated intra-prediction modes in VTM-3.0 and VVC specification draft v.3. [Figure 9]FIG. 2 illustrates an example of filter combination for smoothing, in which a set of reference samples is input to an interpolation filter. [Figure 10] FIG. 13 illustrates an example combination of filters for sharpening interpolation filtering, including a clipping operation. [Figure 11] FIG. 13 illustrates an example combination of filters for sharpening interpolation filtering with alternative positions of clipping operations. [Figure 12A] FIG. 13 illustrates an example combination of filters for sharpening interpolation filtering using filters of adjustable strength. [Figure 12B] FIG. 13 illustrates another exemplary combination of filters for sharpening interpolation filtering using filters of adjustable strength. [Figure 13] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 14] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 15] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 16] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 17] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 18] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 19] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 20] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 21] 1A-1C illustrate various combinations of LUT-based and analytical representations of interpolation filter coefficients. [Figure 22] FIG. 1 illustrates an exemplary implementation of a coefficient calculation method. [Figure 23] 13 is a flowchart of an intra / inter prediction process. [Figure 24] 1 is a flowchart of video coding. [Diagram 25] A block diagram of an intra / inter prediction processing module, including a reference sample acquisition unit, a sub-pixel offset value acquisition unit, and a sub-pixel interpolation filter. [Figure 26] 1 is a block diagram of a video coding module including an inter-prediction processing unit and sub-pixel interpolation filters. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0073] In the following, identical reference signs refer to identical or at least functionally equivalent features, unless expressly specified otherwise.

[0074] In the following description, reference is made to the accompanying figures, which form a part of this disclosure and which show, by way of example, certain aspects of embodiments of the invention or in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other ways and may have structural or logical changes not shown in the figures. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0075] For example, it is understood that disclosure regarding a described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, when one or more particular method steps are described, the corresponding device may include one or more units (e.g., one unit performing one or more steps, or multiple units each performing one or more of the multiple steps), e.g., functional units, for performing the described one or more method steps, even if such one or more units are not explicitly described or shown in the figures. On the other hand, when, for example, a particular apparatus is described based on one or more units, e.g., functional units, the corresponding method may include one step for performing the function of one or more units (e.g., one step performing the function of one or more units, or multiple steps each performing one or more functions of multiple units), even if such one or more steps are not explicitly described or shown in the figures. Furthermore, it is understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically stated otherwise.

[0076] Video coding usually refers to the processing of a sequence of pictures to form a video or a video sequence. Instead of the term "picture", the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or, in general, coding) comprises two parts: video encoding and video decoding. Video encoding is performed at the source side and usually comprises processing an original video picture (e.g., by compression) to reduce the amount of data required to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed at the destination side and usually comprises the reverse processing compared to the encoder to reconstruct the video picture. The embodiments referring to "coding" of a video picture (or, in general, a picture) shall be understood to relate to "encoding" or "decoding" of the video picture or the respective video sequence. The combination of the encoding and decoding parts is also called a codec (coding and decoding).

[0077] In the case of lossless video coding, the original video picture can be reconstructed, i.e., the reconstructed video picture has the same quality as the original video picture (assuming there is no transmission loss or other data loss during storage or transmission). In the case of lossy video coding, further compression is performed, e.g., by quantization, to reduce the amount of data representing the video picture, and the video picture cannot always be completely reconstructed at the decoder, i.e., the quality of the reconstructed video picture is lower, i.e., worse, than the quality of the original video picture.

[0078] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., they combine spatial and temporal prediction in the sample domain with 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is usually partitioned into a set of non-overlapping blocks, and coding is usually performed at the block level. In other words, in the encoder, a video is usually processed or coded at the block (video block) level, for example, by using spatial (intra-picture) and / or temporal (inter-picture) prediction to generate a predictive block, subtracting the predictive block from a current block (the block currently being / to be processed) to obtain a residual block, transforming the residual block, and quantizing the residual block in the transform domain to reduce (compress) the amount of data to be transmitted, while in the decoder, the reverse processing is applied to the coded or compressed block compared to the encoder in order to reconstruct the current block for representation. Furthermore, the encoder replicates the decoder processing loop so that both generate the same prediction (e.g., intra-prediction and inter-prediction) and / or reconstruction for processing or coding a subsequent block.

[0079] In the following, embodiments of a video coding system 10, a video encoder 20, and a video decoder 30 are described based on FIGS.

[0080] 1A is a schematic block diagram illustrating an example coding system 10, such as video coding system 10 (or short coding system 10), that may utilize techniques of the present application. A video encoder 20 (or short encoder 20) and a video decoder 30 (or short decoder 30) of video coding system 10 represent examples of devices that may be configured to perform techniques according to various examples described in the present application.

[0081] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded picture data 21 to a destination device 14 for decoding the encoded picture data 13, for example.

[0082] The source device 12 comprises an encoder 20, and may additionally, i.e. optionally, comprise a picture source 16, a pre-processor (or pre-processing unit) 18, for example a picture pre-processor 18, and a communication interface or unit 22.

[0083] Picture source 16 may comprise or be any kind of picture capture device, e.g., a camera for capturing real-world pictures, and / or any kind of picture generation device, e.g., a computer graphics processor for generating computer-animated pictures, or any kind of other device for obtaining and / or providing real-world pictures, computer-generated pictures (e.g., screen content, virtual reality (VR) pictures), and / or any combination thereof (e.g., augmented reality (AR) pictures). Picture source may be any kind of memory or storage that stores any of the above-mentioned pictures.

[0084] In contrast to the pre-processor 18 and the processing performed by the pre-processing unit 18 , the pictures or picture data 17 are sometimes referred to as raw pictures or raw picture data 17 .

[0085] The pre-processor 18 is configured to receive (raw) picture data 17 and perform pre-processing on the picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. The pre-processing performed by the pre-processor 18 may comprise, for example, cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise removal. It may be understood that the pre-processing unit 18 may be an optional component.

[0086] Video encoder 20 is configured to receive pre-processed picture data 19 and to provide encoded picture data 21 (further details are described below, eg, with reference to FIG. 2).

[0087] Communications interface 22 of source device 12 may be configured to receive encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) via communications channel 13 to another device, e.g., destination device 14 or any other device, for storage or direct reconstruction.

[0088] Destination device 14 comprises a decoder 30 (eg, a video decoder 30), and may additionally, i.e. optionally, comprise a communications interface or unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0089] The communications interface 28 of the destination device 14 is configured to receive the coded picture data 21 (or any further processed version thereof), for example directly from the source device 12 or from any other source, for example a storage device, for example a coded picture data storage device, and to provide the coded picture data 21 to a decoder 30.

[0090] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired connection or a direct wireless connection, or via any type of network, e.g., a wired network or a wireless network or any combination thereof, or any type of private network and public network, or any type of combination thereof.

[0091] The communications interface 22 may be configured, for example, to package the encoded picture data 21 in a suitable format, e.g., in packets, and / or to process the encoded picture data using any type of transmission encoding or processing for transmission over a communications link or network.

[0092] Communications interface 28, which forms the counterpart of communications interface 22, may be configured, for example, to receive transmitted data and process the transmitted data using any type of corresponding transmission decoding or processing and / or depackaging to obtain encoded picture data 21.

[0093] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrow for communication channel 13 in FIG. 1A pointing from source device 12 to destination device 14, or as bidirectional communication interfaces, and may be configured to send and receive messages, e.g., to set up a connection, to acknowledge, respond and exchange any other information related to the communication link and / or data transmission, e.g., encoded picture data transmission.

[0094] The decoder 30 is configured to receive the encoded picture data 21 and to provide decoded picture data 31 or decoded pictures 31 (further details are described below, for example based on Figure 3 or Figure 5).

[0095] Post-processor 32 of destination device 14 is configured to post-process decoded picture data 31 (also referred to as reconstructed picture data), e.g., decoded picture 31, to obtain post-processed picture data 33, e.g., post-processed picture 33. The post-processing performed by post-processing unit 32 may comprise, e.g., color format conversion (e.g., from YCbCr to RGB), color correction, cropping or resampling, or any other processing to prepare the decoded picture data 31 for, e.g., display, by, e.g., display device 34.

[0096] A display device 34 of destination device 14 is configured to receive the post-processed picture data 33, e.g., for displaying the picture to a user or viewer. The display device 34 may be or comprise any type of display, e.g., an integrated or external display or monitor, for presenting the reconstructed picture. The display may comprise, e.g., a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a micro-LED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any type of other display.

[0097] 1A illustrates source device 12 and destination device 14 as separate devices, an embodiment of the devices may also include both or both the functionality of source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such an embodiment, source device 12 or corresponding functionality and destination device 14 or corresponding functionality may be implemented using the same hardware and / or software or by separate hardware and / or software or any combination thereof.

[0098] As will be clear to a person skilled in the art based on the description, the presence and (exact) division of functions of different units or functions within source device 12 and / or destination device 14 as shown in FIG. 1A may vary depending on the actual device and application.

[0099] The encoder 20 (e.g., video encoder 20) or the decoder 30 (e.g., video decoder 30), or both the encoder 20 and the decoder 30, may be implemented via processing circuitry as shown in FIG. 1B, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, dedicated to video coding, or any combination thereof. The encoder 20 may be implemented via processing circuitry 46 to embody various modules as described with respect to the encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. The decoder 30 may be implemented via processing circuitry 46 to embody various modules as described with respect to the decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations as described below. As shown in FIG. 5, if the techniques are implemented in part in software, the device may store instructions for the software in a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either video encoder 20 and video decoder 30 may be integrated into a single device as part of a combined encoder / decoder (codec), for example, as shown in FIG. 1B.

[0100] Source device 12 and destination device 14 may comprise any of a wide range of devices, including any type of handheld or fixed device, e.g., a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or a content delivery server), a broadcast receiver device, a broadcast transmitter device, and the like, and may use no operating system or any type of operating system. In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

[0101] In some cases, the video coding system 10 shown in FIG. 1A is only an example, and techniques of the present application may be applied to video coding settings (e.g., video encoding or video decoding) that do not necessarily include any data communication between encoding and decoding devices. In other examples, data may be retrieved from local memory, streamed over a network, etc. A video encoding device may encode and store data in memory, and / or a video decoding device may retrieve data from memory and decode data. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data into memory and / or retrieve data from memory and decode data.

[0102] For ease of explanation, embodiments of the present invention are described herein by reference to, for example, High-Efficiency Video Coding (HEVC) or to Versatile Video Coding (VVC), a next-generation video coding standard developed by the Joint Collaboration Team on Video Coding (JCT-VC) of the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Motion Picture Experts Group (MPEG). It will be appreciated by those skilled in the art that embodiments of the present invention are not limited to HEVC or VVC.

[0103] Encoder and encoding method FIG. 2 shows a schematic block diagram of an exemplary video encoder 20 configured to implement the techniques of the present application. In the example of FIG. 2, the video encoder 20 includes an input unit 201 (or an input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210 and an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy coding unit 270, and an output unit 272 (or an output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partition unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 as shown in FIG. 2 may also be called a hybrid video encoder, i.e., a video encoder according to a hybrid video codec.

[0104] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be referred to as forming a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be referred to as forming a backward signal path of the video encoder 20, which corresponds to the signal path of the decoder (see video decoder 30 in FIG. 3). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 are also referred to as forming a “built-in decoder” of the video encoder 20.

[0105] Pictures and picture divisions (pictures and blocks) The encoder 20 may be configured to receive, for example via an input 201, a picture 17 (or picture data 17), for example a picture of a sequence of pictures forming a video or a video sequence. The received picture or picture data may also be a preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to picture 17. Picture 17 may also be called a current picture or a picture to be coded (particularly in video coding, to distinguish the current picture from other pictures, for example previously encoded and / or decoded pictures, of the same video sequence, i.e. the video sequence that also comprises the current picture).

[0106] A (digital) picture is or can be considered as a two-dimensional array or matrix of samples with intensity values. The samples in the array are sometimes called pixels (picture elements in short form) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, three color components are usually employed, i.e. a picture may be represented or contain three sample arrays. In an RBG format or color space, a picture comprises corresponding red, green, and blue sample arrays. However, in video coding, each pixel is usually represented in a luminance and chrominance format or color space, e.g. YCbCr, which comprises a luminance component denoted by Y (sometimes L is also used instead) and two chrominance components denoted by Cb and Cr. The luminance (or short luma) component Y represents luminance or gray level intensity (e.g., as in a grayscale picture), and the two chrominance (or short chroma) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format comprises a luminance sample array of luminance sample values ​​(Y) and two chrominance sample arrays of chrominance values ​​(Cb and Cr). A picture in RGB format may be converted or transformed into YCbCr format, or vice versa, a process also called color transformation or color conversion. If the picture is monochrome, the picture may comprise only a luminance sample array. Thus, a picture may be, for example, an array of luma samples in monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats.

[0107] An embodiment of video encoder 20 may comprise a picture partitioning unit (not shown in FIG. 2) configured to partition picture 17 into multiple (usually non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTBs) or coding tree units (CTUs) (H.265 / HEVC and VVC). The picture partitioning unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid that defines the block sizes, or to vary the block size among pictures or subsets or groups of pictures, and to partition each picture into corresponding blocks.

[0108] In further embodiments, the video encoder may be configured to directly receive block 203 of picture 17, e.g., one, multiple, or all of the blocks that form picture 17. Picture block 203 may also be referred to as a current picture block or a picture block to be coded.

[0109] Like picture 17, picture block 203 is again or may be considered as a two-dimensional array or matrix of samples having intensity values ​​(sample values), but with smaller dimensions than picture 17. In other words, block 203 may comprise, for example, one sample array (e.g., a luma array in case of a monochrome picture 17, or a luma array or a chroma array in case of a color picture), or three sample arrays (e.g., a luma array and two chroma arrays in case of a color picture 17), or any other number and / or type of arrays depending on the applied color format. The number of samples in the horizontal and vertical directions (or axes) of block 203 defines the size of block 203. Thus, a block may be, for example, an M×N (M columns×N rows) array of samples, or an M×N array of transform coefficients.

[0110] An embodiment of video encoder 20 as shown in FIG. 2 may be configured to code picture 17 on a block-by-block basis, eg, encoding and prediction are performed on a block 203 basis.

[0111] Residual calculation The residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual 205) based on the picture block 203 and the prediction block 265 (further details about the prediction block 265 are provided later), for example, by subtracting sample values ​​of the prediction block 265 from sample values ​​of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

[0112] conversion The transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values ​​of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may also be referred to as transform residual coefficients and may represent the residual block 205 in the transform domain.

[0113] The transform processing unit 206 may be configured to apply an integer approximation of a DCT / DST, such as the transform specified for H.265 / HEVC. Compared to an orthogonal DCT transform, such an integer approximation is typically scaled by some factors. In order to preserve the norm of the residual block processed by the forward transform and the inverse transform, an additional scaling factor is applied as part of the transform process. The scaling factor is typically chosen based on some constraints, such as the scaling factor being a power of two due to shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. For example, a particular scaling factor may be specified for, e.g., the inverse transform, e.g., by the inverse transform processing unit 212 (and the corresponding inverse transform, e.g., by the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform, e.g., by the transform processing unit 206 in the encoder 20, may be specified accordingly.

[0114] An embodiment of video encoder 20 (respectively, transform processing unit 206) may be configured to output transform parameters, e.g., one or more types of transform, e.g., directly or encoded or compressed via entropy coding unit 270, so that, for example, video decoder 30 may receive and use the transform parameters for decoding.

[0115] Quantization The quantization unit 208 may be configured to quantize the transform coefficients 207, for example by applying scalar quantization or vector quantization, to obtain quantized coefficients 209. The quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0116] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be truncated to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a quantization parameter (QP). For example, in the case of scalar quantization, various scalings may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to a finer quantization, while a larger quantization step size corresponds to a coarser quantization. The applicable quantization step sizes may be indicated by a quantization parameter (QP). The quantization parameter may, for example, be an index into a predefined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size) and a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. The quantization may include a division by the quantization step size, and the corresponding inverse quantization and / or inverse inverse quantization, e.g., by the inverse quantization unit 210, may include a multiplication by the quantization step size. Some standards, e.g., embodiments according to HEVC, may be configured to use a quantization parameter to determine the quantization step size. In general, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation that includes a division. An additional scaling factor may be introduced for the quantization and inverse quantization to restore the norm of the residual block, which may be modified due to the scaling used in the fixed-point approximation of the equation for the quantization step size and the quantization parameter. In one example implementation, the scaling of the inverse transform and the inverse quantization may be combined. Alternatively, a customized quantization table may be used, e.g., signaled from the encoder to the decoder in the bitstream. Quantization is a lossy operation, and the loss increases with increasing quantization step size.

[0117] An embodiment of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP), e.g., encoded directly or via entropy encoding unit 270, such that video decoder 30, for example, may receive and apply the quantization parameter for decoding.

[0118] inverse quantization The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 to the quantized coefficients to obtain the inverse quantized coefficients 211, e.g., by applying the inverse of the quantization scheme applied by the quantization unit 208, based on or using the same quantization step size as the quantization unit 208. The inverse quantized coefficients 211, which may also be referred to as the inverse quantized residual coefficients 211, may correspond to the transform coefficients 207—although they are not usually identical to the transform coefficients due to losses due to quantization.

[0119] Reverse transformation The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, for example, an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST), or other inverse transform, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 213.

[0120] Reconstruction The reconstruction unit 214 (e.g., an adder or summer 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, for example by adding - sample by sample - sample values ​​of the reconstructed residual block 213 and the prediction block 265.

[0121] Filtering The loop filter unit 220 (or short "loop filter" 220) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or in general, to filter the reconstructed samples to obtain filtered samples. The loop filter unit is configured, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may comprise one or more loop filters, such as a deblocking filter, a Sample-Adaptive Offset (SAO) filter, or one or more other filters, for example, a bilateral filter, an Adaptive Loop Filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 220 is illustrated in FIG. 2 as being an in-loop filter, in other configurations the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstruction block 221.

[0122] Embodiments of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as sample adaptive offset information), e.g., directly or encoded via entropy encoding unit 270, such that, for example, decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding.

[0123] Decoded Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or generally reference picture data for encoding video data by the video encoder 20. The DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may further be configured to store other previously filtered blocks, e.g., previously reconstructed and filtered blocks 221 of the same current picture or of a different picture, e.g., previously reconstructed pictures, and may provide, e.g., a previously reconstructed or decoded overall picture (and corresponding reference blocks and samples) and / or a partially reconstructed current picture (and corresponding reference blocks and samples) for inter prediction. For example, if the reconstructed block 215 has not been filtered by the loop filter unit 220 or is any other further processed version of a reconstructed block or sample, the decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215, or, in general, unfiltered reconstructed samples.

[0124] Mode Selection (Segmentation and Prediction) The mode selection unit 260 comprises a partitioning unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original picture data, e.g., original block 203 (current block 203 of current picture 17), as well as reconstructed picture data, e.g., filtered and / or unfiltered reconstructed samples or blocks, from, e.g., a decoded picture buffer 230 or other buffer (e.g., a line buffer, not shown) of the same (current) picture and / or from one or more previously decoded pictures. The reconstructed picture data is used as reference picture data for prediction, e.g., inter prediction or intra prediction, to obtain a prediction block 265 or a predictor 265.

[0125] The mode selection unit 260 may be configured to determine or select a partition for a current block prediction mode (not including a partition) and a prediction mode (e.g., intra or inter prediction mode) and generate a corresponding prediction block 265 used for calculation of the residual block 205 and for reconstruction of the reconstruction block 215.

[0126] An embodiment of the mode selection unit 260 may be configured to select a partition and prediction mode (e.g., from those supported by or available to the mode selection unit 260) that gives the best match, or in other words the smallest residual (smallest residual means better compression for transmission or storage), or the smallest signaling overhead (smallest signaling overhead means better compression for transmission or storage), or considers or balances both. The mode selection unit 260 may be configured to determine the partition and prediction mode based on Rate Distortion Optimization (RDO), i.e., to select the prediction mode that results in the smallest rate distortion. Terms such as "best," "minimum," "optimum," etc. in this context do not necessarily refer to an overall "best," "minimum," "optimum," etc., but may refer to the satisfaction of a termination or selection criterion, such as a value above or below a threshold or other constraint, potentially leading to a "suboptimal selection," but reducing computational effort and processing time.

[0127] In other words, the partitioning unit 262 may be configured to partition the block 203 into smaller block partitions or sub-blocks (which again form blocks) using, for example, a quad-tree partitioning (QT), binary partitioning (BT), or triple-tree partitioning (TT), or any combination thereof in an iterative manner, and to perform, for example, prediction on each of the block partitions or sub-blocks, wherein the mode selection comprises selection of a tree structure of the partitioned block 203, and a prediction mode is applied to each of the block partitions or sub-blocks.

[0128] Below, the partitioning (eg, by partition unit 260) and prediction processes (by inter prediction unit 244 and intra prediction unit 254) performed by the exemplary video encoder 20 are described in more detail.

[0129] classification The partitioning unit 262 may partition (i.e., split) the current block 203 into smaller partitions, e.g., smaller blocks of square or rectangular size. These smaller blocks (sometimes called sub-blocks) may be further partitioned into even smaller partitions. This is also called tree partitioning or hierarchical tree partitioning, e.g., a root block at root tree level 0 (hierarchical level 0, depth 0) may be partitioned recursively, e.g., into two or more blocks at the next lower tree level, e.g., nodes at tree level 1 (hierarchical level 1, depth 1), which may again be partitioned into two or more blocks at the next lower level, e.g., tree level 2 (hierarchical level 2, depth 2), etc., until the partitioning is terminated, e.g., because a termination criterion is met, e.g., a maximum tree depth or a minimum block size has been reached. Blocks that are not partitioned further are also called leaf blocks or leaf nodes of the tree. A tree that uses a partition into two partitions is called a binary tree (BT), a tree that uses a partition into three partitions is called a ternary tree (TT), and a tree that uses a partition into four partitions is called a quad tree (QT).

[0130] As mentioned before, the term "block" as used herein may be a portion of a picture, particularly a square or rectangular portion. For example, with reference to HEVC and VVC, a block may be or may correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit (TU), and / or a corresponding block, such as a coding tree block (CTB), a coding block (CB), a transform block (TB), or a prediction block (PB).

[0131] For example, a coding tree unit (CTU) may be or comprise a CTB of luma samples for a picture with three sample arrays, two corresponding CTBs of chroma samples, or a CTB of samples for a monochrome picture or a picture coded using three separate color planes, and a syntax structure used to code the samples. Correspondingly, a coding tree block (CTB) may be an N×N block of samples for some values ​​of N such that the division of the components into CTBs is partitioned. A coding unit (CU) may be or comprise a coding block of luma samples for a picture with three sample arrays, two corresponding coding blocks of chroma samples, or a coding block of samples for a monochrome picture or a picture coded using three separate color planes, and a syntax structure used to code the samples. Correspondingly, a coding block (CB) may be an M×N block of samples for some values ​​of M and N such that the division of the CTB into coding blocks is partitioned.

[0132] For example, in an HEVC embodiment, a coding tree unit (CTU) may be divided into CUs by using a quad-tree structure, denoted as a coding tree. The decision of whether a picture area should be coded using (temporal) inter-picture prediction or (spatial) intra-picture prediction is made at the CU level. Each CU may be further divided into one, two, or four PUs according to a PU partition type. Inside one PU, the same prediction process is applied, and related information is sent to the decoder on a PU-by-PU basis. After obtaining residual blocks by applying a prediction process based on the PU partition type, the CU may be partitioned into transform units (TUs) according to another quad-tree structure similar to the coding tree for CUs.

[0133] In an embodiment, for example, according to the latest video coding standard currently under development, called versatile video coding (VVC), quad-tree and binary tree (QTBT) partitioning is used to partition the coding block. In the QTBT block structure, the CU can have either a square or rectangular shape. For example, the coding tree unit (CTU) is first partitioned by a quad-tree structure. The quad-tree leaf node is further partitioned by a binary tree or a ternary (or triple) tree structure. Partitioning the tree leaf node is called a coding unit (CU), and its segmentation is used for prediction and transformation processes without further partitioning. This means that the CU, PU, ​​and TU have the same block size in the QTBT coding block structure. In parallel, multiple partitions, for example, triple tree partitioning, have also been proposed to be used with the QTBT block structure.

[0134] In one example, mode selection unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0135] As described above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a set of (predetermined) prediction modes. The set of prediction modes may comprise, for example, intra-prediction modes and / or inter-prediction modes.

[0136] Intra prediction The set of intra prediction modes may, for example, comprise 35 different intra prediction modes, e.g., an omnidirectional mode such as DC (or average) mode and a planar mode, or a directional mode, as specified in HEVC, or may comprise 67 different intra prediction modes, e.g., an omnidirectional mode such as DC (or average) mode and a planar mode, or a directional mode, as specified for VVC.

[0137] The intra prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an intra prediction block 265 according to an intra prediction mode of the set of intra prediction modes.

[0138] The intra prediction unit 254 (or generally, the mode selection unit 260) is further configured to output intra prediction parameters (or generally, information indicating the selected intra prediction mode for the block) to the entropy encoding unit 270 in the form of a syntax element 266 for inclusion in the encoded picture data 21, so that, for example, the video decoder 30 may receive and use the prediction parameters for decoding.

[0139] Inter Prediction The set of inter prediction modes (or possible inter prediction modes) depends on the available reference pictures (i.e., previous pictures that have been at least partially decoded and that are, for example, stored in DBP230) as well as other inter prediction parameters, such as whether the entire reference picture is used to search for the best matching reference block or only a portion of it, for example a search window area around the area of ​​the current block of the reference picture, is used, and / or, for example, whether pixel interpolation, for example half-pel / semi-pel and / or quarter-pel interpolation, is applied.

[0140] In addition to the above prediction modes, skip mode and / or direct mode may be applied.

[0141] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (both not shown in FIG. 2). The motion estimation unit may be configured to receive or obtain the picture block 203 (current picture block 203 of current picture 17) and the decoded picture 231, or at least one or more previously reconstructed blocks, e.g., reconstructed blocks of one or more other / different previously decoded pictures 231, for motion estimation. For example, a video sequence may comprise the current picture and the previously decoded picture 231, or in other words, the current picture and the previously decoded picture 231 may be part of or form a sequence of pictures forming a video sequence.

[0142] The encoder 20 may be configured to, for example, select a reference block from multiple reference blocks of the same or different pictures among multiple other pictures, and provide the reference picture (or reference picture index) and / or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as an inter-prediction parameter to the motion estimation unit, which offset is also called a motion vector (MV).

[0143] The motion compensation unit is configured to obtain, e.g., receive, inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain inter prediction block 265. The motion compensation performed by the motion compensation unit may involve fetching or generating a prediction block based on a motion / block vector determined by motion estimation, possibly performing interpolation to sub-pixel accuracy. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code the picture block. Upon receiving a motion vector for the PU of the current picture block, the motion compensation unit may locate the prediction block to which the motion vector points in one of the reference picture lists.

[0144] The motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices.

[0145] Entropy Coding The entropy coding unit 270 may apply, for example, an entropy coding algorithm or scheme (e.g., a Variable Length Coding (VLC) scheme, a Context Adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, a binarization scheme, a Context Adaptive Binary Arithmetic Coding (CABAC), a Syntax-Based Context-Adaptive Binary Arithmetic Coding (SBAC), a Probability Interval Partitioning Entropy (PIPE), a quantization scheme, ... 2, the video decoder 30 may receive and use the parameters for decoding the encoded picture data 21. The video decoder 30 may be configured to apply a coding scheme (such as entropy coding, or another entropy encoding method or technique), or bypass (no compression) to obtain encoded picture data 21 that may be output via output unit 272, for example, in the form of encoded bitstream 21, so that, for example, video decoder 30 may receive and use the parameters for decoding. The encoded bitstream 21 may be transmitted to video decoder 30 or may be stored in a memory for later transmission or retrieval by video decoder 30.

[0146] Other structural variations of the video encoder 20 may be used to encode the video stream. For example, a non-transform-based encoder 20 may directly quantize the residual signal without using the transform processing unit 206 for some blocks or frames. In another implementation, the encoder 20 may have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0147] Decoder and decoding method 3 shows an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive coded picture data 21 (e.g., coded bitstream 21), e.g., coded by encoder 20, to obtain a decoded picture 331. The coded picture data or bitstream comprises information for decoding the coded picture data, e.g., data representing picture blocks of coded video slices, and associated syntax elements.

[0148] In the example of Figure 3, the decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., adder 314), a loop filter 320, a decoded picture buffer (DBP) 330, an inter prediction unit 344, and an intra prediction unit 354. The inter prediction unit 344 may be or include a motion compensation unit. The video decoder 30 may, in some examples, perform a decoding path that is generally reciprocal to the encoding path described with respect to the video encoder 100 from Figure 2.

[0149] As described with respect to encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, loop filter 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also referred to as forming a “built-in decoder” of video encoder 20. Thus, inverse quantization unit 310 may be identical in function to inverse quantization unit 110, inverse transform processing unit 312 may be identical in function to inverse transform processing unit 212, reconstruction unit 314 may be identical in function to reconstruction unit 214, loop filter 320 may be identical in function to loop filter 220, and decoded picture buffer 330 may be identical in function to decoded picture buffer 230. Thus, the descriptions provided for the respective units and functions of video encoder 20 apply correspondingly to the respective units and functions of video decoder 30.

[0150] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or generally, the coded picture data 21) and, e.g., perform entropy decoding on the coded picture data 21 to obtain, e.g., quantization coefficients 309 and / or decoded coding parameters (not shown in FIG. 3), e.g., any or all of inter prediction parameters (e.g., reference picture indexes and motion vectors), intra prediction parameters (e.g., intra prediction modes or indices), transform parameters, quantization parameters, loop filter parameters, and / or other syntax elements. The entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to an encoding scheme as described with respect to the entropy encoding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter prediction parameters, intra prediction parameters, and / or other syntax elements to the mode selection unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive syntax elements at a video slice level and / or a video block level.

[0151] inverse quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or generally, information related to inverse quantization) and quantized coefficients from encoded picture data 21 (e.g., by parsing and / or decoding, e.g., by entropy decoding unit 304), and apply inverse quantization to the decoded quantized coefficients 309 based on the quantization parameter to obtain inverse quantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may involve use of the quantization parameter determined by video encoder 20 for each video block in a video slice to determine the degree of quantization, and similarly, the degree of inverse quantization to be applied.

[0152] Inverse transformation The inverse transform processing unit 312 may be configured to receive the inverse quantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the inverse quantized coefficients 311 to obtain a reconstructed residual block 213 in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 313. The transform may be an inverse transform, e.g., an inverse DCT transform, an inverse DST transform, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may further be configured to receive transform parameters or corresponding information from the coded picture data 21 (e.g., by parsing and / or decoding, e.g., by the entropy decoding unit 304) to determine a transform to be applied to the inverse quantized coefficients 311.

[0153] Reconstruction The reconstruction unit 314 (e.g., an adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, for example, by adding sample values ​​of the reconstructed residual block 313 and sample values ​​of the prediction block 365, to obtain a reconstructed block 315 in the sample domain.

[0154] Filtering A loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter the reconstruction block 315 to obtain a filtered block 321, e.g., to smooth pixel transitions or otherwise improve video quality. The loop filter unit 320 may comprise one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 320 is illustrated in FIG. 3 as being an in-loop filter, in other configurations, the loop filter unit 320 may be implemented as a post-loop filter.

[0155] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330, which stores the decoded picture 331 as a reference picture for subsequent motion compensation relative to other pictures and / or for output display, respectively.

[0156] The decoder 30 is arranged to output the decoded pictures 311, for example via an output 312, for presentation or viewing to a user.

[0157] prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (in particular, the motion compensation unit), and the intra prediction unit 354 may be identical in function to the inter prediction unit 254, performing the partitioning or partition decision and prediction based on the partition and / or prediction parameters or respective information received (e.g., by parsing and / or decoding by the entropy decoding unit 304) from the coded picture data 21. The mode selection unit 360 may be configured to perform prediction (intra prediction or inter prediction) for each block based on the (filtered or unfiltered) reconstructed picture, block, or respective sample to obtain a prediction block 365.

[0158] When a video slice is coded as an intra-coded (I) slice, the intra prediction unit 354 of the mode selection unit 360 is configured to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from a previously decoded block of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, the inter prediction unit 344 (e.g., a motion compensation unit) of the mode selection unit 360 is configured to produce a prediction block 365 for a video block of the current video slice based on a motion vector and other syntax elements received from the entropy decoding unit 304. For inter prediction, the prediction block may be produced from one of the reference pictures in one of the reference picture lists. The video decoder 30 may construct the reference frame lists, i.e., list 0 and list 1, using a default construction technique based on the reference pictures stored in the DPB 330.

[0159] Mode selection unit 360 is configured to determine prediction information for the video blocks of the current video slice by parsing the motion vectors and other syntax elements, and to use the prediction information to produce predictive blocks for the current video block being decoded. For example, mode selection unit 360 uses some of the received syntax elements to determine the prediction mode (e.g., intra prediction or inter prediction) used to code the video blocks of the video slice, the inter-prediction slice type (e.g., B slice, P slice, or GPB slice), configuration information for one or more of the reference picture lists for the slice, motion vectors for each inter-coded video block of the slice, inter-prediction status for each inter-coded video block of the slice, and other information for decoding video blocks in the current video slice.

[0160] Other variations of the video decoder 30 may be used to decode the encoded picture data 21. For example, the decoder 30 may produce an output video stream without a loop filtering unit 320. For example, a non-transform-based decoder 30 may directly inverse quantize the residual signal without an inverse transform processing unit 312 for some blocks or frames. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0161] It should be understood that in the encoder 20 and the decoder 30, the processing result of the current step may be further processed and then output to the next step. For example, after the interpolation filtering, the motion vector derivation, or the loop filtering, further operations such as clipping or shifting may be performed on the processing result of the interpolation filtering, the motion vector derivation, or the loop filtering.

[0162] It should be noted that further operations may be applied to the derived motion vector of the current block (including but not limited to control point motion vectors in affine mode, sub-block motion vectors in affine mode, planar mode, ATMVP mode, temporal motion vectors, etc.). For example, the value of the motion vector is constrained to a predefined range according to its representation bit. If the representation bit of the motion vector is bitDepth, the range is -2^(bitDepth-1) to 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 to 32767, and if bitDepth is set equal to 18, the range is -131072 to 131071. For example, the value of the derived motion vector (e.g., MVs of four 4x4 sub-blocks in one 8x8 block) is constrained such that the maximum difference between the integer parts of the four 4x4 sub-block MVs is less than or equal to N pixels, such as less than or equal to 1 pixel. Here, we provide two methods for constraining motion vectors according to bitDepth.

[0163] Method 1: Eliminate the overflow MSB (Most Significant Bit) by flowing arithmetic. ux=(mvx+2 bitDepth )%2 bitDepth (1) mvx=(ux>=2 bitDepth-1 ) ? (ux-2 bitDepth ) : ux (2) uy=(mvy+2 bitDepth )%2 bitDepth (3) mvy=(uy>=2 bitDepth-1 ) ? (uy-2 bitDepth ) : uy (4) where mvx is the horizontal component of the motion vector of the image block or sub-block, mvy is the vertical component of the motion vector of the image block or sub-block, and ux and uy denote intermediate values.

[0164] For example, if the value of mvx is -32769, then after applying equation (1) and equation (2), the resulting value is 32767. In computer systems, decimal numbers are stored as two's complement numbers. The two's complement of -32769 is 1, 0111, 1111, 1111, 1111 (17 bits), then the MSB is discarded, so the resulting two's complement is 0111, 1111, 1111, 1111 (decimal 32767), which is the same as the output by applying equation (1) and equation (2). ux=(mvpx+mvdx+2 bitDepth )%2 bitDepth (5) mvx=(ux>=2 bitDepth-1 ) ? (ux-2 bitDepth ) : ux (6) uy=(mvpy+mvdy+2 bitDepth )%2 bitDepth (7) mvy=(uy>=2 bitDepth-1 ) ? (uy-2 bitDepth ) : uy (8)

[0165] As shown in equations (5) through (8), the operation may be applied between the sums of mvp and mvd.

[0166] Method 2: Remove the overflow MSB by clipping the value. vx=Clip3(-2 bitDepth-1 ,2 bitDepth-1 -1,vx) vy=Clip3(-2 bitDepth-1 ,2 bitDepth-1 -1,vy) where vx is the horizontal component of the motion vector of the image block or sub-block, vy is the vertical component of the motion vector of the image block or sub-block, x, y, and z correspond to the three input values ​​of the MV clipping process, respectively, and the definition of the function Clip3 is as follows:

[0167]

number

[0168] 4 is a schematic diagram of a video coding device 400 according to one embodiment of the present disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In one embodiment, the video coding device 400 may be a decoder, such as the video decoder 30 of FIG. 1A, or an encoder, such as the video encoder 20 of FIG. 1A.

[0169] Video coding device 400 comprises an ingress port 410 (or input port 410) and a receiver unit (Rx) 420 for receiving data, a processor, logic unit, or central processing unit (CPU) 430 for processing the data, a transmitter unit (Tx) 440 and an egress port 450 (or output port 450) for transmitting the data, and a memory 460 for storing data. Video coding device 400 may also comprise optical-to-electrical (OE) and electrical-to-optical (EO) components coupled to the ingress port 410, the receiver unit 420, the transmitter unit 440, and the egress port 450 for the egress or ingress of optical or electrical signals.

[0170] The processor 430 is implemented by hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), FPGAs, ASICs, and DSPs. The processor 430 is in communication with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 comprises a coding module 470. The coding module 470 implements the disclosed embodiments described above. For example, the coding module 470 performs, processes, prepares, or provides various coding operations. Thus, the inclusion of the coding module 470 provides a significant improvement in the functionality of the video coding device 400 and provides transformation of the video coding device 400 into different states. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

[0171] Memory 460 may comprise one or more disks, tape drives, and solid state drives, and may be used as an overflow data storage device for storing programs when such programs are selected for execution, and for storing instructions and data read during program execution. Memory 460 may be, for example, volatile and / or non-volatile, and may be read only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random access memory (SRAM).

[0172] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of source device 12 and destination device 14 from FIG. 1 in accordance with an example embodiment.

[0173] The processor 502 in the apparatus 500 may be a central processing unit. Alternatively, the processor 502 may be any other type of device or devices, now existing or later developed, capable of manipulating or processing information. Although the disclosed implementations may be practiced with a single processor, e.g., processor 502, as shown, advantages in speed and efficiency may be achieved using two or more processors.

[0174] The memory 504 in the apparatus 500 may be a read-only memory (ROM) device or a random access memory (RAM) device in one implementation. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 that is accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, which include at least one program that enables the processor 502 to perform the methods described herein. For example, the application programs 510 may include applications 1-N, which further include a video coding application that performs the methods described herein.

[0175] The apparatus 500 may also include one or more output devices, such as a display 518. The display 518, in one example, may be a touch-sensitive display that combines a display with a touch-sensitive element operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0176] Although shown here as a single bus, bus 512 of device 500 may be comprised of multiple buses. Additionally, secondary storage 514 may be directly coupled to other components of device 500 or may be accessed over a network, and may comprise a single integrated unit, such as a memory card, or multiple units, such as multiple memory cards. Thus, device 500 may be implemented in a wide variety of configurations.

[0177] FIG. 6 shows a schematic diagram of multiple intra prediction modes used in the HEVC UIP scheme. For a luminance block, the intra prediction modes may comprise up to 36 intra prediction modes, which may include three omnidirectional modes and 33 directional modes. The omnidirectional modes may comprise a planar prediction mode, a mean (DC) prediction mode, and a luma-to-chroma (LM) prediction mode. The planar prediction mode may perform prediction by assuming a block deflection plane with horizontal and vertical gradients derived from the boundaries of the block. The DC prediction mode may perform prediction by assuming a flat block face with values ​​that match the average values ​​of the block boundaries. The LM prediction mode may perform prediction by assuming that the chroma values ​​for the block match the luma values ​​for the block.

[0178] FIG. 7 shows an example of 67 intra prediction modes, e.g., as proposed for VVC, where the intra prediction modes include planar mode (index 0), dc mode (index 1), and angle modes with indices 2 to 66, where the bottom left angle mode in FIG. 7 refers to index 2 and the index numbering is incremented until index 66 is the top right most angle mode in FIG. 7.

[0179] As shown in FIG. 8, starting with the second version, VVC has several modes corresponding to inclined intra prediction directions, including a wide-angle mode (shown as a dashed line). For any of these modes, to predict a sample in a block, if the corresponding position in the block side is fractional, an interpolation of a set of neighboring reference samples should be performed. HEVC and VVC use linear interpolation between two neighboring reference samples. JEM uses a more sophisticated 4-tap interpolation filter. The filter coefficients are selected to be either Gaussian or cubic filters depending on the width or height value. The decision on whether to use width or height is coordinated with the decision on the dominant reference side selection, i.e., when the intra prediction mode is a diagonal mode or higher, the upper side of the reference sample is selected to be the dominant reference side, and the width value is selected to determine the interpolation filter to be used. Otherwise, the dominant side reference is selected from the left side of the block, and the height controls the filter selection process. In particular, if the selected side length is 8 samples or less, a cubic interpolation 4-tap is applied. Otherwise, the interpolation filter is a 4-tap Gaussian filter.

[0180] Similar to inter prediction, intra prediction may require interpolation filtering when samples in a block are predicted according to a fractional gradient directional mode. If a linear filter is used for this purpose, the filter coefficients can be easily calculated if the samples in the block to be predicted fall within a fractional (sub-pel) position in the reference sample. Therefore, a linear filter does not require a LUT (look-up table) to store its coefficients. However, a LUT may be used rather than direct calculation. However, if the prediction module uses a long-tap (e.g., 4 or 8 tap) interpolation filter, it may require a LUT to hold the coefficients of the interpolation filter, as is done in the inter prediction module, where an 8-tap DCT-IF for luma and a 4-tap DCT-IF for chroma are tabulated as shown in Table 1 (Table 5) and Table 2 (Table 6), respectively.

[0181] [Table 5]

[0182] [Table 6]

[0183] A particular set of coefficients may be defined as shown in Table 3.

[0184] [Table 7]

[0185] The intra predicted samples are calculated by convolving with coefficients specified according to the sub-pixel offset and filter type as follows:

[0186]

number

[0187] In this expression, ">>" denotes a bitwise right shift operation.

[0188] The set of coefficients {c i} are fetched from a look-up table (LUT). Table 3 gives an example of values ​​stored according to the current design of VVC, as described in the draft specification version 3 (JVET-L1001 "Versatile Video Coding (Draft 3)"). The selection between the smoothing (fG) and sharpening (fC) interpolation filters is performed using the MDIS (Mode Dependent Intra Smoothing) condition. Therefore, either fC or fG can be used to generate the predicted samples of a block.

[0189] If a sharpening filter is selected, the predicted samples s(x) are further clipped to a permitted range of values, i.e., either specified using the SPS or derived from the bit depth of the selected component.

[0190] For some use cases, it may be beneficial to avoid having explicit LUTs for the interpolation filters, since LUT processing requires additional memory and therefore increases energy consumption as well as die size. The first one is critical for mobile applications. The second one negatively impacts price.

[0191] For the stated use case, it is reasonable to analytically define the coefficients of the interpolation filter: rather than performing a fetch from a LUT, the filter coefficients can be calculated from the input fractional sample position p.

[0192] According to an embodiment of the present disclosure, there is provided a method for intra or inter prediction processing of a video frame, the method comprising the steps of obtaining a reference sample; obtaining a value of a sub-pixel offset; and filtering the reference sample using a sub-pixel 4-tap interpolation filter to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are:

[0193]

number

[0194] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are the filter coefficients of the sub-pixel 4-tap interpolation filter.

[0195] In one example implementation, the reference sample may be referred to as ref[x], which corresponds to an array of reference samples, ref[x]=p[-1-refIdx+x][-1-refIdx] (where x=0..nTbW+refIdx+1) where "p" refers to an xy two-dimensional array p[x][y] containing sample values. The number of reference samples used may be at least 1. In another example, the number of reference samples may be 4.

[0196] In one exemplary implementation, the sub-pixel offset values ​​obtained are: (y+1+refIdx)*intraPredAngle and "IntraPredAngle" is the value of the intra prediction angle.

[0197] In one exemplary implementation, the predicted sample values ​​“predSamples[x][y]” are

[0198]

number

[0199] where fT[i] refers to filter coefficients. These coefficients may be luma or chroma filter coefficients for inter prediction, referred to as fG and fC, respectively.

[0200] The choice of whether the filter coefficients are luma or chroma can be determined, for example, by fT[j]=filterFlag ? fG[iFact][j] : fC[iFact][j] This may be implemented by using and setting the flag "filterFlag" as follows: iFact=((y+1+refIdx)*intraPredAngle)&31 It is.

[0201] The value "31" refers to the fractional part of the sub-pixel offset value and may take other values ​​different from "31". The values ​​of the filter coefficients fG (luma) and / or fC (chroma) may be obtained analytically on the fly using the above analytical expressions for the filter coefficients of a 4-tap filter. Thus, the filter coefficients are defined according to the sub-pixel offset value.

[0202] Thus, the filter coefficients are obtained without accessing their respective values ​​from the LUT, but rather by calculation.

[0203] Alternatively, the filter coefficients may be calculated using the above equations and the values ​​may be stored in a LUT.

[0204] According to one embodiment of the present disclosure, the filter coefficients of the sub-pixel 4-tap interpolation filter are given in the following table:

[0205] [Table 8A]

[0206] [Table 8B]

[0207] It is specified in.

[0208] According to an embodiment of the present disclosure, there is provided a method for intra or inter prediction processing of a video frame, the method comprising the steps of obtaining a reference sample, obtaining a value of a sub-pixel offset, and filtering the reference sample using a sub-pixel 4-tap interpolation filter to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are as follows, i.e.

[0209] [Table 9]

[0210] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0211] In one example implementation, the values ​​of the filter coefficients may be stored in a LUT, which means that the respective values ​​of the filter coefficients will be fetched from the LUT for sub-pixel interpolation filtering.

[0212] FIG. 23 shows a flowchart of an intra / inter prediction process. In step 2301, a reference sample is obtained. The reference sample may include one or more reference samples. In step 2302, a sub-pixel offset value is then obtained. In step 2303, the reference sample is then calculated using the filter coefficients {c i}, where i=0,...3. This is called a 4-tap filter and / or a 4-point filter.

[0213] The filter coefficients may be obtained from an analytical expression with a given fractional portion p of the sub-pixel offset value. The filter coefficients may also be obtained from a LUT with reference to the p value.

[0214] According to one embodiment of the present disclosure, the bits of p are set to 0.

[0215] According to one embodiment of the present disclosure, p is incremented by 1, and then the least significant bit of the incremented p is set to 0 before it is used to obtain the filter coefficients.

[0216] According to an embodiment of the present disclosure, obtaining the filter coefficients includes:

[0217]

number

[0218] This includes a step of calculating the filter coefficients according to the previous filter coefficients c i to filter coefficient c i+1 This may further reduce the time for calculating the filter coefficients.

[0219] The proposed invention allows both approaches to derive the filter coefficients, i.e., LUT fetch and guide the calculations according to the proposed formulas.

[0220] One of the features of an interpolation filter consists of a linear dependence of its phase shift on the fractional sample position p. An embodiment of the present invention exploits this dependence to obtain the values ​​of the filter coefficients using simple arithmetic for the fractional sample position p.

[0221] The linear dependence is used to derive the smoothing interpolation filter coefficients fG. The derivation of the sharpening interpolation filter coefficients fC is based on taking the absolute value of the linear expression based on p.

[0222] According to an embodiment of the present disclosure, a method of video coding is provided, the method comprising intra prediction processing of blocks of a video frame, the method comprising filtering reference samples of the video frame using a sub-pixel 4-tap interpolation filter, the sub-pixel 4-tap interpolation filter being a combination of filters, and filter coefficients of at least one of the filters being:

[0223]

number

[0224] where p is the fractional sample position of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0225] A flowchart of video coding is shown in Figure 24. In step 2410, an intra prediction process is performed by filtering the reference samples of the block using a sub-pixel 4-tap interpolation filter.

[0226] According to one embodiment of the present disclosure, the sub-pixel 4-tap interpolation filter is a smoothing filter that is a parallel combination of two phase-dependent linear filters and a low-pass filter.

[0227] According to one embodiment of the present disclosure, the sub-pixel 4-tap interpolation filter is a sharpening filter that is a parallel combination of one phase-dependent linear filter and an intensity-varying high-pass filter.

[0228] According to one embodiment of the present disclosure, the intensity-varying high-pass filter is a phase-independent high-pass finite impulse response FIR filter, the output of which is multiplied by a phase-dependent intensity parameter.

[0229] According to any one of the previous embodiments of this disclosure, the least significant bits of p are set to 0.

[0230] According to one embodiment of the present disclosure, p is incremented by 1, then the least significant bits of the incremented value are set to 0 before this value is used to derive the interpolation filter coefficients.

[0231] According to one embodiment of the present disclosure, a clipping operation is performed on the output of the intensity variation high pass filter.

[0232] An embodiment of the present invention represents the filter coefficients as a combination of two or more FIR (Finite Impulse Response) filters, which may have the following options: - Successive combination, i.e. convolution of coefficients. - Parallel combination, i.e. weighted sum of coefficients.

[0233] Each of these filters may or may not depend on a phase parameter P, which is a function of the fractional sample position p. The coefficients of the filters belonging to the combination have a simple expression in terms of the phase parameter P.

[0234] In one embodiment, in FIG. 9, a set of reference samples is input to an interpolation filter.

[0235] In one embodiment, for the smoothing interpolation filters, the value of the phase parameter P is the same as the value of the fractional sample position p. In Figure 9, blocks F1 and F2 represent linear interpolation filters. The coefficients for each of these filters are expressed in terms of the phase parameter p as follows:

[0236]

number

[0237] In one example, here, and further, a division operation may be defined with or without rounding, i.e.

[0238]

number

[0239] or

[0240]

number

[0241] where "a" is the division designator and "n" is the power of the two parameters in the denominator.

[0242] Block F3 is a constant coefficient c0=16 c1=16 represents a two-tap low-pass filter having

[0243] In one example, filters F1..F3 are not normalized, F3 has a larger DC gain than F1, and F3 has a larger DC gain than F2.

[0244] The outputs of the filters F1..F3 are summed and normalized. Normalization (block “>>”) can be performed, for example, by right shifting or by division with rounding as explained above.

[0245] The resulting equation for this combination (an equivalent 4-tap filter) is expressed as follows:

[0246]

number

[0247] This embodiment allows for a LUT-based implementation, according to which the coefficient values ​​can also be defined using a LUT, the values ​​stored in which are defined using Table 4 (for both rounded and unrounded cases).

[0248] [Table 10]

[0249] From Table 4 it can be noted that the coefficients are in the range [0,31]. This fact explains the technical advantage of the present invention, which consists in the possibility of using 16-bit multipliers for 8-bit and 10-bit pictures, which are and will be most frequently used, at least in the medium term. A typical implementation of the present invention will comprise four parallel multiplication operations, the operands of the multiplication having a bit depth of up to 6 for the filter coefficients and 10 for the samples. The result of the multiplication will not exceed a 16-bit value, thus making the proposed coefficients favorable from an implementation point of view.

[0250] In inter prediction mode, block motion compensation is performed. The motion compensation may comprise a step of interpolation filtering similar to intra interpolation filtering. Another beneficial property of the present invention is that the coefficients of the interpolation filter have the same precision for both intra prediction and inter prediction modes (i.e., the bit depth of the values ​​of the coefficients is the same). If the precision of the interpolation filter coefficients is higher in the intra prediction case, it may have a negative impact on the computational complexity of the video codec. The reason is that intra prediction is inherently continuous, since it requires reconstructed samples of previous blocks. In contrast, inter prediction may be performed in parallel. Therefore, if the precision of the interpolation is higher for intra prediction than for inter prediction, it may deepen the implementation misbalance between the intra prediction pipeline and the inter prediction pipeline. This matching of precision allows to avoid such a negative conclusion.

[0251] Another advantage of the proposed invention is the reduction of coefficient diversity: considering that pairs of adjacent rows in Table 4 are identical, a practical implementation of the invention would fetch from a LUT with only 16 rows (those corresponding to even values ​​of p in the "no rounding" case, and those corresponding to odd values ​​of p in the "rounding" case) instead of 32 rows.

[0252] The technical effect of the present invention is that the present invention has at least the following types of implementations: - a LUT-less implementation that uses the value of p to calculate the filter coefficients, the calculation of which is based on the analytical formula described above; and - A LUT-based implementation that fetches the filter coefficients from the LUT using an index value based on the value of p. The aim is to make it possible.

[0253] The precision of the value of p is reduced when calculating the value of the coefficient. In particular, the value of the coefficient is calculated using an integer division by 2, i.e.,

[0254]

number

[0255] In the case of a LUT-based implementation, this precision reduction results in a reduction in the memory required to store the LUT. In hardware, this also reduces the number of wires in the address bus of the LUT.

[0256] According to an embodiment of the present disclosure, an apparatus for intra or inter prediction processing of a video frame is provided, the apparatus including: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of a sub-pixel offset; and a sub-pixel 4-tap interpolation filter configured to filter the reference sample to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are:

[0257]

number

[0258] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are the filter coefficients of the sub-pixel 4-tap interpolation filter.

[0259] According to one embodiment of the present disclosure, the filter coefficients of the sub-pixel 4-tap interpolation filter are given in the following table:

[0260] [Table 11A]

[0261] [Table 11B]

[0262] It is specified in.

[0263] According to an embodiment of the present disclosure, an apparatus for intra or inter prediction processing of a video frame is provided, the apparatus comprising: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of a sub-pixel offset; and a sub-pixel 4-tap interpolation filter configured to filter the reference sample to obtain a predicted sample value, wherein filter coefficients of the sub-pixel 4-tap interpolation filter are as follows, i.e.

[0264] [Table 12]

[0265] where p is the fractional part of the value of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0266] FIG. 25 shows a schematic diagram of an intra / inter processing module 2500, which includes a reference sample obtaining unit 2510, a sub-pixel offset value obtaining unit 2520, and a sub-pixel interpolation filter 2530.

[0267] According to an embodiment of the present disclosure, an apparatus for video coding is provided, the apparatus comprising: an intra-prediction processing unit configured to intra-predict a block of a video frame; and a sub-pixel 4-tap interpolation filter configured to filter reference samples of the video frame, the sub-pixel 4-tap interpolation filter being a combination of filters, and at least one filter coefficient of the filters being:

[0268]

number

[0269] where p is the fractional sample position of the sub-pixel offset, and c0, c1, c2, and c3 are filter coefficients.

[0270] FIG. 26 shows a schematic diagram of a video coding module 2600, comprising an intra-prediction processing unit 2610 and a sub-pixel interpolation filter 2620.

[0271] According to one embodiment of the present disclosure, there is provided an encoder (20) comprising processing circuitry for performing a method according to any one of the previous embodiments of the present disclosure.

[0272] According to one embodiment of the present disclosure, there is provided a decoder (30) comprising processing circuitry for performing a method according to any one of the previous embodiments of the present disclosure.

[0273] According to an embodiment of the present disclosure, there is provided a computer program product comprising a program code for performing a method according to any one of the previous embodiments of the present disclosure.

[0274] According to one embodiment of the present disclosure, there is provided a decoder comprising one or more processors and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processors, configuring the decoder to perform a method according to any one of the previous embodiments of the present disclosure.

[0275] According to one embodiment of the present disclosure, there is provided an encoder comprising one or more processors and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, the programming, when executed by the processors, configuring the encoder to perform a method according to any one of the previous embodiments of the present disclosure.

[0276] The present disclosure according to any of the previous embodiments may provide the advantage of performing fast intra / inter prediction of video frames, since the filter coefficients of the interpolation filter are obtained analytically, i.e., the coefficients are calculated on the fly, which avoids storing the coefficients in a look-up table (LUT), which requires access time to read the coefficients from memory.

[0277] Therefore, the prediction becomes more efficient and places less demand on the required memory. This also allows for a low-cost implementation of the prediction. Moreover, the analytical filter coefficients {c i Because {x,y,z} are linear in the fractional sample position p and involve division by two operations, the respective operations can be efficiently performed by employing fast low-level bit operations. The time to perform the bit operations and to calculate the filter coefficients is less than the time to access the stored coefficients from the LUT. Thus, latency is reduced.

[0278] Moreover, the particular analytical structure of the filter coefficients may provide the advantage of low-complexity implementation of the filter unit. In addition, the filter responses (i.e., frequency responses) for different sub-pixel positions are matched in terms of magnitude and phase, avoiding artifacts in the response, especially at high frequencies. The linearity of the filter coefficients may provide the advantage of hardware reuse.

[0279] In one embodiment, for the sharpening interpolation filter, the strength parameter S is defined as:

[0280]

number

[0281] This intensity parameter S is defined to have a maximum value at half-pel positions (p=16). For sub-pixel positions closer to integer positions, the intensity parameter S has smaller values. An exemplary combination of filters is shown in Figure 10. Block F1 in this figure represents a linear filter whose coefficients are defined as follows: c0=64-(p<<1) c1=p<<1

[0282] Block F2 represents a high pass filter with the following coefficients: c0=-1 c1=1 c2=1 c3=-1

[0283] The output of block F2 is being multiplied by a strength parameter S. The result of the multiplication is further summed with the output of linear filter F1 and the resulting sum is normalized.

[0284] The resulting equation for this combination (an equivalent 4-tap filter) is expressed as follows: c0=-S c1=64-(p<<1)+S c2=(p<<1)+S c3=-S

[0285] A LUT-based implementation is also possible for this formula. Table 5 gives the values ​​of the coefficients.

[0286] [Table 13]

[0287] When filter F2 has negative coefficients, the normalized result is further clipped to fit into a range of allowed values, which may either be signaled in the SPS or derived from the bit depth of the samples.

[0288] An alternative embodiment is to specify an alternative position of the clipping operation (see FIG. 11). This alternative design is based on the fact that the linear filter F1 may not have output values ​​lower or higher than any of its input values.

[0289] In one embodiment, the clipping block operates using the following steps.

[0290] Step 1 is to decide whether minimum or maximum thresholding should be performed.

[0291] Step 2 depends on the outcome of step 1. In particular, either minimum or maximum thresholding is performed.

[0292] If the input to the clipping block is negative, then minimum thresholding is applied. Otherwise, maximum thresholding is applied. The output of step 2 (and of the clipping block), v c may be defined as follows:

[0293]

number

[0294] For an input value v, the output of the minimum threshold process is v cmin is calculated as follows:

[0295]

number

[0296] The output of the maximum thresholding is calculated as follows:

[0297]

number

[0298] p max is the maximum value of the range of acceptable values ​​for the sample.

[0299] Value ref x and ref x-1 are the input reference samples shown in FIG. 11, which are the input of the linear filter F1.

[0300] In one embodiment, if clipping is performed after the multiplication operation, v c is calculated as follows:

[0301]

number

[0302] In some embodiments, filter F3 in Fig. 9 and filter F2 in Fig. 10 and Fig. 11 may not depend on the phase parameter P. These embodiments simplify the implementation because the output of these filters may be the same for each input row of prediction samples, and therefore this step may be performed before starting the interpolation process, for example at the stage of the reference sample filtering process. This approach increases the parallelism and therefore reduces the latency of directional filtering.

[0303] Another alternative embodiment (see FIG. 12) uses a filter of adjustable strength, rather than just a multiplier of the filter output. FIG. 12A shows the case where clipping is performed on the output of the high-pass filter F2. FIG. 12B shows the case where clipping is performed on the output of the normalized output of the combination of F1 and F2. Examples of filters of adjustable strength can be the following: bilateral filters, inverse transform filters, etc.

[0304] Another embodiment uses a reduced resolution of p, i.e., only 16 of the 32 entries are used. This is achieved, for example, by setting the least significant bit of p to 0.

[0305] As shown in Figures 13-21, various combinations of LUT-based and analytical representations of interpolation filter coefficients are possible for both intra-prediction and inter-prediction. For example, Figure 14 shows a use case where coefficients for a smoothing interpolation filter used in an intra-prediction case are calculated, while coefficients for other interpolation filters for both intra-prediction and inter-prediction are stored in a LUT. In addition, a video coding specification may include both LUT-based and analytical representations of interpolation filter coefficients to enable various implementations. If both representations are described, the LUT-based and analytical representations should provide identical coefficients.

[0306] FIG. 22 illustrates an implementation of the coefficient calculation method shown in FIG.

[0307] c0=-S c1=64-(p<<1)+S c2=(p<<1)+S c3=-S In this equation, the strength parameter S is defined as follows:

[0308]

number

[0309] This implementation corresponds to a different way to derive the intensity parameter S (shown as the obtained value of "q" in FIG. 22). The value of the fractional sample position p is transferred into a demultiplexer DEMUX controlled by an input 1-bit signal SEL, which is set to the value of the 5th least significant bit of p (which has an index of 4 if indexing starts from 0). If this bit is equal to "1", the SEL signal indicates that the value of p is greater than 16 and the following value should be calculated: q=-(not(31 xor p)) where "not" and "xor" are the bitwise NOT and XOR operations, respectively. This expression is equivalent to q=(32-p), which in the C / C++ programming language is q=-(~(0x1F^p)) can be written as:

[0310] Otherwise (i.e., if the input signal SEL of the demultiplexer DEMUX is equal to "0"), any calculations are bypassed and the signal p is forwarded to the multiplexer MUX, as is the signal q. The output signal r of the multiplexer MUX is passed to a module that calculates the value of t as follows: t=((r<<1)+r)>>3 Here, "<<" and ">>" are left-shift and right-shift operations, respectively.

[0311] Effectively, this value of t is the strength parameter S. Further optimization is possible by performing the steps shown in FIG. 22 in parallel with one of the coefficients of the linear filter. z=(64-(p<<1))

[0312] Once the values ​​of both z and S are calculated, they can be added together to get c1=z+S.

[0313] Although embodiments of the present invention are described primarily in terms of video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and correspondingly, system 10), as well as other embodiments described herein, may also be configured for still image processing or coding, i.e., processing or coding of individual pictures independent of any preceding or subsequent pictures, as in video coding. In general, when picture processing coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functionality (also called tools or techniques) of the video encoder 20 and the video decoder 30 may be equally used for still image processing, e.g., residual calculation 204 / 304, transform 206, quantization 208, inverse quantization 210 / 310, (inverse) transform 212 / 312, partitioning 262 / 362, intra prediction 254 / 354 and / or loop filter processing 220, 320, as well as entropy coding 270 and entropy decoding 304.

[0314] For example, the embodiments of the encoder 20 and the decoder 30, and the functions described herein with reference to the encoder 20 and the decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or codes and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or a communication medium, which includes any medium that facilitates the transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, the computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementation of the techniques described in this disclosure. The computer program product may include a computer-readable medium.

[0315] By way of example, and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of media. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer readable media.

[0316] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the above structures or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a combined codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0317] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by various hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or may be provided by a collection of interoperable hardware units including one or more processors as described above, along with suitable software and / or firmware.

[0318] In summary, this disclosure relates to intra or inter prediction for video encoding and decoding. For that purpose, the apparatus and method obtain a reference sample and a sub-pixel offset value. To obtain a predicted sample value, a sub-pixel 4-tap interpolation filter is used to filter the reference sample.

[0319]

number

[0320] As such, the filter coefficients of the sub-pixel 4-tap interpolation filter are defined according to the value of the sub-pixel offset, where p is the fractional part of the value of the sub-pixel offset.

[0321] Additional embodiments are summarized in the following sections.

[0322] Section 1: A method for an intra or inter prediction process of a video coding technique, the method comprising: Obtaining a reference sample (i.e., at least one reference sample, in one example the number of reference samples may be four); obtaining a value of a sub-pixel offset; filtering the reference samples using a sub-pixel interpolation filter to obtain predicted sample values, where filter coefficients of the sub-pixel interpolation filter are obtained according to the value of the sub-pixel offset.

[0323] Section 2: The method of section 1, wherein filter coefficients of the sub-pixel interpolation filter are obtained according to a fractional part of the value of the sub-pixel offset.

[0324] Clause 3: The method of clause 1 or clause 2, wherein the subpixel interpolation filter is an equivalent 4-tap filter.

[0325] Section 4: The filter coefficients of the subpixel interpolation filter are

[0326]

number

[0327] where p is the fractional part of the value of the sub-pixel offset.

[0328] Section 5: The filter coefficients of the subpixel interpolation filter are c0=-S c1=64-(p<<1)+S c2=(p<<1)+S c3=-S and the intensity parameter S is obtained as follows, i.e.,

[0329]

number

[0330] where p is the fractional part of the value of the sub-pixel offset.

[0331] Clause 6: Any one of clauses 1-5, wherein a bit (e.g., a least significant bit, or a lower bit) of the subpixel offset p is set to 0.

[0332] Clause 7: The method of any one of clauses 1 to 5, wherein the value of the subpixel offset p is incremented by 1, then the low-order bit of the incremented value is set to 0, and then this value is used to derive the filter coefficients.

[0333] Section 8: A method of video coding, the method comprising an intra prediction process for a block comprising a sub-pixel interpolation filtering process applied to reference samples, The sub-pixel interpolation filter is a combination of filters, at least one of which is determined according to the sub-pixel offset.

[0334] Section 9: The method of section 8, wherein the interpolation filter is a smoothing filter that is a parallel combination of two phase-dependent linear filters and a low-pass filter.

[0335] Section 10: The method of section 8, wherein the interpolation filter is a sharpening filter that is a parallel combination of one phase-dependent linear filter and an intensity-varying high-pass filter.

[0336] Section 11: The method of section 10, wherein the intensity variation high pass filter is a phase independent high pass FIR filter, the output of which is multiplied by a phase dependent intensity parameter.

[0337] Section 12: Combining filters

[0338]

number

[0339] where p is the fractional sample position p.

[0340] Section 13: Combining filters c0=-S c1=64-(p<<1)+S c2=(p<<1)+S c3=-S and the strength parameter S is specified as follows, i.e.,

[0341]

number

[0342] The method of section 11 is as follows:

[0343] Clause 14: Any one of the methods in the previous clauses, wherein the low-order bit of fractional sample position p is set to 0.

[0344] Clause 15: Any one of clauses 8 to 13, wherein the fractional sample position p is incremented by 1, then the lower bit of the incremented value is set to 0, and then this value is used to derive the interpolation filter coefficients.

[0345] Clause 16: The method of clause 10 or clause 11, wherein a clipping operation is performed on the output of the intensity variation high pass filter.

[0346] Clause 17: An encoder (20) comprising processing circuitry for carrying out a method according to any one of clauses 1 to 16.

[0347] Clause 18: A decoder (30) comprising processing circuitry for carrying out the method according to any one of clauses 1 to 16.

[0348] Clause 19: A computer program product comprising a program code for performing the method according to any one of clauses 1 to 16.

[0349] Section 20: A decoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of clauses 1 to 16.

[0350] Section 21: An encoder, one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform a method according to any one of clauses 1 to 16.

[0351] Section 22: A method for an intra or inter prediction process of a video coding technique, the method comprising: Obtaining a reference sample (i.e., at least one reference sample, in one example the number of reference samples may be four); obtaining fractional sample positions; and filtering the reference samples using a sub-pixel interpolation filter to obtain predicted sample values, the filter coefficients of the sub-pixel interpolation filter being: c0=-S c1=64-(p<<1)+S c2=(p<<1)+S c3=-S where S is the intensity parameter, p is the fractional sample position, and c0, c1, c2, c3 are the filter coefficients.

[0352] Section 23: The method obtaining a value of the SEL signal by taking the Nth least significant bit of a fractional sample position p, where N is a positive integer; obtaining an intermediate value, q, where q is set equal to the value of fractional sample position p when the SEL signal is zero, or q is set to −(not(31 xor p)) when the SEL signal is not zero; One addition and shift operation, i.e. S=((q<<1)+q)>>3 and obtaining an intensity parameter S using

[0353] Section 24: The method of section 23, where N is equal to 5.

[0354] Clause 25: The method of any one of clauses 22 to 24, wherein the subpixel interpolation filter is an equivalent 4-tap filter.

[0355] Section 26: The intensity parameter S is calculated in parallel with the coefficients of the linear filter z, which are used to obtain the filter coefficients c1 of the sub-pixel interpolation filter; z=64-(p<<1) Any one of the methods in paragraphs 22 to 25.

[0356] Clause 27: Any one of clauses 22 to 25, wherein a bit (e.g., a least significant bit, or a lower bit) of fractional sample position p is set to 0.

[0357] Clause 28: Any one of clauses 22 to 26, wherein the fractional sample position p is incremented by 1, then the lower bit of the incremented value is set to 0, and then this value is used to derive the filter coefficients.

[0358] Clause 29: A method of video coding, the method comprising an intra prediction process for a block comprising a sub-pixel interpolation filtering process applied to reference samples, The subpixel interpolation filter is a combination of filters, at least one of which is determined according to the fractional sample position.

[0359] Clause 29: The method of clause 28, wherein the interpolation filter is a smoothing filter that is a parallel combination of two phase-dependent linear filters and a low-pass filter.

[0360] Clause 30: The method of clause 29, wherein the interpolation filter is a sharpening filter that is a parallel combination of one phase-dependent linear filter and an intensity-varying high-pass filter.

[0361] Clause 31: The method of clause 30, wherein the intensity variation high pass filter is a phase independent high pass FIR filter, the output of which is multiplied by a phase dependent intensity parameter.

[0362] Clause 32: An encoder (20) comprising processing circuitry for carrying out a method according to any one of clauses 22 to 31.

[0363] Clause 33: A decoder (30) comprising processing circuitry for carrying out the method according to any one of clauses 22 to 31.

[0364] Clause 34: A computer program product comprising a program code for performing the method according to any one of clauses 22 to 31.

[0365] Section 35: A decoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of clauses 22 to 31.

[0366] Section 36: An encoder, one or more processors; and a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform a method according to any one of clauses 22 to 31. [Explanation of symbols]

[0367] Figure 1A 10. Video Coding System 12 Source Device 13 Communication Channels 14 Destination Device 16 Picture Source 17 Picture Data 18 Preprocessors 19 Preprocessed Picture Data 20 Video Encoder 21 Encoded Picture Data 22 Communication Interface 28 Communication Interface 30 Video Decoder 31 Decoded Picture Data 32 Post Processor 33 Post-Processed Picture Data 34 Display Devices Figure 1B 40 Video Coding System 41 Imaging Devices 42 Antenna 43 Processors 44 Memory Store 45 Display Devices 46 Processing circuit configuration 20 Video Encoder 30 Video Decoder Figure 2 17 Picture (data) 19 Preprocessed picture (data) 20 Video Encoder 21 Encoded Picture Data 201 Input section (interface) 204 Residual Calculation [Unit or Step] 206 Conversion Processing Unit 208 Quantization Units 210 Inverse Quantization Unit 212 Inverse Transformation Processing Unit 214 Reconstruction Unit 220 Loop Filter Unit 230 Decoded Picture Buffer (DPB) 260 Mode Selection Unit 270 Entropy Coding Unit 272 Output section (interface) 244 Inter Prediction Units 254 intra prediction units 262 Division Unit 203 Picture Block 205 Residual Blocks 213 Reconstruction Residual Block 215 Reconstruction Block 221 Filtered Blocks 231 Decoded Picture 265 predicted blocks 266 Syntax Elements 207 Conversion Factors 209 Quantization Coefficients 211 Inverse quantization coefficients Figure 3 21 Encoded Picture Data 30 Video Decoder 304 Entropy Decoding Unit 309 Quantization Coefficients 310 Inverse Quantization Unit 311 Inverse quantization coefficients 312 Inverse Transformation Processing Unit 313 Reconstruction Residual Block 314 Reconstruction Unit 315 Reconstruction Block 320 Loop Filter 321 Filtered Blocks 330 Decoded Picture Buffer DBP 331 Decoded Picture 360 mode application unit 365 predicted blocks 366 Syntax Elements 344 Inter Prediction Units 354 intra prediction units Figure 4 400 Video Coding Device 410 Inlet port / Input port 420 Receiver Unit Rx 430 Processor 440 Transmitter unit Tx 450 Exit Port / Output Port 460 Memory 470 Coding Module Figure 5 500 source or destination devices 502 processor 504 Memory 506 Code and Data 508 Operating Systems 510 Application Program 512 Bus 518 Display Figure 23 2300 Flowchart of intra / inter prediction processing method Fig. 24 2400 Video coding method flow chart Fig. 25 2500 Intra / Inter Processing Module 2510 Reference Sample Acquisition Unit 2520 Subpixel offset value acquisition unit 2530 Subpixel Interpolation Filter Fig. 26 2600 Video Coding Module 2610 Intra Prediction Processing Unit 2620 Subpixel Interpolation Filter

Claims

1. 1. A method for intra or inter prediction processing of video frames, comprising: obtaining a reference sample; obtaining a value of a sub-pixel offset; filtering the reference samples using a sub-pixel 4-tap interpolation filter to obtain predicted sample values; Equipped with The filter coefficients of the sub-pixel 4-tap interpolation filter are [0031] Fulfilling p is the fractional part of the value of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients of the sub-pixel 4-tap interpolation filter, method.

2. The filter coefficients of the sub-pixel 4-tap interpolation filter are stored in a table as follows: 【Table 1A】 【Table 1B】 The method of claim 1, wherein

3. 1. A method for intra or inter prediction processing of video frames, comprising: obtaining a reference sample; obtaining a value of a sub-pixel offset; filtering the reference samples using a sub-pixel 4-tap interpolation filter to obtain predicted sample values; Equipped with The filter coefficients of the sub-pixel 4-tap interpolation filter are as follows: 【Table 2A】 【Table 2B】 It is defined as follows: p is the fractional part of the value of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients. method.

4. 4. The method of claim 1, wherein bits of p are set to 0.

5. 4. The method of claim 1, wherein p is incremented by 1, and then a lower bit of the incremented p is set to 0 before p is used to obtain the filter coefficients.

6. Obtaining the filter coefficients [0032] The method of claim 1 , further comprising the step of calculating the filter coefficients according to:

7. 1. A method of video coding, comprising: an intra prediction process for a block of a video frame, the intra prediction process comprising filtering reference samples of the video frame using a sub-pixel 4-tap interpolation filter; The sub-pixel 4-tap interpolation filter is a combination of filters, and the filter coefficients of at least one of the filters are: [Equation 33] Fulfilling p is the fractional sample position of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients. method.

8. The method of claim 7 , wherein the sub-pixel 4-tap interpolation filter is a smoothing filter that is a parallel combination of two phase-dependent linear filters and a low-pass filter.

9. The method of claim 7 , wherein the sub-pixel 4-tap interpolation filter is a sharpening filter that is a parallel combination of one phase-dependent linear filter and an intensity-varying high-pass filter.

10. 10. The method of claim 9, wherein the intensity-varying high-pass filter is a phase-independent high-pass finite impulse response FIR filter, the output of which is multiplied by a phase-dependent intensity parameter.

11. 11. A method according to claim 7, wherein the least significant bits of p are set to 0.

12. 11. A method according to claim 7, wherein p is incremented by 1, after which the least significant bits of the incremented value are set to 0 before this value is used to derive the interpolation filter coefficients.

13. The method according to claim 9 or 10, wherein a clipping operation is performed on the output of the intensity variation high pass filter.

14. An apparatus for intra or inter prediction processing of video frames, comprising: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of the sub-pixel offset; a sub-pixel 4-tap interpolation filter configured to filter the reference samples to obtain predicted sample values; Including, The filter coefficients of the sub-pixel 4-tap interpolation filter are [0034] Fulfilling p is the fractional part of the value of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients of the sub-pixel 4-tap interpolation filter, Device.

15. The filter coefficients of the sub-pixel 4-tap interpolation filter are stored in a table as follows: 【Table 3A】 【Table 3B】 15. The apparatus of claim 14, wherein:

16. An apparatus for intra or inter prediction processing of video frames, comprising: a reference sample obtaining unit configured to obtain a reference sample; a sub-pixel offset value obtaining unit configured to obtain a value of the sub-pixel offset; a sub-pixel 4-tap interpolation filter configured to filter the reference samples to obtain predicted sample values; Equipped with The filter coefficients of the sub-pixel 4-tap interpolation filter are as follows: 【Table 4A】 【Table 4B】 It is defined as follows: p is the fractional part of the value of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients. Device.

17. An apparatus for video coding, comprising: an intra-prediction processing unit configured to intra-predict blocks of a video frame; a sub-pixel 4-tap interpolation filter configured to filter reference samples of the video frames; Equipped with The sub-pixel 4-tap interpolation filter is a combination of filters, and the filter coefficients of at least one of the filters are: [Equation 35] Fulfilling p is the fractional sample position of the sub-pixel offset, and c 0 , c 1 , c 2 , and c 3 are the filter coefficients. Device.

18. An encoder (20) comprising processing circuitry for carrying out the method of any one of claims 1 to 13.

19. A decoder (30) comprising processing circuitry for carrying out the method of any one of claims 1 to 13.

20. A computer program product comprising program code for carrying out the method according to any one of claims 1 to 13.

21. A decoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor; Equipped with The programming, when executed by the processor, configures the decoder to perform the method of any one of claims 1 to 13. decoder.

22. 1. An encoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor; Equipped with The programming, when executed by the processor, configures the encoder to perform the method of any one of claims 1 to 13. Encoder.

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