Transform unit design for video coding

Abstract

An example device for decoding video data includes a memory configured to store video data and one or more processors coupled to the memory. The one or more processors are configured to reorganize 2-dimensional dequantized coefficients according to a first ordering. The one or more processors are configured to apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients. The one or more processors are configured to reorganize the inverse transform coefficients according to a second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and the values in the array represent indices of the 2-dimensional block in a defined order. The one or more processors are configured to decode the video data based on the second ordered inverse transform coefficients.

Description

[0001] This application is a divisional application of the application with the application date of September 19, 2020, application number 202080065798.1, and the title of “TRANSFORM UNIT DESIGN FOR VIDEO CODING”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Application No. 17 / 025,529, filed September 18, 2020, which claims the benefit of provisional patent application number 62 / 902,862, entitled “TRANSFORM UNIT DESIGN FOR VIDEO CODING,” filed September 19, 2019; U.S. Provisional Patent Application No. 62 / 904,494, entitled “TRANSFORM UNIT DESIGN FOR VIDEO CODING,” filed September 23, 2019; and U.S. Provisional Patent Application No. 62 / 951,837, entitled “TRANSFORM UNIT DESIGN FOR VIDEO CODING,” filed December 20, 2019; the entire contents of each of which are incorporated herein by reference. TECHNICAL FIELD

[0004] The present disclosure relates to video encoding and video decoding. BACKGROUND

[0005] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct 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 gaming devices, video game consoles, cellular or satellite radio telephones, so-called “smart phones,” video teleconferencing devices, video streaming devices, and the like. 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. The video devices can implement video coding techniques to encode, decode, and / or store digital video information more efficiently.

[0006] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy of the video sequence. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) can be partitioned into video blocks, which can 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 coded using spatial prediction with respect to reference samples in a same picture. Video blocks in an inter-coded (P or B) slice of a picture can be coded using either spatial prediction with respect to reference samples in a neighboring block in the same picture or temporal prediction with respect to reference samples in another reference picture. SUMMARY

[0007] In general, this disclosure describes techniques for optimized matrices and reorganization patterns / scanning of 8x8 low-frequency non-separable transforms (LFNSTs) in video coding. Designs of LFNSTs, such as those disclosed in some video coding standards, can require a relatively large number of multiplications and a relatively large amount of memory when applied by a video coder. According to the techniques of this disclosure, 8x8 LFNSTs can be simplified and coefficients can be reorganized to efficiently apply 8x8 LFNSTs.

[0008] In one example, a method includes reorganizing, by one or more processors, 2-dimensional dequantized coefficients according to a first ordering; applying, by the one or more processors, an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST including an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients to be reconstructed after applying the inverse LFNST; reorganizing, by the one or more processors, the inverse transform coefficients according to a second ordering, the second ordering based on an array including values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and decoding, by the one or more processors, the video data based on the inverse transform coefficients that are second ordered.

[0009] In another example, a device comprises: a memory configured to store the video data; and one or more processors implemented in circuitry and communicably coupled to the memory, the one or more processors configured to: reorganize 2-dimensional dequantized coefficients according to a first ordering; apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of reconstructed LFNST coefficients after applying the inverse LFNST; reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and decode the video data based on the second ordered inverse transform coefficients.

[0010] In another example, a device comprises: means for reorganizing 2-dimensional dequantized coefficients according to a first ordering; means for applying an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of reconstructed LFNST coefficients after applying the inverse LFNST; means for reorganizing the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and means for decoding the video data based on the second ordered inverse transform coefficients.

[0011] In another example, a non-transitory computer-readable storage medium having instructions stored thereon that, when executed by one or more processors, cause the one or more processors to: reorganize 2-dimensional dequantized coefficients according to a first ordering; apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of reconstructed LFNST coefficients after applying the inverse LFNST; reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and decode the video data based on the second ordered inverse transform coefficients.

[0012] 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 DRAWINGS

[0013] Figure 1 is a block diagram illustrating an example video encoding and decoding system that can perform the techniques of this disclosure.

[0014] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and corresponding coding tree unit (CTU).

[0015] Figure 3 is a block diagram illustrating an example video encoder that can perform the techniques of this disclosure.

[0016] Figure 4 is a block diagram illustrating an example video decoder that can perform the techniques of this disclosure.

[0017] Figure 5 is a conceptual diagram illustrating low-frequency non-separable transform (LFNST) at an encoder and a decoder, where the LFNST includes a stage between a separable transform and quantization in the codec.

[0018] Figure 6 is a conceptual diagram illustrating an inverse transform process with LFNST.

[0019] Figure 7 is a conceptual diagram illustrating a 4x4 inverse LFNST for reconstructing 16 intermediate coefficients from a list of 16 input coefficients.

[0020] Figure 8 is a conceptual diagram illustrating an 8x8 inverse LFNST for reconstructing 48 intermediate coefficients from a list of 16 input coefficients.

[0021] Figure 9 is a conceptual diagram illustrating an inverse LFNST process.

[0022] Figure 10 is a conceptual diagram illustrating input reorganization based on raster scan.

[0023] Figure 11 is a conceptual diagram illustrating a 4x4 block pattern with 16 samples in an 8x8 LFNST.

[0024] Figure 12 is a conceptual diagram illustrating a 5x5 block pattern with 25 samples in an 8x8 LFNST.

[0025] Figure 13 is a conceptual diagram illustrating a 6x6 block pattern with 36 samples in an 8x8 LFNST.

[0026] Figure 14 is a conceptual diagram illustrating a circular pattern with 48 samples in an 8x8 LFNST.

[0027] Figure 15 is a conceptual diagram illustrating another variation of a circular pattern with 48 samples in an 8x8 LFNST.

[0028] Figure 16 is a conceptual diagram illustrating an 8x8 block pattern with 64 samples for an 8x8 LFNST.

[0029] Figure 17 is a conceptual diagram illustrating Figure 13 Table of test results for the example of FIG. 1 1 for VTM-6.0 under common test conditions (CTC).

[0030] Figure 18 is a conceptual diagram illustrating Figure 14 Table of test results for the example of FIG. 1 1 for VTM-6.0 under CTC.

[0031] Figure 19 is a conceptual diagram illustrating Figure 13 Table of test results for the example of the unoptimized 4x4 LFNST matrix of FIG. 1 1 for VTM-6.0 under CTC.

[0032] Figure 20 is a conceptual diagram illustrating Figure 14 Table of test results for the example of the unoptimized 4x4 LFNST matrix of FIG. 1 1 for VTM-6.0 under CTC.

[0033] Figure 21 is a flowchart illustrating reorganizing coefficients according to the techniques of this disclosure.

[0034] Figure 22 is a flowchart illustrating an encoding method according to the techniques of this disclosure.

[0035] Figure 23 is a flowchart illustrating a decoding method according to the techniques of this disclosure. DETAILED DESCRIPTION

[0036] Designs of low-frequency non-separable transforms (LFNSTs), such as those disclosed in some video coding standards, can require a relatively large number of multiplications and a relatively large amount of memory when applied by a video coder. These designs can also be relatively inefficient.

[0037] According to the techniques of this disclosure, an 8x8 LFNST can be simplified and coefficients can be reorganized to efficiently apply the 8x8 LFNST. The 8x8 LFNST and reorganized coefficients of this disclosure can reduce the number of multiplications required and can also reduce memory requirements. In addition, the 8x8 LFNST and reorganized coefficients of this disclosure can provide coding gain compared to other LFNST designs without increasing complexity.

[0038] Figure 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of this disclosure. The techniques of this disclosure generally relate to coding (encoding and / or decoding) video data. In general, video data includes any data for processing video. Thus, video data can include raw, uncoded video, coded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0039] As Figure 1 shown in FIG. 1, 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. In particular, source device 102 provides the video data to destination device 116 via a computer-readable medium 110. Source device 102 and destination device 116 can comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, or the like. In some cases, source device 102 and destination device 116 can be equipped for wireless communication, and thus can be referred to as wireless communication devices.

[0040] In Figure 1 the example of FIG. 1, source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. Destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. In accordance with this disclosure, video encoder 200 of source device 102 and video decoder 300 of destination device 116 can be configured to apply the techniques of optimized matrix and reorganization pattern / scanning for 8x8 LFNST for video coding. Thus, source device 102 represents an example of a video encoding device, while destination device 116 represents an example of a video decoding device. In other examples, a source device and a destination device can include other components or arrangements. For example, source device 102 can receive video data from an external video source, such as an external camera. Likewise, destination device 116 can interface with an external display device, rather than include an integrated display device.

[0041] As Figure 1The system 100 illustrated in FIG. 1 is merely one example. In general, any digital video encoding and / or decoding device can perform the techniques for optimized matrices and reorganization patterns / scanning of 8x8 LFNST for video coding. The source device 102 and the destination device 116 are merely examples of such coding devices in which the source device 102 generates coded video data for transmission to the destination device 116. This disclosure refers to a "coding" device as a device that performs coding (encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of coding devices, in particular, examples of 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 such that each of the source device 102 and the destination device 116 includes video encoding and decoding components. Hence, the system 100 can support one-way or two-way video transmission between the source device 102 and the destination device 116, e.g., for video streaming, video playback, video broadcasting, or video telephony.

[0042] In general, the video source 104 represents a source of video data (i.e., raw, unencoded video) and provides a sequential series of pictures (also referred to as "frames") of the video data to the video encoder 200, which encodes data for the pictures. The video source 104 of the source device 102 can include a video capture device, such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface to receive video from a video content provider. As a further alternative, the video source 104 can generate computer graphics-based data as the source video, or a combination of live video, archived video, and computer-generated video. In each case, the video encoder 200 encodes the captured, pre-captured, or computer-generated video data. The video encoder 200 can rearrange the pictures from the reception order (sometimes referred to as "display order") into the coding order for coding. The video encoder 200 can generate a bitstream including encoded video data. The source device 102 can then output the encoded video data via the output interface 108 onto the computer- readable medium 110 for reception and / or retrieval by, for example, the input interface 122 of the destination device 116.

[0043] Memory 106 of source device 102 and memory 120 of destination device 116 represent general purpose memories. In some examples, memories 106, 120 can store raw video data, e.g., raw video from video source 104 and raw, decoded video data from video decoder 300. Additionally or alternatively, memories 106, 120 can store software instructions executable by, e.g., video encoder 200 and video decoder 300, respectively. Although memories 106 and 120 are shown as separate from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 can also each include internal memories for functional similar or equivalent purposes. Furthermore, memories 106, 120 can store encoded video data output from video encoder 200 and input to video decoder 300, for example. In some examples, portions of memories 106, 120 can be allocated as one or more video buffers to, for example, store raw, decoded, and / or encoded video data.

[0044] Computer-readable medium 110 can represent any type of medium or device capable of transporting the encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium to enable source device 102 to transmit encoded video data directly to destination device 116 in real-time, e.g., via a radio frequency network or computer-based network. Output interface 108 can modulate a transmission signal including the encoded video data, and input interface 122 can demodulate the received transmission signal, according to a communication standard, such as a wireless communication protocol. The communication medium can comprise any wireless or wired communication medium, such as a video (RF) spectrum or one or more physical transmission lines. The communication medium can form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium can include routers, switches, base stations, or any other equipment that can be useful to facilitate communication from source device 102 to destination device 116.

[0045] In some examples, source device 102 can output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 can access encoded data from storage device 112 via input interface 122. Storage device 112 can include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage media for storing encoded video data.

[0046] In some examples, source device 102 can output encoded video data to a file server 114 or another intermediate storage device that can store encoded video generated by source device 102. Destination device 116 can access stored video data from file server 114 via streaming or download. File server 114 can be any type of server device capable of storing encoded video data and transmitting that encoded video data to destination device 116. File server 114 can represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device 116 can access encoded video data from file server 114 through any standard data connection, including an Internet connection. This can include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), a cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on file server 114. File server 114 and input interface 122 can be configured to operate according to a streaming transmission protocol, a download transmission protocol, or a combination thereof.

[0047] Output interface 108 and input interface 122 can represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components operating according to any of a variety of IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 comprise wireless components, output interface 108 and input interface 122 can be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 can be configured to transfer data, such as encoded video data, according to other wireless standards, such as an IEEE 802.11 specification, an IEEE 802.15 specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. In some examples, source device 102 and / or destination device 116 can include respective system on a chip (SoC) devices. For example, source device 102 can include a SoC device to perform functionality for video encoder 200 and / or output interface 108, and destination device 116 can include a SoC device to perform functionality for video decoder 300 and / or input interface 122.

[0048] The techniques of this disclosure can be applied to video coding in support of any of a variety of multimedia applications, such as over-the-air television broadcasts, cable television transmissions, satellite television transmissions, Internet streaming video transmissions, digital video that is encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0049] Input interface 122 of destination device 116 receives an encoded video bitstream from computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, or the like). The encoded video bitstream can include signaling information defined by video encoder 200, which is also used by video decoder 300, such as syntax elements having values

[0050] Although not shown in FIG. 7, in some examples, video encoder 200 and video decoder 300 can each be integrated with an audio encoder and / or audio decoder. The video and audio encoders can communicate with one another either directly or indirectly through Figure 1 Although not shown in FIG. 7, in some examples, video encoder 200 and video decoder 300 can each be integrated with an audio encoder and / or audio decoder. The video and audio encoders can communicate with one another either directly or indirectly through

[0051] Video encoder 200 and video decoder 300 each can be implemented as any of a variety of suitable encoder and / or decoder circuitry, 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 combinations thereof. When the techniques are implemented partially in software, a device can store instructions for the software in a suitable, non- transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of video encoder 200 and video decoder 300 can be included in one or more encoders or decoders, either of which can be integrated as part of a combined video encoder / decoder (CODEC) in a respective device. A device including video encoder 200 and / or video decoder 300 can comprise an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular telephone.

[0052] Video encoder 200 and video decoder 300 can operate according to a video coding standard, such as ITU-T H.265, also referred to as High Efficiency Video Coding (HEVC), or extensions thereof, such as the multi-view and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 can operate according to other proprietary or industry standards, such as the Joint Exploration Test Model (JEM) or ITU-T H.266, also referred to as Versatile Video Coding (VVC). A draft of the VVC standard is described in Bross, et al. “Versatile Video Coding (Draft 6),” JVET-O2001-vE, 15th Meeting of ITU-T SG 15 WP 3 and ISO / IEC JTC 3 / SC 29 / WG 11, Joint Video Expert Team (JVET), Gothenburg, SE, 3-12 July 2019 (hereinafter “VVC Draft 6”). A latest draft of the VVC standard is described in Bross, et al. “Versatile Video Coding (Draft 10),” JVET-S2001-vA, 19th Meeting of ITU-T SG 15 WP 22 and ISO / IEC JTC 3 / SC 29 / WG 11, Joint Video Expert Team (JVET), Online, 22 June - 1 July 2020 (hereinafter “VVC Draft 10”). The techniques of this disclosure, however, are not limited to any particular coding standard.

[0053] In general, video encoder 200 and video decoder 300 can perform block-based coding of pictures. The term “block” generally refers to a structure containing data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block can include a two-dimensional matrix of luma and / or chroma samples. In general, video encoder 200 and video decoder 300 can code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding samples of picture in a red, green, and blue (RGB) format, video encoder 200 and video decoder 300 can code luma and chroma components, where the chroma components can include both red hue and blue hue chroma components. In some examples, video encoder 200 converts received RGB formatted data to a YUV representation prior to encoding, and video decoder 300 converts the YUV representation to the RGB format. Alternatively, pre- and post-processing units (not shown) can perform these conversions.

[0054] The present disclosure can generally relate to coding (e.g., encoding and decoding) of pictures to include processes that encode or decode data of pictures. Similarly, the present disclosure can relate to coding of blocks of pictures to include processes that encode or decode data of blocks, such as prediction and / or residual coding. An encoded video bitstream generally includes a series of values for syntax elements that represent coding decisions (e.g., coding modes) and partitioning of pictures into blocks. Thus, references to coding of pictures or blocks should generally be understood to refer to coding of values for syntax elements used to form the pictures or blocks.

[0055] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder, such as video encoder 200, partitions coding tree units (CTUs) into CUs according to a quadtree structure. That is, the video coder partitions CTUs and CUs into four identical, non overlapping squares, and each node of the quadtree has either zero or four child nodes. Nodes with no child nodes can be referred to as “leaf nodes,” and CUs of such leaf nodes can include one or more PUs and / or one or more TUs. The video coder can further partition PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents partitioning of TUs. In HEVC, PUs represent inter-predicted data, while TUs represent residual data. Intra-predicted CUs include intra-prediction information, such as an intra-mode indication.

[0056] As another example, video encoder 200 and video decoder 300 can be configured to operate according to JEM or VVC. According to JEM or VVC, a video coder (such as video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). Video encoder 200 can partition a CTU according to a tree structure, such as a quad tree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure removes the multiple split type concepts, such as the separation between CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels: a first level of partitioning according to quad tree partitioning, and a second level of partitioning according to binary tree partitioning. A root node of the QTBT structure corresponds to a CTU. Leaf nodes of the binary trees correspond to coding units (CUs).

[0057] In the MTT partitioning structure, a block can be partitioned using quad tree (QT) splitting, binary tree (BT) splitting, and one or more types of ternary tree (TT) (also referred to as tri-tree (TT)) splitting. Ternary or tri-tree splitting is a split in which a block is split into three sub-blocks. In some examples, a ternary or tri-tree split divides a block into three sub-blocks rather than dividing the original block through the center. The split types (e.g., QT, BT, and TT) in the MTT can be symmetric or asymmetric.

[0058] In some examples, video encoder 200 and video decoder 300 can use a single QTBT or MTT structure to represent each of luma and chroma components, while in other examples, video encoder 200 and video decoder 300 can use two or more QTBT or MTT structures, such as one QTBT / MTT structure for luma components and another QTBT / MTT structure for two chroma components (or two QTBT / MTT structures for respective chroma components).

[0059] Video encoder 200 and video decoder 300 can be configured to use quad tree partitioning according to HEVC, QTBT partitioning, MTT partitioning, or other partition structures. For explanatory purposes, the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure also apply to video coders configured to use quad tree partitioning or other types of partitioning.

[0060] CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTUs 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 region of CTUs 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 can be partitioned into multiple bricks, each of which can include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks can also be referred to as a brick. However, a brick that is a proper subset of a tile cannot be referred to as a tile.

[0062] Bricks in a picture can also be arranged in the form of slices. A slice can be an integer number of bricks of a picture, which can be exclusively contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes a consecutive sequence of consecutive bricks of multiple complete tiles or only one tile.

[0063] The disclosure can use “NxN” and “N by N” interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, e.g., 16x16 samples or 16 by 16 samples. In general, a 16x16 CU will have 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Likewise, an NxN CU generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a nonnegative integer value. The samples in a CU can be arranged in columns and rows. Moreover, a CU need not have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU can include NxM samples, where M need not equal N.

[0064] Video encoder 200 encodes video data for a CU, including prediction and / or residual information, among other information. Prediction information indicates how the CU is to be predicted in order to form a prediction block for the CU. Residual information generally represents sample-by-sample differences between the CU prior to encoding and the prediction block.

[0065] To predict a CU, video encoder 200 can generally form a prediction block for the CU through inter prediction or intra prediction. Inter prediction generally refers to predicting the CU from data of a previously coded picture, whereas intra prediction generally refers to predicting the CU from previously coded data of the same picture. To perform inter prediction, video encoder 200 can use one or more motion vectors to generate the prediction block. Video encoder 200 can generally perform a motion search to identify a reference block that closely matches the CU, e.g., in terms of difference between the CU and the reference block. Video encoder 200 can calculate a difference metric using a sum of absolute difference (SAD), sum of squared difference (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculations to determine whether a reference block closely matches a current CU. In some examples, video encoder 200 can use single or bi-prediction to predict a current CU.

[0066] Some examples of JEM and VVC also provide an affine motion compensation mode, which can be considered an inter prediction mode. In affine motion compensation mode, video encoder 200 can determine two or more motion vectors that represent non-translational motion, such as scaling or zooming, rotation, perspective motion, or other irregular types of motion.

[0067] To perform intra prediction, video encoder 200 can select an intra prediction mode to generate the prediction block. Some examples of JEM and VVC provide sixty-seven intra prediction modes, including various directional modes as well as a planar mode and a DC mode. Generally, video encoder 200 selects an intra prediction mode that describes neighboring samples in the same picture as the current block (e.g., block of a CU) to predict samples of the current block from. Given that video encoder 200 codes CTUs and CUs in a raster scan order (left-to-right, top-to-bottom), such samples can generally be above, above-and-to-the-left of, or to the left of the current block in the same picture.

[0068] Video encoder 200 encodes data representing the prediction mode for the current block. For example, for inter prediction modes, video encoder 200 can encode data that indicates which of various available inter prediction modes to use and motion information for the corresponding mode. For example, for uni- or bi-prediction, video encoder 200 can use advanced motion vector prediction (AMVP) or merge mode to encode motion vectors. For affine motion compensation mode, video encoder 200 can use a similar mode to encode motion vectors.

[0069] Following prediction of a block, such as intra prediction or inter prediction, video encoder 200 can calculate residual data for the block. Residual data, such as a residual block, represents sample-by-sample differences between the block and a prediction block for the block formed using the corresponding prediction mode. Video encoder 200 can apply one or more transforms to the residual block to produce transformed data in a transform domain rather than the sample domain. For example, video encoder 200 can apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, video encoder 200 can apply a secondary transform following a primary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), or the like. Video encoder 200 produces transform coefficients following application of the one or more transforms.

[0070] As noted above, following any transforms that produce transform coefficients, video encoder 200 can perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing the quantization process, video encoder 200 can reduce the bit depth of some or all of the transform coefficients. For example, video encoder 200 can round n-bit values to m-bit values during quantization, where n is greater than m. In some examples, to perform quantization, video encoder 200 can perform a bitwise right-shift of the values to be quantized.

[0071] Following quantization, video encoder 200 can scan the transform coefficients, producing a one-dimensional vector from the two-dimensional matrix that includes the quantized transform coefficients. The scan can be designed to place higher energy (and thus lower frequency) transform coefficients at the front of the vector, and lower energy (and thus higher frequency) transform coefficients at the back of the vector. In some examples, video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and subsequently entropy encode the quantized transform coefficients of the vector. In other examples, video encoder 200 can perform an adaptive scan. Following scanning of the quantized transform coefficients to form a one-dimensional vector, video encoder 200 can entropy encode the one-dimensional vector, e.g., according to context adaptive binary arithmetic coding (CABAC). Video encoder 200 can also entropy encode values for syntax elements describing metadata associated with the encoded video data for use by video decoder 300 in decoding the video data.

[0072] To perform CABAC, video encoder 200 can assign a context within a context model to a symbol to be transmitted. The context can relate to, for example, whether neighboring values of the symbol are zero-valued or not. The probability determination can be based on the context assigned to the symbol.

[0073] Video encoder 200 can further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, e.g., in picture headers, block headers, slice headers, or other syntax data such as sequence parameter sets (SPS), picture parameter sets (PPS), or video parameter sets (VPS), to video decoder 300. Video decoder 300 can likewise decode such syntax data to determine how to decode corresponding video data.

[0074] In this way, video encoder 200 can generate a bitstream including encoded video data, e.g., syntax elements describing partitioning of pictures into blocks, e.g., CUs, and prediction and / or residual information for the blocks. Ultimately, video decoder 300 can receive the bitstream and decode the encoded video data.

[0075] In general, video decoder 300 performs a reciprocal process to that performed by video encoder 200 to decode the encoded video data of the bitstream. For example, video decoder 300 can decode values for syntax elements of the bitstream using CABAC in substantially a reciprocal manner to the CABAC encoding process of video encoder 200. The syntax elements can define partitioning information for pictures into CTUs and partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements can further define prediction and residual information for blocks, e.g., CUs.

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

[0077] According to techniques of this disclosure, a method of decoding video data includes: reorganizing, by one or more processors, 2-dimensional dequantized coefficients according to a first ordering; applying, by the one or more processors, an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients to be reconstructed after applying the inverse LFNST; reorganizing, by the one or more processors, the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and

[0078] decoding, by the one or more processors, the video data based on the inverse transform coefficients second ordered.

[0079] According to techniques of this disclosure, a device for decoding video data includes: a memory configured to store the video data; and one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors configured to: reorganize 2-dimensional dequantized coefficients according to a first ordering; apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients to be reconstructed after applying the inverse LFNST; reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and decode the video data based on the inverse transform coefficients second ordered.

[0080] According to techniques of this disclosure, a device for decoding video data includes: means for reorganizing 2-dimensional dequantized coefficients according to a first ordering; means for applying an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients to be reconstructed after applying the inverse LFNST; means for reorganizing the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and means for decoding the video data based on the inverse transform coefficients second ordered.

[0081] According to techniques of this disclosure, a non-transitory computer- readable storage medium having instructions stored thereon that, when executed by one or more processors, cause the one or more processors to: reorganize 2-dimensional dequantized coefficients according to a first ordering; apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of reconstructed LFNST coefficients after applying the inverse LFNST; reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array comprising values, where each value in the array corresponds to a position in a 2-dimensional block and the values in the array indicate indices of the 2-dimensional block in a defined order; and decode the video data based on the second ordered inverse transform coefficients.

[0082] This disclosure can generally refer to "signaling" certain information, such as syntax elements. The term "signaling" can generally refer to communication of values for syntax elements and / or other data used for decoding encoded video data. That is, video encoder 200 can signal values of syntax elements in a bitstream. In general, signaling refers to generating values in a bitstream. As mentioned above, source device 102 can transmit the bitstream to destination device 116 substantially in real time, or not in real time, such as can occur when storing syntax elements to storage device 112 for later retrieval by destination device 116.

[0083] Figure 2A and Figure 2B FIG. 1 1 is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splitting, while dashed lines indicate binary tree splitting. In each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where 0 indicates a horizontal split and 1 indicates a vertical split in this example. For quadtree splitting, no split type indication is needed because quadtree nodes split a block horizontally and vertically into 4 equally sized sub-blocks. Thus, video encoder 200 can encode and video decoder 300 can decode syntax elements, such as split information, for the region tree level (i.e., solid lines) of QTBT structure 130 and syntax elements, such as split information, for the prediction tree level (i.e., dashed lines) of QTBT structure 130. Video encoder 200 can encode and video decoder 300 can decode video data, such as prediction data and transform data, for CUs represented by terminal leaf nodes of QTBT structure 130.

[0084] In general, Figure 2BA CTU 132 can be associated with parameters defining the sizes of blocks corresponding to nodes of the QTBT structure 130 at the first and second levels. These parameters can include a CTU size (representing the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, representing the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, representing the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, representing the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, representing the minimum allowed binary tree leaf node size).

[0085] A root node of a QTBT structure corresponding to a CTU can have four child nodes at the first level of the QTBT structure, each of which can be split according to quadtree partitioning. That is, a node of the first level is either a leaf node (having no child nodes) or has four child nodes. The example of the QTBT structure 130 represents such nodes as including parent and child nodes represented by branches in solid lines. If a node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the node can be further partitioned by a corresponding binary tree. The binary tree split of a node can be iterated until the nodes resulting from the split reach 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 nodes as including parent and child nodes represented by branches in dashed lines. Binary tree leaf nodes are referred to as coding units (CUs), which are used for prediction (e.g., intra-picture or inter-picture prediction) and transform without any further partitioning. As discussed above, a CU can also be referred to as a “video block” or “block.”

[0086] In one example of the QTBT partitioning structure, the CTU size is set to 128x128 (luma samples and two corresponding 64x64 chroma samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quad-tree partitioning is first applied to the CTU to generate quad-tree leaf nodes. The size of the quad-tree leaf nodes can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If a leaf quad-tree node is 128x128, it will not be further split by binary tree because the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the leaf quad-tree node will be further partitioned by binary tree. Thus, the quad-tree leaf node is also the root node of binary tree and its binary tree depth is 0. When the binary tree depth reaches MaxBTDepth (4 in this example example), no further splitting is allowed. When the width of a binary tree node is equal to MinBTSize (4 in this example example), it implies no further horizontal splitting is allowed. Similarly, a binary tree node with height equal to MinBTSize implies no further vertical splitting is allowed for that binary tree node. As described above, the leaf nodes of binary tree are referred to as CUs and are further processed according to prediction and transform without further partitioning.

[0087] Figure 3 FIG. 2 is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure. Figure 3 FIG. 2 is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure.

[0088] In Figure 3In the example of FIG. 2, video encoder 200 includes video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, decoded picture buffer (DPB) 218, and entropy encoding unit 220. Any or all of video data memory 230, mode select unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 can be implemented in one or more processors or in processing circuitry. Additionally, video encoder 200 can include additional or alternative processors or processing circuitry to perform these and other functions.

[0089] Video data memory 230 can store video data to be encoded by the components of video encoder 200. Video encoder 200 can receive the video data stored in video data memory 230 from, for example, video source 104 Figure 1 DPB 218 can function as a reference picture memory that stores reference video data for use in encoding by video encoder 200 of subsequent video data. 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 separate memory devices. In various examples, video data memory 230 can be on-chip with other components of video encoder 200, as illustrated, or off-chip relative to those components.

[0090] In this disclosure, reference to video data memory 230 should not be construed as being limited to memory that is internal to video encoder 200, unless specifically so described, or memory that is external to video encoder 200, unless specifically so described. Rather, reference to video data memory 230 should be understood as a reference to a memory that stores video data that video encoder 200 receives for encoding (e.g., video data of a current block that is to be encoded). Figure 1 Memory 106 of video encoder 200 can also provide temporary storage of the outputs from the various units of video encoder 200.

[0091] Figure 3The various units of video encoder 200 are shown to assist with understanding the operations performed by 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 particular functionality, and are preset on the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For instance, programmable circuits can execute software or firmware that cause the programmable circuits to operate in the 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 that the fixed-function circuits perform are generally immutable. In some examples, one or more of the units can be distinct circuit blocks (fixed-function or programmable), and in some examples, one or more of the units can be integrated circuits.

[0092] Video encoder 200 can include arithmetic logic units (ALUs), elementary function units (EFUs), digital circuits, analog circuits, and / or programmable cores formed from programmable circuits. In examples where the operations of video encoder 200 are performed using software executed by the programmable circuits, memory 106 Figure 1 ) can store the instructions (e.g., object code) of the software that video encoder 200 receives and executes, or another memory within video encoder 200 (not shown) can store such instructions.

[0093] Video data memory 230 is configured to store received video data. Video encoder 200 can retrieve pictures of the video data from video data memory 230 and provide the video data to residual generation unit 204 and mode selection unit 202. Video data in video data memory 230 can be raw video data that is to be encoded.

[0094] Mode selection unit 202 includes motion estimation unit 222, motion compensation unit 224, and intra-prediction unit 226. Mode selection unit 202 can include additional functional units to perform video prediction according to other prediction modes. As examples, mode selection unit 202 can include a palette unit, an intra block copy unit (which can be part of motion estimation unit 222 and / or motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0095] Mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values for such combinations. The encoding parameters can include partitioning of CTUs into CUs, prediction modes for CUs, transform types for residual data of CUs, quantization parameters for residual data of CUs, and so forth. Mode selection unit 202 can ultimately select the combination of encoding parameters that has the best rate-distortion value, of the combinations that are tested.

[0096] Video encoder 200 can partition a picture retrieved from video data memory 230 into a series of CTUs, and encapsulate one or more CTUs within a slice. Mode select unit 202 can partition CTUs of a picture in accordance with a tree structure such as the QTBT structure described above or the quadtree structure of HEVC. As described above, video encoder 200 can form one or more CUs by partitioning a CTU according to the tree structure. The CU can also be referred to generally as a“video block” or“block.”

[0097] In general, mode select unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for a current block (e.g., a current CU, or a portion of a PU and TU that overlap in HEVC). For inter prediction of a current block, motion estimation unit 222 can 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 coded pictures stored in DPB 218). Specifically, motion estimation unit 222 can calculate a value that represents a degree of similarity of a potential reference block to the current block, e.g., according to a sum of absolute difference (SAD), a sum of squared differences (SSD), a mean absolute difference (MAD), a mean squared differences (MSD), etc. Motion estimation unit 222 can generally perform these calculations using point-wise differences between the current block and a considered reference block. Motion estimation unit 222 can identify the reference block with the smallest value resulting from these calculations, indicating the reference block that most closely matches the current block.

[0098] Motion estimation unit 222 can form one or more motion vectors (MVs) that define a position of a reference block in a reference picture relative to a current block in a current picture. Motion estimation unit 222 can then provide the motion vector(s) to motion compensation unit 224. For example, for single -direction inter prediction, motion estimation unit 222 can provide a single motion vector, while for bi-directional inter prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vector(s) to generate the prediction block. For example, motion compensation unit 224 can use the motion vector(s) to retrieve data for the reference block. As another example, if the motion vector(s) have fractional sample precision, motion compensation unit 224 can interpolate values of the prediction block according to one or more interpolation filters. Further, for bi-directional inter prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by respective motion vectors, and combine the retrieved data, e.g., by point-wise averaging or weighted averaging.

[0099] As another example, for intra prediction or intra prediction coding, the intra prediction unit 226 can generate a prediction block from samples neighboring the current block. For example, for directional modes, the intra prediction unit 226 can mathematically combine values of the neighboring samples and interpolate these calculated values across a defined direction to produce the prediction block. As another example, for a DC mode, the intra prediction unit 226 can calculate an average of the values of the samples neighboring the current block and generate the prediction block to include this resulting average for each sample of the prediction block.

[0100] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original, unencoded version of the current block from the video data memory 230 and the original, unencoded version of 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 also determine the difference between sample values in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 can be formed using one or more subtractor circuits that perform binary subtraction.

[0101] In examples in which the mode selection unit 202 partitions the CU into PUs, each PU can be associated with a luma prediction unit and corresponding chroma prediction units. Video encoder 200 and video decoder 300 can support PUs having various sizes. As indicated above, the size of a CU can refer to the size of the luma coding block of the CU, while the size of a PU can refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, video encoder 200 can support PU sizes of 2Nx2N or NxN for intra prediction, and 2Nx2N, 2NxN, Nx2N, NxN, or similar symmetric PU sizes for inter prediction. Video encoder 200 and video decoder 300 can also support asymmetric partitioning for inter prediction for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N.

[0102] In examples in which the mode selection unit 202 does not further partition the CU into PUs, each CU can be associated with a luma coding block and corresponding chroma coding blocks. As shown above, the size of a CU can refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 can support CU sizes of 2N x 2N, 2N x N, or Nx 2N.

[0103] For other video coding techniques such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, as a number of examples, the mode selection unit 202 generates, via a respective unit associated with the coding technique, a prediction block for the current block being coded. In some examples, such as palette mode coding, the mode selection unit 202 can not generate a prediction block, but rather generate syntax elements that indicate a way to reconstruct the block based on a selected palette. In such modes, the mode selection unit 202 can provide these syntax elements to the entropy encoding unit 220 for encoding.

[0104] As described above, the residual generation unit 204 receives video data for the 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 computes a sample-by-sample difference between the prediction block and the current block.

[0105] 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 the transform coefficient block. For example, the transform processing unit 206 can apply an LFNST, 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 such as a rotational transform. In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0106] In some examples, the transform processing unit 206 can reorder the primary transform coefficients according to a scan. The transform processing unit 206 can also apply an LFNST to the reordered primary transform coefficients to create LFNST coefficients.

[0107] The quantization unit 208 can quantize the transform coefficients in the transform coefficient block, to produce a quantized transform coefficient block. The quantization unit 208 can quantize transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) can 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 can introduce loss of information, and thus, quantized transform coefficients can have lower precision than the original transform coefficients produced by the transform processing unit 206.

[0108] Inverse quantization unit 210 and inverse transform processing unit 212 can apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. Quantized transform coefficients that have been inverse quantized can be referred to herein as dequantized coefficients. For example, inverse transform processing unit 212 can reorganize the 2-dimensional dequantized coefficients according to the first ordering. Inverse transform processing unit 212 can also apply an inverse transform LFNST to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients. Inverse transform processing unit 212 can also reorganize the inverse transform coefficients according to the second ordering. Inverse transform processing unit 212 can also decode video data based on the second ordered inverse transform coefficients. For example, inverse transform processing unit 212 can apply an inverse separable transform, such as an inverse DCT-2, to the reorganized inverse transform coefficients.

[0109] Reconstruction unit 214 can generate a reconstructed block corresponding to the current block based on the reconstructed residual block and the prediction block generated by mode selection unit 202 (although possibly with some degree of distortion). For example, reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples from the prediction block generated by mode selection unit 202 to produce the reconstructed block.

[0110] Filter unit 216 can perform one or more filter operations on the reconstructed block. For example, filter unit 216 can perform a deblocking operation to reduce blocking artifacts along the edges of the CU. In some examples, the operations of filter unit 216 can be skipped.

[0111] Video encoder 200 stores the reconstructed block in DPB 218. For example, in examples where the operations of filter unit 216 are not needed, reconstruction unit 214 can store the reconstructed block to DPB 218. In examples where the operations of filter unit 216 are needed, filter unit 216 can store the filtered reconstructed block to DPB 218. Motion estimation unit 222 and motion compensation unit 224 can retrieve reference pictures formed from the reconstructed (and possibly filtered) blocks in DPB 218 to inter-predict blocks of subsequent encoded pictures. In addition, intra-prediction unit 226 can use the reconstructed blocks of the current picture in DPB 218 to intra-predict other blocks in the current picture.

[0112] In general, entropy encoding unit 220 can entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 can entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy encoding unit 220 can entropy encode prediction syntax elements (e.g., motion information for inter-prediction or intra-mode information for intra-prediction) from mode select unit 202. Entropy encoding unit 220 can perform one or more entropy encoding operations on the syntax elements, which are another example of video data, to generate entropy encoded data. For example, entropy encoding unit 220 can 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, entropy encoding unit 220 can operate in a bypass mode where the syntax elements are not entropy encoded.

[0113] Video encoder 200 can output a bitstream that includes the entropy encoded syntax elements needed to reconstruct blocks of a slice or picture. Specifically, entropy encoding unit 220 can output the bitstream.

[0114] The operations described above are described with respect to blocks. This description should be understood to be operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and the chroma coding blocks are luma and chroma components of a CU. In some examples, the luma coding blocks and the chroma coding blocks are luma and chroma components of a PU.

[0115] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As one example, the operations to identify a motion vector (MV) and a reference picture for a luma coding block need not be repeated to identify an MV and a reference picture for a chroma block. Rather, the MV for the luma coding block can be scaled to determine the MV for the chroma block, and the reference picture can be the same. As another example, the intra-prediction procedure can be the same for luma coding blocks and chroma coding blocks.

[0116] Video encoder 200 represents an example of a device configured to encode video data, the device including: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to decode the video data, for example, in a reconstruction loop. The one or more processors are configured to: reassemble 2D dequantization coefficients according to a first sort; apply an inverse low-frequency non-separable transform (LFNST) to the reassembled 2D dequantization coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates the number of basis vectors and the number of rows, and N indicates the number of LFNST coefficients reconstructed after applying the inverse LFNST; reassemble the inverse transform coefficients according to a second sort based on an array comprising values, where each value in the array corresponds to a position in a 2D block and the values ​​in the array indicate the index of the 2D block in a defined order; and decode the video data based on the second-sorted inverse transform coefficients.

[0117] Figure 4 This is a block diagram illustrating an exemplary video decoder 300 that can perform the techniques disclosed herein. Figure 4 This disclosure is provided for illustrative purposes and is not intended to limit the techniques extensively illustrated and described herein. For illustrative purposes, this disclosure describes the video decoder 300 in accordance with the techniques of JEM, VVC, and HEVC. However, the techniques of this disclosure may be implemented by video codec devices configured for other video codec standards.

[0118] exist Figure 4 In the example, the video decoder 300 includes a pass-through decoded 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, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or processing circuits. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0119] 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 based on other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copying 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.

[0120] CPB memory 320 can store video data, such as an encoded video bitstream, to be decoded by the components of video decoder 300. The video data stored in CPB memory 320 can be obtained, for example, from computer-readable medium 110 ( Figure 1 ). CPB memory 320 can include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. Also, CPB memory 320 can store video data other than syntax elements of a decoded picture, such as temporary data representing outputs from the various units of video decoder 300. DPB 314 generally stores decoded pictures, which video decoder 300 can output and / or use as reference video data when decoding subsequent data or pictures of an encoded video bitstream. CPB memory 320 and DPB 314 can 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 can be provided by the same memory devices or by separate memory devices. In various examples, CPB memory 320 can be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0121] Additionally or alternatively, in some examples, video decoder 300 can retrieve decoded video data from memory 120 ( Figure 1 ). That is, memory 120 can store data as discussed above in connection with CPB memory 320. 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 can store the instructions to be executed by video decoder 300.

[0122] Figure 4 The various units illustrated in FIG. 3 are shown as distinct illustrative units to aid in understanding the functionality implemented by video decoder 300. These units can be implemented as fixed-function or programmable circuitry, or combinations thereof. Fixed-function circuitry refers to circuitry that provides particular functionality, and is preset on the operations that can be performed by the circuitry. Programmable circuitry refers to circuitry that can be programmed to perform various tasks, and provides flexible functionality in the operations that can be performed by the circuitry. For example, programmable circuitry can execute software or firmware that Figure 3 defines the manner in which the programmable circuitry operates. Fixed-function circuitry can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuitry executes are generally unalterable. In some examples, one or more of the units can be distinct circuit blocks (fixed-function or programmable), and in some examples, one or more of the units can be integrated circuitry.

[0123] Video decoder 300 can include ALUs, EFUs, digital circuits, analog circuits, and / or programmable cores formed from programmable circuitry. In examples where the operations of video decoder 300 are performed by software executing on the programmable circuitry, on-chip or off-chip memory can store instructions (e.g., object code) of the software that video decoder 300 receives and executes.

[0124] Entropy decoding unit 302 can receive encoded video data from the CPB and entropy decode the video data to reconstruct syntax elements. Prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0125] In general, video decoder 300 reconstructs a picture on a block-by-block basis. Video decoder 300 can perform reconstruction operations separately for each block, where the block that is currently being reconstructed (i.e., decoded) can be referred to as the “current block.”

[0126] Entropy decoding unit 302 can entropy decode syntax elements defining quantized transform coefficient blocks of quantized transform coefficients, as well as transform information such as a quantization parameter (QP) and / or transform mode indication(s). Inverse quantization unit 306 can use a QP associated with a quantized transform coefficient block to determine a degree of quantization and, likewise, a degree of inverse quantization for inverse quantization unit 306 to apply. Inverse quantization unit 306 may, for example, perform a bit- shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 may

[0127] After inverse quantization unit 306 forms a transform coefficient block, inverse transform processing unit 308 can apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, inverse transform processing unit 308 can apply an inverse LFNST, 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.

[0128] For example, inverse transform processing unit 308 can reorganize the 2-dimensional dequantized coefficients according to a first ordering. Inverse transform processing unit 308 can also apply an inverse transform LFNST to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients. Inverse transform processing unit 308 can also reorganize the inverse transform coefficients according to a second ordering. Inverse transform processing unit 308 can also decode the video data based on the second ordered inverse transform coefficients. For example, inverse transform processing unit 308 can apply an inverse separable transform, such as an inverse DCT-2, to the reorganized inverse transform coefficients.

[0129] Furthermore, the prediction processing unit 304 generates the prediction block from the prediction information syntax elements entropy decoded by the entropy decoding unit 302. For instance, if the prediction information syntax elements indicate that the current block is inter-predicted, the motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements can indicate a reference picture in the DPB 314 from which to retrieve the reference block as well as a motion vector that identifies a location of the reference block in the reference picture relative to a location of the current block in the current picture. The motion compensation unit 316 can generally perform the inter-prediction process in substantially a manner as described with respect to the motion compensation unit 224( Figure 3 ) above.

[0130] As another example, if the prediction information syntax elements indicate that the current block is intra-predicted, the intra-prediction unit 318 can generate the prediction block according to an intra-prediction mode indicated by the prediction information syntax elements. Also, the intra-prediction unit 318 can generally perform the intra-prediction process in substantially a manner as described with respect to the intra-prediction unit 226( Figure 3 ) above. The intra-prediction unit 318 can retrieve data for neighboring samples of the current block from the DPB 314.

[0131] The reconstruction unit 310 can use the prediction block and the residual block to reconstruct the current block. For instance, the reconstruction unit 310 can add the samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

[0132] The filter unit 312 can perform one or more filtering operations on the reconstructed block. For instance, the filter unit 312 can perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 are not necessarily performed in all examples.

[0133] The video decoder 300 can store the reconstructed block in the DPB 314. For instance, in examples in which the operations of the filter unit 312 are not performed, the reconstruction unit 310 can store the reconstructed block to the DPB 314. In examples in which the operations of the filter unit 312 are performed, the filter unit 312 can store the filtered reconstructed block to the DPB 314. As discussed above, the DPB 314 can provide reference information, such as samples of the current picture for intra-prediction and previously decoded pictures for subsequent motion compensation, to the prediction processing unit 304. Furthermore, the video decoder 300 can output decoded pictures (e.g., decoded video) from the DPB 314 for subsequent presentation on a display device, such as the display device 118 of FIG. 1. Figure 1

[0134] ​As such, video decoder 300 represents an example of a video decoding device including a memory configured to store video data and one or more processing units implemented in circuitry and configured to: reorganize 2-dimensional dequantized coefficients according to a first ordering; apply an inverse low-frequency non-separable transform (LFNST) to the reorganized 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST including an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of reconstructed LFNST coefficients after applying the inverse LFNST; reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array including values, where each value in the array corresponds to a position in a 2-dimensional block and values in the array indicate indices of the 2-dimensional block in a defined order; and decode the video data based on the second ordered inverse transform coefficients.

[0135] The present disclosure relates to transform coding. Transform coding is an essential element of modern video compression standards. See M. Wien, High Efficiency Video Coding: Coding Tools and Specifications, Springer, Berlin, 2015. The present disclosure covers various low-frequency non-separable transform designs that can improve coding efficiency or simplify design in video coding, including designs that improve coding efficiency and simplicity relative to VVC Draft 6. The techniques of the present disclosure can be used in other advanced video codecs, including extensions of HEVC and next generation video coding standards. In implementations of video coding standards prior to HEVC, only fixed separable transforms were used, with DCT-2 used vertically and horizontally. In implementations of HEVC, in addition to DCT-2, DST-7 was also used as a fixed separable transform for 4x4 blocks. Multiple transform selection (MTS) methods are described below: U.S. Patent No. 10,306,229, entitled “Enhanced Multiple Transforms for Prediction Residual,” published May 28, 2019, and claiming priority to U.S. Provisional Patent Application 62 / 107,996, filed January 26, 2015; U.S. Publication 2018-0020218 Al, entitled “Look-Up Table for Enhanced Multiple Transform,” published January 18, 2018, and claiming priority to U.S. Provisional Patent Application No. 62 / 363,188, filed July 15, 2016; and U.S. Patent Publication No. 2019-0373261 Al, entitled “Coding Adaptive Multiple Transform Information for Video Coding,” filed May 30, 2019, and claiming priority to U.S. Provisional Patent Application No. 62 / 679,570, filed June 1, 2018. MTS was previously known as adaptive multiple transform (AMT). The example of MTS in U.S. Patent Publication No. 2019-0373261 Al has been adopted in the Joint Experimental Model (JEM-7.0) of the Joint Video Team (JVET). See Joint Video Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, JEM Software. Later, a simplified version of MTS was adopted in VVC.

[0136] Figure 5is a conceptual diagram illustrating low-frequency non-separable transform (LFNST) at an encoder and a decoder (e.g., video encoder 200 and video decoder 300), where the LFNST includes a stage between a separable transform and quantization in the codec. In Figure 5 In the example of FIG. 4, video encoder such as video encoder 200 can apply separable transform 400. Video encoder can then apply LFNST 402. Video encoder can then quantize LFNST coefficients 404. Video decoder such as video decoder 300 can inverse quantize quantized coefficients 406. Video decoder can then apply inverse LFNST 408. Video decoder can then apply inverse separable transform 410.

[0137] Figure 5The LFNST shown in the middle is used in JEM-7.0 to further improve the coding efficiency of MTS, where the implementation of LFNST is based on the hypercube Givens transform (HyGT) disclosed in U.S. Patent No. 10,448,053, titled “Multi-Pass Non-Separable Transforms for Video Coding,” published on October 15, 2019, and claiming the benefit of U.S. Provisional Patent Application Nos. 62 / 295,440 and 62 / 295,448, both filed on February 15, 2016 (see U.S. Patent No. 10,491,922, titled “Non-Separable Secondary Transform for Video Coding,” filed on November 26, 2019, for alternative designs and other details; U.S. Patent No. 10,349,085, titled “Efficient Parameter Storage for Compact Multi-Pass Transforms,” published on July 9, 2019, and claiming the benefit of U.S. Provisional Patent Application Nos. 62 / 295,456 and 62 / 295,448, both filed on February 15, 2016, and U.S. Patent Publication No. 2019-0297351, titled “Minimization of Transform Memory and Latency Via Parallel Factorizations,” published on September 26, 2019). The LFNST was previously known as the non-separable secondary transform (NSST) or secondary transform, where all the acronyms are the same. Recently, Koo et al. adopted the LFNST, i.e., ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11 Joint Video Expert Team (JVET) “CE6: Reducing Secondary Transform (RST)” (CE6-3.1), published on March 19-27, 2019, in Geneva, Switzerland, 14th Meeting, JVET-N0193.

[0138] Figure 6 is a conceptual diagram showing an exemplary inverse transform process with the LFNST. The inverse transform with the LFNST involves Figure 6The following techniques are shown and can be performed, for example, by the inverse transform processing unit 212 of the video encoder 200 and the inverse transform processing unit 308 of the video decoder 300. The decoded transform coefficients in the 2D block 420 are used as input to the inverse LFNST by first converting the 2D block 420 into a 1D coefficient list (or vector) via a predefined scan / sort. Zero-return coefficients 422 are not used. Zero-return coefficients can be coefficients whose values ​​are set to zero based on their position within the 2D block according to predefined rules. The inverse LFNST is applied to the 1D input coefficient list, and the output coefficients are reconstructed into a 2D block 424 via a predefined scan / sort. Zero-return coefficients 426 are not used. The inverse transform LFNST coefficients are used as input to a separable inverse DCT-2 to obtain the reconstructed residual 428.

[0139] Figure 7 This is a conceptual diagram illustrating a 4x4 inverse LFNST used to reconstruct 16 intermediate coefficients from a list of 16 input coefficients. Figure 8 This is a conceptual diagram illustrating an 8x8 inverse LFNST used to reconstruct 48 intermediate coefficients from a list of 16 input coefficients. In VVC Draft 6, LFNST can be applied to 4x4 or 8x8 subblocks. In both cases, 16 decoded coefficients (some of which may be canonically zeroed) in the 4x4 subblock are input to the inverse LFNST. For the 4x4 subblock 430, the video decoder 300 can use a 16x16 inverse LFNST to construct 16 intermediate coefficients 432 before applying the separable inverse DCT-2, as shown below. Figure 7 As shown. For the 8x8 sub-block 440, the video decoder 300 can use 16x48 inverse LFNST to construct 48 intermediate coefficients 442 before the separable inverse DCT-2, as... Figure 8 As shown. Note that the 48 intermediate coefficients 442 are reassembled into an L-shaped pattern. The remaining coefficients 444 are zeroed out. The inverse LFNST process can be fully defined based on (i) the transform (e.g., LFNST) matrix and (ii) the reassembled pattern / scan of the intermediate coefficients. An example of the details of the zeroing process in VCC Draft 6 is described in U.S. Patent Application No. 15 / 931,271, filed May 13, 2020, entitled “Low-Frequency Non-Separable Transformation Signaling Based on Zero-Out Patterns for Video Coding”, which claims priority to U.S. Provisional Patent Application No. 62 / 849,689, filed May 17, 2019.

[0140] For 4x4 LFNST, video encoder 200 and video decoder 300 can use one of the following two patterns / scans depending on the intra mode:

[0141]

[0142] where the above two patterns / scans indicate reordering of the intermediate coefficients. For example, lfnstRGScan4x4 does not change the row-wise reordering of the coefficients. However, lfnstRGTranScan4x4 reorders the coefficients by transposing the order of the coefficients (e.g., the coefficients at 1, 2, 3, 6, 7, and 11 are swapped with the coefficients at 4, 8, 12, 9, 13, and 14, respectively). In some examples, lfnstRGScan4x4 can be used for intra modes with indices between 0 and 34, inclusive, while lfnstRGTranScan4x4 can be used for intra modes with indices higher than 34.

[0143] For 4x4 LFNST, the following eight 16x16 matrices can be used according to VVC Draft 6.

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[0154] For 8x8 LFNST, video encoder 200 or video decoder 300 can use the following two patterns / scans depending on the intra mode:

[0155]

[0156] where the above two patterns / scans indicate reordering of the intermediate coefficients. Specifically, lfnstRGScan8x8 reorganizes the 48 intermediate coefficients in an L-shaped pattern (e.g., the 48th coefficient is mapped toFigure 8 Scan4x4 reorders the L-shaped pattern by transposing the coefficients (e.g., the 48th coefficient is mapped to Figure 8 In some examples, lfnstRGScan4x4 can be used to index intra modes between 0 and 34, inclusive, while lfnstRGTranScan4x4 can be used to index intra modes higher than 34.

[0157] For 8x8 LFNST, the following eight 16x48 matrices are used in VVC Draft 6.

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[0174] The present disclosure describes various optimized matrices and reorganization patterns / scans for 8x8 LFNST relative to the techniques for LFNST in VVC Draft 6. The disclosed techniques can simplify the 8x8 LFNST design in VVC Draft 6 by reducing the number of multiplications needed to perform LFNST or inverse LFNST. The disclosed techniques can also reduce memory requirements and / or provide coding gain without increasing encoder or decoder complexity.

[0175] After the video decoder 300 obtains the 2-dimensional list of dequantized coefficients based on the coefficient decoding steps, the video decoder 300 can apply an inverse LFNST to reconstruct the subset of coefficients. The video decoder 300 can then use an inverse separable transform (e.g., DCT-2) to reconstruct the residual in the 2-dimensional block / array (such as shown in Figure 7 and Figure 8 .

[0176] The LFNST decoding process can be specified based on the reorganization pattern / scans, which are used to define how to organize the LFNST input and output coefficients, and the transform matrices, which define the non-separable transform for the decoded subset of coefficients.

[0177] Figure 9 is a conceptual diagram showing the inverse LFNST process. Using LFNST, the 2-dimensional block / array of decoded coefficients can be organized so as to match the entries of the matrix with the input of the inverse LFNST. As shown in Figure 9 , this can be achieved by, for example, the inverse transform processing unit 212 or the inverse transform processing unit 308: constructing a 1-dimensional list 452 of M coefficients from the 2-dimensional block of coefficients 450, applying the inverse LFNST (of size MxN) on the 1-dimensional list 452 of M coefficients to reconstruct N LFNST coefficients 454, and outputting the coefficients are reorganized in a 2-dimensional block / array 456, which are input to the separable transform (inverse DCT-2) that reconstructs the residual block.

[0178] In VVC Draft 6, the LFNST design allows for up to M=16 non-zero coefficients (located in the top-left 4x4 subblock), while the remaining coefficients are normatively set to zero (such as shown in Figure 11 . However, the techniques of the present disclosure can be applied to designs that allow for all coefficients to be non-zero. One example can be the case where M=N. For example, none of the coefficients are normatively zeroed.

[0179] Figure 10is a conceptual diagram illustrating input reorganization based on raster scan. Raster scan is a line-by-line scan that moves from the top-left coefficient to the top-right coefficient, then the row immediately below the top row (second row) again from left to right, then the row immediately below the second row again from left to right, and so on. Input reorganization is now further discussed. In one example, reorganization can be done in raster scan order (also referred to as row-major order, as shown in Figure 10 It can be seen that the order of the coefficients in the 4x4 block 460 is reorganized in the 1 -dimensional list 462 based on raster scan order. For example, the video decoder 300 can reorganize the coefficients in the top row of the 4x4 block 460 from right to left into the first, second, third, and fourth positions (e.g., the left-most four positions) in the 1 -dimensional list 462. The video decoder 300 can place the coefficients from the second row of the 4x4 block 460 in the next four positions in the 1 -dimensional list 462, and so on. In another example, the video decoder 300 can perform reorganization in column-major order (e.g., by column instead of by row). In another example, the video decoder 300 can reorganize the coefficients based on block size and / or intra mode.

[0180] If a subset of input coefficients is normatively set to zero by a codec (e.g., the video encoder 200 or the video decoder 300), the input coefficient list of the LFNST can not include those zeroed coefficients. The reorganization step can include only coefficients that can be non-zero (e.g., coefficients that are not normatively zeroed).

[0181] The LFNST transform matrix is now further discussed. The size of the LFNST transform matrix within the inverse transform processing unit 212 and the inverse transform processing unit 308 can be MxN, where M indicates the number of basis vectors and also indicates the number of rows, and N indicates the number of reconstructed LFNST coefficients (also referred to as the number of support samples used for the transform) after the transform is applied. The transform matrix entries can be 8-bit, 9-bit, or 10-bit precision. The sign of all entries in a row of the transform matrix can be flipped. In other words, the row vector in the transform matrix can be multiplied by -1. In some examples, all rows in the transform matrix can be multiplied by -1. In some examples, a subset of rows in the transform matrix can be multiplied by -1, while other entries are unchanged.

[0182] Now further discuss the output reorganization pattern / scan. The inverse transform processing unit 212 and the inverse transform processing unit 308 can reorganize a 1-D list of N output LFNST coefficients based on an array (defining a pattern / scan), where each value in the array corresponds to a position / location in a 2-D block. The values in the array (for reorganization) can indicate indices of the 2-D block in any predefined order. In one example, the index values can correspond to positions in the 2-D block. Given an index value v, the corresponding position in the 2-D block can be calculated as:

[0183] Row index: r = floor(v / w)

[0184] Column index: c = mod(v,w),

[0185] where w indicates the width of the LFNST subblock (in VVC Draft 6, w can be 4 or 8).

[0186] According to this formula, the following array of reorganization pattern corresponds to the raster order of 4x4 block:

[0187]

[0188] So that the i-th element in the 1-D coefficient list is mapped to the row and column position in the 2-D block as for i = 0, 1, …, 15:

[0189] r[i] = floor(raster_order[i] / w)

[0190] c[i] = mod(raster_order[i],w)

[0191] Now discuss an example of 8x8 LFNST. Figure 11 is a conceptual diagram showing a 4x4 block pattern with 16 samples in 8x8 LFNST. In the example of Figure 11 , the video decoder 300 can perform input reorganization in raster scan order for M = 16 decoded coefficients. The 1-D list 470 can be reorganized and output as shown, where the coefficients in the 1-D list 470 are reorganized into the top-left 4x4 portion 472 of the 8x8 block 474. Other coefficients in the 8x8 block 474 can be normatively zeroed. An optimized output reorganization pattern / scan can be specified in the array g_lfnstRGScan8x8 or g_lfnstRGTranScan8x8, where one of these arrays is used depending on the intra mode. A set of optimized transform (LFNST) matrices can be defined as g_lfnst8x8.

[0192] 4x4 block pattern with N = 16 samples in 8x8 LFNST:

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[0203] Figure 12 is a conceptual diagram showing a 5x5 block pattern with 25 samples in 8x8 LFNST. The 1-D list 480 can be reorganized and output as shown, where the coefficients in the 1-D list 480 are reorganized into the top-left 5x5 portion 482 of the 8x8 block 484. The remaining coefficients in the 8x8 block 484 can be normed to zero. The optimized output reorganization pattern / scan can be specified in the arrays g_lfnstRGScan8x8 and g_lfnstRGTranScan8x8, where one of these arrays is used depending on the intra mode. The set of optimized transform (LFNST) matrices can be defined as g_lfnst8x8.

[0204] The 5x5 block pattern with N=25 samples in 8x8 LFNST can include:

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[0216] Figure 13 is a conceptual diagram showing a 6x6 block pattern with 36 samples in 8x8 LFNST. This example can simplify the VVC Draft 6 8x8 LFNST design by replacing the L-shaped 48-sample support pattern with a 6x6 square block pattern. Experiments show that the 6x6 block pattern with an optimized transform matrix can provide 0.01% all intra and 0.00% random access over VTM-6.0. Figure 13 The example of can provide -0.01% all intra and 0.00% random access over VTM-6.0. Compared to the 8x8 LFNST of VVC Draft 6, Figure 13 The example of can reduce the number of multiplications and memory for storing the transform matrix of 8x8 LFNST. Figure 13 The memory requirement and number of multiplications of the example of can be the same as the technology tested in Zhou et al., “CE6-2.3a: Simplification with LFNST Transform Basis,” JVET-P0065 (hereinafter “JVET-P0065”), presented at the 16th Meeting of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG11 Joint Video Expert Team (JVET), Geneva, Switzerland, 2-12 October 2019, which proposed a pattern with 36 samples. Figure 13 The example of can further simplify CE6-2.3a by using a single 6x6 square block, while JVET-P0065 uses two irregular (non-square) separate patterns according to LFNST index. Figure 13 The example of can simplify the existing LFNST design with negligible Bjontegaard rate difference (BD rate). The 1D list 490 can be reorganized and output as shown, where the coefficients in the 1D list 490 are reorganized into the top-left 6x6 portion 492 of the 8x8 block 494. The remaining coefficients in the 8x8 block 494 can be normed to zero. The optimized output reorganization pattern / scan can be specified in the arrays g_lfnstRGScan8x8 and g_lfnstRGTranScan8x8. The set of optimized transform (LFNST) matrices can be defined as g_lfnst8x8. The 6x6 block pattern with N = 36 samples in 8x8 LFNST can include:

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[0232] Figure 14 is a conceptual diagram showing a circular pattern with 48 samples in 8x8 LFNST. This example aims to provide additional coding gain by introducing a circular 48-sample support pattern for 8x8 LFNST. Experimental results show that -0.09% for all intra and -0.04% for random access BD rate can be achieved against VVC Test Model 6 (VTM-6.0), the description of which can be found in Chen et al., “Algorithm description for Versatile Video Coding and Test Model 6 (VTM 6),” published in the 15th Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC1 / SC 29 / WG 11, July 3-12, 2019, Gothenburg, Sweden. Figure 14Examples can provide additional coding gain over VTM-6.0 without increasing memory requirements and multiplication number. The 1-D list 500 can be reorganized and output as shown, with the coefficients in the 1-D list 500 reorganized into the dark shaded portion 502 of the 8x8 block 504. The remaining coefficients of the 8x8 block 504 can be normed to zero. The optimized output reorganization pattern / scan can be specified in the arrays g_lfnstRGScan8x8 and g_lfnstRGTranScan8x8. The set of optimized transform (LFNST) matrices can be defined as g_lfnst8x8. The circular pattern with N = 48 samples in the 8x8 LFNST can include:

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[0251] Figure 15is a conceptual diagram illustrating another variation of a 48-sample circular pattern for 8x8 LFNST. The 1-D list 510 can be reorganized and output as shown, with the coefficients in the 1-D list 510 reorganized into the dark-shaded portion 512 of the 8x8 block 514. The remaining coefficients of the 8x8 block 514 can be normed to zero.

[0252] Figure 16 is a conceptual diagram illustrating an 8x8 block pattern with 64 samples for 8x8 LFNST. The 1-D list 520 can be reorganized and output as shown, with the coefficients in the 1-D list 520 reorganized into the 8x8 block 522. For the example of Figure 16

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[0276] Figure 17 is a table of test results for an example of Figure 13 under common test conditions (CTC) for VTM-6.0. Figure 18 is a table of test results for an example of Figure 14 under CTC for VTM-6.0. Figure 19 is a table of test results for an example of Figure 13 unoptimized 4x4 LFNST matrix under CTC for VTM-6.0. The techniques of this disclosure are implemented on top of VTM-6.0 and evaluated according to CTC. Note that low delay B results are omitted because LFNST is disabled for low delay B in CTC. Test results are shown in Figure 20 Figure 14 is a table of test results for an example of Figures 17 to 20 unoptimized 4x4 LFNST matrix under CTC for VTM-6.0. The techniques of this disclosure are implemented on top of VTM-6.0 and evaluated according to CTC. Note that low delay B results are omitted because LFNST is disabled for low delay B in CTC. Test results are shown in

[0277] Figure 21 is a flowchart illustrating example reordering coefficients according to the techniques of this disclosure. Inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can reorder 2-dimensional dequantized coefficients according to a first ordering (530). For example, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can perform input reordering such as in the examples of Figure 9 and 10 In some examples, the first ordering is a raster scan ordering. In some examples, the first ordering is a column-first ordering. In some examples, the first ordering includes a 1-dimensional list. In some examples, the reordered 2-dimensional dequantized coefficients include one of 25 dequantized coefficients, 36 dequantized coefficients, 48 dequantized coefficients, or 64 dequantized coefficients. In some examples, the first ordering is based on block size and / or intra mode. In some examples, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 determines which of the 2-dimensional dequantized coefficients are not normatively zeroed, and only reorders the 2-dimensional dequantized coefficients that are not normatively zeroed, such that the first ordering only includes the 2-dimensional dequantized coefficients that are not normatively zeroed. ​

[0278] Inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can apply an inverse LFNST to the reorganized 2-D dequantized coefficients to create inverse transform coefficients (532). For example, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can apply an inverse LFNST of any of the examples in Figures 11 to 16 In some examples, the inverse LFNST includes an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients that are reconstructed after applying the inverse LFNST. In some examples, entries in the MxN matrix have one or more of 8-bit precision, 9-bit precision, or 10-bit precision. In some examples, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can multiply one row in the MxN matrix by -1. In some examples, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can multiply all rows in the MxN matrix by -1.

[0279] Inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can reorganize the inverse transform coefficients according to a second ordering, the second ordering based on an array of values (534). For example, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can reorganize the inverse transform coefficients such that the inverse transform coefficients are in the correct position for application of a separable transform. In some examples, each value in the array corresponds to a position in a 2-dimensional block. In some examples, the values in the array represent indices of the 2-dimensional block in a defined order. In some examples, an index value v points to a corresponding position in the 2-dimensional block as follows: row index: r = floor(v / w); column index: c = mod(v,w), where w indicates a width of an LFNST subblock. In some examples, the second ordering is a raster scan ordering. In some examples, the second ordering is a column-first ordering. In some examples, the reorganized inverse transform coefficients are at a top-left corner of the 2-dimensional block.

[0280] Inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can decode the video data based on the second-ordered inverse transform coefficients (536). For example, inverse transform processing unit 212 of video encoder 200 or inverse transform processing unit 308 of video decoder 300 can apply an inverse separable transform, such as an inverse DCT-2 transform, to the second-ordered inverse transform coefficients.

[0281] Figure 22is a flowchart illustrating an exemplary method for encoding a current block. The current block can include a current CU. Although described with respect to video encoder 200 Figure 1 and Figure 3 ) it should be understood that other devices can be configured to perform methods similar to the method of Figure 22

[0282] In this example, video encoder 200 first predicts the current block (350). For example, video encoder 200 can form a prediction block for the current block. Video encoder 200 can then calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 can calculate a difference between an original, unencoded block of the current block and the prediction block. Video encoder 200 can then transform and quantize coefficients of the residual block (354). In some examples, transform processing unit 206 can reorder the primary transform coefficients according to the ordering. Transform processing unit 206 can also apply an LFNST to the reordered primary transform coefficients to create LFNST coefficients.

[0283] Next, video encoder 200 can scan the quantized transform coefficients of the residual block (356). During or after the scan, video encoder 200 can entropy encode the transform coefficients (358). For example, video encoder 200 can encode the transform coefficients using CAVLC or CABAC. Video encoder 200 can then output the entropy encoded data for the block (360).

[0284] Figure 23 is a flowchart illustrating an exemplary method for decoding a current block of video data. The current block can include a current CU. Although described with respect to video decoder 300 Figure 1 and Figure 4 ) it should be understood that other devices can be configured to perform methods similar to the method of Figure 23

[0285] Video decoder 300 can receive entropy encoded data for the current block, such as entropy encoded prediction information and entropy encoded data corresponding to coefficients of a residual block for the current block (370). Video decoder 300 can entropy decode the entropy encoded data to determine prediction information for the current block and to reproduce the coefficients of the residual block (372). Video decoder 300 can predict the current block (374), e.g., using intra- or inter-prediction as indicated by the prediction information for the current block, to calculate a prediction block for the current block. Video decoder 300 can then inverse scan the reproduced coefficients (376) to produce a block of quantized transform coefficients. Video decoder 300 can then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). When inverse transforming the coefficients to produce the residual block, video decoder 300 can perform Figure 21 ​​of the example. Video decoder 300 can finally decode the current block by combining the prediction block with the residual block (380).

[0286] According to the techniques of this disclosure, 8x8 LFNST can be simplified and coefficients can be reorganized to efficiently apply 8x8 LFNST. The 8x8 LFNST and reorganized coefficients of this disclosure can reduce the number of multiplications required and can also reduce memory requirements. In addition, the 8x8 LFNST and reorganized coefficients of this disclosure can provide coding gain compared to other LFNST designs without increasing complexity.

[0287] This disclosure includes the following examples.

[0288] Example 1. A method of coding video data, the method comprising: reorganizing a list of 2-dimensional dequantized coefficients according to a first ordering; applying an inverse low-frequency non-separable transform (LFNST) to the reorganized list of 2-dimensional dequantized coefficients to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates a number of basis vectors and indicates a number of rows, and N indicates a number of LFNST coefficients to be reconstructed after applying the inverse LFNST; reorganizing the inverse transform coefficients according to a second ordering; and coding the video data based on the second ordered inverse transform coefficients.

[0289] Example 2. The method of example 1, wherein the first ordering is a raster scan ordering or a column-first ordering.

[0290] Example 3. The method of example 1, wherein the first ordering is based on a block size or an intra mode.

[0291] Example 4. The method of any combination of examples 1-3, further comprising: determining which of the 2-dimensional dequantized coefficients are not zeroed out; and reorganizing only the 2-dimensional dequantized coefficients that are not zeroed out so that the inverse LFNST is applied only to the 2-dimensional dequantized coefficients that are not zeroed out.

[0292] Example 5. The method of any combination of examples 1-4, wherein entries in the MxN matrix comprise one or more of 8-bit precision, 9-bit precision, or 10-bit precision.

[0293] Example 6. The method of any combination of examples 1-5, further comprising multiplying one row in the MxN matrix by -1.

[0294] Example 7. The method of any combination of examples 1-6, further comprising multiplying multiple rows in the MxN matrix by -1.

[0295] Example 8. The method of any combination of examples 1-7, further comprising multiplying all rows in the MxN matrix by -1.

[0296] Example 9. The method of any combination of examples 1-8, wherein the second ordering is based on an array and wherein each value in the array corresponds to a position in the 2-dimensional block.

[0297] Example 10. The method of example 9, wherein the values in the array indicate indices of the 2-dimensional block in a defined order.

[0298] Example 11. The method of example 10, wherein the indices comprise index values and the index values point to positions in the 2-dimensional block.

[0299] Example 12. The method of example 11, wherein an index value v points to a corresponding position in the 2-dimensional block as follows: row index: r = floor(v / w); column index: c = mod(v,w), where w indicates a width of the LFNST sub-block.

[0300] Example 13. The method of example 12, wherein the second ordering is a raster scan ordering or a column-first ordering.

[0301] Example 14. The method of any of examples 1-13, wherein the coding comprises decoding.

[0302] Example 15. The method of any of examples 1-14, wherein the coding comprises encoding.

[0303] Example 16. A device for coding video data, the device comprising one or more means for performing the method of any of examples 1-15.

[0304] Example 17. The device of example 16, wherein the one or more means comprise one or more processors implemented in circuitry.

[0305] Example 18. The device of any of examples 16 and 17, further comprising a memory for storing video data.

[0306] Example 19. The device of any of examples 16-18, further comprising a display configured to display decoded video data.

[0307] Example 20. The device of any of examples 16-19, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0308] Example 21. The device of any of examples 16-20, wherein the device comprises a video decoder.

[0309] Example 22. The device of any of examples 16-21, wherein the device comprises a video encoder.

[0310] Example 23. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of examples 1-13.

[0311] It should be appreciated that, depending on the example, certain acts or events of any of the techniques described herein can be performed in a different sequence, can be added, modified or omitted (e.g., all described acts or events can not be necessary to practice the techniques), and the like. In some examples, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially.

[0312] In one or more examples, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer- readable media generally can correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product can include a computer-readable medium.

[0313] By way of example, and not limitation, such computer-readable storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0314] Instructions can 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 circuitry. Accordingly, the term "processor" as used herein can refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0315] The techniques of this disclosure can be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or IC package (e.g., a chip set), among others. Various components, modules, or units are described herein as being configured to perform a particular function or task. Unless otherwise specified, the particular function or task can be performed by one or more of the components, modules, or units. For example, various components, modules, or units can be configured to perform one or more functions or tasks described herein. Also, the description of various components, modules, or units herein as performing a particular function or task is intended to encompass one or more components, modules, or units configured to perform the particular function or task.

[0316] 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: The array of dequantized coefficients is reorganized by one or more processors according to a first sort, wherein the first sort comprises a 1-dimensional list; The inverse low-frequency inseparable transform (LFNST) is applied to the reconstructed dequantized coefficient array by one or more processors to create inverse transform coefficients, the inverse LFNST comprising an M x N matrix, where M indicates the number of basis vectors and the number of rows, and N indicates the number of LFNST coefficients reconstructed after applying the inverse LFNST; Based on the intra-frame mode and the number of LFNST coefficients reconstructed after applying the inverse LFNST, an array is selected from multiple arrays, where each array includes values, each value corresponding to a position in a 2D block and indicating the index of the 2D block in a defined order; The inverse transform coefficients are reorganized by the one or more processors according to a second sorting using a selected array; as well as The video data is decoded by the one or more processors based on the second sorted inverse transform coefficients to reconstruct the residuals in the 2D array.

2. The method according to claim 1, wherein the dequantization coefficient array is a two-dimensional dequantization coefficient.

3. The method according to claim 1, wherein the first sorting is raster scan sorting or column priority sorting.

4. The method according to claim 1, wherein, For each number of LFNST coefficients reconstructed after applying the inverse LFNST, the plurality of arrays include a first array configured to reconstruct the inverse transform coefficients according to raster scan sorting and a second array configured to reconstruct the inverse transform coefficients according to column priority sorting.

5. The method according to claim 1, wherein the recombined dequantization coefficient array comprises one of 25 dequantization coefficients, 36 dequantization coefficients, 48 ​​dequantization coefficients, or 64 dequantization coefficients.

6. The method according to claim 1, wherein the inverse transformation coefficients of the recombination are located at the upper left corner of the 2D block.

7. The method of claim 1, wherein the first sorting is based on block size or intra-frame mode.

8. The method according to claim 1, further comprising: The one or more processors determine which components of the dequantization coefficient array were not normalized to zero; as well as The one or more processors reorganize only the array of dequantized coefficients that have not been canonically zeroed, such that the first sorting includes only the array of dequantized coefficients that have not been canonically zeroed.

9. The method of claim 1, wherein the entries in the MxN LFNST transform matrix include one or more of 8-bit precision, 9-bit precision, or 10-bit precision.

10. The method of claim 1, further comprising multiplying one row of the MxN LFNST transformation matrix by -1 by the one or more processors.

11. The method of claim 1, further comprising multiplying all rows of the MxN LFNST transformation matrix by -1 by the one or more processors.

12. The method according to claim 1, wherein the index value v within the array of the plurality of arrays points to the corresponding position in the 2D block as follows: Row index: r = floor(v / w) Column index: c = mod(v, w) Where w indicates the width of the LFNST sub-block.

13. An apparatus for decoding video data, the apparatus comprising: A memory configured to store the video data; as well as One or more processors, implemented in a circuit and communicatively coupled to the memory, are configured to: Reorganize the dequantized coefficient array according to a first sort, wherein the first sort comprises a 1-dimensional list; The inverse low-frequency inseparable transform (LFNST) is applied to the reconstructed dequantized coefficient array to create inverse transform coefficients. The inverse LFNST comprises an M x N matrix, where M indicates the number of basis vectors and the number of rows, and N indicates the number of LFNST coefficients reconstructed after applying the inverse LFNST. Based on the intra-frame mode and the number of LFNST coefficients reconstructed after applying the inverse LFNST, an array is selected from multiple arrays, where each array includes values, each value corresponding to a position in a 2D block and indicating the index of the 2D block in a defined order; The inverse transform coefficients are reorganized according to a second sorting, which uses a selected array; as well as The video data is decoded based on the inverse transform coefficients after a second sort to reconstruct the residuals in the 2D array.

14. The device of claim 13, wherein the dequantization coefficient array is a two-dimensional dequantization coefficient.

15. The device of claim 13, wherein the first sorting is raster scan sorting or column priority sorting.

16. The device according to claim 13, wherein, For each number of LFNST coefficients reconstructed after applying the inverse LFNST, the plurality of arrays include a first array configured to reconstruct the inverse transform coefficients according to raster scan sorting and a second array configured to reconstruct the inverse transform coefficients according to column priority sorting.

17. The device of claim 13, wherein the recombined dequantization coefficient array comprises one of 25 dequantization coefficients, 36 dequantization coefficients, 48 ​​dequantization coefficients, or 64 dequantization coefficients.

18. The device of claim 13, wherein the inverse transformation coefficient of the recombination is located at the upper left corner of the 2D block.

19. The device of claim 13, wherein the first sorting is based on block size or intra-frame mode.

20. The device according to claim 13, further comprising: Determine which components of the dequantization coefficient array were not normalized to zero; as well as Only the array of dequantized coefficients that has not been normalized to zero is reorganized, such that the first sorting includes only the array of dequantized coefficients that has not been normalized to zero.

21. The device of claim 13, wherein the entries in the MxN LFNST transform matrix include one or more of 8-bit precision, 9-bit precision, or 10-bit precision.

22. The apparatus of claim 13 further comprises multiplying one row of the MxN LFNST transformation matrix by -1.

23. The apparatus of claim 13 further comprises multiplying all rows of the MxN LFNST transformation matrix by -1.

24. The device of claim 13, wherein the index value v within the array of the plurality of arrays points to the corresponding position in the 2D block as follows: Row index: r = floor(v / w) Column index: c = mod(v, w) Where w indicates the width of the LFNST sub-block.

25. A non-transitory computer-readable storage medium having instructions stored thereon, the instructions, when executed by one or more processors, causing the one or more processors to: Reorganize the dequantized coefficient array according to a first sort, wherein the first sort comprises a 1-dimensional list; The inverse low-frequency inseparable transform (LFNST) is applied to the reconstructed dequantized coefficient array to create inverse transform coefficients. The inverse LFNST comprises an M x N matrix, where M indicates the number of basis vectors and the number of rows, and N indicates the number of LFNST coefficients reconstructed after applying the inverse LFNST. Based on the intra-frame mode and the number of LFNST coefficients reconstructed after applying the inverse LFNST, an array is selected from multiple arrays, where each array includes values, each value corresponding to a position in a 2D block and indicating the index of the 2D block in a defined order; The inverse transform coefficients are reorganized according to a second sorting, which uses a selected array; as well as The video data is decoded based on the inverse transform coefficients after a second sort to reconstruct the residuals in the 2D array.

26. The non-transitory computer-readable storage medium of claim 25, wherein the array of dequantization coefficients is a two-dimensional dequantization coefficient array.

27. The non-transitory computer-readable storage medium of claim 25, wherein the first sorting is a raster scan sort or a column-first sort.

28. The non-transitory computer-readable storage medium according to claim 25, wherein, For each number of LFNST coefficients reconstructed after applying the inverse LFNST, the plurality of arrays include a first array configured to reconstruct the inverse transform coefficients according to raster scan sorting and a second array configured to reconstruct the inverse transform coefficients according to column priority sorting.

29. The non-transitory computer-readable storage medium of claim 25, wherein the recombined array of dequantization coefficients comprises one of 25 dequantization coefficients, 36 dequantization coefficients, 48 ​​dequantization coefficients, or 64 dequantization coefficients.

30. An apparatus for decoding video data, the apparatus comprising: A component for reorganizing the dequantized coefficient array according to a first sort, wherein the first sort comprises a 1-dimensional list; A component for applying the inverse low-frequency inseparable transform LFNST to the reconstructed dequantized coefficient array to create inverse transform coefficients, the inverse LFNST comprising an MxN matrix, where M indicates the number of basis vectors and the number of rows, and N indicates the number of LFNST coefficients reconstructed after applying the inverse LFNST. For the number of LFNST coefficients reconstructed based on the intra-frame mode and the inverse LFNST applied, a component of an array is selected from multiple arrays, wherein each array includes a value, each value corresponding to a position in a 2D block and indicating the index of the 2D block in a defined order; A component for reorganizing the inverse transform coefficients according to a second sorting using a selected array; as well as A component for decoding the video data based on the second sorted inverse transform coefficients to reconstruct the residuals in a 2D array.

31. The device according to claim 30, wherein the dequantization coefficient array is a two-dimensional dequantization coefficient.

32. A computer program product comprising computer-readable instructions that, when executed by a processor, cause the processor to perform the method according to any one of claims 1 to 12.

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