Prediction mode signaling in video codecs

Abstract

A method for encoding video data, comprising: obtaining a parameter set associated with a non-skip mode coding block; sending a first semantic element in a bitstream through a signal based on determining that the parameter set includes information that satisfies a first condition; sending a second semantic element in the bitstream through a signal based on determining that the parameter set includes information that satisfies a second condition; sending a third semantic element in the bitstream through a signal based on determining that the parameter set includes information that satisfies a third condition; when the first semantic element has a first value and the third semantic element has the first value, encoding the video data corresponding to the non-skip mode coding block using a palette mode; when the first semantic element has the first value and the third semantic element has a second value, encoding the video data corresponding to the non-skip mode coding block using an intra-frame prediction mode; when the first semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an inter-frame prediction mode; and sending the video data corresponding to the non-skip mode coding block through the bitstream.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number "202080059859.3", application date "September 8, 2020", and invention name "Prediction Mode Signaling in Video Coding and Decoding". Technical Field

[0002] Embodiments of the present invention generally relate to video encoding and decoding, and more particularly to methods and systems for prediction mode signaling in video encoding and decoding. Background Art

[0003] Various electronic devices support digital video, such as digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video game consoles, smart phones, 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-TH.263, ITU-TH.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, each slice having multiple video blocks, which may also be referred to as coding tree units (CTUs). Each CTU may contain a coding unit (CU) or be recursively split into smaller CUs until a predefined 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 can be coded in intra, inter, 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 within the same video frame. Video blocks in an inter-coded (P or B) slice of a video frame can use spatial prediction with respect to reference samples in neighboring blocks within the same video frame or temporal prediction with respect to reference samples in other previous and / or future reference videos.

[0004] A prediction block for the current video block to be encoded is generated based on spatial or temporal prediction of previously encoded reference blocks (e.g., neighboring blocks). The process of finding the reference block can be accomplished using a block matching algorithm. The residual data representing the pixel differences between the current block to be encoded and the prediction block is called a residual block or prediction error. Inter-coded blocks are encoded based on the motion vector pointing to the reference block in the reference frame that formed the prediction block and the residual block. The process of determining the motion vector is generally referred to as motion estimation. Intra-coded blocks are encoded based on the intra-frame prediction mode and the residual block. For further compression, the residual block is transformed from the pixel domain to a transform domain, such as the frequency domain, to produce residual transform coefficients, which can then be quantized. The quantized transform coefficients, initially arranged in a two-dimensional array, can be scanned to produce a one-dimensional vector of transform coefficients, which is then entropy encoded into the video bitstream to achieve even greater compression.

[0005] The coded video bitstream is then stored in a computer-readable storage medium (e.g., flash memory) for access by another electronic device with digital video capabilities or directly transmitted to the electronic device in a wired or wireless manner. The electronic device then performs video decompression (which is the reverse process of the above-mentioned video compression) by, for example, parsing the coded video bitstream to obtain semantic elements from the bitstream and reconstructing digital video data from the coded video bitstream to its original format based at least in part on the semantic elements obtained from the bitstream, and presents the reconstructed digital video data on a display of the electronic device.

[0006] As digital video quality evolves from HD to 4K×2K and even 8K×4K, the amount of video data to be encoded / decoded is growing exponentially. How to encode / decode video data more efficiently while maintaining the image quality of the decoded video data is an ongoing challenge. Summary of the Invention

[0007] The present application describes embodiments related to video data encoding and decoding, and more particularly, describes a system and method for prediction mode signaling in video encoding and decoding.

[0008] According to a first aspect of the present application, a method for encoding video data is performed on a computing device having one or more processors and a memory storing multiple programs executed by the one or more processors, including: obtaining a parameter set associated with a non-skip mode coding block; sending a first semantic element through a signal in a bitstream based on determining that the parameter set includes information that satisfies a first condition; sending a second semantic element through a signal in the bitstream based on determining that the parameter set includes information that satisfies a second condition; sending a third semantic element through a signal in the bitstream based on determining that the parameter set includes information that satisfies a third condition; when the first semantic element has a first value and the third semantic element has the first value, encoding the video data corresponding to the non-skip mode coding block using a palette mode; when the first semantic element has the first value and the third semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an intra-frame prediction mode; when the first semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an inter-frame prediction mode; and sending the video data corresponding to the non-skip mode coding block through the bitstream.

[0009] According to a second aspect of the present application, a computing device includes one or more processors, a memory, and a plurality of programs stored in the memory. When executed by the one or more processors, the programs enable the computing device to perform the operations described above.

[0010] According to a third aspect of the present application, a non-transitory computer-readable storage medium stores a plurality of programs for execution by a computing device having one or more processors. When executed by the one or more processors, the programs cause the computing device to perform the operations described above. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0012] Figure 1 is a block diagram illustrating an exemplary video encoding and decoding system according to some embodiments of the present invention.

[0013] Figure 2 is a block diagram illustrating an exemplary video encoder according to some embodiments of the present invention;

[0014] Figure 3 is a block diagram illustrating an exemplary video decoder according to some embodiments of the present invention;

[0015] Figures 4A to 4E is a block diagram illustrating how a frame is recursively quadtree partitioned into multiple video blocks of different sizes according to some embodiments of the present application.

[0016] Figure 5 is a block diagram illustrating different prediction modes for a coding unit according to some implementations of the present application.

[0017] Figure 6 is a flow chart illustrating an exemplary process by which a video codec implements a technique for signaling a prediction mode according to some embodiments of the present invention. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to specific embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth to assist in understanding the subject matter presented herein. However, it will be apparent to those skilled in the art that various alternatives may be employed 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 those skilled in the art that the subject matter presented herein may be implemented on a variety of electronic devices having digital video capabilities.

[0019] Figure 1 is a block diagram illustrating an exemplary system 10 for encoding and decoding video blocks in parallel according to some embodiments of the present invention. Figure 1 As shown, system 10 includes a source device 12 that generates and encodes video data that is subsequently decoded by a destination device 14. Source device 12 and destination device 14 may comprise any of a variety of electronic devices, including a desktop or laptop computer, a tablet computer, a smartphone, a set-top box, a digital television, a video camera, a display device, a digital media player, a video game console, a video streaming device, etc. In some embodiments, source device 12 and destination device 14 are equipped with wireless communication capabilities.

[0020] In some embodiments, target device 14 may receive the encoded video data to be decoded via link 16. Link 16 may include any type of communication medium or device capable of moving the encoded video data from source device 12 to target device 14. In one example, link 16 may include a communication medium to enable source device 12 to transmit the encoded video data directly to target 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 target 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 device that may help facilitate communication from source device 12 to target device 14.

[0021] In some other embodiments, the encoded video data can be transferred from the output interface 22 to a storage device 32. Subsequently, the target device 14 can access the encoded video data in the storage device 32 through 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 for storing encoded video data. In a further example, the storage device 32 may correspond to a file server or another intermediate storage device that can store the encoded video data generated by the source device 12. The target device 14 can access the stored video data from the storage device 32 by streaming or downloading. The file server can be any type of computer capable of storing the encoded video data and transmitting the encoded video data to the target device 14. Exemplary file servers include network servers (e.g., for websites), FTP servers, network attached storage (NAS) devices, or local disk drives. The target device 14 can access the encoded video data through any standard data connection, including a wireless channel suitable for accessing encoded video data stored on a file server (e.g., a Wi-Fi connection), a wired connection (e.g., DSL, cable modem, etc.), or a combination of the two. The transmission of the encoded video data from the storage device 32 can be a streaming transmission, a download transmission, or a combination of the two.

[0022] like Figure 1As shown, source device 12 includes a video source 18, a video encoder 20, and an output interface 22. Video source 18 may include a source such as a video capture device, such as a 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 source video, or a combination of these sources. As an example, if video source 18 is a camera of a security monitoring system, source device 12 and target device 14 may form a camera phone or a video phone. However, the embodiments described in this application are generally applicable to video encoding and decoding, and may be applicable to wireless and / or wired applications.

[0023] Captured, pre-captured, or computer-generated video may be encoded by video encoder 20. The encoded video data may be transmitted directly to target device 14 via output interface 22 of source device 12. The encoded video data may also (or alternatively) be stored on storage device 32 for subsequent access by target device 14 or other devices for decoding and / or playback. Output interface 22 may also include a modem and / or a transmitter.

[0024] Target device 14 includes input interface 28, video decoder 30, and display device 34. Input interface 28 may include a receiver and / or a modem and receives encoded video data via link 16. The encoded video data transmitted via link 16 or provided on storage device 32 may include various semantic elements generated by video encoder 20 for use by video decoder 30 in decoding the video data. These semantic elements may be included within the encoded video data transmitted over a communication medium, stored on a storage medium, or stored on a file server.

[0025] In some implementations, the target device 14 may include a display device 34, which may be an integrated display device or an external display device configured to communicate with the target device 14. The 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 (LCD), a plasma display, an organic light emitting diode (OLED) display, or other types of display devices.

[0026] The video encoder 20 and the video decoder 30 may operate according to proprietary or industry standards, 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 specific video encoding / decoding standard and may be applicable to other video encoding / decoding standards. It is generally envisioned that the video encoder 20 of the source device 12 may be configured to encode video data according to any of these current or future standards. Similarly, it is generally envisioned that the video decoder 30 of the target device 14 may be configured to decode video data according to any of these current or future standards.

[0027] The video encoder 20 and the video decoder 30 can each 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. When partially implemented in software, the electronic device can store instructions for the software in a suitable non-transitory computer-readable medium and use one or more processors to execute these instructions in hardware to perform the video encoding / decoding operations disclosed in the present invention. Each of the video encoder 20 and the video decoder 30 can be included in one or more encoders or decoders, any of which can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device.

[0028] Figure 2 is a block diagram illustrating an exemplary video encoder 20 according to some embodiments described herein. Video encoder 20 can perform intra-frame and inter-frame predictive coding of video blocks within a video frame. Intra-frame predictive coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter-frame 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.

[0029] like Figure 2As shown, 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 also includes motion estimation unit 42, motion compensation unit 44, segmentation unit 45, intra-prediction processing unit 46, and intra-block copy (BC) unit 48. In some embodiments, 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 located between adder 62 and DPB 64 to filter block boundaries, thereby removing blocking artifacts from the reconstructed video. In addition to the deblocking filter, a loop filter (not shown) may also be used to filter the output of adder 62. Video encoder 20 may take the form of fixed or programmable hardware units, or may be divided among one or more of the fixed or programmable hardware units shown.

[0030] Video data memory 40 may store video data 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 used by video encoder 20 when encoding video data (e.g., in intra-frame or inter-frame prediction coding modes). Video data memory 40 and DPB 64 may be formed from 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 off-chip relative to these components.

[0031] like Figure 2 As shown, after receiving video data, a segmentation unit 45 within the prediction processing unit 41 divides the video data into video blocks. This segmentation may also include dividing 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 divided into a plurality of video blocks (or groups of video blocks referred to as tiles). The prediction processing unit 41 may select a prediction coding mode for the current video block from one of a plurality of possible prediction coding modes based on error results (e.g., coding rate and distortion level), such as one of one or more inter-frame prediction coding modes from a plurality of intra-frame prediction coding modes. The prediction processing unit 41 may provide the resulting intra-frame or inter-frame prediction coding block to an adder 50 to generate a residual block, and to an adder 62 to reconstruct the coding block for subsequent use as part of a reference frame. The prediction processing unit 41 also provides semantic elements, such as motion vectors, intra-frame mode indicators, segmentation information, and other such semantic information, to the entropy coding unit 56.

[0032] 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 may perform inter-prediction coding of the current video block relative to one or more prediction blocks in one or more reference frames to provide temporal prediction. Video encoder 20 may perform multiple coding passes, e.g., to select an appropriate coding mode for each block of video data.

[0033] In some embodiments, motion estimation unit 42 determines the inter-prediction mode for the current video frame by generating a motion vector based on a predetermined pattern within a sequence of video frames. The motion vector indicates the displacement of a prediction unit (PU) of a video block within the current video frame relative to a prediction block within a reference video frame. Motion estimation performed by motion estimation unit 42 is the process of generating motion vectors that estimate the motion of a video block. A motion vector, for example, may indicate the displacement of a PU of a video block within the current video frame or picture relative to a prediction block within a reference frame (or other coded unit) relative to a current block (or other coded unit) being coded within the current frame. The predetermined pattern may designate video frames in the sequence as P-frames or B-frames. Intra BC unit 48 may determine a vector, such as a block vector, for intra BC coding in a manner similar to the motion vectors determined by motion estimation unit 42 for inter-prediction, or may utilize motion estimation unit 42 to determine the block vector.

[0034] A prediction block is a block of a reference frame that is considered to closely match the PU of the video block to be encoded in terms of pixel difference, which can be determined by sum of absolute difference (SAD), sum of squared difference (SSD), or other difference metrics. In some embodiments, video encoder 20 can calculate values ​​for sub-integer pixel positions of the reference frame stored in DPB 64. For example, video encoder 20 can interpolate quarter-pixel positions, eighth-pixel positions, or other fractional pixel positions of the reference frame. Thus, motion estimation unit 42 can perform motion searches relative to full-pixel positions and fractional pixel positions and output motion vectors with fractional pixel precision.

[0035] Motion estimation unit 42 calculates a motion vector for a PU of a video block in an inter-prediction coded frame by comparing the position of the PU to the position of a prediction block of a reference frame selected from a first reference frame list (list 0) or a second reference frame list (list 1), 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 encoding unit 56.

[0036] Motion compensation performed by motion compensation unit 44 may involve obtaining or generating a prediction 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 prediction block pointed to by the motion vector in one of the reference frame lists, retrieve the prediction block from DPB 64, and forward the prediction block to adder 50. Adder 50 then forms a residual video block of pixel difference values ​​by subtracting the pixel values ​​of the prediction block provided by motion compensation unit 44 from the pixel values ​​of the current video block being encoded. These pixel difference values ​​forming the residual video block may include luma difference components, chroma difference components, or both. Motion compensation unit 44 may also generate semantic elements associated with the video block of the video frame for use by video decoder 30 when decoding the video block of the video frame. These semantic elements may include, for example, a semantic element defining a motion vector identifying the predictive block, any flag indicating the prediction mode, or any other semantic 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.

[0037] In some embodiments, intra BC unit 48 may generate vectors and obtain prediction blocks in a manner similar to that described above in conjunction with motion estimation unit 42 and motion compensation unit 44, except that these prediction blocks are within the same frame as the current block being encoded and these vectors are referred to as block vectors rather than motion vectors. Specifically, intra BC unit 48 may determine an intra prediction mode to use for encoding the current block. In some examples, intra BC unit 48 may encode the current block using various intra prediction modes, for example, during separate encoding passes, and test their performance using rate-distortion analysis. Intra BC unit 48 may then select an appropriate intra prediction mode from among the various tested intra prediction modes and generate an intra mode indicator accordingly. For example, intra BC unit 48 may calculate rate-distortion values ​​using the rate-distortion analysis for the various tested intra prediction modes and select the intra prediction mode with the best rate-distortion characteristics from among the tested modes as the appropriate intra prediction mode to use. Rate-distortion analysis typically determines the amount of distortion (or error) between a coded block and the original, uncoded block that was coded to produce the coded block, as well as the bit rate (i.e., the number of bits) used to produce the coded block. Intra BC unit 48 may calculate ratios from the distortion and rate for various coded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block.

[0038] 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 in accordance with embodiments described herein. In either case, for intra block copying, the prediction block may be a block that is considered to closely match the block to be encoded, in terms of pixel differences, which may be determined by sum of absolute differences (SAD), sum of squares (SSD), or other difference metrics, and identification of the prediction block may include calculation of values ​​for sub-integer pixel positions.

[0039] Regardless of whether the prediction block is from the same frame according to intra-frame prediction or from different frames according to inter-frame prediction, video encoder 20 can form a residual video block by subtracting the pixel values ​​of the prediction block from the pixel values ​​of the current video block being encoded, thereby forming pixel difference values. These pixel difference values ​​forming the residual video block may include luma and chroma component differences.

[0040] As described above, intra-prediction processing unit 46 may perform intra-prediction on 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. Specifically, intra-prediction processing unit 46 may determine an intra-prediction mode to use for encoding the current block. To do so, intra-prediction processing unit 46 may encode the current block using various intra-prediction modes, for example, during separate encoding passes, and intra-prediction processing unit 46 (or a mode selection unit in some examples) may select an appropriate intra-prediction mode to use from the tested intra-prediction modes. Intra-prediction processing unit 46 may provide information indicating the selected intra-prediction mode for the block to entropy encoding unit 56. Entropy encoding unit 56 may encode the information indicating the selected intra-prediction mode in the bitstream.

[0041] After prediction processing unit 41 determines a prediction block for the current video block through inter-frame prediction or intra-frame prediction, adder 50 forms a residual video block by subtracting the prediction 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 provided to transform processing unit 52. Transform processing unit 52 transforms the residual video data into residual transform coefficients using a transform such as a discrete cosine transform (DCT) or a conceptually similar transform.

[0042] Transform processing unit 52 may send the resulting transform coefficients to quantization unit 54. Quantization unit 54 quantizes these transform coefficients to further reduce the bit rate. This quantization process may also reduce the bit depth associated with some or all coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, quantization unit 54 may then scan the matrix containing the quantized transform coefficients. Alternatively, entropy coding unit 56 may perform this scan.

[0043] After quantization, entropy coding 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), semantic-based context adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or other entropy coding methods or techniques. This encoded bitstream may then be transmitted to video decoder 30 or archived in storage device 32 for later transmission to or retrieval by video decoder 30. Entropy coding unit 56 may also entropy encode these motion vectors and other semantic elements for the current video frame being encoded.

[0044] 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 to generate a reference block used to predict other video blocks. As described above, motion compensation unit 44 may generate a motion compensated prediction block 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 ​​used for motion estimation.

[0045] Summer 62 adds the reconstructed residual block to the motion compensated prediction block produced by motion compensation unit 44 to produce a reference block stored in DPB 64. This reference block may then be used as a prediction block by intra BC unit 48, motion estimation unit 42, and motion compensation unit 44 to inter-predict another video block in a subsequent video frame.

[0046] Figure 3 is a block diagram illustrating an exemplary video decoder 30 according to some embodiments 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-frame prediction processing unit 84, and an intra-frame BC unit 85. The video decoder 30 performs a decoding process, which is generally combined with Figure 2 The encoding process described with respect to video encoder 20 is reciprocal. For example, motion compensation unit 82 may generate prediction data based on motion vectors received from entropy decoding unit 80, and intra-prediction unit 84 may generate prediction data based on intra-prediction mode indicators received from entropy decoding unit 80.

[0047] In some examples, units of video decoder 30 may be assigned the task of performing embodiments of the present invention. Furthermore, in some examples, embodiments of the present invention may be divided among one or more units of video decoder 30. For example, intra BC unit 85 may perform embodiments of the present invention alone or in combination with other units of video decoder 30, such as motion compensation unit 82, intra prediction processing unit 84, and entropy decoding unit 80. In some examples, video decoder 30 may not include intra BC unit 85, and the functionality of intra BC unit 85 may be performed by other components of prediction processing unit 81, such as motion compensation unit 82.

[0048] The video data memory 79 may store video data, such as an encoded video bitstream, to be decoded by other components of the video decoder 30. The video data stored in the video data memory 79 may be obtained, for example, from the storage device 32 via a wired or wireless network communication of video data, from a local video source (such as a camera), or may be obtained by accessing a physical data storage medium (such as a flash drive or hard disk). The video data memory 79 may include a coded picture buffer (CPB) that stores encoded video data from the encoded video bitstream. The decoded picture buffer (DPB) 92 of the video decoder 30 stores reference video data for use when the video decoder 30 decodes the video data (such as in an intra-frame or inter-frame prediction coding mode). The video data memory 79 and the DPB 92 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. For illustrative purposes, the ... Figure 3 92 are shown as two distinct components of the video decoder 30. However, it will be apparent to those skilled in the art that the video data memory 79 and the DPB 92 may be provided by the same memory device or separate memory devices. In some examples, the video data memory 79 may be on-chip with the other components of the video decoder 30, or off-chip relative to these components.

[0049] During the decoding process, the video decoder 30 receives an encoded video bitstream representing video blocks of an encoded video frame and associated semantic elements. The video decoder 30 may receive these semantic elements at the video frame level and / or the video block level. The entropy decoding unit 80 of the video decoder 30 performs entropy decoding on the bitstream to generate quantization coefficients, motion vectors or intra-frame prediction mode indicators, and other semantic elements. The entropy decoding unit 80 then forwards these motion vectors and other semantic elements to the prediction processing unit 81.

[0050] When the video frame is encoded as an intra-frame prediction (I) frame or as an intra-frame prediction block for other types of frames, the intra-frame prediction processing unit 84 of the prediction processing unit 81 can generate prediction data for the video block of the current video frame based on the intra-frame prediction mode sent by the signal and the reference data from the previously decoded block of the current frame.

[0051] When the video frame is encoded as an inter-frame prediction coded (i.e., B or P) frame, the motion compensation unit 82 of the prediction processing unit 81 generates one or more prediction blocks for the video block of the current video frame based on the motion vectors and other semantic elements received from the entropy decoding unit 80. Each of these prediction blocks can be generated from a reference frame in one of the reference frame lists. The video decoder 30 can use a default construction technique to construct the reference frame lists, i.e., List 0 and List 1, based on the reference frames stored in the DPB 92.

[0052] In some examples, when encoding the video block according to the intra BC mode described herein, intra BC unit 85 of prediction processing unit 81 generates prediction blocks for the current video block based on the block vector and other semantic elements received from entropy decoding unit 80. These prediction blocks may be within the same reconstruction region of the picture as the current video block as defined by video encoder 20.

[0053] Motion compensation unit 82 and / or intra BC unit 85 parse these motion vectors and other semantic elements to determine prediction information for the video blocks of the current video frame and then use the prediction information to generate a prediction frame for the current video block being decoded. For example, motion compensation unit 82 uses some of the received semantic elements to determine the prediction mode (e.g., intra or inter prediction) used to encode the video blocks of the video frame, the inter prediction frame type (e.g., B or P), construction information for one or more reference frame lists for the frame, motion vectors for each inter-prediction-encoded video block of the frame, inter prediction status for each inter-prediction-encoded video block of the frame, and other information used to decode the video blocks in the current video frame.

[0054] Similarly, the intra BC unit 85 may use some of the received semantic elements (e.g., flags) to determine construction information for predicting the current video block using the intra BC mode, which video blocks of the frame are within the reconstruction region and should be stored in the 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 these video blocks in the current video frame.

[0055] Motion compensation unit 82 may also use the interpolation filters to interpolate during encoding of the video blocks to calculate interpolated values ​​for sub-integer pixels of reference blocks, as did video encoder 20. In this case, motion compensation unit 82 may determine the interpolation filters used by video encoder 20 from the received syntax elements and use the interpolation filters to produce the prediction block.

[0056] Inverse quantization unit 86 inverse quantizes the quantized transform coefficients provided in the bitstream and entropy decoded by entropy decoding unit 80 to determine the degree of quantization using the same quantization parameter calculated by video encoder 20 for each video block in the video frame. 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 to reconstruct the residual block in the pixel domain.

[0057] After the motion compensation unit 82 or the intra BC unit 85 generates a prediction block for the current video block based on these vectors and other semantic elements, the adder 90 reconstructs the encoded video block for the current video block by adding the residual block from the inverse transform processing unit 88 and the corresponding prediction block generated by the motion compensation unit 82 and the intra BC unit 85. An in-loop filter (not shown) can be located between the adder 90 and the DPB 92 to perform further processing on the decoded video block. The decoded video block in a given frame is then stored in the DPB 92, which stores reference frames for subsequent motion compensation of future video blocks. The DPB 92, or a memory device separate from the DPB 92, can also store the decoded video for later display on a display device such as a video frame. Figure 1 is presented on a display device 34).

[0058] In a typical video encoding process, a video sequence typically consists of an ordered set of frames or pictures. Each frame may include three sample arrays, denoted as 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 cases, a frame may be monochrome and therefore include only a single two-dimensional array of luma samples.

[0059] like Figure 4A As shown, the video encoder 20 (or more specifically, the segmentation unit 45) generates an encoded representation of the frame by first dividing the frame into a set of coding tree units (CTUs). A video frame may include an integer number of CTUs that are consecutively sorted in a raster scan order from left to right and from top to bottom. Each CTU is the largest logical coding unit and the width and height of the CTU are signaled by the video encoder 20 in a sequence parameter set so that all CTUs in the video sequence have the same size, i.e., 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 specific size. Figure 4BAs shown, each CTU may include one coding tree block (CTB) of luma samples, two corresponding coding tree blocks of chroma samples, and semantic elements for encoding the samples of these coding tree blocks. These semantic elements describe the characteristics of different types of units of the coded blocks of coded pixel blocks and how to reconstruct the video sequence at the video decoder 30, including inter-frame or intra-frame prediction, intra-frame prediction mode, motion vector, and other parameters. In a monochrome picture or a picture with three separate color planes, a CTU may include a single coding tree block and semantic elements for encoding the samples of the coding tree block. A coding tree block may be an N×N block of samples.

[0060] To achieve better performance, the video encoder 20 may recursively perform tree partitioning on the coding tree blocks of the CTU, such as binary tree partitioning, ternary tree partitioning, quadtree partitioning, or a combination thereof, and partition the CTU into smaller coding units (CUs). Figure 4C As shown, a 64×64 CTU 400 is first divided into four smaller CUs, each with a block size of 32×32. Of these four smaller CUs, CU 410 and CU 420 are each divided into four 16×16 CUs based on block size. The two 16×16 CUs 430 and 440 are each further divided into four 8×8 CUs based on block size. Figure 4D A quadtree data structure is shown in FIG. Figure 4C The final result of the CTU 400 partitioning process is shown in FIG, where each leaf node of the quadtree corresponds to a CU with a size ranging from 32×32 to 8×8. Figure 4B Like the CTU shown in , each CU may include a coding block (CB) of luma samples and two corresponding coding blocks of chroma samples of the same size frame, and semantic elements for encoding these samples of these coding blocks. In a monochrome picture or a picture with three separate color planes, a CU may include a single coding block and semantic structures for encoding these samples of the coding block. It should be noted that in Figure 4C and 4D The quadtree partitioning shown in FIG is for illustration purposes only, and a CTU can be split into CUs to accommodate different local characteristics based on quadtree / ternary / binary tree partitioning. In the multi-type tree structure, a CTU is partitioned by a quadtree structure, and each quadtree leaf CU can be further partitioned by a binary tree and a ternary tree structure. Figure 4E As shown, there are five types of segmentation, namely, quadrifugal segmentation, horizontal binary segmentation, vertical binary segmentation, horizontal trifurcated segmentation, and vertical trifurcated segmentation.

[0061] In some embodiments, the video encoder 20 may further partition the coding block of the CU into one or more M×N prediction blocks (PBs). A prediction block is a rectangular (square or non-square) block of samples on which the same (inter or intra) prediction is applied. The prediction unit (PU) of a CU may include a prediction block of luma samples, two corresponding prediction blocks of chroma samples, and semantic elements for prediction of these prediction blocks. In a monochrome picture or a picture with three separate color planes, a PU may include a single prediction block and a semantic structure for predicting the prediction block. The video encoder 20 may generate predicted luma, Cb, and Cr blocks for the luma, Cb, and Cr prediction blocks of each PU of the CU.

[0062] Video encoder 20 may use intra prediction or inter prediction to generate a prediction block for a PU. If video encoder 20 uses intra prediction to generate a prediction block for a PU, video encoder 20 may generate the prediction block for the PU based on decoded samples of a frame associated with the PU. If video encoder 20 uses inter prediction to generate a prediction block for a PU, video encoder 20 may generate the prediction block for the PU based on decoded samples of one or more frames other than the frame associated with the PU.

[0063] After the video encoder 20 generates predicted luma, Cb, and Cr blocks for one or more PUs of a CU, the video encoder 20 may generate a luma residual block for the CU by subtracting the predicted luma block of the CU from its original luma coding block, so that each sample in the luma residual block of the CU indicates the difference between a luma sample in one of the predicted luma blocks of the CU and a corresponding sample in the original luma coding block of the CU. Similarly, the video encoder 20 may generate a Cb residual block and a Cr residual block for the CU, respectively, so that each sample in the Cb residual block of the CU indicates the difference between a Cb sample in 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 may indicate the 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.

[0064] In addition, if Figure 4CAs shown, the video encoder 20 may employ 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 include a transform block of luma samples, two corresponding transform blocks of chroma samples, and semantic elements for transforming 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 the TU may be a subblock of the luma residual block of the CU. The Cb transform block may be a subblock of the Cb residual block of the CU. The Cr transform block may be a subblock of the Cr residual block of the CU. In a monochrome picture or a picture with three separate color planes, a TU may include a single transform block and a semantic structure for transforming the samples of the transform block.

[0065] Video encoder 20 may apply one or more transforms to the luma transform block of a TU to generate a luma coefficient block for the TU. A coefficient block may be a two-dimensional array of multiple transform coefficients. A transform coefficient may be a scalar. Video encoder 20 may apply one or more transforms to the Cb transform block of a TU to generate a Cb coefficient block for the TU. Video encoder 20 may apply one or more transforms to the Cr transform block of a TU to generate a Cr coefficient block for the TU.

[0066] 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 the process of quantizing transform coefficients to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. After the video encoder 20 quantizes the coefficient block, the video encoder 20 may entropy encode semantic elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform context-adaptive binary arithmetic coding (CABAC) on the semantic elements indicating the quantized transform coefficients. Finally, the video encoder 20 may output a bitstream comprising a sequence of bits forming a representation of the encoded frame and associated data, which may be stored in the storage device 32 or transmitted to the destination device 14.

[0067] After receiving the bitstream generated by the video encoder 20, the video decoder 30 may parse the bitstream to obtain semantic elements from the bitstream. The video decoder 30 may reconstruct a frame of the video data based at least in part on the semantic elements obtained from the bitstream. The process of reconstructing the video data is generally reciprocal to the encoding process performed by the video encoder 20. For example, the video decoder 30 may inversely transform the coefficient blocks associated with the TUs of the current CU to reconstruct the residual blocks associated with the TUs of the current CU. The video decoder 30 may also reconstruct the coding blocks of the current CU by adding the samples of the prediction blocks for the PUs of the current CU to the samples of the transform blocks of the TUs of the current CU. After reconstructing the coding blocks for each CU of the frame, the video decoder 30 may reconstruct the frame.

[0068] As mentioned above, video codecs mainly use two modes to achieve video compression, namely intra-frame prediction and inter-frame prediction. Palette-based codecs are another coding scheme adopted by many video coding standards. In palette-based codecs, which may be particularly suitable for screen-generated content codecs, a video codec (e.g., video encoder 20 or video decoder 30) forms a palette table representing the colors of the video data of a given block. The palette table includes the most important (e.g., frequently used) pixel values ​​in the given block. Pixel values ​​that are not frequently represented in the video data of the given block are either not included in the palette table or included in the palette table as escape colors.

[0069] Each entry in the palette table includes an index into the palette table for the corresponding pixel value. The palette index for a sample in the block can be encoded to indicate which entry from the palette table will be used to predict or reconstruct which sample. The palette mode begins with the process of generating a palette predictor for the first block of a picture, slice, tile, or other such 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 illustration, it is assumed that the palette predictor is defined at the picture level. In other words, a picture may include multiple coding blocks, each with its own palette table, but there is only one palette predictor for the entire picture.

[0070] In order to reduce the bits required to signal palette entries in the video bitstream, a video decoder can utilize a palette predictor to determine new palette entries in a palette table for reconstructing a video block. For example, the palette predictor can include palette entries from a previously used palette table, or even be initialized with a most recently used palette table by including all entries of the most recently used palette table. In some embodiments, the palette predictor can include fewer than all entries of the most recently used palette table and then merge some entries from other previously used palette tables. The palette predictor can have the same size as the palette table used to encode a different block, or can be larger or smaller than the palette table used to encode a different block. In one example, the palette predictor is implemented as a first-in-first-out (FIFO) table that includes 64 palette entries.

[0071] To generate a palette table for a block of video data from the palette predictor, a video decoder can receive a one-bit flag for each entry of the palette predictor from an encoded video bitstream. The one-bit flag can have a first value (e.g., binary 1) indicating that the associated entry of the palette predictor is to be included in the palette table or a second value (e.g., binary 0) indicating that the associated entry of the palette predictor is not to be included in the palette table. If the size of the palette predictor is larger than the palette table for the block of video data, the video decoder can stop receiving more flags once the maximum size of the palette table is reached.

[0072] In some embodiments, some entries in the palette table can be directly signaled in the coded video bitstream rather than determined using the palette predictor. For these entries, the video decoder can receive three separate m-bit values ​​from the coded video bitstream, which indicate the pixel values ​​for the luminance and two chrominance components associated with the entry, where m represents the bit depth of the video data. The palette entries derived from the palette predictor only require a one-bit flag, compared to the multiple m-bit values ​​required for palette entries sent directly by signal. Therefore, using the palette predictor to signal some or all palette entries can significantly reduce the number of bits required to signal new palette table entries, thereby improving the overall coding efficiency of palette mode encoding.

[0073] In many cases, the palette predictor for a block is determined based on the palette table used to encode one or more previously encoded blocks. However, when encoding the first coding tree unit in a picture, slice, or tile, the palette table for the previously encoded block may not be available. Therefore, the palette predictor cannot be generated using the entries of the previously used palette table. In this case, a sequence of initial values ​​for the palette predictor can be signaled in a sequence parameter set (SPS) and / or a picture parameter set (PPS), which are the values ​​used to generate the palette predictor when the previously used palette table is not available. An SPS generally refers to the semantic structure of semantic elements applied to a series of consecutively coded video pictures called a coded video sequence (CVS), the coded video sequence being determined by the content of the semantic elements found in the PPS, with the semantic elements found in each slice segment header referencing the semantic elements found in the PPS. A PPS generally refers to the semantic structure of semantic elements applied to one or more individual pictures within a CVS, with the one or more individual pictures being determined by the semantic elements found in each slice segment header. Therefore, the SPS is generally considered to be a higher-level semantic structure than the PPS, which means that the semantic elements included in the SPS generally change less and apply to a larger portion of the video data than the semantic elements included in the PPS.

[0074] Figure 5 is a block diagram illustrating different prediction modes for a coding unit according to some implementations of the present application.

[0075] In VVC, each CU can be encoded in skip mode or non-skip mode. For CUs encoded in skip mode, a semantic element is further sent by signal to indicate whether the current CU is in regular skip mode (similar to the skip mode in HEVC) or IBC skip mode. For CUs encoded in non-skip mode, multiple semantic elements are further sent by signal to indicate whether the current CU is encoded in 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" in the VVC specification respectively. For CUs encoded in intra mode, only spatially adjacent reconstructed pixels in the same picture / slice can be used to generate prediction signals for the current CU. For CUs encoded in inter mode, prediction signals can be generated by pixels from reference pictures that are not the current picture. Details of the IBC mode can be found in document JVET-N1002 (http: / / phenix.int-evry.fr / jvet / ). At the 15th JVET meeting, the palette (PLT) mode was newly adopted into VVC, and its details are described in the document JVET-O0119 at http: / / phenix.int-evry.fr / jvet / .

[0076] 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, that is, whether IBC and / or PLT modes are allowed in the relevant bitstream.

[0077]

[0078] Table 1: Constraints for enabling / signaling non-skip related modes The semantics of mode signaling in current VVC are shown in the following table.

[0079]

[0080] Table 2. Semantics of prediction mode signaling in current VVC

[0081] The semantics of mode signaling in current VVC is described below.

[0082] cu_skip_flag[x0][y0] equal to 1 indicates that for the current coding unit, when decoding P or B slices, no semantic elements are parsed after cu_skip_flag[x0][y0] except one or more of the following: the IBC mode flag pred_mode_ibc_flag[x0][y0] and the merge_data() semantic structure; when decoding I slices, no semantic elements are parsed after cu_skip_flag[x0][y0] except merge_idx[x0][y0]. cu_skip_flag[x0][y0] equal to 0 indicates that the coding unit is not skipped. The array indices x0, y0 represent 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. When cu_skip_flag[x0][y0] is not present, it is inferred to be equal to 0.

[0083] pred_mode_flag is equal to 0, indicating that the current coding unit is encoded in inter-frame prediction mode. pred_mode_flag is equal to 1, indicating that the current coding unit is encoded in intra-frame prediction mode. When pred_mode_flag is not present, the following is inferred:

[0084] If cbWidth is equal to 4 and cbHeight is equal to 4, then pred_mode_flag is inferred to be equal to 1.

[0085] Otherwise, if modeType is equal to MODE_TYPE_INTRA, then pred_mode_flag is inferred to be equal to 1.

[0086] Otherwise, if modeType is equal to MODE_TYPE_INTER, then pred_mode_flag is inferred to be equal to 0.

[0087] Otherwise, pred_mode_flag is inferred to be equal to 1 when decoding an I slice and equal to 0 when decoding a P or B slice, respectively.

[0088] For x = x0..x0+cbWidth-1 and y = y0..y0+cbHeight-1, the variable CuPredMode[chType][x][y] is derived as follows:

[0089] If pred_mode_flag is equal to 0, CuPredMode[chType][x][y] is set equal to MODE_INTER.

[0090] Otherwise (pred_mode_flag is equal to 1), CuPredMode[chType][x][y] is set equal to MODE_INTRA.

[0091] pred_mode_ibc_flag is equal to 1, indicating that the current coding unit is encoded in IBC prediction mode. pred_mode_ibc_flag is equal to 0, indicating that the current coding unit is not encoded in IBC prediction mode. When pred_mode_ibc_flag is not present, the following is inferred:

[0092] 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.

[0093] Otherwise, if cbWidth and cbHeight are both equal to 128, then pred_mode_ibc_flag is inferred to be equal to 0.

[0094] Otherwise, if modeType is equal to MODE_TYPE_INTER, then pred_mode_ibc_flag is inferred to be equal to 0.

[0095] Otherwise, if treeType is equal to DUAL_TREE_CHROMA, pred_mode_ibc_flag is inferred to be equal to 0.

[0096] 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 be 0 when decoding a P or B slice, respectively.

[0097] When pred_mode_ibc_flag is equal to 1, the variable CuPredMode[chType][x][y] is set equal to MODE_IBC, since x=x0..x0+cbWidth-1 and y=y0..y0+cbHeight-1.

[0098] pred_mode_plt_flag indicates the palette mode to be used 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. When pred_mode_plt_flag is not present, it is inferred to be equal to 0. When pred_mode_plt_flag is equal to 1, the variable CuPredMode[x][y] is set to equal MODE_PLT for x = x0..x0 + cbWidth-1 and y = y0..y0 + cbHeight-1.

[0099] In summary, in the current VVC, the semantics (i.e., associated flags) signaled to indicate the corresponding non-skipped mode are shown in Tables 4 to 10, each corresponding to a different condition for the allowed prediction mode. It should be noted that in these tables, the 0s and 1s in the codewords can all be reversed, and the functionality of the generated codewords is the same.

[0100] Furthermore, the naming of the semantic elements can be changed to other names without changing the functionality of the signalling pattern.

[0101] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 0 0 - IBC 0 1 - PLT 1 - 1 Intraframe 1 - 0

[0102] Table 3. Signaling of non-skipped CU prediction modes in the current VVC when all modes (inter, intra, IBC and PLT modes) are allowed

[0103] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag IBC - 1 - PLT - 0 1 Intraframe - 0 0

[0104] Table 4. Signaling of non-skipped CU mode in current VVC when only intra, IBC and PLT modes are allowed

[0105] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 0 - 0 PLT 0 - 1 Intraframe 1 - -

[0106] Table 5. Signaling of non-skipped CU mode in current VVC when only intra, inter, and PLT modes are allowed

[0107] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 0 0 - IBC 0 1 - Intraframe 1 - -

[0108] Table 6. Signaling of non-skipped CU modes in current VVC when only intra, inter, and IBC modes are allowed

[0109] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag IBC - 1 - Intraframe - 0 -

[0110] Table 7. Signaling of non-skipped CU mode in current VVC when only intra and IBC modes are allowed

[0111] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag PLT - - 1 Intraframe - - 0

[0112] Table 8. Signaling of non-skipped CU mode in the current VVC when only intra and PLT modes are allowed

[0113] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 0 - - Intraframe 1 - -

[0114] Table 9. Signaling of non-skipped CU mode in current VVC when only intra and inter modes are allowed

[0115] Figure 6 is a flow chart illustrating an exemplary process by which a video codec implements a technique for signaling a prediction mode according to some embodiments of the present invention.

[0116] In the current VVC, the IBC mode is considered to be a mode more similar to the inter mode, while the PLT mode is considered to be a mode more similar 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 a similar inter mode. 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 a similar intra mode. However, there is an exception when only intra, inter, and PLT modes 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. This exception not only destroys the physical meaning of the pred_mode_flag flag, but also complicates the signaling conditions of pred_mode_plt_flag because different signaling conditions are used depending on whether the IBC mode is allowed.

[0117] Furthermore, in the current VVC, the conditional checking for signaling pred_mode_ibc_flag and pred_mode_plt_flag is complex, as shown in Table 2. Several methods are proposed to simplify the conditional checking for signaling these prediction modes.

[0118] According to a first embodiment of the present application, a flag indicating the activation of the palette mode (such as pred_mode_plt_flag in the VVC specification) is signaled only in a mode similar to the intra mode, without considering the conditions of the allowed prediction modes. In an example, the palette mode flag pred_mode_plt_flag is signaled only when a semantic element indicating intra mode or inter mode (such as pred_mode_flag) is signaled or inferred to be similar to the intra mode (for example, pred_mode_flag is 1 in the current VVC). According to this embodiment, when only inter, intra, and PLT modes are allowed, the corresponding codewords are shown in Table 10, which is different from Table 5. In addition, the signaling conditions of pred_mode_plt_flag can be simplified, as highlighted in Table 11.

[0119] Pred_Modes pred_mode_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 0 - - PLT 1 - 1 Intraframe 1 - 0

[0120] Table 10. Signaling of non-skipped CU mode when only intra, inter, and PLT modes are allowed based on the first embodiment

[0121]

[0122] Table 11. Semantics of proposed mode signaling for VVC (modified parts are highlighted)

[0123] According to a second embodiment of the present application, these 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 require a corresponding flag because it can be inferred to be enabled when all previously signaled modes (or flags) are not enabled. In one example, the inter-frame mode, IBC mode, and PLT mode are indicated by flags pred_mode_inter_flag, pred_mode_ibc_flag, and pred_mode_plt_flag, respectively. In this case, the method is basically the same as assigning truncated binary codewords to the modes based on a predefined signaling order. The relevant codewords are shown in Tables 12 to 18. The signaling conditions for pred_mode_ibc_flag and pred_mode_plt_flag can also be simplified, as highlighted in Table 19.

[0124] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag Interframe 1 - - IBC 0 1 - PLT 0 0 1 Intraframe 0 0 0

[0125] Table 12. Signaling of non-skipped CU mode when all modes (inter, intra, IBC and PLT modes) are allowed based on the second embodiment

[0126] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag IBC - 1 - PLT - 0 1 Intraframe - 0 0

[0127] Table 13. Signaling of non-skipped CU mode when only intra, IBC and PLT modes are allowed based on the second embodiment

[0128] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag INTER 1 - - PLT 0 - 1 INTRA 0 - 0

[0129] Table 14. Signaling of non-skipped CU mode when only intra, inter, and PLT modes are allowed based on the second embodiment

[0130] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag INTER 1 - - IBC 0 1 - INTRA 0 0 -

[0131] Table 15. Signaling of non-skipped CU mode when only intra, inter, and IBC modes are allowed based on the second embodiment

[0132] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag IBC - 1 - Intraframe - 0 -

[0133] Table 16. Signaling of non-skipped CU mode when only intra and IBC modes are allowed based on the second embodiment

[0134] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag PLT - - 1 INTRA - - 0

[0135] Table 17. Signaling of non-skipped CU mode when only intra and PLT modes are allowed based on the second embodiment

[0136] Pred_Modes pred_mode_inter_flag pred_mode_ibc_flag pred_mode_plt_flag Inter-frame 1 - - Intra-frame 0 - -

[0137] Table 18. Signaling of non-skipped CU mode when only intra and inter modes are allowed based on the second embodiment

[0138]

[0139] Table 19. Semantics of proposed mode signaling for VVC (modified parts are highlighted)

[0140] According to a third embodiment of the present invention, these modes are signaled by first sending a semantic element to indicate whether the current block uses a conventional mode (such as inter and intra modes) or a new mode (such as IBC and PLT modes). After the first semantic element, additional semantic elements are signaled to indicate which mode is used. The associated codewords are shown in Tables 20 to 26. It should be noted that according to this embodiment, the naming of the codeword bins (or flags) has been changed to reflect their physical meaning.

[0141] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag Inter-frame 1 1 - IBC 0 - 1 PLT 0 - 0 Intra-frame 1 0 -

[0142] Table 20. Signaling of non-skipped CU mode when all modes (inter, intra, IBC, and PLT modes) are allowed based on the third embodiment

[0143] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag IBC 0 - 1 PLT 0 - 0 Intra-frame 1 - -

[0144] Table 21. Signaling of non-skipped CU mode when only intra, IBC and PLT modes are allowed based on the third embodiment

[0145] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag Inter-frame 1 1 - PLT 0 - - Intra-frame 1 0 -

[0146] Table 22. Signaling of non-skipped CU mode when only intra, inter, and PLT modes are allowed based on the third embodiment

[0147] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag Inter-frame 1 1 - IBC 0 - - Intra-frame 1 0 -

[0148] Table 23. Signaling of non-skipped CU mode when only intra, inter, and IBC modes are allowed based on the third embodiment

[0149] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag IBC 0 - - Intra-frame 1 - -

[0150] Table 24. Signaling of non-skipped CU mode when only intra and IBC modes are allowed based on the third embodiment

[0151] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag [[ID=,49]]pred_mode_ibc_flag PLT 0 - - Intra-frame 1 - -

[0152] Table 25. Signaling of non-skipped CU mode when only intra and PLT modes are allowed based on the third embodiment

[0153] Pred_Modes pred_mode_regular_flag pred_mode_inter_flag pred_mode_ibc_flag Inter-frame - 1 - Intra-frame - 0 -

[0154] Table 26. Signaling of non-skipped CU mode when only intra and inter modes are allowed based on the third embodiment

[0155] To signal a prediction mode, the video codec first receives video data corresponding to a non-skip mode coding block from a bitstream (610) and determines a parameter set associated with the non-skip mode coding block (620). The parameter set (e.g., sequence parameter set) includes information to indicate which mode (e.g., IBC, PLT, etc.) is allowed in the associated bitstream, as shown in Table 1.

[0156] Thereafter, the video codec selectively receives a first, second, or third semantic element from the bitstream. If the parameter set includes information satisfying the first condition, the video codec retrieves the first semantic element from the bitstream (e.g., pred_mode_flag in Table 2) (630). If the parameter set includes information satisfying the second condition, the video codec retrieves the second semantic element from the bitstream (e.g., pred_mode_ibc_flag in Table 2) (640). If the parameter set includes information satisfying the third condition, the video codec retrieves the third semantic element from the bitstream (e.g., pred_mode_plt_flag in Table 2) (650). For the conditions associated with each corresponding semantic element, refer to Table 2. In some embodiments, if the corresponding condition is not satisfied, the video codec does not receive the corresponding semantic element (e.g., the video codec may assign default values ​​to the semantic elements or not use the semantic elements during decoding).

[0157] Next, the video codec decodes the video data corresponding to the non-skip mode coding block using the corresponding mode according to the received values ​​of the first, second, and third semantic elements. Specifically:

[0158] When the first semantic element (such as pred_mode_flag in Table 1) and the third semantic element (such as pred_mode_plt_flag in Table 1) both have a first value (such as "1"), the video codec decodes the video data using the palette mode, and the second condition is not met (for example, the video codec does not receive pred_mode_ibc_flag) (660).

[0159] The video codec decodes the video data using the intra prediction mode when the first semantic element (e.g., pred_mode_flag in Table 1) has a first value (e.g., "1") and the third semantic element has a second value (e.g., "0") and the second condition is not met (e.g., the video codec does not receive pred_mode_ibc_flag) (670).

[0160] When the first syntax element has the second value (eg, "0") and the second and third conditions are not satisfied (eg, the video codec does not receive pred_mode_ibc_flag and pred_mode_plt_flag), the video codec decodes the video data using the inter prediction mode (680).

[0161] 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 as one or more instructions or codes on or transmitted via a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to tangible media such as data storage media, or communication media including any media that facilitates the transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, computer-readable media may generally correspond to (1) non-transitory tangible computer-readable storage media or (2) communication media such as signals or carrier waves. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures to implement the embodiments described in this application. A computer program product may include computer-readable media.

[0162] The terms used in the description of the embodiments herein are only used for the purpose of describing specific embodiments and are not intended to limit the scope of the claims. The singular forms "a" and "the" used in the description of the embodiments and the appended claims are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and covers any and all possible combinations of one or more associated listed items. It will be further understood that when used in this specification, the term "comprising" specifies the presence of stated features, elements and / or components, but does not exclude the presence or addition of other one or more features, elements, components and / or groups thereof.

[0163] It should also be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited to these terms. These terms are merely used to distinguish one element from another. For example, without departing from the scope of the embodiments, a first electrode may be referred to as a second electrode, and similarly, a second electrode may be referred to as a first electrode. The first electrode and the second electrode are both electrodes, but not the same electrode.

[0164] The description of this application is presented for the purpose of illustration and description and is not intended to be exhaustive or to limit the invention in the form disclosed. Many modifications, variations, and alternative embodiments will be apparent to those skilled in the art having the benefit of the teachings presented in the foregoing description and the associated drawings. The embodiments are 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 various implementations of the invention and to best utilize the basic principles with various modifications and various implementations, as appropriate for the particular use contemplated. Therefore, it should be understood that the scope of the claims is not limited to the specific examples of the disclosed embodiments, and that modifications and other embodiments are intended to be included within the scope of the appended claims.

Claims

1. A method for encoding video data, the method comprising: Obtaining a parameter set associated with a non-skip mode coding block; signaling a first semantic element in the bitstream based on determining that the parameter set includes information satisfying a first condition; signaling a second semantic element in the bitstream based on determining that the parameter set includes information satisfying a second condition; signaling a third semantic element in the bitstream based on determining that the parameter set includes information satisfying a third condition; encoding the video data corresponding to the non-skip mode coding block using a palette mode when the first syntax element has a first value and the third syntax element has the first value; When the first semantic element has the first value and the third semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an intra prediction mode; When the first semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an inter prediction mode; as well as Video data corresponding to the non-skip mode coding block is transmitted via the bitstream.

2. The method according to claim 1, wherein When encoding video data corresponding to the non-skip mode coding block using the palette mode, the second condition is not satisfied and the second syntax element is not sent.

3. The method according to claim 1, wherein When encoding the video data corresponding to the non-skip mode coding block using the intra prediction mode, the second condition is not satisfied and the second syntax element is not sent.

4. The method according to claim 1, wherein When the video data corresponding to the non-skip mode coding block is encoded using the inter prediction mode, the second condition and the third condition are not satisfied and the second semantic element and the third semantic element are not transmitted.

5. The method according to claim 1, wherein The method further comprises: When the first syntax element has the second value or the first syntax element is not sent, the second syntax element has the first value, and the third syntax element is not sent, video data corresponding to the non-skip mode coding block is encoded using intra block copy mode.

6. A computing device comprising: one or more processors; a memory coupled to the one or more processors; as well as A plurality of programs stored in the memory, which, when executed by the one or more processors, cause the computing device to perform the video data encoding method according to any one of claims 1 to 5 to form a bit stream to be transmitted and store the bit stream in the memory.

7. A non-transitory computer-readable storage medium storing a plurality of programs executed by a computing device having one or more processors, wherein the plurality of programs, when executed by the one or more processors, causes the computing device to perform the video data encoding method according to any one of claims 1 to 5 to form a bit stream to be transmitted and store the bit stream in the non-transitory computer-readable storage medium.

8. A non-transitory computer-readable storage medium storing a program and a bit stream, wherein when the program is executed by one or more processors, the computing device performs the video data encoding method according to any one of claims 1 to 5 on the bit stream.

9. A computer program product comprising one or more programs for execution by a computing device having one or more processors, wherein: When the program is executed by the one or more processors, the computing device executes the video data encoding method according to any one of claims 1 to 5.

10. A method for storing a bitstream, wherein the bitstream is generated by an encoding method comprising the steps of: Obtaining a parameter set associated with a non-skip mode coding block; signaling a first semantic element in the bitstream based on determining that the parameter set includes information satisfying a first condition; signaling a second semantic element in the bitstream based on determining that the parameter set includes information satisfying a second condition; signaling a third semantic element in the bitstream based on determining that the parameter set includes information satisfying a third condition; encoding the video data corresponding to the non-skip mode coding block using a palette mode when the first syntax element has a first value and the third syntax element has the first value; When the first semantic element has the first value and the third semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an intra prediction mode; When the first semantic element has the second value, encoding the video data corresponding to the non-skip mode coding block using an inter prediction mode; as well as Video data corresponding to the non-skip mode coding block is transmitted via the bitstream.

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