Parameterized graph-based separable transform for video decoding

Abstract

A video decoder may be configured to: receive picture-related information in a syntax structure applied to a current block; determine a transform matrix based on the received picture-related syntax information; perform an inverse transform based on the determined transform matrix of one or more coefficient values ​​to generate a residual block; and reconstruct a current block of video data based on the residual block.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 17 / 077,587, filed on October 22, 2020, which claims the benefit of U.S. Provisional Patent Application No. 62 / 926,284, filed on October 25, 2019, and the entire contents of each of the above U.S. applications are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to video encoding and video decoding. Background Art

[0004] Digital video capabilities may be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones (so-called "smart phones"), video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques (such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Coding (AVC)), ITU-T H.265 / High Efficiency Video Coding (HEVC), and extensions of such standards). By implementing such video coding techniques, video devices may more efficiently send, receive, encode, decode, and / or store digital video information.

[0005] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial predictions relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial predictions relative to reference samples in neighboring blocks in the same picture or temporal predictions relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0006] In general, the present disclosure describes techniques for a graph-based separable transform that can be used by a video encoder to transform residual values ​​from a sample domain (also known as a pixel domain) to a transform domain (also known as a frequency domain) and by a video decoder to transform (e.g., inverse transform) from the transform domain back to the sample domain. In an example video decoding system, a separable transform (e.g., a two-dimensional DCT-2) has been used to decode a block residual signal obtained after prediction. The present disclosure describes an example of a method for establishing parameters for a graph-based separable transform (GBST) for video decoding. As an example, a GBST can be derived from a pair of line graphs whose weights are determined based on two non-negative parameters. The present disclosure describes example techniques that can optimize graph parameters for a GBST to better capture residual block statistics and thereby improve video compression efficiency.

[0007] In one example, the present disclosure describes a method for decoding video data, the method comprising: receiving picture-related information in a syntax structure applied to a current block of video data; determining a transformation matrix based on the received picture-related syntax information; performing an inverse transformation based on the determined transformation matrix of one or more coefficient values ​​to generate a residual block; and, reconstructing the current block of video data based on the residual block.

[0008] In another example, the present disclosure describes a device for decoding video data, the device comprising a memory and a processing circuit, the memory being configured to store the video data; the processing circuit being configured to: receive picture-related information in a syntax structure applied to a current block of the video data; determine a transformation matrix based on the received picture-related syntax information; perform an inverse transformation based on the determined transformation matrix of one or more coefficient values ​​to generate a residual block; and reconstruct the current block of the video data based on the residual block.

[0009] In another example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, configure a processor to: receive image-related information in a syntax structure applied to a current block of video data; determine a transformation matrix based on the received image-related syntax information; perform an inverse transform based on the determined transformation matrix of one or more coefficient values ​​to generate a residual block; and, reconstruct the current block of video data based on the residual block.

[0010] In another example, the present disclosure describes a device for decoding video data, the device comprising: a unit for receiving image-related information in a syntax structure applied to a current block of video data; a unit for determining a transformation matrix based on the received image-related syntax information; a unit for performing an inverse transform based on the determined transformation matrix of one or more coefficient values ​​to generate a residual block; and a unit for reconstructing the current block of video data based on the residual block.

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0013] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0014] Figure 3A-3E is a table showing examples of transformation types.

[0015] Figure 4 is a conceptual diagram illustrating an example of a residual quadtree-based transform scheme.

[0016] Figure 5 is a flow chart illustrating an example for deriving an integer transform for a given graph and graph parameters.

[0017] Figure 6 is a conceptual diagram showing a line graph having N vertices.

[0018] Fig. 7A and Figure 7B is a conceptual diagram illustrating an example of a graph weight corresponding to a generalized graph Laplacian (GGL) matrix.

[0019] Figure 8A-8D The average and per-class performance of the N-point Graph-based Separable Transform (GBST) are shown.

[0020] Fig. 9 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0021] Fig.10 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0022] Fig.11 is a flow chart illustrating an example method for encoding a current block.

[0023] Fig.12 is a flow chart illustrating an example method for decoding a current block of video data.

[0024] Fig.13 is a flow diagram illustrating example operations for decoding video data in accordance with one or more techniques of this disclosure. DETAILED DESCRIPTION

[0025] Video coding (e.g., video encoding and / or video decoding) typically involves predicting a block of video data from an already encoded block of video data in the same picture (e.g., intra-frame prediction) or an already encoded block of video data in a different picture (e.g., inter-frame prediction). In some cases, the video encoder also calculates residual data by comparing the predicted block to the original block. Thus, the residual data represents the difference between the predicted block and the original block. To reduce the number of bits required to signal the residual data, the video encoder transforms and quantizes the residual data and signals the transformed and quantized residual data in the coded bitstream.

[0026] The video decoder dequantizes and inverse transforms the received transformed and quantized residual data to approximately reproduce the residual calculated by the video encoder. The video decoder adds the residual data to the prediction block to produce a reconstructed video block that more closely matches the original video block than the prediction block alone. However, the compression achieved by the transform and quantization process can be lossy, meaning that the transform and quantization process can introduce artifacts or distortion into the decoded video data. One common type of artifact or distortion is called blockiness, where the boundaries of the blocks used to decode the video data are visible.

[0027] In order to further improve the quality of the decoded video, the video decoder can perform one or more filtering operations on the reconstructed video blocks. Examples of these filtering operations include deblocking filtering, sample adaptive offset (SAO) filtering, and adaptive loop filtering (ALF). The parameters for these filtering operations can be determined by the video encoder and explicitly signaled in the coded video bitstream, or can be implicitly determined by the video decoder without explicitly signaling in the coded video bitstream.

[0028] The present disclosure relates to transform coding, and more specifically, to a parameterized method for designing transforms. The techniques described in the present disclosure can be used for advanced video codecs and next generation video coding standards such as VVC. Several multiple transform selection (MTS) designs extend the current MTS tools in the general video coding (VVC) standard. The techniques described in the present disclosure allow video encoders and video decoders to better capture residual block statistics and thus improve coding efficiency by enabling the video encoder and video decoder to use a larger number of different transforms. However, by receiving image-related information in a syntax structure applied to a current block and determining a transform matrix based on the received image-related syntax information, the techniques of the present disclosure allow video encoders and video decoders to implement this larger number of different conversions without significantly increasing signaling overhead or memory requirements for storing additional conversions.

[0029] In some video compression systems prior to the High Efficiency Video Coding (HEVC) standard (G. J. Sullivan, J.-R. Ohm, W.-J. Han, and T. Wiegand, “Overview of the High Efficiency Video Coding (HEVC) Standard,” IEEE Trans. Circuits Syst. Video Technol., vol. 22, no. 12, pp. 1649–1668, Dec. 2012), only the type 2 discrete cosine transform (DCT-2) was used to transform the rows and columns of the residual block signal in a separable manner. One problem with using DCT-2 as the only transform option is the implicit assumption that all residual blocks share the same statistical properties. However, in practice, residual blocks may have different statistical properties, depending on the video content, prediction mode, and block size.

[0030] Tests have shown that the separable type 7 discrete sine transform (DST-7) can provide significant decoding gain over DCT-2 for small blocks, and DST-7 is adopted in HEVC to decode 4x4 intra-prediction blocks. To further increase the diversity of transform choices with decoding benefits, the general video coding standard (VVC) currently under development adopts MTS among five candidates based on DCT-2, DCT-8 and DST-7, where MTS can be applied to blocks up to size 32x32, as described in the Joint Video Study Group of ITU-T SG16 WP3 and ISO / IEC JTC 1 / SC29 / WG11, input document JVET-K0026, A. Said and X. Zhao, "CE6: Summary report on transforms and transform signalling", Ljubljana, Slovenia, July 2018.

[0031] This disclosure describes a graph-based separable transform (GBST) as an alternative or supplement to DST-7 and DCT-8 for MTS design in VVC. Graph-based transforms (GBTs) can improve decoding efficiency by providing better adaptability to various block statistics, as shown in HE Egilmez, A. Said, Y.-H. Chao, and A. Ortega, “Graph-based transforms for inter predicted video coding,” in IEEE International Conference on ImageProcessing(ICIP), Sept 2015, pp. 3992–3996, E. Pavez, HE Egilmez, Y. Wang, and A. Ortega, “GTT: Graph template transforms with applications to image coding,” in Picture Coding Symposium(PCS), 2015, May 2015, pp. 199–203, HE Egilmez, YH Hao, A. Ortega, B. Lee, and S. Yea, “GBST: Separable transforms based on line graphs for predictive video coding,” in 2016 IEEE International Conference on ImageProcessing(ICIP), Sept 2016, pp.2375–2379, HEEgilmez, YHChao, and A.Ortega, “Graph-based transforms for video coding," CoRR, vol.abs / arXiv:1909.00952, 2019. [Online]. Available: https: / / arxiv.org / abs / 1909.00952, and HEEgilmez, O. Teke, A. Said, V. Seregin, M. Karczewicz, "Parametric Graph-based Separable Transforms for Video Coding," IEEE International Conference on Image Processing (ICIP), 2020 as described.

[0032] In “GBST: Separable transforms based on line graphs for predictive video coding,” and “Graph-based transforms for video coding,” a separable GBT (i.e., GBST) is optimized by learning a pair of line graphs from the data described by H.E. Gilmez, E. Pavez, and A. Ortega, “Graph learning from data under Laplacian and structural constraints,” IEEE Journal of Selected Topics in Signal Processing, vol. 11, no. 6, pp. 825–841, Sept 2017, to model the basic row and column statistics of the block residual signal, where the associated graph Laplacian matrix is ​​used to derive the GBST.

[0033] “Graph-based transforms for video coding” shows that GBT can outperform the Karhunen-Loeve transform (KLT) derived from the sample covariance matrix in terms of decoding efficiency because graph learning methods provide better model estimates than using sample covariance to derive KLT (e.g., better generalization and variance-bias trade-offs as described in V.N. Apnik, “An overview of statistical learning theory,” IEEE Transactions on Neural Networks, vol. 10, no. 5, pp. 988–999, Sep 1999 and U. von Luxburg and B. Sch¨olkopf, Statistical Learning Theory: Models, Concepts, and Results. Amsterdam, Netherlands: Elsevier North Holland, May 2011, vol. 10, pp. 651–706). One possibility from “Graph-based transforms for video coding” is that learning models with fewer parameters (which alleviates the overfitting problem) generally leads to more general and robust model estimates, so graph learning techniques can be used to design better transforms for video coding.

[0034] This disclosure describes techniques for one or more parameterized methods to determine a line graph whose weights are determined based on two non-negative parameters. For example, GBST can be constructed from a graph with constant edge weights (given by w c Represents) and a single vertex weight v c (also called self-loops), as described in more detail. Compared to the GBST construction technique in "Graph-based transforms for video coding" that allows arbitrary graph weights, an example of a parameterized approach may be a more constrained variant, which leads to a simpler model defined by fewer parameters. In addition, the empirical results in "GBST: Separable transforms based on line graphs for predictive video coding" and "Graph-based transforms for video coding" may have provided their theoretical basis in a simple simulation setting. The present disclosure presents experimental results in a more realistic setting, where the proposed GBST was tested on the VVC reference software.

[0035] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of the present disclosure. In general, the techniques of the present disclosure relate to decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0036] like Figure 1 As shown in , in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 may include any of a wide variety of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0037] exist Figure 1In the example of , source device 102 includes video source 104, memory 106, video encoder 200 and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120 and display device 118. According to the present disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply the technology for parameter transformation derivation described herein. Therefore, source device 102 represents an example of a video encoding device, and destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may be docked with an external display device instead of including an integrated display device.

[0038] like Figure 1 The system 100 shown is only one example. In general, any digital video encoding and / or decoding device can perform the described techniques for parameter transformation derivation. The source device 102 and the destination device 116 are only examples of such decoding devices, wherein the source device 102 generates decoded video data for transmission to the destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (e.g., encoding and / or decoding) of data. Therefore, the video encoder 200 and the video decoder 300 represent examples of decoding devices (specifically, video encoders and video decoders), respectively. In some examples, the source device 102 and the destination device 116 can operate in a substantially symmetrical manner, so that each of the source device 102 and the destination device 116 includes a video encoding and decoding component. Therefore, the system 100 can support one-way or two-way video transmission between the source device 102 and the destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0039] Typically, the video source 104 represents the source of video data (i.e., the original, undecoded video data), and provides a series of pictures (also referred to as "frames") of the order of the video data to the video encoder 200, which encodes the data for the pictures. The video source 104 of the source device 102 may include a video capture device, such as a camera, a video archive unit containing previously captured original video, and / or a video feed interface for receiving video from a video content provider. As another alternative, the video source 104 may generate computer graphics-based data as the source video, or a combination of real-time video, archived video, and computer-generated video. In each case, the video encoder 200 may encode captured, pre-captured, or computer-generated video data. The video encoder 200 may rearrange the pictures from the received order (sometimes referred to as "display order") to a decoding order for decoding. The video encoder 200 may generate a bitstream comprising encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 to be received and / or retrieved by, for example, input interface 122 of destination device 116 .

[0040] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 can store original video data, for example, original video from the video source 104 and original decoded video data from the video decoder 300. In addition or alternatively, the memories 106, 120 can store software instructions that can be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although the memory 106 and the memory 120 are shown as separate from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 can also include internal memories for functionally similar or equivalent purposes. In addition, the memories 106, 120 can store, for example, encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memories 106, 120 can be allocated as one or more video buffers, for example, to store original decoded and / or encoded video data.

[0041] The computer-readable medium 110 may represent any type of medium or device capable of delivering the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to directly send the encoded video data to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. According to a communication standard such as a wireless communication protocol, the output interface 108 may modulate a transmission signal including the encoded video data, and the input interface 122 may demodulate the received transmission signal. The communication medium may include any wireless or wired communication medium, for example, a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form a portion 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 a router, a switch, a base station, or any other device that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0042] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0043] In some examples, source device 102 may output the encoded video data to file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading.

[0044] The file server 114 may be any type of server device capable of storing encoded video data and sending the encoded video data to the destination device 116. The file server 114 may represent a network server (e.g., for a website) configured to provide file transfer protocol services (e.g., file transfer protocol (FTP) or file delivery over unidirectional transport (FLUTE) protocol, a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a multimedia broadcast multicast service (MBMS) or enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. Additionally or alternatively, the file server 114 may implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Real-Time Streaming (HLS), Real-Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, and the like.

[0045] Destination device 116 may access the encoded video data from file server 114 through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of both, suitable for accessing the encoded video data stored on file server 114. Input interface 122 may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from file server 114 or other such protocols for retrieving media data.

[0046] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to a cellular communication standard (such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to other wireless standards (such as IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee TM ),Bluetooth TMStandards, etc.) to transmit data (such as encoded video data). In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing the functions assigned to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing the functions assigned to video decoder 300 and / or input interface 122.

[0047] The techniques of the present disclosure may be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (such as Dynamic Adaptive Streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0048] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream 110 may include signaling information such as the following syntax elements defined by the video encoder 200 (which are also used by the video decoder 300): the syntax elements have values ​​that describe the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to the user. The display device 118 may represent 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 another type of display device.

[0049] Despite Figure 1 200 and 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including both audio and video in a common data stream. If applicable, the MUX-DEMUX units may follow the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0050] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder 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 the technology is partially implemented in software, the device can store instructions for the software in a suitable non-transitory computer-readable medium, and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, and any of the encoders or decoders can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. The device including the video encoder 200 and / or the video decoder 300 can include an integrated circuit, a microprocessor, and / or a wireless communication device (e.g., a cellular phone).

[0051] The video encoder 200 and the video decoder 300 may operate according to a video coding standard, such as ITU-T H.265 (also known as the High Efficiency Video Coding (HEVC) standard) or an extension thereof, such as a multi-view and / or scalable video coding extension. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also known as Versatile Video Coding (VVC). A draft of the VVC standard was described in “Versatile Video Coding (Draft 4)” by Bross et al. at the 13th meeting of the Joint Video Experts Group (JVET) of ITU-T SG16WP 3 and ISO / IEC JTC1 / SC 29 / WG 11, held in Marrakech, Morocco, from January 9 to 18, 2019, JVET-M1001-v7 (hereinafter referred to as “VVC Draft 10”). However, the technology of the present disclosure is not limited to any specific coding standard.

[0052] Typically, the video encoder 200 and the video decoder 300 can perform block-based decoding of the picture. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 can decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding red, green, and blue (RGB) data for samples of a picture, the video encoder 200 and the video decoder 300 can decode luminance and chrominance components, wherein the chrominance components may include both red hue and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Optionally, a pre-processing and post-processing unit (not shown) can perform these conversions.

[0053] The present disclosure may generally relate to the decoding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding data for the picture. Similarly, the present disclosure may relate to the decoding of a block of a picture to include the process of encoding or decoding data for the block (e.g., prediction and / or residual decoding). The encoded video bitstream generally includes a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or a block should generally be understood as decoding the values ​​of the syntax elements used to form the picture or the block.

[0054] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as the video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video decoder may further partition the PU and TU. For example, in HEVC, the residual quadtree (RQT) represents the partitioning of the TU. In HEVC, PU represents inter-frame prediction data, and TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0055] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video decoder (e.g., the video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). The video encoder 200 may partition the CTU according to a tree structure (e.g., a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the partition between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0056] In the MTT partitioning structure, blocks can be partitioned using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) (also known as ternary tree (TT)) partitioning. A ternary tree or ternary tree partitioning is a partitioning in which a block is divided into three sub-blocks. In some examples, the ternary tree or ternary tree partitioning divides the block into three sub-blocks without dividing the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0057] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the respective chroma components).

[0058] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures per HEVC. For purposes of explanation, a description of the techniques of the present disclosure is given with respect to QTBT segmentation. However, it should be understood that the techniques of the present disclosure may also be applied to video decoders configured to use quadtree segmentation or also use other types of segmentation.

[0059] In some examples, a CTU includes: a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a black and white picture or a picture encoded using three independent color planes and syntax structures for encoding samples. A CTB can be an NxN block of samples for some value of N, so that the division of a component into multiple CTBs is a single partition. A component is an array or a single sample from one of the three arrays (luminance and two chroma) that make up a picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array that makes up a picture in black and white format. In some examples, a decoding block is an M×N block of samples for some values ​​of M and N, so that the division of a CTB into multiple decoding blocks is a single partition.

[0060] Blocks (e.g., CTUs or CUs) may be grouped in a picture in various ways. As an example, a brick may refer to a rectangular area of ​​a CTU row within a particular tile in a picture. A tile may be a rectangular area of ​​a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular area of ​​a CTU having a height equal to the height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular area of ​​a CTU having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

[0061] In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. Tiles that are not partitioned into multiple bricks may also be referred to as bricks. However, bricks that are true subsets of tiles may not be referred to as tiles.

[0062] Tiles in a picture can also be arranged in slices. A slice can be an integer number of tiles of a picture that can be uniquely contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes a continuous sequence of multiple complete tiles or only complete tiles of one tile.

[0063] This disclosure may use "N×N" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, for example, 16×16 samples or 16 by 16 samples. Typically, a 16×16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. In addition, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include N×M samples, where M is not necessarily equal to N.

[0064] The video encoder 200 encodes video data representing prediction and / or residual information and other information for a CU. The prediction information indicates how the CU will be predicted in order to form a prediction block for the CU. The residual information typically represents a sample-by-sample difference between samples of the CU before encoding and the prediction block.

[0065] In order to predict a CU, the video encoder 200 can generally form a prediction block for the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU based on data of a previously decoded picture, while intra-frame prediction generally refers to predicting a CU based on previously decoded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate a prediction block. The video encoder 200 can generally perform motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 can use the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean square difference (MSD), or other such difference calculations to calculate a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional prediction or bidirectional prediction to predict the current CU.

[0066] Some examples of VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (e.g., zooming in or out, rotation, perspective motion, or other irregular motion types).

[0067] To perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. Some examples of VVC provide sixty-seven intra prediction modes, including various directional modes, as well as planar modes and DC modes. Typically, the video encoder 200 selects an intra prediction mode that describes neighboring samples of the current block according to which the samples of the current block (e.g., a block of a CU) are to be predicted. Assuming that the video encoder 200 decodes the CTU and CU in a raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0068] The video encoder 200 encodes data representing a prediction mode for the current block. For example, for an inter-frame prediction mode, the video encoder 200 may encode data representing which of the various available inter-frame prediction modes is used and motion information for the corresponding mode. For unidirectional or bidirectional inter-frame prediction, for example, the video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0069] After a prediction such as intra prediction or inter prediction of a block, the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents a sample-by-sample difference between a block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in a transform domain rather than in a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0070] As described above, after any transform to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all transform coefficients. For example, the video encoder 200 may round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0071] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place the transform coefficients of higher energy (and therefore lower frequency) in front of the vector and the transform coefficients of lower energy (and therefore higher frequency) in the back of the vector. In some examples, the video encoder 200 can scan the quantized transform coefficients using a predefined scan order to generate a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 can also entropy encode the values ​​of the syntax elements used to describe the metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0072] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0073] The video encoder 200 may also generate syntax data (e.g., block-based syntax data, picture-based syntax data, and sequence-based syntax data) or other syntax data (e.g., sequence parameter set (SPS), picture parameter set (PPS), or video parameter set (VPS)) for the video decoder 300, for example, in a picture header, a block header, a slice header. Likewise, the video decoder 300 may decode such syntax data to determine how to decode the corresponding video data.

[0074] In this way, the video encoder 200 can generate a bitstream, which includes the encoded video data, for example, a syntax element describing the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0075] In general, the video decoder 300 performs a process that is the reverse of the process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements for the bitstream in a manner substantially similar to, but reverse to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning of the picture into CTUs, and partitioning each CTU according to a corresponding partitioning structure (e.g., a QTBT structure) to define CUs of the CTU. The syntax elements may also define prediction and residual information for a block (e.g., a CU) of video data.

[0076] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reconstruct a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra-frame prediction or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reconstruct the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0077] The present disclosure may generally involve "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the transmission of values ​​for syntax elements and / or other data used to decode encoded video data. That is, the video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As described above, the source device 102 may transmit the bitstream to the destination device 116 in substantially real time or not in real time (e.g., as may occur when storing syntax elements to the storage device 112 for later retrieval by the destination device 116).

[0078] Figure 2A and Figure 2B1 is a conceptual diagram showing an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, while dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where, in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, because the quadtree node splits a block horizontally and vertically into 4 sub-blocks of equal size, there is no need to indicate the split type. Therefore, the video encoder 200 can encode the following, and the video decoder 300 can decode the following: syntax elements (such as split information) for the regional tree level (i.e., solid line) of the QTBT structure 130, and syntax elements (such as split information) for the prediction tree level (i.e., dashed line) of the QTBT structure 130. The video encoder 200 may encode video data (such as prediction and transform data) for a CU represented by a terminal leaf node of the QTBT structure 130 , and the video decoder 300 may decode the video data.

[0079] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes at the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, which indicates the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, which indicates the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, which indicates the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, which indicates the minimum allowed binary tree leaf node size).

[0080] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be segmented according to a quadtree segmentation. That is, the node of the first level is a leaf node (without child nodes) or has four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and a child node with a solid line branch. If the node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the node may be further segmented by the corresponding binary tree. The binary tree splitting of a node may be iterated until the node generated from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having a dotted line branch. The binary tree leaf node is called a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further segmentation. As discussed above, a CU may also be referred to as a "video block" or "block".

[0081] In one example of a QTBT partitioning structure, the CTU size is set to 128×128 (luminance sample and two corresponding 64×64 chrominance samples), MinQTSize is set to 16×16, MaxBTSize is set to 64×64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate a quadtree leaf node. The quadtree leaf node can have a size from 16×16 (i.e., MinQTSize) to 128×128 (i.e., CTU size). If the quadtree leaf node is 128×128, because the size exceeds MaxBTSize (i.e., 64×64 in this example), the leaf quadtree node will not be further split by the binary tree. Otherwise, the quadtree leaf node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. A binary tree node having a width equal to MinBTSize (4 in this example) means that no further vertical splitting (i.e., dividing the width) is allowed for the binary tree node. Similarly, a binary tree node having a height equal to MinBTSize means that no further horizontal splitting (i.e., dividing the height) is allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0082] As described above, the video coding standard may transform residual data in the sample domain to the transform domain using transforms such as discrete sine transform (DST) and discrete cosine transform (DCT) at the video encoder 200, and transform (e.g., inverse transform) the residual data in the transform domain back to the sample domain at the video decoder 300. The following describes an overview of DCT and DST and also describes a transform scheme used in HEVC.

[0083] Assume that the input N-point vector is represented as x=[x 0 ,x 1 ,…,x N-1 ] T , and is transformed by multiplying the matrix into y = [y 0 ,y 1 ,…,y N-1 ] T Another N-point transformation coefficient vector can be further described according to one of the following transformation formulas, where k ranges from 0 to N-1, and the transformation formula includes:

[0084] DCT Type-I (DCT-1):

[0085]

[0086] in,

[0087] DCT Type-II (DCT-2):

[0088]

[0089] in

[0090] DCT Type-III (DCT-3):

[0091]

[0092] in

[0093] DCT Type-IV (DCT-4):

[0094]

[0095] DCT Type-V (DCT-5):

[0096]

[0097] in

[0098] DCT Type-VI (DCT-6):

[0099]

[0100] in

[0101] DCT Type-VII (DCT-7):

[0102]

[0103] in

[0104] DCT Type-VIII (DCT-8):

[0105]

[0106] DST Type-I (DST-1):

[0107]

[0108] DST Type-II (DST-2):

[0109]

[0110] in

[0111] DST Type-III (DST-3):

[0112]

[0113] in

[0114] DST Type-IV (DST-4):

[0115]

[0116] DST Type-V (DST-5):

[0117]

[0118] DST Type-VI (DST-6):

[0119]

[0120] DST Type-VII (DST-7):

[0121]

[0122] DST Type-VIII (DST-8):

[0123]

[0124] in

[0125] The transformation type is specified by the mathematical formula of the transformation basis function, for example, 4-point DST-VII and 8-point DST-VII have the same transformation type, regardless of the value of N. Without loss of generality, the following general formula can be used to express the above transformation types:

[0126]

[0127] In the above formula, T is the transformation matrix specified by the definition of a particular transform (e.g., DCT type-I to DCT type-VIII, or DST type-I to DST type-VIII), and the row vectors of T, e.g., [T i,0 ,T i,1 ,T i,2 ,…,T i,N-1 ] is the i-th transformation basis vector. A transformation applied to an N-point input vector is called an N-point transformation.

[0128] The above transformation formula applied to 1-D input data x can be expressed in matrix multiplication form as follows:

[0129] y=T·x

[0130] In the above equation, T represents the transformation matrix, x represents the input data vector, and y represents the output transformation coefficient vector.

[0131] Transformations for two-dimensional (2-D) input data are described below. The above transformations apply to 1-D input data, and can also be extended for 2-D input data sources. Assume X is the input MxN data array. Typical methods for applying transformations to 2-D input data include separable and non-separable 2-D transformations.

[0132] The separable 2-D transform applies a 1-D transform to the horizontal and vertical vectors of X in sequence, as follows:

[0133] Y=C·X·R T

[0134] In the above equations, C and R represent the given MxM and NxN transformation matrices, respectively. As can be seen from the formula, C applies a 1-D transformation to the column vectors of X, while R applies a 1-D transformation to the row vectors of X. In the present disclosure, for simplicity, C and R may be used to represent the left (vertical) transformation and the right (horizontal) transformation, which form a transformation pair. In some cases, C is equal to R and is an orthogonal matrix. In this case, the separable 2-D transformation is determined by only one transformation matrix.

[0135] For example, a non-separable 2-D transformation first reorganizes all elements of X into a single vector, X', by doing the following mathematical mapping:

[0136] X′ (i·N+j) =X i,j

[0137] Then apply a 1-D transformation T' to X' as follows:

[0138] Y=T′·X

[0139] In the above equation, T' is a (M*N)x(M*N) transformation matrix.

[0140] In video coding, separable 2-D transforms can always be applied because 2-D transforms require much fewer operation (addition, multiplication) counts compared to 1-D transforms.

[0141] The transform types applied in HEVC are described below. In some video coding standards (e.g., H.264 / AVC), integer approximations of 4-point and 8-point discrete cosine transform (DCT) type-II are always applied to both intra-frame prediction residuals and inter-frame prediction residuals. In order to better adapt to various statistics of residual samples, a more flexible type of transform different from DCT type-II is used in new generation video codecs. For example, in HEVC, an integer approximation of a 4-point type VII discrete sine transform (DST) is used for intra-frame prediction residuals, which was theoretically proved and experimentally verified in J. Han, A. Saxena and K. Rose, “Towards jointly optimalspatial prediction and adaptive transform in video / image coding,” IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), March 2010, pp. 726-729: DST type VII is more efficient than DCT type II for residual vectors generated along the intra-frame prediction direction. For example, for row residual vectors generated by the horizontal intra-frame prediction direction, DST type VII is more efficient than DCT type II.

[0142] In HEVC, the integer approximation of 4-point DST Type-VII is only applied to 4x4 luma intra prediction residual blocks. Figure 3A4-point DST-VII for HEVC is shown in FIG. In HEVC, for residual blocks that are not 4x4 luma intra prediction residual blocks, integer approximations of 4-point, 8-point, 16-point, and 32-point DCT type-II are also applied, as shown in Figure 3B-Figure 3E as shown in .

[0143] In order to adapt to the various characteristics of the residual block, a transform decoding structure using a residual quad tree (RQT) is applied in HEVC, which is briefly described in X. Zhao, J. Chen, M. Karczewicz, L. Zhang, X. Li, and W.-J. Chien, “Enhanced multiple transform for video coding,” Proc. Data Compression Conference, pp. 73-82, March 2016.

[0144] Each picture is divided into multiple coding tree units (CTUs), which are decoded in raster scan order for a specific tile or slice. A CTU is a square block and represents the root of a quadtree, i.e., a coding tree. The CTU size can range from 8×8 to 64×64 luma samples, but 64×64 is typically used. Each CTU can be further divided into smaller square blocks, called coding units (CUs). After the CTU is recursively split into CUs, each CU is further divided into prediction units (PUs) and transform units (TUs). The partitioning of CUs into TUs is performed recursively based on a quadtree method, so the residual signal of each CU is decoded by a tree structure, i.e., a residual quadtree (RQT). RQT allows TU sizes from 4×4 to 32×32 luma samples.

[0145] Figure 4 An example is shown in which a CU includes 10 TUs labeled with letters a to j and corresponding block partitions. Each node of the RQT is actually a transform unit (TU). Each TU is processed in a depth-first tree traversal order, which is shown in alphabetical order in the figure, following a recursive Z scan with depth-first traversal. The quadtree method enables the transform to adapt to the changing spatial frequency characteristics of the residual signal. Generally, a larger transform block size with a larger spatial support provides better frequency resolution. However, a smaller transform block size with a smaller spatial support provides better spatial resolution. The trade-off between spatial resolution and frequency resolution is selected by the encoder mode decision, for example, based on the rate-distortion optimization technique. The rate-distortion optimization technique calculates the weighted sum of the decoded bits and the reconstruction distortion, i.e., the rate-distortion cost, for each coding mode (e.g., a specific RQT split structure), and selects the decoding mode with the smallest rate-distortion cost as the best mode.

[0146] Three parameters are defined in RQT: the maximum depth of the tree, the minimum allowed transform size, and the maximum allowed transform size. The minimum and maximum transform sizes can vary from 4×4 to 32×32 samples, which corresponds to the supported block transforms mentioned in the previous paragraph. The maximum allowed depth of RQT limits the number of TUs. A maximum depth equal to 0 means that if each of the contained TBs reaches the maximum allowed transform size, for example 32x32, the CB cannot be split further.

[0147] All these parameters interact and affect the RQT structure. Consider a case where the root CB size is 64×64, the maximum depth is equal to 0, and the maximum transform size is equal to 32×32. In this case, the CB is split at least once, because the split does not result in a 64×64 TB, which is not allowed. The RQT parameters, i.e., maximum RQT depth, minimum and maximum transform size, are signaled in the bitstream at the sequence parameter set level. Regarding the RQT depth, different values ​​can be specified and signaled for intra- and inter-coded CUs.

[0148] The quadtree transform is applied to intra and inter residual blocks. Typically, a DCT-II transform of the same size as the current residual quadtree partition is applied to the residual block. However, if the current residual quadtree block is 4x4 and is generated by intra prediction, the above-mentioned 4x4 DST-VII transform is applied. In HEVC, larger size transforms, such as 64x64 transforms, are not adopted mainly because of the limited benefits in view of the relatively high complexity for relatively small resolution video.

[0149] The current MTS design in VVC uses five transform candidates derived based on a combination of DCT-2, DST-7 and DCT-8. The techniques described in this disclosure allow for the derivation of more general one-dimensional transforms, and using more transforms can outperform the existing MTS design in VVC in terms of coding gain.

[0150] As also described in more detail, the transformation matrix may be derived by eigendecomposition of a graph Laplacian matrix defined based on a set of parameters. Figure 5 A flow chart of the process is shown in FIG. Figure 5 In the example of , the graph Laplacian matrix L is defined based on the graph parameter set (140). The eigendecomposition (i.e., diagonalization) of L gives L = UΛU T, so the columns of U are the basis vectors of the transform in double precision, and Λ is a diagonal matrix consisting of the eigenvalues ​​of L (142). Since the entries of U are real-valued, U can be converted to an integer transform by scaling the values ​​(i.e., by multiplying each of its entries) and then rounding to the nearest integer value (144). For example, the scaling may depend on the size (e.g., length) of the transform.

[0151] The video encoder 200 may signal the graph, graph parameters, or associated graph Laplacian matrices to the video decoder 300, and the video decoder 300 may decode the graph by Figure 5 to generate a set of inverse transforms for the decoding process. For a particular block being decoded, the video decoder 300 can select one or more transforms from the generated set. In this case, the graph can refer to a generalized graph Laplacian, as discussed in more detail below. The graph can effectively be set in the form of graph parameters. The graph, graph parameters, or graph Laplacian matrix can be signaled by the video encoder 200 using a high-level syntax such as SPS or PPS. As part of PPS-level signaling, the graph-related syntax can be inferred or predicted based on previously decoded elements (e.g., frames). The graph, graph parameters, or graph Laplacian matrix can also be signaled as a low-level syntax.

[0152] For example, signaling may be done on a CU / TU basis. Signaling may be done by sending an index value associated with a table of picture related information. For example, picture parameters may be listed in a table and signaling may be done by decoding an index value pointing to a specific picture parameter set. The picture information signaled may depend on the block size (i.e., TU, CU, or transform size). Different picture parameter sets may be signaled for different block sizes.

[0153] Alternatively, the graphs, graph parameters or their associated graph Laplacian matrices required for transform derivation may be predefined and known at both the encoder and the decoder.The predefined graph Laplacian may depend on the block size.

[0154] Example techniques are described as utilizing a parameterized graph-based separable transformation (GBST). In some examples, GBST is derived from a graph with c and a single vertex weight v c (also called self-loops) are derived from line graphs of constant edge weights, such as Fig. 7A and Figure 7B For example, Fig. 7A shows that the edge with constant weight (w c ) and a single self-loop weight (v c )'s first line graph corresponding to the generalized graph Laplacian (GGL). Figure 7Bshows that the edge weight (w c ) and a single self-loop weight (v c ) corresponding to the GGL of the second line graph. The following describes examples of GGL, GGL matrix, and first and second line graphs. Parameter w c and v c An example representing graph parameters.

[0155] In the present disclosure, a graph of interest can be represented algebraically by a GGL matrix. An example of a GGL matrix is ​​as follows. Assuming a weighted graph G(W,V), the generalized graph Laplacian can be defined as: L = D-W + V (Equation 1), where W is an adjacency matrix with non-negative edge weights, D is a diagonal matrix, and V is a diagonal matrix representing weighted self-loops (e.g., vertex weights). The D-W term can be a combined Laplacian matrix described in FRK Chung, "Spectral Graph Theory." USA: American Mathematical Society, 1997, and GGL is obtained by adding the vertex weights in V.

[0156] GBST can be defined by a pair of GBTs derived from GGL associated with two weighted line graphs. Examples of GBT and GBST are as follows. The GBT of a graph G(W,V) is obtained by the eigendecomposition of the generalized graph Laplace, L = D – W + V = UΛU T (Equation 2), where the columns of U are the basis vectors of GBT and Λ is the diagonal eigenvalue matrix. For GBST, let U row and U col is an NxN GBT associated with two line graphs with N vertices, then the GBST of the NxN matrix X is Among them U row and U col are the transformations applied to the rows and columns of the block signal X respectively.

[0157] In one example, a line graph with N vertices can be used to define Figure 6 The Laplacian matrix of the graph shown in . Weights can be assigned to edges and / or vertices.

[0158] An example of a parameterized framework for GBST construction is described below. For example, there may be a target GGL representing a line graph. An example of a line graph may be Fig. 7A and Figure 7B The first line graph and the second line graph.

[0159] The two sets of GGL matrices representing line graphs below can be viewed as deriving GBSTs, where the first GGL matrix is ​​for the first line graph and the second GGL matrix is ​​for the second line graph. Below can be a collection of graph Laplaces, also known as generalized graph Laplaces.

[0160]

[0161] and

[0162]

[0163] In the above text, w c represents the constant edge weight of the line graph, and v c is the vertex weight (e.g., self-loop weight). Fig. 7A and 7B As shown in , the structural difference in the GGL set and perhaps the only structural difference is the position of the weighted vertices (e.g. Fig. 7A The beginning and Figure 7B at the end of ).

[0164] Since it can be based on the parameter w c and v c to fully define the picture information, so the video encoder 200 can signal only w c and v c To construct a graph Laplacian for deriving the corresponding inverse transform at the decoder side (e.g., at the video decoder 300). To determine the set of graph Laplacians used, another signaling element may be used. For example, a signaling flag may also be used to identify: c and v c In addition, have you used or Depending on the block size, different w c and v c right.

[0165] DCT and DST are described below as GBTs derived from line graphs. Some examples of GBST (e.g., examples with certain parameter choices) can be consistent with discrete sine transform (DST) and discrete cosine transform (DCT) types used in video coding standards (including DCT-2, DST-7, and DCT-8). For example, certain types of DCT and DST, including DCT-2, DCT-8, and DST-7, are actually GBTs that can be derived from some form of GGL. Based on G. Strang, “The discrete cosine transform,” SIAM Rev., vol. 41, no. 1, pp. 135–147, Mar. 1999 and MP ¨ The results in uschel and J. MF Moura, “Algebraic signal processing theory: 1-D space,” IEEE Transactions on Signal Processing, vol. 56, no. 8, pp. 3586–3599, 2008, parameter v c and w c can be chosen so that a given set of GGLs in L1 or L2 corresponds to different types of DCT and DST. L1 and L2 are corresponding examples of line graphs with the matrices shown above.

[0166] For example, for GGL sets L1 and L2, v c and w c Different choices of result in the following five DCT / DST types:

[0167] DCT-2 is achieved by setting v in L1 or L2 c =0 derived;

[0168] ·DST-7 is achieved by setting v in L1 c =w c derived;

[0169] ·DCT-8 is achieved by setting v in L2 c =w c derived;

[0170] ·DST-4 is achieved by setting v in L1 c =2w c derived; and

[0171] ·DCT-4 is achieved by setting v in L2 c =2w c Derived.

[0172] The relationship between different types of DCTs and graph Laplacians may be discussed in "The discrete cosine transform", where the DCT-2 is shown to be equal to the GBT uniquely obtained from a combined graph Laplacian of the form:

[0173]

[0174] The above equation represents a uniformly weighted linear graph without self-loops (e.g., all edge weights are equal to positive constants and vertex weights are zero). c In addition, “GBST: Separable transforms based on line graphs for predictive video coding,” “Graph-based transforms for video coding,” and W.Hu, G.Cheung, and A.Ortega, “Intra-prediction and generalized graph fouriertransform for image coding,” IEEE Signal Processing Letters, vol. 22, no. 11, pp. 1913–1917, Nov 2015 show that DST-7 is equivalent to GBT derived from GGL in L1, where v c =w c Similarly, DCT-8 is a GBT derived from GGL in L2, where v c =w c DST-7 and DCT-8 can be considered closely related transforms, where the basis vectors of one are the inverse (flipped) version of the other, as described in A.Said, HE Egilmez, and Y.Chao, “Low-complexity transform adjustments for video coding,” in 2019 IEEE International Conference on Image Processing (ICIP), Sep. 2019, pp. 1188–1192, because the only difference in their association graphs is the location of the self-loops. DST-4 and DCT-4 also share this property.

[0175] To learn the graph from data, we formulate the following parameterized GGL estimation problem:

[0176]

[0177] Limited by

[0178] In Equation 5, S represents the sample covariance matrix obtained from the data, and L(w c ,v c ) is the parameter v c and w c The GGL variables are defined. As described in H.E.E.gilmez, E.Pavez, and A.Ortega, “Graph learning from dataunder Laplacian and structural constraints,” IEEE Journal of Selected Topicsin Signal Processing, vol.11, no.6, pp.825–841, Sept 2017, the minimization criterion is based on the negative log-likelihood of the Gaussian-Markov random field (GMRF) whose precision matrix is ​​the GGL, which is used to obtain the GGL in the model with parameters v. c and w c The constrained maximum likelihood (ML) problem of estimating GGL on the defined constraint set Lt.

[0179] The present disclosure describes an example of solving (Equation 5), where the constraint set Lt can be L1 or L2 as described above. Since (Equation 5) is a convex optimization problem and the dimension of the problem is very small, as described in S. Boyd and L. Vandenberghe, "Convex Optimization" New York, NY, USA: Cambridge University Press, 2004, CVX software (e.g., M. Grant and S. Boyd, "CVX: Matlab software for disciplined convex programming, version 2.1," http: / / cvxr.com / cvx, Mar. 2014) can be used to find the optimal solution for wc and vc.

[0180] As a more efficient alternative to CVX, the GGL estimation algorithm proposed in “Graph learning from data under Laplacian and structural constraints” and H.E. Gilmez, E. Pavez, and A. Ortega, “GLL: GraphLaplacian learning package, version 1.0,” https: / / github.com / STAC-USC / GraphLearning, 2017, can be modified to accommodate constraints in L1 and L2 by introducing a projected descent step.

[0181] To design GBST, as an example, this disclosure describes a two-step process for optimizing the GGL matrix used to derive the transformation. In the first step, the problem in (Equation 5) is solved to find the optimal parameters ( ) that best capture the input data statistics (sample covariance S) in the sense of maximum likelihood. and ). The residual data is collected using the VVC reference software (version 2) VTM-2.0, where row and column statistics (S) are obtained from intra-coded residual blocks.

[0182] After solving (Eq. 5), the second step refines the optimized GGL matrix by normalizing the entries of GGL and then rounding the normalized vertex weights to the allowed precision. The refinement step may require limiting the precision of the parameters used for the decoding system. In addition, normalization of GGL can make analysis of models with different numbers of vertices (dimensionality) easier.

[0183] For example, the estimated GGL is calculated by dividing and is normalized to Therefore, with The associated graph has edge weights equal to 1 and its non-zero vertex weights equal to The normalization of GGL may not have an impact on its corresponding GBT, because the set of eigenvectors (i.e., U) in (Eq. 2) is invariant to the scaling of L. For rounding, the normalized vertex weights is rounded to the nearest multiple of 0.25. The resulting rounded vertex weight can be expressed as α N , where N is the transform length (or number of vertices).

[0184] The proposed two-step approach can be applied to design GBST as an alternative to DST-7 and DCT-8 in VVC. Since VVC allows 4, 8, 16, and 32-point DST-7 / DCT-8, GBST can be optimized for the same transform length. For 4, 8, 16, and 32-point GBST, the example technique may lead to α 4 =2, α 8 =1, α 16 =0.75 and α 32 =0.25.

[0185] (referred to as L1) or (abbreviated as L2) c The parameter can be set to 1, and only α N =v c can be used to define the graph Laplace and derive the associated transform. In this case, only α can be signaled N =v c value.

[0186] For different block sizes (i.e., for different N), different α can be signaled. N Value. N It can be directly signaled using unary or fixed length codes. N The index of the table of candidates is used to signal α N For different N (i.e., block size), the table entries may be different. A table may contain α N The index may be a list of values ​​ranging from 0 to 3. For example, the table may contain the following values: [0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3]. The index may be a unary or fixed length code. Alternatively, for certain block sizes (N), the index may be inferred and not signaled.

[0187] In some examples, α can be inferred based on the block size (N). N For example, for a 4-point transformation, α 4 Can be set to 2, for 8-point transformation, α 8 Can be set to 1 for 16-point transformation, α 16 Can be set to 0.75, and for 32-point transformation, α 32 Can be set to 0.25.

[0188] Based on the above description of DCT and DST as GBT derived from line graphs, the results of the proposed method can be explained as follows:

[0189] Due to the α for L1 and L2 4 =2 corresponds to DST-4 and DCT-4 respectively, so the proposed method can indicate replacing DST-7 with DST-4 and replacing DCT-8 with DCT-4 for 4-point transform to improve decoding gain.

[0190] For 8-point transforms, the method can indicate to keep DST-7 and DCT-8, because the α for L1 and L2 8 =1 results in DST-7 and DCT-8 respectively.

[0191] Due to α N = 0 indicates the use of DCT-2, and αN = 1 corresponds to DST-7 / DCT-8. The 16-point GBST derived from α16 = 0.75 results in a transform that is closer to DST-7 / DCT-8 than DCT-2, and α 32 =0.25 generates a 32-point GBST, which is closer to DCT-2 than DST-7 / DCT-8.

[0192] Some performance data related to the above-described example techniques are described below. The performance data is provided only as an example and should not be considered a limitation or requirement that the example techniques must generate the example performance data.

[0193] The performance of the proposed GBST is tested by replacing DST-7 and DCT-8 with GBST for different transform lengths (i.e., 4, 8, 16, and 32-point transforms) under the common test conditions described in F. Bossen, J. Boyce, K. S¨uhring, X. Li, and V. Seregin, “JVET common test conditions and software reference configurations for SDR video,” Joint Video Exploration Team (JVET) of ITU-T SG16WP3 and ISO / IEC JTC 1 / SC29 / WG11, Macao, CN, Output Document JVET L1010, Oct. 2018 on the VVC reference software (version 2), VTM-2.0.

[0194] The following Table 1 shows: The calculation technique described in "Calculation of average PSNRdifferences between RD-curves," ITU-T SG16 Q.6, Austin, TX, Tech. Rep. VCEG-M33, Apr. 2001, shows the decoding gain obtained by using the proposed GBST set on VTM-2.0 anchors with DST-7 and DCT-8 in terms of BD rate. In Table 1, the decoding performance of GBST on VTM-2.0 in terms of BD rate (BDR) for all intra configurations is shown. Negative percentage values ​​indicate decoding gain improvements.

[0195]

[0196] Table 1

[0197] On average, the techniques described in this disclosure can provide a luma coding gain of 0.36% (in the Y component). In practice, no loss of chroma channels (in the U and V components) is observed because VTM-2.0 applies multiple separable transform candidates only on luma blocks. Luma coding gains are observed for all sequences in CTC, and for some ultra-high definition (UHD) sequences in category A1, gains of up to 0.6% are achieved.

[0198] Figure 8A-8D shows the VTM-2.0 across different α N The average of the N-point GBST values ​​and the brightness BD rate performance of each category. For example, Figure 8A-8D It is shown that for different α N value, only replace the BD rate of N-point DST-7 and DCT-8 with N-point GBST. For example, in Figure 8C In this case, only 16 points of transformation are derived from different α 16 GBST, while maintaining 4, 8, and 32-point DST-7 and DCT-8 (i.e., α 4 =α 8 =α 32 =1). The results show that the technology described in this disclosure is effective. 4 =2, α 8 =1, α 16 =0.75 and α 32 = 0.25, all of which are very close to Figure 8A-8D The best α with the smallest BDR(Y) N .

[0199] Figure 8A-8D It also shows the change of α N The effect on BDR(Y) depends on the resolution of the sequence. Fig. 8AIn the example, the decoding gain for categories A1 and A2 with high resolution is very limited, while for categories with lower resolution (e.g., category C), the gain is relatively small for larger α 4 is significant. However, Fig.8D In , a smaller α32 leads to significant decoding gain for classes A1 and A2, but for class C the gain is negligible.

[0200] Therefore, this disclosure describes a parameterized approach for building a graph-based separable transform (GBST) that captures residual block statistics better than DST-7 and DCT-8. By replacing DST-7 and DCT-8 in VVC, a set of optimized GBSTs are built and tested on the VVC reference software VTM-2.0. Experimental results show that the proposed GBST significantly improves the decoding efficiency of VTM-2.0 anchors.

[0201] The following references may provide additional information related to transformations: U.S. Patent No. 10,306,229, U.S. Patent Publication No. 2018 / 0020218, and U.S. Patent Serial No. 16 / 426,749.

[0202] Fig. 9 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Fig. 9 The above description is provided for the purpose of explanation and should not be considered to limit the techniques generally exemplified and described in this disclosure. For the purpose of explanation, this disclosure describes the video encoder 200 in the context of video coding standards such as the HEVC video coding standard under development and the H.266 video coding standard. However, the techniques of this disclosure are not limited to these video coding standards and are generally applicable to video encoding and decoding.

[0203] exist Fig. 9In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any one or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 can be implemented in one or more processors or in processing circuits. For example, the units of the video encoder 200 can be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0204] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives the video data stored in the video data memory 230. DPB 218 can act as a reference picture memory, which stores reference video data for use when subsequent video data is predicted by the video encoder 200. Video data memory 230 and DPB 218 can 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. Video data memory 230 and DPB 218 can be provided by the same memory device or a separate memory device. In various examples, video data memory 230 can be on chip with other components of the video encoder 200 (as shown), or off chip relative to those components.

[0205] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or to memory external to the video encoder 200 (unless specifically described as such). Rather, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data for a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0206] Shows Fig. 9 The various units of the video encoder 200 are described to help understand the operations performed by the video encoder 200. These units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of the units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0207] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example in which the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store instructions (eg, object code) for software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0208] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve pictures of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be original video data to be encoded.

[0209] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0210] The mode selection unit 202 typically coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of a CTU into CUs, a prediction mode for a CU, a transform type for residual data of a CU, a quantization parameter for residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0211] The video encoder 200 may partition the picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0212] Typically, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). In order to inter-predict the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in the DPB 218). Specifically, the motion estimation unit 222 may calculate a value representing how similar the potential reference block will be to the current block, for example, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0213] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the values ​​for the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0214] As another example, for intra prediction or intra prediction decoding, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of adjacent samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 can calculate the average value of adjacent samples of the current block and generate a prediction block to include the obtained average value for each sample of the prediction block.

[0215] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 can generate the residual block using residual differential pulse coding modulation (RDPCM) by calculating the difference between the sample values ​​in the residual block. In some examples, the residual generation unit 204 can be formed using one or more subtractor circuits that perform binary subtraction.

[0216] In an example in which the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As noted above, the size of the CU may refer to the size of the luma coding block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support PU sizes of 2N×2N or N×N for intra-prediction, and symmetric PU sizes of 2N×2N, 2N×N, N×2N, N×N, or the like for inter-prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter-prediction.

[0217] In an example where the mode selection unit does not further partition a CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. The video encoder 200 and the video decoder 300 may support a CU size of 2N×2N, 2N×N, or N×2N.

[0218] For other video coding techniques (such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, to name a few examples), the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the coding technique. In some examples (such as palette mode coding), the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy coding unit 220 for encoding.

[0219] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates a sample-by-sample difference between the prediction block and the current block.

[0220] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 can apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 can apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 can perform multiple transforms on the residual block, such as a primary transform and a secondary transform (e.g., a rotation transform). In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0221] Quantization unit 208 may quantize transform coefficients in a transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a QP value associated with the current block. Video encoder 200 (e.g., via mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause a loss of information, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients produced by transform processing unit 206.

[0222] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0223] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edge of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0224] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In examples where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve a reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on blocks of subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0225] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode a quantized transform coefficient block from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on syntax elements as another example of video data to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0226] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required for reconstructing a block of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0227] The above operations are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a PU.

[0228] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Specifically, the MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0229] The video encoder 200 represents an example of a device configured to encode video data, the device comprising a memory and one or more processing units, the memory being configured to store the video data, the one or more processing units being implemented in a circuit and being configured to: determine residual information in a sample domain, determine a set of graph Laplacians to be used, determine at least one of edge weights and vertex weights of a line graph for the determined graph Laplacian, determine a graph Laplacian matrix based on the edge weights and vertex weights and the graph Laplacian, and apply a graph-based separable transform (GBST) to the residual information to transform the residual information from the sample domain to a transform domain, wherein applying the GBST comprises: applying the GBST based on the graph Laplacian matrix.

[0230] Fig.10 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Fig.10 It is provided for the purpose of explanation and does not limit the techniques generally illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes the video decoder 300 according to the techniques of JEM, VVC and HEVC. However, the techniques of this disclosure can be performed by a video decoding device configured for other video decoding standards.

[0231] exist Fig.10In the example of , the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 134 can be implemented in one or more processors or in processing circuits. For example, the units of the video decoder 300 can be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0232] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units that perform predictions according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0233] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. For example, the video bitstream may be obtained from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. In addition, CPB memory 320 may store video data other than syntax elements of decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, and video decoder 300 may output decoded pictures, and / or use decoded pictures as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as DRAM (including SDRAM), MRAM, RRAM, or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or a separate memory device. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0234] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) retrieves the decoded video data. That is, memory 120 may utilize CPB memory 320 to store data as discussed above. Likewise, when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0235] Shows Fig.10 The various units shown in FIG. 3 are used to help understand the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Fig. 9 , fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with respect to the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of these units may be integrated circuits.

[0236] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0237] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to reconstruct syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0238] Generally, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0239] The entropy decoding unit 302 may entropy decode syntax elements defining quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. For example, the entropy decoding unit 302 may receive the image-related information in a syntax structure applicable to the current block, as described above. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization, and likewise, determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0240] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block. The inverse transform unit 308 may determine a transform matrix, for example, based on received graph-related syntax information, and perform an inverse transform based on the determined transform matrix of one or more coefficient values ​​to generate a residual block.

[0241] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, motion compensation unit 316 can generate a prediction block. In this case, the prediction information syntax element can indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 can generally generate a prediction block in the same manner as described with respect to motion compensation unit 224 ( Fig. 9 )The inter-frame prediction process is performed in a manner substantially similar to that described in detail above.

[0242] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally generate a prediction block in the same manner as described for the intra-prediction unit 226 ( Fig. 9 The intra prediction process is performed in a manner substantially similar to that described in the foregoing description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0243] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may reconstruct the current block by adding samples of the residual block to corresponding samples of the prediction block.

[0244] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0245] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block to the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block to the DPB 314. As discussed above, the DPB 314 may provide reference information (such as samples of the current picture for intra-frame prediction and previously decoded pictures for subsequent motion compensation) to the prediction processing unit 304. In addition, the video decoder 300 may output a decoded picture (e.g., a decoded video) from the DPB 314 for use in, for example, Figure 1 Subsequent presentation on a display device such as display device 118.

[0246] In this way, the video decoder 300 represents an example of a video decoding device, the video decoding device including a memory and one or more processing units, the memory being configured to store video data, the one or more processing units being implemented in a circuit and being configured to: receive residual information in a transform domain, and, apply a graph-based separable transform (GBST) to the residual information so as to transform the residual information from the transform domain to a sample domain. To apply GBST, the video decoder 300 may be configured to: determine a set of graph Laplacians to be used, determine at least one of edge weights and vertex weights of a line graph for the determined graph Laplacian, determine a graph Laplacian matrix based on the edge weights and vertex weights and the graph Laplacian, and, apply GBST based on the graph Laplacian matrix.

[0247] Fig.11 2 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although for the video encoder 200 ( Figure 1 and Fig. 9 ), but it should be understood that other devices may be configured to perform the same Fig.11 A similar approach to the one used in this paper.

[0248] In this example, the video encoder 200 initially predicts the current block (350). For example, the video encoder 200 may form a prediction block for the current block. Then, the video encoder 200 may calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate the difference between the original unencoded block and the prediction block for the current block. Then, the video encoder 200 may transform and quantize the coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (358). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. Then, the video encoder 200 may output the entropy encoded data of the block (360). The entropy encoded data may include: graphic related information for determining the transform used by the video encoder 200 to transform the quantized coefficients.

[0249] Fig.12 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although for video decoder 300 ( Figure 1 and Fig.10 ), but it should be understood that other devices may be configured to perform the same Fig.12 A similar approach to the one used in this paper.

[0250] The video decoder 300 may receive entropy-encoded data for a current block (e.g., entropy-encoded prediction information and entropy-encoded data for coefficients of a residual block corresponding to the current block) (370). The video decoder 300 may entropy decode the entropy-encoded data to determine prediction information for the current block and reproduce coefficients of the residual block (372). The video decoder 300 may predict the current block (374), for example, using an intra-frame or inter-frame prediction mode as indicated by the prediction information for the current block, in order to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the reproduced coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). The video decoder 300 may determine, for example, based on the received image-related information, an inverse transform to be applied to the transform coefficients, as described throughout the present disclosure. The video decoder 300 may ultimately decode the current block (380) by combining the prediction block and the residual block.

[0251] Fig.13 is a flowchart illustrating example operations for decoding video data in accordance with one or more techniques of this disclosure. Fig.13As seen in the example of FIG. 4 , the video decoder 300 may initially receive the image-related information in a syntax structure applied to the current block (400). As described above, the image-related information may, for example, include one or more of the image, the image parameters, or the image Laplacian matrix. The syntax structure may, for example, be an SPS or a PPS. In some examples, to receive the image-related syntax information, the video decoder 300 may be configured to receive an index in a lookup table for the image-related information.

[0252] Next, the video decoder 300 may determine a transformation matrix based on the received graph-related syntax information (405). In order to determine the transformation matrix based on the received graph-related syntax information, the video decoder 300 may be configured to determine a graph Laplacian matrix based on the graph-related information; perform an eigendecomposition operation on the graph Laplacian matrix to determine one or more basis vectors; scaling values ​​of one or more basis vectors; and round the scaling values ​​to integer values ​​to determine the transformation matrix. In some examples, the graph-related information may include one or more constant edge weights and one or more vertex weights, and in order to determine the graph Laplacian matrix based on the graph-related information, the video decoder 300 may be configured to apply one or more constant edge weights and one or more vertex weights to the generalized graph Laplacian matrix to determine the graph Laplacian matrix. The graph-related information may also include: a syntax element identifying a generalized graph Laplacian matrix in a set of generalized graph Laplacian matrices.

[0253] Next, video decoder 300 may perform an inverse transform based on the determined transform matrix of the one or more coefficient values ​​to generate a residual block (410).

[0254] Next, the video decoder 300 may reconstruct the current block of video data based on the residual block (415). For example, the video decoder 300 may output the filtered reconstructed block as part of a picture of the decoded video data. The video decoder 300 may perform one or more filtering operations on the reconstructed block before outputting it. The video decoder 300 may output the picture of the decoded video data by displaying the picture of the decoded video data, storing the picture of the decoded video data for later display, or storing the picture of the decoded video data for use in decoding other pictures of the video data.

[0255] The following clauses are within the scope of the above description and represent example techniques and implementations for the video encoder 200 and / or the video decoder 300 .

[0256] Clause 1: A method for decoding video data, comprising: receiving residual information in a transform domain; and applying a graph-based separable transform (GBST) to the residual information so as to transform the residual information from the transform domain to a sample domain; wherein applying the GBST comprises: determining a set of graph Laplacians to be used; determining at least one of edge weights and vertex weights of a line graph for the determined graph Laplacian; determining a graph Laplacian matrix based on the edge weights and vertex weights and the graph Laplacian; and, based on the graph Laplacian matrix, applying the GBST to the residual information in the transform domain.

[0257] Clause 2: The method of clause 1, wherein determining the set of graph Laplacians to use comprises receiving information indicating the set of graph Laplacians to use.

[0258] Clause 3: A method according to any one of clauses 1 and 2, wherein determining at least one of edge weights and vertex weights of the line graph for the determined graph Laplacian includes: receiving information indicating at least one of edge weights and vertex weights of the line graph.

[0259] Clause 4: The method of clause 1, wherein determining the set of graph Laplacians to use comprises inferring information indicative of the set of graph Laplacians to use.

[0260] Clause 5: A method according to any one of clauses 1 and 4, wherein determining at least one of edge weights and vertex weights of the line graph for the determined graph Laplacian includes: inferring information indicative of at least one of the edge weights and vertex weights of the line graph.

[0261] Clause 6: A method for encoding video data, comprising: determining residual information in a sample domain; determining a set of graph Laplacians to be used; determining at least one of edge weights and vertex weights of a line graph for the determined graph Laplacian; determining a graph Laplacian matrix based on the edge weights and vertex weights and the graph Laplacian; and applying a graph-based separable transform (GBST) to the residual information in the sample domain so as to transform the residual information from the sample domain to a transform domain, wherein applying the GBST comprises: applying the GBST based on the graph Laplacian matrix.

[0262] Clause 7: The method of clause 6, further comprising: signaling information indicating one or more of a graph Laplacian, edge weights, and vertex weights to be used.

[0263] Clause 8: An apparatus for decoding video data, comprising a memory configured to store the video data; and a processing circuit configured to perform the method according to any of clauses 1-5.

[0264] Clause 9: An apparatus for encoding video data, comprising a memory configured to store the video data; and a processing circuit configured to perform the method according to any one of clauses 6 and 7.

[0265] Clause 10: The apparatus of any of clauses 8 and 9, further comprising: a display configured to display the decoded video data.

[0266] Clause 11: The device of any of clauses 8-10, wherein the device comprises one or more of: a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0267] Clause 12: A computer-readable storage medium having stored thereon instructions which, when executed, cause one or more processors to perform the method of any of clauses 1-5 or clauses 6 and 7.

[0268] Clause 13: An apparatus for decoding video data, the apparatus comprising: means for performing the method of any of clauses 1-5 or clauses 6 and 7. 14. Any combination of the techniques described in this disclosure.

[0269] It is to be appreciated that, depending on the examples, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary to implement the techniques). In addition, in some examples, actions or events may be performed concurrently rather than sequentially, such as through multithreading, interrupt handling, or multiple processors.

[0270] 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 through a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium or a communication medium, the communication medium including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-temporary tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, codes, and / or data structures for implementing the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0271] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program codes in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (e.g., infrared, radio and microwave), coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology (e.g., infrared, radio and microwave) are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals or other temporary media, but are instead directed to non-temporary tangible storage media. As used herein, disks and optical disks include compact disks (CDs), laser optical disks, optical disks, digital versatile disks (DVDs), floppy disks and blue-ray disks, wherein disks usually copy data magnetically, while optical disks use lasers to optically copy data. Combinations of the above should also be included within the scope of computer-readable media.

[0272] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuitry" as used herein may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. In addition, the techniques may be implemented entirely in one or more circuits or logic elements.

[0273] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize the functional aspects of a device configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. Specifically, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and / or firmware.

[0274] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: Receiving graph-related information in a syntax structure applied to a current block of the video data, wherein the graph-related information includes one or more constant edge weights, one or more vertex weights, and a syntax element identifying a generalized graph Laplacian matrix in a set of generalized graph Laplacian matrices; Determining a transformation matrix based on the received image-related information, wherein determining the transformation matrix comprises: applying the one or more constant edge weights and the one or more vertex weights to the generalized graph Laplacian matrix to determine a graph Laplacian matrix; performing an eigendecomposition operation on the graph Laplacian matrix to determine one or more basis vectors; scaling the values ​​of the one or more basis vectors; and rounding the scaled value to an integer value to determine the transformation matrix; Based on the determined transform matrix, performing an inverse transform on one or more coefficient values ​​for the current block to generate a residual block; and The current block of the video data is reconstructed based on the residual block.

2. The method according to claim 1, wherein: The graph-related information also includes one or more of the following: a graph, a graph parameter, or a graph Laplacian matrix.

3. The method according to claim 1, wherein: The syntax structure includes: one of a sequence parameter set or a picture parameter set.

4. The method according to claim 1, wherein: Receiving the graph-related information includes: receiving an index for the graph-related information in a lookup table.

5. A device for decoding video data, the device comprising: A memory configured to store the video data; as well as One or more processors implemented in circuitry and configured to: Receiving graph-related information in a syntax structure applied to a current block of the video data, wherein the graph-related information includes one or more constant edge weights, one or more vertex weights, and a syntax element identifying a generalized graph Laplacian matrix in a set of generalized graph Laplacian matrices; Determine a transformation matrix based on the received image-related information, wherein, to determine the transformation matrix, the one or more processors are configured to: applying the one or more constant edge weights and the one or more vertex weights to the generalized graph Laplacian matrix to determine a graph Laplacian matrix; performing an eigendecomposition operation on the graph Laplacian matrix to determine one or more basis vectors; scaling the values ​​of the one or more basis vectors; and rounding the scaled value to an integer value to determine the transformation matrix; Based on the determined transform matrix, performing an inverse transform on one or more coefficient values ​​for the current block to generate a residual block; and The current block of the video data is reconstructed based on the residual block.

6. The device according to claim 5, wherein: The graph-related information also includes one or more of the following: a graph, a graph parameter, or a graph Laplacian matrix.

7. The device according to claim 5, wherein: The syntax structure includes: one of a sequence parameter set or a picture parameter set.

8. The device according to claim 5, wherein: To receive the graph-related information, the one or more processors are further configured to: receive an index for the graph-related information in a lookup table.

9. The device according to claim 5, wherein: The device is a wireless communication device and also includes a receiver configured to receive encoded video data.

10. The device according to claim 9, wherein: The wireless communication device is a telephone, and wherein the receiver is configured to demodulate a signal comprising the encoded video data in accordance with a wireless communication standard.

11. The apparatus according to claim 5, further comprising: A display is configured to display the decoded video data.

12. The device according to claim 5, wherein: The device also includes one or more of the following: a camera, a computer, a broadcast receiver device.

13. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, configure a processor to: The picture related information is received in a syntax structure applicable to a current block of video data, wherein The graph-related information includes one or more constant edge weights, one or more vertex weights, and a syntax element identifying a generalized graph Laplacian matrix in a set of generalized graph Laplacian matrices; Determine a transformation matrix based on the received image-related information, wherein, in order to determine the transformation matrix, the instructions configure the processor to: applying the one or more constant edge weights and the one or more vertex weights to the generalized graph Laplacian matrix to determine a graph Laplacian matrix; performing an eigendecomposition operation on the graph Laplacian matrix to determine one or more basis vectors; scaling the values ​​of the one or more basis vectors; and rounding the scaled value to an integer value to determine the transformation matrix; Based on the determined transform matrix, performing an inverse transform on one or more coefficient values ​​for the current block to generate a residual block; and The current block of the video data is reconstructed based on the residual block.

14. The non-transitory computer-readable storage medium of claim 13, wherein: The graph-related information also includes one or more of the following: a graph, a graph parameter, or a graph Laplacian matrix.

15. The non-transitory computer-readable storage medium of claim 13, wherein: The syntax structure includes: one of a sequence parameter set or a picture parameter set.

16. The non-transitory computer-readable storage medium of claim 13, wherein: The instructions further configure the processor to receive an index into a lookup table for the graph-related information.

17. A device for decoding video data, the device comprising: means for receiving graph-related information in a syntax structure applied to a current block of the video data, wherein the graph-related information comprises one or more constant edge weights, one or more vertex weights, and a syntax element identifying a generalized graph Laplacian matrix in a set of generalized graph Laplacian matrices; A unit for determining a transformation matrix based on the received image-related information, wherein the unit for determining the transformation matrix comprises: means for applying the one or more constant edge weights and the one or more vertex weights to the generalized graph Laplacian matrix to determine a graph Laplacian matrix; for performing an eigendecomposition operation on the graph Laplacian matrix to determine elements of one or more basis vectors; means for scaling the values ​​of the one or more basis vectors; and for rounding the scaled values ​​to integer values ​​to determine elements of the transformation matrix; means for performing an inverse transform on one or more coefficient values ​​for the current block based on the determined transform matrix to generate a residual block; and Means for reconstructing the current block of the video data based on the residual block.

18. The apparatus according to claim 17, wherein: The graph-related information also includes one or more of the following: a graph, a graph parameter, or a graph Laplacian matrix.

19. The apparatus according to claim 17, wherein: The syntax structure includes: one of a sequence parameter set or a picture parameter set.

20. The apparatus of claim 17, wherein: The means for receiving the graph-related information includes means for receiving an index in a lookup table for the graph-related information.

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