METHOD FOR DECODING VIDEO DATA, COMPUTING DEVICE, NON-TRANSITORY COMPUTER-READABLE STORAGE MEDIUM, AND COMPUTER PROGRAM - Patent application

Abstract

1. A method of decoding video data, comprising: receiving, from a bitstream, video data corresponding to a non-skip mode coded block; determining a parameter set associated with the non-skip mode coded block; obtaining a first syntax element from the bitstream if the parameter set satisfies a first condition; obtaining a second syntax element from the bitstream if the parameter set satisfies a second condition; obtaining a third syntax element from the bitstream if the parameter set satisfies a third condition; decoding the video data corresponding to the non-skip mode coded block using a palette mode when the first and third syntax elements have a first value; decoding the video data using an intra prediction mode when the first and third syntax elements have a second value; and decoding the video data using an inter prediction mode when the first syntax element has a second value.

Description

[Technical field]

[0001] The present application relates generally to encoding and decoding of video data, and more particularly to a method and system for prediction mode signaling in video encoding. [Background technology]

[0002] Digital video is supported by a variety of electronic devices, such as digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video game consoles, smartphones, video teleconferencing devices, video streaming devices, etc. Electronic devices transmit, receive, encode, decode, and / or store digital video data by implementing video compression / decompression standards defined by MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), High Efficiency Video Coding (HEVC), and Versatile Video Coding (VVC) standards. Video compression typically involves performing spatial (intra-frame) prediction and / or temporal (inter-frame) prediction to reduce or remove redundancy inherent in video data. For block-based video coding, a video frame is divided into one or more slices, with each slice having multiple video blocks, which may also be referred to as coding tree units (CTUs). Each CTU may contain one coding unit (CU) or may be recursively divided into smaller CUs until a predetermined minimum CU size is reached. Each CU (also called a leaf CU) contains one or more transform units (TUs), and each CU also contains one or more prediction units (PUs). Each CU may be coded in either intra mode, inter mode, or IBC mode. Video blocks in an intra-coded (I) slice of a video frame are coded using spatial prediction with respect to reference samples in neighboring blocks in the same video frame. Video blocks in an inter-coded (P or B) slice of a video frame may use spatial prediction with respect to reference samples in neighboring blocks in the same video frame, or temporal prediction with respect to reference samples in other previous and / or future reference video frames.

[0003] Spatial or temporal prediction based on previously coded reference blocks, e.g., neighboring blocks, results in a predicted block for the current video block to be coded. The process of finding the reference block can be achieved by a block matching algorithm. Residual data representing pixel differences between the current block to be coded and the predicted block is called a residual block or prediction error. Inter-coded blocks are coded according to reference blocks in a reference frame that form the predicted block, and a motion vector that points to the residual block. The process of determining the motion vector is typically called motion estimation. Intra-coded blocks are coded according to an intra-prediction mode and a residual block. For further compression, the residual block may be transformed from the pixel domain to a transform domain, e.g., the frequency domain, resulting in residual transform coefficients, which may then be quantized. The quantized transform coefficients may first be arranged in a two-dimensional array, scanned to generate a one-dimensional vector of transform coefficients, and then entropy coded into a video bitstream to achieve even more compression.

[0004] The encoded video bitstream is then stored on a computer-readable recording medium (e.g., flash memory) for access by another electronic device having digital video capabilities or for direct transmission to the electronic device via wired or wireless connection. The electronic device then performs video decompression (which is the opposite process to the video compression described above) by parsing the encoded video bitstream to obtain syntax elements from the bitstream, reconstructing digital video data from the encoded video bitstream into its original format based at least in part on the syntax elements obtained from the bitstream, and rendering the reconstructed digital video data on a display of the electronic device. Summary of the Invention [Problem to be solved by the invention]

[0005] With digital video quality ranging from high definition to 4K×2K or 8K×4K, the amount of video data to be encoded / decoded increases exponentially. How to encode / decode video data more efficiently while maintaining the image quality of the decoded video data is always a challenge. [Means for solving the problem]

[0006] This application describes implementations related to encoding and decoding video data, and more particularly, describes systems and methods for prediction mode signaling in video encoding.

[0007] According to a first aspect of the present application, a method for decoding video data is performed on a computing device having one or more processors and a memory storing a plurality of programs executed by the one or more processors, the method includes receiving video data corresponding to a non-skip mode coded block from a bitstream, determining a parameter set associated with the non-skip mode coded block, obtaining a first syntax element from the bitstream if the parameter set satisfies a first condition, obtaining a second syntax element from the bitstream if the parameter set satisfies a second condition, obtaining a third syntax element from the bitstream if the parameter set satisfies a third condition, decoding the video data corresponding to the non-skip mode coded block using a palette mode when the first syntax element and the third syntax element have a first value, decoding the video data using an intra prediction mode when the first syntax element has a first value and the third syntax element has a second value, and decoding the video data using an inter prediction mode when the first syntax element has a second value.

[0008] According to a second aspect of the present application, a computing device includes one or more processors, a memory, and a number of programs stored in the memory, the programs, when executed by the one or more processors, causing the computing device to perform operations as described above.

[0009] According to a third aspect of the present application, a non-transitory computer-readable storage medium stores a number of programs for execution by a computing device having one or more processors, the programs, when executed by the one or more processors, causing the computing device to perform operations as described above. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram illustrating an example video encoding and decoding system according to some implementations of the present disclosure. [Diagram 2] 1 is a block diagram illustrating an example video encoder according to some implementations of the present disclosure. [Diagram 3] 1 is a block diagram illustrating an example video decoder according to some implementations of the present disclosure. [Figure 4A] A block diagram showing how a frame is recursively quadtree partitioned into multiple video blocks of different sizes in accordance with some implementations of this disclosure. [Figure 4B] A block diagram showing how a frame is recursively quadtree partitioned into multiple video blocks of different sizes in accordance with some implementations of this disclosure. [Figure 4C] A block diagram showing how a frame is recursively quadtree partitioned into multiple video blocks of different sizes in accordance with some implementations of this disclosure. [Figure 4D] A block diagram showing how a frame is recursively quadtree partitioned into multiple video blocks of different sizes in accordance with some implementations of this disclosure. [Figure 4E]A block diagram showing how a frame is recursively quadtree partitioned into multiple video blocks of different sizes in accordance with some implementations of this disclosure. [Diagram 5] A block diagram illustrating different prediction modes of a coding unit in accordance with some implementations of this disclosure. [Figure 6] 1 is a flowchart illustrating an example process for implementing a technique for a video coder signaling a prediction mode according to some implementations of this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The accompanying drawings, which are included to provide a further understanding of the embodiments, are incorporated in and constitute a part of this specification, illustrate the described embodiments, and together with the description, serve to explain the underlying principles, like reference numerals refer to corresponding parts.

[0012] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth to aid in understanding the subject matter presented herein. However, it will be apparent to one skilled in the art that various alternatives may be used without departing from the scope of the claims, and that the subject matter may be practiced without these specific details. For example, it will be apparent to one skilled in the art that the subject matter presented herein may be implemented on many types of electronic devices having digital video capabilities.

[0013] 1 is a block diagram illustrating an example system 10 for encoding and decoding video blocks in parallel, according to some implementations of the present disclosure. As shown in FIG. 1, the system 10 includes a source device 12, which generates and encodes video data that is subsequently decoded by a destination device 14. The source device 12 and the destination device 14 may include any of a wide variety of electronic devices, including desktop or laptop computers, tablet computers, smartphones, set-top boxes, digital televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, and the like. In some implementations, the source device 12 and the destination device 14 may include wireless communication capabilities.

[0014] In an implementation, the destination device 14 may receive the encoded video data to be decoded via the link 16. The link 16 may include any type of communication medium or apparatus capable of moving the encoded video data from the source device 12 to the destination device 14. In one example, the link 16 may comprise a communication medium to enable the source device 12 to transmit the encoded video data directly to the destination device 14 in real time. The encoded video data may be modulated according to a communication standard, such as a wireless communication protocol, and transmitted to the destination device 14. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network, such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from the source device 12 to the destination device 14.

[0015] In some other implementations, the encoded video data may be transmitted from the output interface 22 to the storage device 32. The encoded video data in the storage device 32 may then be accessed by the destination device 14 via the input interface 28. The storage device 32 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, a Blu-ray disc, a DVD, a CD-ROM, a flash memory, a volatile or non-volatile memory, or any other suitable digital storage medium that stores the encoded video data. In a further example, the storage device 32 may correspond to a file server or another intermediate storage device that may hold the encoded video data generated by the source device 12. The destination device 14 may access the stored video data from the storage device 32 via streaming or download. The file server may be any type of computer that may store the encoded video data and transmit the encoded video data to the destination device 14. Exemplary file servers include a web server, an FTP server, a Network Attached Storage (NAS) device, or a local disk drive. Destination device 14 may access the encoded video data via any standard data connection, including a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of both suitable for accessing encoded video data stored on a file server. The transmission of the encoded video data from storage device 32 may be a streaming transmission, a download transmission, or a combination of both.

[0016] As shown in FIG. 1, source device 12 includes a video source 18, a video encoder 20, and an output interface 22. Video source 18 may include sources such as a video capture device, e.g., a video camera, a video archive containing previously captured video, a video feed interface for receiving video from a video content provider, and / or a computer graphics system for generating computer graphics data as the source video, or a combination of such sources. As an example, if video source 18 is a video camera in a security surveillance system, source device 12 and destination device 14 may form a camera phone or video phone. However, the implementations described in this application are applicable to video encoding in general and may be applicable to wireless and / or wired applications.

[0017] The captured, pre-captured, or computer-generated video may be encoded by video encoder 20. The encoded video data may be transmitted directly to destination device 14 via output interface 22 of source device 12. The encoded video data may also be stored in storage device 32 for subsequent access by destination device 14 or other devices for decoding and / or playback. Output interface 22 may further include a modem and / or a transmitter.

[0018] Destination device 14 includes an input interface 28, a video decoder 30, and a display device 34. Input interface 28 may include a receiver and / or modem and may receive encoded video data over link 16. The encoded video data communicated over link 16 or provided on storage device 32 may include various syntax elements generated by video encoder 20 for use by video decoder 30 in decoding the video data. Such syntax elements may be transmitted over a communication medium, stored on a storage medium, or stored on a file server, or may be included within the encoded video data.

[0019] In some implementations, destination device 14 may include a display device 34, which may be an integrated display device, and an external display device configured to communicate with destination device 14. Display device 34 displays the decoded video data to a user and may include any of a variety of display devices, such as a liquid crystal display, a plasma display, an organic light emitting diode, or another type of display device.

[0020] Video encoder 20 and video decoder 30 may operate according to a proprietary or industry standard, such as VVC, HEVC, MPEG-4, Part 10, Advanced video Coding (AVC), or extensions of such standards. It should be understood that the present application is not limited to a particular video encoding / decoding standard, but is applicable to other video encoding / decoding standards. In general, it is contemplated that video encoder 20 of source device 12 may be configured to encode video data according to any of these current or future standards. Similarly, it is also contemplated that video decoder 30 of destination device 14 may be generally configured to decode video data according to any of these current or future standards.

[0021] Each of the video encoder 20 and the video decoder 30 may be implemented as any of a variety of suitable encoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. If implemented partially in software, the electronic device may store the software instructions on a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the video encoding / decoding operations disclosed in this disclosure. Each of the video encoder 20 and the video decoder 30 may be included in one or more encoders or decoders, any of which may be integrated as part of a composite encoder / decoder (CODEC) within the respective device.

[0022] 2 is a block diagram illustrating an example video encoder 20 according to some implementations described in this application. Video encoder 20 may perform intra-predictive and inter-predictive coding of video blocks within a video frame. Intra-predictive coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter-predictive coding relies on temporal prediction to reduce or remove temporal redundancy in video data within adjacent video frames or pictures of a video sequence.

[0023] As shown in FIG. 2, video encoder 20 includes video data memory 40, prediction processing unit 41, decoded picture buffer (DPB) 64, adder 50, transform processing unit 52, quantization unit 54, and entropy coding unit 56. Prediction processing unit 41 further includes motion estimation unit 42, motion compensation unit 44, division unit 45, intra prediction processing unit 46, and intra block copy (BC) unit 48. In some implementations, video encoder 20 also includes inverse quantization unit 58, inverse transform processing unit 60, and adder 62 for video block reconstruction. A deblocking filter (not shown) may be disposed between adder 62 and DPB 64 to filter block boundaries to remove block noise artifacts from the reconstructed video. An in-loop filter (not shown) may be used to filter the output of adder 62 in addition to the deblocking filter. Video encoder 20 may take the form of fixed or programmable hardware units, or may be divided among one or more of the illustrated fixed or programmable hardware units.

[0024] Video data memory 40 may store video data to be encoded by components of video encoder 20. The video data in video data memory 40 may be obtained, for example, from video source 18. DPB 64 is a buffer that stores reference video data for use in encoding video data by video encoder 20 (e.g., for intra-predictive or inter-predictive encoding modes). Video data memory 40 and DPB 64 may take the form of any of a variety of memory devices. In various examples, video data memory 40 may be on-chip with other components of video encoder 20 or may be off-chip relative to these components.

[0025] As shown in FIG. 2, after receiving the video data, a partitioning unit 45 in the prediction processing unit 41 partitions the video data into video blocks. This partitioning may also include partitioning the video frame into slices, tiles, or other larger coding units (CUs) according to a predefined partitioning structure, such as a quadtree structure, associated with the video data. The video frame may be partitioned into a number of video blocks (or a set of video blocks called tiles). The prediction processing unit 41 may select one of a number of possible predictive coding modes, such as one of a number of intra-predictive coding modes or one of a number of inter-predictive coding modes, for the current video block based on the error result (e.g., the code rate and the level of distortion). The prediction processing unit 41 may provide the resulting intra- or inter-predictive coding block to an adder 50 to generate a residual block and subsequently to an adder 62 that reconstructs the coding block for use as part of the reference frame. The prediction processing unit 41 also provides syntax elements, such as motion vectors, intra-mode indicators, partitioning information, and other such syntax information, to an entropy coding unit 56.

[0026] To select an appropriate intra-prediction coding mode for the current video block, intra-prediction processing unit 46 within prediction processing unit 41 may perform intra-prediction coding of the current video block relative to one or more neighboring blocks in the same frame as the current block to be encoded to provide spatial prediction. Motion estimation unit 42 and motion compensation unit 44 within prediction processing unit 41 perform inter-prediction coding of the current video block relative to one or more predictive blocks in one or more reference frames to provide temporal prediction. Video encoder 20 may perform multiple encoding passes to select an appropriate coding mode for each block of video data, for example.

[0027] In some implementations, motion estimation unit 42 determines the inter prediction mode of the current video frame by generating a motion vector indicating the displacement of a prediction unit (PU) of a video block in the current video frame relative to a predictive block in a reference video frame according to a predetermined pattern in a sequence of video frames. Motion estimation performed by motion estimation unit 42 is a process of generating motion vectors, which estimate the motion of a video block. The motion vector may indicate, for example, the displacement of a PU of a video block in a current video frame or picture relative to a predictive block in a reference frame (or other coding unit) relative to a current block being coded in the current frame (or other coding unit). The predetermined pattern may designate a video frame in the sequence as a P frame or a B frame. Intra BC unit 48 may determine vectors, e.g., block vectors, for intra BC coding in a manner similar to the determination of motion vectors by motion estimation unit 42 for inter prediction, or may utilize motion estimation unit 42 to determine block vectors.

[0028] A prediction block is a block of a reference frame that is deemed to closely match a PU of a video block to be encoded in terms of pixel differences, which may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metrics. In some implementations, video encoder 20 may calculate values ​​for sub-integer pixel locations of a reference frame stored in DPB 64. For example, video encoder 20 may interpolate values ​​for quarter-pixel locations, eighth-pixel locations, or other fractional pixel locations of a reference frame. Thus, motion estimation unit 42 may perform motion search for whole pixel locations and fractional pixel locations and output motion vectors with fractional pixel accuracy.

[0029] Motion estimation unit 42 calculates a motion vector of a PU of a video block in an inter-predictively coded frame by comparing the position of the PU with the position of a predictive block of a reference frame selected from a first reference frame list (List0) or a second reference frame list (List1), each of which identifies one or more reference frames stored in DPB 64. Motion estimation unit 42 sends the calculated motion vector to motion compensation unit 44 and then to entropy coding unit 56.

[0030] The motion compensation performed by motion compensation unit 44 may include fetching or generating a predictive block based on the motion vector determined by motion estimation unit 42. Upon receiving the motion vector for the PU of the current video block, motion compensation unit 44 may locate the predictive block pointed to by the motion vector in one of the reference frame lists, retrieve the predictive block from DPB 64, and forward the predictive block to summer 50. Summer 50 then forms a residual video block of pixel difference values ​​by subtracting pixel values ​​of the predictive block provided by motion compensation unit 44 from pixel values ​​of the current video block being encoded. The pixel difference values ​​forming the residual video block may include luma or chroma components or both. Motion compensation unit 44 may also generate syntax elements associated with the video blocks of the video frames for use by video decoder 30 in decoding the video blocks of the video frames. The syntax elements may include, for example, syntax elements defining the motion vector used to identify the predictive block, any flags indicating a prediction mode, or any other syntax information described herein. It should be noted that motion estimation unit 42 and motion compensation unit 44 may be highly integrated, but are illustrated separately for conceptual purposes.

[0031] In some implementations, the intra BC unit 48 may generate vectors and fetch the predictive block in a manner similar to that described above in connection with the motion estimation unit 42 and the motion compensation unit 44, but the predictive block is in the same frame as the current block being coded, and the vectors are referred to as block vectors as opposed to motion vectors. In particular, the intra BC unit 48 may determine an intra prediction mode to use to code the current block. In some examples, the intra BC unit 48 may code the current block using various intra prediction modes, e.g., during separate coding passes, and test their performance through rate-distortion analysis. The intra BC unit 48 may then use a suitable intra prediction mode among the various tested intra prediction modes and generate an intra mode indicator accordingly. For example, the intra BC unit 48 may calculate rate-distortion values ​​using a rate-distortion analysis for the various tested intra prediction modes, and select the intra prediction mode with the best rate-distortion characteristics among the tested modes as the suitable intra prediction mode to use. The rate-distortion analysis generally determines the amount of distortion (or error) between a coded block and the original uncoded block that was coded to generate the coded block, as well as the bitrate (i.e., number of bits) used to generate the coded block. Intra BC unit 48 can calculate ratios from the distortions and rates for the various coded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block.

[0032] In other examples, intra BC unit 48 may use, in whole or in part, motion estimation unit 42 and motion compensation unit 44 to perform such functions for intra BC prediction according to implementations described herein. In either case, for intra block copying, the predictive block may be a block that is deemed to closely match the block to be coded in terms of pixel differences, which may be determined by sum of absolute differences (SAD), sum of squared differences (SSD), or other difference metrics, and identification of the predictive block may include calculation of values ​​of sub-integer pixel positions.

[0033] Regardless of whether the predictive block is from the same frame according to intra prediction or from a different frame according to inter prediction, video encoder 20 may form a residual video block by subtracting pixel values ​​of the predictive block from pixel values ​​of the current video block being encoded to form pixel difference values. The pixel difference values ​​that form the residual video block may include both luma and chroma component differences.

[0034] Intra-prediction processing unit 46 may intra-predict the current video block as an alternative to inter-prediction performed by motion estimation unit 42 and motion compensation unit 44, or intra-block copy prediction performed by intra-BC unit 48, as described above. In particular, intra-prediction processing unit 46 may determine an intra-prediction mode to use to encode the current block. To do so, intra-prediction processing unit 46 may, for example, encode the current block using various intra-prediction modes during separate encoding passes, and intra-prediction processing unit 46 (or, in some examples, a mode selection unit) may select an appropriate intra-prediction mode to use from the tested intra-prediction modes. Intra-prediction processing unit 46 may provide information indicative of the selected intra-prediction mode for the block to entropy coding unit 56. Entropy coding unit 56 may encode the information indicative of the selected intra-prediction mode into the bitstream.

[0035] After prediction processing unit 41 determines a predictive block for the current video block via either inter- or intra-prediction, summer 50 forms a residual video block by subtracting the predictive block from the current video block. The residual video data in the residual block may be included in one or more transform units (TUs) and are provided to transform processing unit 52. Transform processing unit 52 converts the residual video data into residual transform coefficients using a transform, such as a discrete cosine transform (DCT) or a conceptually similar transform.

[0036] The transform processor 52 may send the resulting transform coefficients to a quantizer 54, which quantizes the transform coefficients to further reduce the bit rate. The quantization process may also reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, the quantizer 54 may then perform a scan of a matrix containing the quantized transform coefficients. Alternatively, the entropy coding unit 56 may perform the scan.

[0037] Following quantization, entropy encoding unit 56 entropy encodes the quantized transform coefficients into a video bitstream using, for example, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy encoding method or technique. The encoded bitstream may then be transmitted to video decoder 30 or archived to storage device 32 for subsequent transmission to or retrieval from video decoder 30. Entropy encoding unit 56 may also entropy encode motion vectors and other syntax elements for the current video frame being encoded.

[0038] Inverse quantization unit 58 and inverse transform processing unit 60 apply inverse quantization and inverse transform, respectively, to reconstruct the residual video block in the pixel domain for generating reference blocks for prediction of other video blocks. As mentioned above, motion compensation unit 44 may generate motion compensated prediction blocks from one or more reference blocks of a frame stored in DPB 64. Motion compensation unit 44 may also apply one or more interpolation filters to the prediction block to calculate sub-integer pixel values ​​for use in motion estimation.

[0039] Summer 62 adds the reconstructed residual block to the motion compensated prediction block generated by motion compensation unit 44 to generate a reference block for storage in DPB 64. The reference block may then be used by intra BC unit 48, motion estimation unit 42, and motion compensation unit 44 as a predictive block to predict another video block in a subsequent video frame.

[0040] 3 is a block diagram illustrating an example video decoder 30 according to some implementations of the present application. The video decoder 30 includes a video data memory 79, an entropy decoding unit 80, a prediction processing unit 81, an inverse quantization unit 86, an inverse transform processing unit 88, an adder 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra-prediction processing unit 84, and an intra-BC unit 85. The video decoder 30 may perform a decoding process that is generally the reverse of the encoding process described above for the video encoder 20 in relation to FIG. 2. For example, the motion compensation unit 82 may generate prediction data based on a motion vector received from the entropy decoding unit 80, while the intra-prediction unit 84 may generate prediction data based on an intra-prediction mode index received from the entropy decoding unit 80.

[0041] In some examples, the units of the video decoder 30 may be tasked with performing implementations of the present application. Also, in some examples, implementations of the present disclosure may be divided among one or more of the units of the video decoder 30. For example, the intra BC unit 85 may perform implementations of the present application alone or in combination with other units of the video decoder 30, such as the motion compensation unit 82, the intra prediction processing unit 84, and the entropy decoding unit 80. In some examples, the video decoder 30 may not include the intra BC unit 85, and the functionality of the intra BC unit 85 may be performed by other components of the prediction processing unit 81, such as the motion compensation unit 82.

[0042] Video data memory 79 may store video data, such as an encoded video bitstream, for decoding by other components of video decoder 30. The video data stored in video data memory 79 may be obtained, for example, from storage device 32, a local video source, such as a camera, via wired or wireless network communication of the video data, or by accessing a physical data storage medium (e.g., a flash drive or hard disk). Video data memory 79 may include a coded picture buffer (CPB) that stores coded video data from the coded video bitstream. A decoded picture buffer (DPB) 92 of video decoder 30 stores reference video data for use in decoding video data by video decoder 30 (e.g., in intra- or inter-predictive coding modes). Video data memory 79 and DPB 92 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magneto-resistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. For purposes of illustration, video data memory 79 and DPB 92 are shown as two separate components of video decoder 30 in Figure 3. However, it will be apparent to one skilled in the art that video data memory 79 and DPB 92 may be provided by the same memory device or separate memory devices. In some examples, video data memory 79 may be on-chip with other components of video decoder 30 or may be off-chip relative to those components.

[0043] During the decoding process, video decoder 30 receives an encoded video bitstream representing video blocks of encoded video frames and associated syntax elements. Video decoder 30 may receive the syntax elements at the video frame level and / or the video block level. Entropy decoding unit 80 of video decoder 30 entropy decodes the bitstream to generate quantized coefficients, motion vectors or intra-prediction mode indicators, and other syntax elements. Entropy decoding unit 80 then forwards the motion vectors and other syntax elements to prediction processing unit 81.

[0044] If a video frame is coded as an intra-predictive coded (I) frame, or for intra-coded predictive blocks in other types of frames, intra-prediction processing unit 84 of prediction processing unit 81 may generate predictive data for video blocks of the current video frame based on the signaled intra-prediction mode and reference data from previously decoded blocks of the current frame.

[0045] When a video frame is coded as an inter-predictive (i.e., B or P) frame, motion compensation unit 82 of prediction processing unit 81 generates one or more predictive blocks for video blocks of the current video frame based on the motion vectors and other syntax elements received from entropy decoding unit 80. Each of the predictive blocks may be generated from a reference frame in one of the reference frame lists. Video decoder 30 may construct the reference frame lists, List 0 and List 1, using a default construction technique based on the reference frames stored in DPB 92.

[0046] In some examples, when a video block is encoded according to the intra BC mode described herein, intra BC unit 85 of prediction processing unit 81 generates a predictive block for the current video block based on the block vectors and other syntax elements received from entropy decoding unit 80. The predictive block may be within the same reconstructed region of the picture as the current video block defined by video encoder 20.

[0047] Motion compensation unit 82 and / or intra BC unit 85 determine prediction information for video blocks of the current video frame by parsing the motion vectors and other syntax elements, and then use the prediction information to generate predictive blocks for the current video block being decoded. For example, motion compensation unit 82 uses some of the received syntax elements to determine the prediction mode (e.g., intra prediction or inter prediction) used to encode the video blocks of the video frame, the inter prediction frame type (e.g., B or P), configuration information for one or more of the reference frame lists for the frame, the motion vectors for each inter predictive coded video block of the frame, the inter prediction status for each inter predictive coded video block of the frame, and other information for decoding video blocks in the current video frame.

[0048] Similarly, intra BC unit 85 may use some of the received syntax elements, such as flags, to determine that the current video block was predicted using intra BC mode, configuration information about which video blocks of the frame are within the reconstruction domain and should be stored in DPB 92, block vectors for each intra BC predicted video block of the frame, intra BC prediction status for each intra BC predicted video block of the frame, and other information for decoding video blocks in the current video frame.

[0049] Motion compensation unit 82 may also perform interpolation using an interpolation filter, such as that used by video encoder 20 during encoding of the video block, to calculate interpolated values ​​for sub-integer pixels of the reference block. In this case, motion compensation unit 82 may determine the interpolation filter used by video encoder 20 from the received syntax elements and use the interpolation filter to generate the predictive block.

[0050] Inverse quantization unit 86 inverse quantizes the quantized transform coefficients provided to the bitstream and entropy decoded by entropy decoding unit 80 using the same quantization parameters calculated by video encoder 20 for each video block in a video frame to determine the degree of quantization. Inverse transform processing unit 88 applies an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients in order to reconstruct residual blocks in the pixel domain.

[0051] After motion compensation unit 82 or intra BC unit 85 generates a predictive block for the current video block based on the vectors and other syntax elements, summer 90 reconstructs a decoded video block for the current video block by adding the residual block from inverse transform processing unit 88 and the corresponding predictive block generated by motion compensation unit 82 and intra BC unit 85. An in-loop filter (not shown) may be disposed between summer 90 and DPB 92 to further process the decoded video block. The decoded video blocks in a given frame are stored in DPB 92, which stores reference frames used for subsequent motion compensation of the next video block. DPB 92, or a memory device separate from DPB 92, may also store decoded video for later presentation on a display device, such as display device 34 of FIG. 1.

[0052] In a typical video coding process, a video sequence typically contains an ordered set of frames or pictures. Each frame may contain three sample arrays, denoted SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of Cb chroma samples. SCr is a two-dimensional array of Cr chroma samples. In other examples, a frame may be monochromatic and therefore contain only one two-dimensional array of luma samples.

[0053] As shown in FIG. 4A, video encoder 20 (or more specifically, splitting unit 45) generates a coded representation of a frame by first splitting the frame into a set of coding tree units (CTUs). A video frame may contain an integer number of CTUs consecutively ordered in a raster scan order from left to right and top to bottom. Each CTU is the largest logical coding unit, and the width and height of the CTUs are signaled by video encoder 20 in a sequence parameter set such that all CTUs in a video sequence have the same size, which is one of 128×128, 64×64, 32×32, and 16×16. However, it should be noted that the present application is not necessarily limited to a particular size. As shown in FIG. 4B, each CTU may comprise one coding tree block (CTB) of luma samples, two corresponding coding tree blocks of chroma samples, and syntax elements used to code the samples of the coding tree block. The syntax elements describe properties of different types of units of coding blocks of pixels, including inter or intra prediction, intra prediction mode, motion vectors, and other parameters, and how the video sequence may be reconstructed at video decoder 30. For monochrome pictures or pictures with three separate color planes, a CTU may comprise a single coding tree block and syntax elements used to code samples of the coding tree block. A coding tree block may be an N×N block of samples.

[0054] To achieve better performance, video encoder 20 may recursively perform tree partitioning, such as binary tree partitioning, ternary tree partitioning, quad tree partitioning, or a combination of both, on the coding tree blocks of the CTU to partition the CTU into smaller coding units (CUs). As shown in FIG. 4C, 64×64 CTU 400 is first partitioned into four smaller CUs, each with a block size of 32×32. Among the four smaller CUs, CU 410 and CU 420 are partitioned into four CUs of 16×16 by block size, respectively. Two 16×16 CUs 430 and 440 are further partitioned into four CUs of 8×8 by block size, respectively. FIG. 4D shows a quad tree data structure illustrating the final result of the partitioning process of CTU 400 as shown in FIG. 4C, where each leaf node of the quad tree corresponds to one CU of a respective size ranging from 32×32 to 8×8. Similar to the CTU shown in FIG. 4B, each CU may comprise a coding block (CB) of luma samples, two corresponding coding blocks of chroma samples for the same size frame, and syntax elements used to code the samples of the coding block. In a monochrome picture or a picture with three separate color planes, a CU may comprise a single coding block and syntax structures used to code the samples of the coding block. It should be noted that the quad-tree partitioning shown in FIG. 4C and FIG. 4D is for illustrative purposes only, and one CTU can be partitioned into CUs to adapt to various local characteristics based on quad-tree / ternary-tree / binary-tree partitioning. In the multi-type tree structure, one CTU is partitioned by a quad-tree structure, and each quad-tree leaf CU can be further partitioned by binary-tree and ternary-tree structures. As shown in FIG. 4E, there are five partition types, namely, 4-partition, horizontal 2-partition, vertical 2-partition, horizontal 3-partition, and vertical 3-partition.

[0055] In some implementations, video encoder 20 may further partition the coding blocks of a CU into one or more M×N prediction blocks (PBs). A prediction block is a rectangular (square or non-square) block of samples to which the same prediction, inter or intra, is applied. A prediction unit (PU) of a CU may comprise a prediction block of luma samples, two corresponding prediction blocks of chroma samples, and syntax elements used to predict the prediction block. In a monochrome picture or a picture with three separate color planes, a PU may comprise a single prediction block and syntax structures used to predict the prediction block. Video encoder 20 may generate predicted luma, Cb, and Cr blocks for the luma, Cb, and Cr prediction blocks of each PU of a CU.

[0056] Video encoder 20 may use intra prediction or inter prediction to generate the predictive blocks for a PU. If video encoder 20 uses intra prediction to generate the predictive blocks for a PU, video encoder 20 may generate the predictive blocks for the PU based on decoded samples of a frame associated with the PU. If video encoder 20 uses inter prediction to generate the predictive blocks for a PU, video encoder 20 may generate the predictive blocks for the PU based on decoded samples of one or more frames other than the frame associated with the PU.

[0057] After video encoder 20 generates the predicted luma, Cb, and Cr blocks for one or more PUs of a CU, video encoder 20 may generate a luma residual block for the CU by subtracting the predicted luma block of the CU from the original luma coding block such that each sample in the luma residual block of the CU indicates a difference between a luma sample of one of the predicted luma blocks of the CU and a corresponding sample in the original luma coding block of the CU. Similarly, video encoder 20 may generate a Cb residual block and a Cr residual block for the CU such that each sample in the Cb residual block of the CU indicates a difference between a Cb sample of one of the predicted Cb blocks of the CU and a corresponding sample in the original Cb coding block of the CU, and each sample in the Cr residual block of the CU indicates a difference between a Cr sample in one of the predicted Cr blocks of the CU and a corresponding sample in the original Cr coding block of the CU, respectively.

[0058] Further, as shown in FIG. 4C, video encoder 20 may use quadtree partitioning to decompose the luma, Cb, and Cr residual blocks of a CU into one or more luma, Cb, and Cr transform blocks. A transform block is a rectangular (square or non-square) block of samples to which the same transform is applied. A transform unit (TU) of a CU may comprise a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax elements used to transform the transform block samples. Thus, each TU of a CU may be associated with a luma transform block, a Cb transform block, and a Cr transform block. In some examples, the luma transform block associated with a TU may be a sub-block of the luma residual block of the CU. The Cb transform block may be a sub-block of the Cb residual block of the CU. The Cr transform block may be a sub-block of the Cr residual block of the CU. In a monochrome picture or a picture with three separate color planes, a TU may comprise a single transform block and syntax structures used to transform samples of the transform block.

[0059] Video encoder 20 may apply one or more transforms to a luma transform block of the TU to generate a luma coefficient block for the TU. The coefficient block may be a two-dimensional array of transform coefficients. The transform coefficients may be scalar quantities. Video encoder 20 may apply one or more transforms to a Cb transform block of the TU to generate a Cb coefficient block for the TU. Video encoder 20 may apply one or more transforms to a Cr transform block of the TU to generate a Cr coefficient block for the TU.

[0060] After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block, or a Cr coefficient block), the video encoder 20 may quantize the coefficient block. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients and provide further compression. After the video encoder 20 quantizes the coefficient block, the video encoder 20 may entropy encode syntax elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform context-adaptive binary arithmetic coding (CABAC) on the syntax elements indicating the quantized transform coefficients. Finally, the video encoder 20 may output a bitstream including a string of bits forming a representation of the encoded frame and associated data, which is either stored in the storage device 32 or transmitted to the destination device 14.

[0061] After receiving the bitstream generated by video encoder 20, video decoder 30 may parse the bitstream to obtain syntax elements from the bitstream. Video decoder 30 may reconstruct a frame of video data based at least in part on the syntax elements obtained from the bitstream. The process of reconstructing the video data is generally the reverse of the encoding process performed by video encoder 20. For example, video decoder 30 may perform an inverse transform on coefficient blocks associated with the TUs of the current CU to reconstruct residual blocks associated with the TUs of the current CU. Video decoder 30 also reconstructs the coding blocks of the current CU by adding samples of the predictive blocks for the PUs of the current CU to corresponding samples of the transform blocks of the TUs of the current CU. After reconstructing the coding blocks for each CU of the frame, video decoder 30 may reconstruct the frame.

[0062] As mentioned above, video coding mainly uses two modes, intra-frame prediction (or intra-prediction) and inter-frame prediction (or inter-prediction), to achieve video compression. Palette-based coding is another coding scheme adopted by many video coding standards. In palette-based coding, which may be particularly suitable for screen generation content coding, a video coder (e.g., video encoder 20 or video decoder 30) forms a palette table of colors to represent a given block of video data. The palette table includes the most dominant (e.g., frequently used) pixel values ​​in the given block. Pixel values ​​that are not frequently represented in the video data of a given block are either not included in the palette table or are included in the palette table as escape colors.

[0063] Each entry in the palette table contains an index of the corresponding pixel value in the palette table. The palette index for a sample in a block may be coded to indicate which entry from the palette table is used to predict or reconstruct which sample. This palette mode begins with the process of generating a palette predictor for the first block of a picture, slice, tile, or other grouping of video blocks. As described below, palette predictors for subsequent video blocks are typically generated by updating a previously used palette predictor. For purposes of explanation, it is assumed that the palette predictor is defined at the picture level. In other words, there is one palette predictor for the entire picture, although a picture may contain multiple coded blocks, each with its own palette table.

[0064] To reduce the bits required for signaling palette entries in a video bitstream, a video decoder may utilize a palette predictor to determine new palette entries in a palette table used to reconstruct a video block. For example, the palette predictor may contain palette entries from a previously used palette table, or may even be initialized with the last used palette table by including all entries of the last used palette table. In some implementations, the palette predictor may contain less than all entries from the last used palette table and then incorporate some entries from other previously used palette tables. The palette predictor may have the same size as the palette table used to encode different blocks, or may be larger or smaller than the palette table used to encode different blocks. In one example, the palette predictor is implemented as a first-in-first-out (FIFO) table containing 64 palette entries.

[0065] To generate a palette table for a block of video data from the palette predictor, the video decoder may receive a one-bit flag for each entry of the palette predictor from the encoded video bitstream. The one-bit flag may have a first value (e.g., a binary 1) indicating that the associated entry of the palette predictor is included in the palette table, or a second value (e.g., a binary 0) indicating that the associated entry of the palette predictor is not included in the palette table. If the size of the palette predictor is larger than the palette table used for the block of video data, the video decoder may stop receiving more flags when a maximum size of the palette table is reached.

[0066] In some implementations, some entries of the palette table may be directly signaled in the encoded video bitstream instead of being determined using the palette predictor. For such entries, the video decoder may receive from the encoded video bitstream three separate m-bit values ​​indicating the pixel value of the luma and two chroma components associated with the entry, where m represents the bit depth of the video data. Compared to the multiple m-bit values ​​required for directly signaled palette entries, those palette entries derived from the palette predictor require only a one-bit flag. Thus, signaling some or all palette entries using the palette predictor can significantly reduce the number of bits required to signal new palette table entries, thereby improving the overall coding efficiency of palette mode coding.

[0067] In many cases, the palette predictor for a block is determined based on the palette table used to code one or more previously coded blocks. However, when coding the first coding tree unit in a picture, slice, or tile, the palette table of the previously coded block may not be available. Thus, the palette predictor cannot be generated using entries in the previously used palette table. In such cases, a sequence of palette predictor initializers may be signaled in a sequence parameter set (SPS) and / or a picture parameter set (PPS), which are values ​​used to generate the palette predictor when the previously used palette table is not available. An SPS generally refers to a syntactic structure of syntax elements that apply to a series of consecutive coded video pictures, called a coded video sequence (CVS), as determined by the contents of syntax elements found in a PPS referenced by syntax elements found in each slice segment header. A PPS generally refers to a syntactic structure of syntax elements that apply to one or more individual pictures in a CVS, as determined by syntax elements found in each slice segment header. Therefore, an SPS is generally considered to be a higher level syntax structure than a PPS, meaning that the syntax elements contained in an SPS generally change less frequently and apply to a larger portion of the video data compared to the syntax elements contained in a PPS.

[0068] FIG. 5 is a block diagram illustrating different prediction modes of a coding unit according to some implementations of this disclosure.

[0069] In VVC, each CU can be coded as skip mode or non-skip mode. For CUs coded as skip mode, one syntax element is further signaled to indicate whether the current CU is in normal skip mode (similar to skip mode in HEVC) or IBC skip mode. For CUs coded as non-skip mode, one syntax element is further signaled to indicate whether the current CU is coded as intra mode, inter mode, intra block copy (IBC) mode, or palette (PLT) mode. These modes are called "MODE_INTRA", "MODE_INTER", "MODE_IBC" and "MODE_PLT" respectively in the VVC specification. For CUs coded as intra mode, only spatially neighboring reconstructed pixels in the same picture / slice could be used to generate a prediction signal for the current CU. For CUs coded as inter mode, the prediction signal could be generated by pixels from a reference picture that is not the current picture. Details of IBC mode are described in JVET-N1002 (http: / / phenix.int-evry.fr / jvet / ). The Palette (PLT) mode was newly adopted for VVC at the 15th JVET meeting, detailed in the document JVET-O119, available at http: / / phenix.int-evry.fr / jvet / .

[0070] In the current VVC, the constraints and conditions for enabling each different mode are different, as summarized in Table 1 below. In addition, a flag is signaled in the Sequence Parameter Set (SPS) to indicate the on / off of IBC and PLT modes, i.e., whether IBC and / or PLT modes are allowed in the associated bitstream.

[0071] [Table 1]

[0072] The current syntax of mode signaling in VVC is shown in the table below.

[0073] [Table 2]

[0074] [Table 3]

[0075] The current meaning of mode signaling in VVC is shown below.

[0076] cu_skip_flag[x0][y0] equal to 1 specifies that in the current coding unit, when coding a P or B slice, no further syntax elements are parsed after cu_skip_flag[x0][y0], except for one or more of the following syntax elements: the IBC mode flag pred_mode_ibc_flag[x0][y0], and the merge_data() syntax structure; when decoding an I slice, no syntax elements are parsed after cu_skip_flag[x0][y0], except for merge_idx[x0][y0]. cu_skip_flag[x0][y0] equal to 0 specifies that the coding unit is not skipped. The array index x0,y0 specifies the position (x0,y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture. If cu_skip_flag[x0][y0] is not present, it is inferred to be equal to 0.

[0077] When pred_mode_flag is equal to 0, it specifies that the current coding unit is coded in inter-prediction mode. When pred_mode_flag is equal to 1, it specifies that the current coding unit is coded in intra-prediction mode. If pred_mode_flag is not present, it is inferred as follows: ●If cbWidth is equal to 4 and cbHeight is equal to 4, pred_mode_flag is inferred to be equal to 1. ● Otherwise, if modeType is equal to MODE_TYPE_INTRA, pred_mode_flag is inferred to be equal to 1. ● Otherwise, if modeType is equal to MODE_TYPE_INTER, pred_mode_flag is inferred to be equal to 0. ● Otherwise, pred_mode_flag is inferred to be equal to 1 when decoding an I slice and to be equal to 0 when decoding a P or B slice. ● The variables CuPredMode[chType][x][y], where x=x0..x0+cbWidth-1 and y=y0..y0+cbHeight-1, are derived as follows: If pred_mode_flag is equal to 0, CuPredMode[chType][x][y] is set equal to MODE_INTER. ● Otherwise (pred_mode_flag is equal to 1), CuPredMode[chType][x][y] is set equal to MODE_INTRA.

[0078] When pred_mode_IBC_flag is equal to 1, it specifies that the current coding unit is coded in IBC prediction mode. When pred_mode_IBC_flag is equal to 0, it specifies that the current coding unit is not coded in IBC prediction mode. If pred_mode_ibc_flag is not present, it is inferred as follows: ●If cu_skip_flag[x0][y0] is equal to 1, cbWidth is equal to 4, and cbHeight is equal to 4, then pred_mode_ibc_flag is inferred to be equal to 1. ● Otherwise, if both cbWidth and cbHeight are equal to 128, pred_mode_ibc_flag is inferred to be equal to 0. ● Otherwise, if modeType is equal to MODE_TYPE_INTER, pred_mode_ibc_flag is inferred to be equal to 0. ● Otherwise, if treeType is equal to DUAL_TREE_CHROMA, pred_mode_ibc_flag is inferred to be equal to 0. ● Otherwise, pred_mode_ibc_flag is inferred to be equal to the value of sps_ibc_enabled_flag when decoding an I slice, and to 0 when decoding a P or B slice, respectively. ● If pred_mode_ibc_flag is equal to 1, then the variable CuPredMode[chType][x][y] is set equal to MODE_IBC, with x=x0..x0+cbWidth-1 and y=y0..y0+cbHeight-1.

[0079] pred_mode_plt_flag specifies the use of palette mode in the current coding unit. pred_mode_plt_flag equal to 1 indicates that palette mode is applied in the current coding unit. pred_mode_plt_flag equal to 0 indicates that palette mode is not applied in the current coding unit. If pred_mode_plt_flag is not present, it is inferred to be equal to 0. If pred_mode_plt_flag is equal to 1, the variable CuPredMode[x][y] is set equal to MODE_PLT, where x=x0..x0+cbWidth-1, y=y0..y0+cbHeight-1.

[0080] In summary, in current VVC, the syntax (i.e., associated flags) signaled to indicate the corresponding non-skip mode are shown in Tables 4 through 10, with each table corresponding to a different condition of the allowed prediction modes. Note that in these tables, the 0s and 1s in the codewords can all be inverted and the resulting codewords will perform equally well. Furthermore, the naming of the syntax elements can be changed to other names without changing the functionality of the signaled modes.

[0081] [Table 4]

[0082] [Table 5]

[0083] [Table 6]

[0084] [Table 7]

[0085] [Table 8]

[0086] [Table 9]

[0087] [Table 10]

[0088] FIG. 6 is a flowchart illustrating an example process for implementing a technique for a video coder signaling a prediction mode according to some implementations of this disclosure.

[0089] In the current VVC, the IBC mode is closer to the inter mode, and the PLT mode is closer to the intra mode. Therefore, in VVC, when pred_mode_flag is signaled as 0, the IBC mode flag (pred_mode_ibc_flag) is signaled, which means that the current CU is similar to the inter mode. Also, when pred_mode_flag is signaled as 1, the PLT mode flag (pred_mode_plt_flag) is signaled, which means that the current CU is similar to the intra mode. However, there is an exception where only intra mode, inter mode, and PLT mode are allowed (i.e., IBC mode is not allowed). As shown in Table 5, when pred_mode_flag is signaled as 0, the PLT mode flag (pred_mode_plt_flag) is signaled. Such exceptions not only destroy the physical meaning of the flags in pred_mode_flag, but also complicate the signaling conditions for pred_mode_plt_flag, since different signaling conditions are used depending on whether IBC mode is enabled or not.

[0090] Furthermore, in the current VVC, the condition checks for signaling pred_mode_ibc_flag and pred_mode_plt_flag are complicated, as shown in Table 2. Several methods have been proposed to simplify the condition checks when signaling these prediction modes.

[0091] According to the first embodiment of the disclosure, the flag indicating the enablement of the palette mode (e.g., pred_mode_plt_flag in the VVC specification) is signaled only in the intra-like mode, regardless of the conditions of the allowed prediction modes. In one example, the palette mode flag pred_mode_plt_flag is signaled only if the syntax element (e.g., pred_mode_flag) used to indicate the intra-like or inter-like mode is signaled or inferred as the intra-like mode (e.g., in the current VVC, pred_mode_flag is signaled as 1). The corresponding codeword according to this embodiment when only inter-mode, intra-mode and PLT mode are allowed is shown in Table 10. Table 10 is different from Table 5. Furthermore, the signaling conditions of pred_mode_plt_flag can be simplified as highlighted in Table 11.

[0092] [Table 11]

[0093] [Table 12]

[0094] [Table 13] Table 11. Proposed VVC mode signaling syntax (changes highlighted)

[0095] According to the second embodiment of the present disclosure, the modes are signaled based on a predefined order, and each mode is indicated by a corresponding flag, except for the last mode. The last mode does not need a corresponding flag, because it can be inferred to be enabled if all previously signaled modes (or flags) are not enabled. In one example, the inter, IBC, and PLT modes are indicated by flags pred_mode_inter_flag, pred_mode_ibc_flag, and pred_mode_plt_flag, respectively. In this case, the method of assigning the truncated binary codewords to the modes based on the predefined signaling order is basically similar. The associated codewords are shown in Tables 12 to 18. The signaling conditions of pred_mode_ibc_flag and pred_mode_plt_flag can also be simplified as shown in Table 19.

[0096] [Table 14]

[0097] [Table 15]

[0098] [Table 16]

[0099] [Table 17]

[0100] [Table 18]

[0101] [Table 19]

[0102] [Table 20]

[0103] [Table 21] Table 19. Proposed VVC mode signaling syntax (changes highlighted)

[0104] According to a third embodiment of the present disclosure, the mode is signaled by first transmitting a syntax element indicating whether the normal mode (e.g., Inter and Intra modes) or the new mode (e.g., IBC and PLT modes) is used in the current block. After the first syntax element, an additional syntax element is signaled indicating which mode is used. The relevant codewords are shown in Tables 20 to 26. It should be noted that in this embodiment, the naming of the codeword bins (or flags) has been changed to reflect their physical meaning.

[0105] [Table 22]

[0106] [Table 23]

[0107] [Table 24]

[0108] [Table 25]

[0109] [Table 26]

[0110] [Table 27]

[0111] [Table 28]

[0112] To signal a prediction mode, the video coder first receives video data corresponding to a non-skip mode coded block from a bitstream (610) and determines a parameter set associated with the non-skip mode coded block (620). The parameter set (e.g., a sequence parameter set) includes information including which modes (e.g., IBC, PLT, etc.) are allowed in the associated bitstream, as shown by Table 1.

[0113] The video coder then selectively receives the first, second, or third syntax element from the bitstream. If the parameter set includes information satisfying the first condition, the video coder retrieves the first syntax element (e.g., pre_mode_flag in Table 2) from the bitstream (630). If the parameter set includes information satisfying the second condition, the video coder retrieves the second syntax element (e.g., pre_mode_ibc_flag in Table 2) from the bitstream (640). If the parameter set includes information satisfying the third condition, the video coder retrieves the third syntax element (e.g., pre_mode_plt_flag in Table 2) from the bitstream (650). See Table 2 for conditions associated with each syntax element. In an embodiment, if the respective condition is not satisfied, the video coder does not receive the respective syntax element (e.g., the video coder may assign a default value to the syntax element or may not use the syntax element during decoding).

[0114] The video coder then decodes the video data corresponding to the non-skip mode coded block using the respective modes depending on the values ​​of the received first, second, and third syntax elements. In particular:

[0115] The video coder decodes the video data using palette mode if the first syntax element (e.g., pred_mode_flag in Table 1) and the third syntax element (e.g., pre_mode_plt_flag in Table 1) both have a first value (e.g., “1”) and the second condition is not satisfied (e.g., the video coder does not receive pre_mode_ibc_flag) (660).

[0116] The video coder decodes the video data using an intra-prediction mode when the first syntax element (e.g., pred_mode_flag in Table 1) has a first value (e.g., “1”) and the third syntax element has a second value (e.g., “0”). The second condition is not met (e.g., the video coder does not receive pred_mode_ibc_flag) (670).

[0117] The video coder decodes the video data using an inter prediction mode if the first syntax element has a second value (e.g., "0") and the second and third conditions are not satisfied (e.g., the video coder does not receive pred_mode_ibc_flag and pre_mode_plt_flag) (680).

[0118] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. A 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 transfer of a computer program from one place to another, for example according to a communication protocol. In this manner, a 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. A data storage medium may be any available medium accessible by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation as described herein. A computer program product may include a computer-readable medium.

[0119] The terms used in the description of the embodiments herein are intended to describe particular embodiments only and are not intended to limit the scope of the claims. As used in the description of the embodiments and the appended claims, the singular form "a," "an," and the like are intended to include the plural, unless the context clearly dictates otherwise. The term "and / or," as used herein, will also be understood to refer to and include any possible combination of one or more of the associated listed items. Furthermore, as used herein, the term "comprise," and the like, will be understood to specify the presence of stated features, elements, and / or components, but not to exclude the presence or addition of one or more other features, elements, components, and / or groups thereof.

[0120] It will also be understood that terms such as first, second, etc. may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first electrode can be called a second electrode, and similarly, a second electrode can be called a first electrode, without departing from the scope of implementation. Although a first electrode and a second electrode are both electrodes, they are not the same electrode.

[0121] The description in this application has been presented for purposes of illustration and description and is not intended to be exhaustive or to be limited to the invention in the disclosed form. Numerous modifications, variations, and alternative embodiments will become apparent to those skilled in the art having the benefit of the teachings presented in the foregoing description and the associated drawings. The present embodiments have been chosen and described in order to best explain the principles of the invention, its practical application, and to enable others skilled in the art to understand the invention for various implementations and to best utilize the underlying principles and various implementations with various modifications suited to the particular applications contemplated. It is therefore to be understood that the scope of the claims should not be limited to the particular examples of the disclosed embodiments, and that modifications and other embodiments are intended to be included within the scope of the appended claims.

[0122] CROSS-REFERENCE TO RELATED APPLICATIONS

[0123] This application claims priority to U.S. Provisional Application No. 62 / 897,292, filed Sep. 7, 2019, and entitled “Prediction Mode Signaling in Video Encoding,” which is incorporated by reference in its entirety.

Claims

1. receiving video data from a bitstream corresponding to a non-skip mode coded block; determining information relating to the non-skip mode coded block; extracting a first syntax element pred_mode_flag from the bitstream in response to a determination that first information included in the information satisfies a first condition; extracting a second syntax element pred_mode_ibc_flag from the bitstream in response to a determination that second information included in the information satisfies a second condition; extracting a third syntax element pred_mode_plt_flag from the bitstream in accordance with a determination that third information included in the information satisfies a third condition, where the third condition includes a condition that the non-skip mode coding block is in intra mode (CuPredMode[x0][y0]==MODE_INTRA) and does not include a condition that the non-skip mode coding block is not in intra mode (CuPredMode[x0][y0]!=MODE_INTRA); when the first syntax element pred_mode_flag has a first value and the third syntax element pred_mode_plt_flag has the first value, decode the video data corresponding to the non-skip mode coded block using a palette mode; When the first syntax element pred_mode_flag has the first value and the third syntax element pred_mode_plt_flag has a second value, decode the video data corresponding to the non-skip mode coded block using an intra prediction mode; When the first syntax element pred_mode_flag has the second value, decoding the video data corresponding to the non-skip mode coded block using an inter prediction mode. A method for decoding video data.

2. When decoding the video data corresponding to the non-skip mode coded block using the palette mode, the second condition is not met and the second syntax element pred_mode_ibc_flag is not received. The method of claim 1.

3. When decoding the video data corresponding to the non-skip mode coded block using the intra prediction mode, the second condition is not met and the second syntax element pred_mode_ibc_flag is not received. The method of claim 1.

4. When decoding the video data corresponding to the non-skip mode coded block using the inter prediction mode, the second condition and the third condition are not met, and the second syntax element pred_mode_ibc_flag and the third syntax element pred_mode_plt_flag are not received. The method of claim 1.

5. decode the video data corresponding to the non-skip mode coded block using an intra block copy mode when the first syntax element pred_mode_flag has a second value or the first syntax element pred_mode_flag is not received, the second syntax element pred_mode_ibc_flag has the first value, and the third syntax element pred_mode_plt_flag is not received; The method of claim 1.

6. receiving video data from a bitstream corresponding to a non-skip mode coded block; determining information relating to the non-skip mode coded block; extracting a first syntax element from the bitstream in response to a determination that first information included in the information satisfies a first condition; extracting a second syntax element from the bitstream in response to a determination that second information included in the information satisfies a second condition; extracting a third syntax element from the bitstream in accordance with a determination that third information included in the information satisfies a third condition, wherein the third condition includes a condition that the non-skip mode coded block is in intra mode (CuPredMode[x0][y0]==MODE_INTRA) and does not include a condition that the non-skip mode coded block is not in intra mode (CuPredMode[x0][y0]!=MODE_INTRA); decode the video data corresponding to the non-skip mode coded block using an inter prediction mode when the first syntax element has a first value or the first syntax element is not signaled, the second syntax element has a first value, and the third syntax element is not signaled; decode the video data corresponding to the non-skip mode coded block using an intra block copy mode when the first syntax element has a second value and the second syntax element is not signaled, and the third syntax element has the first value or the third syntax element is not signaled; decode the video data corresponding to the non-skip mode coded block using a palette mode when the first syntax element has the second value and the second syntax element is not signaled and the third syntax element has the second value or the third syntax element is not signaled; decode the video data corresponding to the non-skip mode coded block using an intra prediction mode when the first syntax element has the first value and the second syntax element has the second value or when the second syntax element is not signaled and the third syntax element is not signaled. A method for decoding video data.

7. 1. A computing device comprising: one or more processors; a memory coupled to the one or more processors; a plurality of programs stored in the memory which, when executed by the one or more processors, cause the computing device to perform the operations of any one of claims 1 to 6; Including, Computing device.

8. A non-transitory computer-readable storage medium storing a plurality of programs for execution by a computing device having one or more processors, The plurality of programs, when executed by the one or more processors, cause the computing device to perform the operations of any one of claims 1 to 6. A non-transitory computer-readable storage medium.

9. A computer program executable by a computing device including one or more processors, comprising: When executed by the one or more processors, the computer program causes the computer device to perform a method for decoding video data according to any one of claims 1 to 6. Computer program.

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