Bit depth of coefficients in adaptive loop filter in video decoding

Abstract

An apparatus for decoding encoded video data is configured to: determine blocks from the encoded video data; determine a bit depth for an adaptive loop filter from a plurality of available bit depths for the adaptive loop filter; determine coefficient values ​​for a set of filter coefficients for the adaptive loop filter based on the bit depth; apply the adaptive loop filter to the blocks to determine filtered blocks of video data; determine a decoded version of the video data blocks based on the filtered blocks of video data; and output a decoded picture of video data including the decoded versions of the video data blocks.

Description

[0001] This application claims priority to U.S. Patent Application No. 18 / 944,572, filed November 12, 2024, and U.S. Provisional Patent Application No. 63 / 599,358, filed November 15, 2023, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 18 / 944,572, filed November 12, 2024, claims the benefit of U.S. Provisional Patent Application No. 63 / 599,358, filed November 15, 2023. Technical Field

[0002] This disclosure relates to video encoding and video decoding. Background Technology

[0003] Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcasting systems, personal digital assistants (PDAs), laptops or desktop computers, tablets, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite wireless phones (so-called "smartphones"), video conferencing equipment, video streaming devices, and more. Digital video devices implement video decoding technologies, such as those defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 (Part 10, Advanced Video Decoding (AVC)), ITU-T H.265 / High Efficiency Video Decoding (HEVC), ITU-T H.266 / Variety Video Decoding (VVC) and extensions to these standards, as well as proprietary video codecs / formats such as AOMedia Video1 (AV1) developed by the Open Media Alliance. By implementing such video decoding technologies, video devices can more efficiently send, receive, encode, decode, and / or store digital video information.

[0004] Video decoding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video decoding, video slices (e.g., video pictures or portions of video pictures) can be divided into video blocks, which may also be referred to as decoding tree units (CTUs), decoding units (CUs), and / or decoding nodes. Video blocks in a slice after intra-frame decoding (I) of a picture are encoded using spatial prediction relative to reference samples in adjacent blocks within the same picture. Video blocks in a slice after inter-frame decoding (P or B) of a picture can use spatial prediction relative to reference samples in adjacent blocks within the same picture or temporal prediction relative to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005] The present disclosure relates generally to signaling filter coefficients used for adaptive loop filtering (ALF). As will be explained in more detail below, generally, a fixed bit depth (such as 8 bits) is used to signal the filter coefficients used for ALF. For example, the video decoder receives a syntax element (e.g., alf_chroma_coeff_abs hereinafter) indicating the absolute value of the coefficients at a fixed bit depth. Thus, if the bit depth is 8 bits, the syntax element uses 8 bits to represent the fractional part of the value, and the actual decimal value is equal to the signaled value divided by 2^(bit depth - 1). The video decoder also receives a syntax element (e.g., alf_chroma_coeff_sign hereinafter) indicating the sign (negative or positive) of the coefficients. When the filter is applied, the video decoder then determines the value of the coefficient as the absolute value multiplied by the sign (1 or -1) and divided by 2^(bit depth - 1). Therefore, the filter coefficient 0.5 is signaled as an 8-bit absolute value 01000000, which is equal to 64, and 64 is signaled in the bit stream, which is equal to 64 / 128 when divided by 2^(8-1), i.e., 0.5.

[0006] Generally, using a larger bit depth for filter coefficients allows for a greater number of possible values, which improves filtering quality. However, a larger bit depth also increases the signaling overhead of the filter coefficients. In contrast, using a smaller bit depth reduces this overhead. For example, for a filter coefficient of 0.5, if a bit depth of 6 is used, the value 0.5 will be signaled in the bit stream. (2^(6-1)) = 16, which is smaller than 64 and uses fewer bits. However, some values ​​that can be obtained using 8 bits cannot be obtained using only 6 bits.

[0007] This disclosure introduces an ALF with adaptive (i.e., non-fixed) bit depth coefficients. By determining the bit depth for the ALF from a plurality of available bit depths and determining the coefficient values ​​of a set of filter coefficients for the ALF based on the bit depth, a video decoder configured according to the techniques of this disclosure can reduce the signaling burden associated with the ALF for decoding scenarios where sufficient filtering is achieved with a smaller number of possible coefficient values, while maintaining the ability to use a larger bit depth for decoding scenarios where a larger number of possible coefficient values ​​are desired. Therefore, the techniques of this disclosure can improve the rate-distortion tradeoff in some video decoding scenarios and provide greater flexibility for video encoders and decoders to achieve the desired bit rate.

[0008] According to an example of this disclosure, a method for decoding encoded video data includes: determining a block from the encoded video data; determining a bit depth for an adaptive loop filter from a plurality of available bit depths for the adaptive loop filter; determining coefficient values ​​of a set of filter coefficients for the adaptive loop filter based on the bit depth; applying the adaptive loop filter to the block to determine a filtered block of video data; determining a decoded version of the block of video data based on the filtered block of video data; and outputting a decoded picture of video data including the decoded version of the block of video data.

[0009] According to an example of this disclosure, an apparatus for decoding encoded video data includes: a memory; and one or more processors implemented in a circuit, coupled to the memory, and configured to: determine a block from the encoded video data; determine a bit depth for an adaptive loop filter from a plurality of available bit depths for the adaptive loop filter; determine coefficient values ​​of a set of filter coefficients for the adaptive loop filter based on the bit depth; apply the adaptive loop filter to the block to determine a filtered block of video data; determine a decoded version of the block of video data based on the filtered block of video data; and output a decoded picture of video data including the decoded version of the block of video data.

[0010] According to an example of this disclosure, a method for encoding video data includes: determining coefficient values ​​for a set of one or more filters for encoding a block group of video data, wherein the set of filters is used for an adaptive loop filtering process; determining a bit depth for signaling the coefficient values; and outputting encoded video data, wherein the encoded video data includes an indication of the bit depth.

[0011] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the description, drawings, and claims. Attached Figure Description

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

[0013] Figure 2 This is a block diagram illustrating an example video encoder that can perform the techniques of this disclosure.

[0014] Figure 3 This is a block diagram illustrating an example video decoder that can perform the techniques of this disclosure.

[0015] Figure 4 This is a flowchart illustrating an example process for encoding the current block according to the technology of this disclosure.

[0016] Figure 5 This is a flowchart illustrating an example process for decoding the current block according to the technology of this disclosure.

[0017] Figure 6 This is a flowchart illustrating an example process for encoding the current block according to the technology of this disclosure.

[0018] Figure 7 This is a flowchart illustrating an example process for decoding the current block according to the technology of this disclosure. Detailed Implementation

[0019] Video decoding (e.g., video encoding and / or video decoding) typically involves predicting video data blocks based on decoded video data blocks within the same frame (e.g., intra-frame prediction) or based on decoded video data blocks in different frames (e.g., inter-frame prediction). In some cases, the video encoder also computes residual data by comparing the predicted block with the original block. Therefore, the residual data represents the difference between the predicted block and the original block. To reduce the number of bits required to signal the residual data, the video encoder transforms and quantizes the residual data, and signals the transformed and quantized residual data in the encoded bitstream. Compression achieved through the transform and quantization process can be lossy, meaning that the transform and quantization process may introduce distortion into the decoded video data.

[0020] The video decoder decodes the residual data and adds it to the predicted blocks to produce a reconstructed video block that more closely matches the original video block compared to individual predicted blocks. Due to losses introduced by the transformation and quantization of the residual data, the first reconstructed block may have distortion or artifacts. A common type of artifact or distortion is called block artifacts, where the boundaries of the blocks used to decode the video data are visible.

[0021] To further improve the quality of the decoded video, the video decoder can perform one or more filtering operations on the reconstructed video blocks. Examples of these filtering operations include deblocking filtering, Sample Adaptive Offset (SAO) filtering, and Adaptive Loop Filtering (ALF). The parameters of these filtering operations can be determined by the video encoder and explicitly signaled in the encoded video bitstream, or they can be implicitly determined by the video decoder without needing to be explicitly signaled in the encoded video bitstream.

[0022] The present disclosure relates generally to signaling filter coefficients used in an ALF. As will be explained in more detail below, filter coefficients in an ALF are generally signaled using a fixed bit depth (such as 8). For example, a video decoder receives a syntax element (e.g., alf_chroma_coeff_abs hereinafter) indicating the absolute value of the coefficients at a fixed bit depth. Thus, if the bit depth is 8, the syntax element uses 8 bits to represent the fractional part of the value, and the actual decimal value is equal to the signaled value divided by 2^(bit depth - 1). The video decoder also receives a syntax element (e.g., alf_chroma_coeff_sign hereinafter) indicating the sign (negative or positive) of the coefficients. When a filter is applied, the video decoder then determines the value of the coefficient as the absolute value multiplied by the sign (1 or -1) and divided by 2^(bit depth - 1). Therefore, the filter coefficient 0.5 is signaled as an 8-bit absolute value 01000000, which is equal to 64, and 64 is signaled in the bit stream, which is equal to 64 / 128 when divided by 2^(8-1), i.e., 0.5.

[0023] Generally, using a larger bit depth for filter coefficients allows for a greater number of possible values, which improves filtering quality. However, a larger bit depth also increases the signaling overhead of the filter coefficients. In contrast, using a smaller bit depth reduces this overhead. For example, for a filter coefficient of 0.5, if a bit depth of 6 is used, the value 0.5 will be signaled in the bit stream. (2^(6-1)) = 16, which is smaller than 64 and uses fewer bits. However, some values ​​that can be obtained using 8 bits cannot be obtained using only 6 bits.

[0024] This disclosure introduces an ALF with adaptive (i.e., non-fixed) bit depth coefficients. By determining the bit depth for the ALF from a plurality of available bit depths and determining the coefficient values ​​of a set of filter coefficients for the ALF based on the bit depth, a video decoder configured according to the techniques of this disclosure can reduce the signaling burden associated with the ALF for decoding scenarios where sufficient filtering is achieved with a smaller number of possible coefficient values, while maintaining the ability to use a larger bit depth for decoding scenarios where a larger number of possible coefficient values ​​are desired. Therefore, the techniques of this disclosure can improve the rate-distortion tradeoff in some video decoding scenarios and provide greater flexibility for video encoders and decoders to achieve the desired bit rate.

[0025] Figure 1This is a block diagram illustrating an example video encoding and decoding system 100 capable of performing the techniques of this disclosure. The techniques of this disclosure generally involve decoding (encoding and / or decoding) video data. Typically, video data includes any data used for processing video. Thus, video data may include unencoded raw video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0026] like Figure 1 As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 can be or may include any of a wide range of devices, such as desktop computers, laptop computers, mobile devices, tablet computers, set-top boxes, mobile phones (such as smartphones), televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 may be configured for wireless communication and are therefore referred to as wireless communication devices.

[0027] exist Figure 1 In the example, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, video decoder 300, memory 120, and display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply techniques for ALF and to signal ALF coefficients. 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, the source device and destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may interface with an external display device, rather than including an integrated display device.

[0028] like Figure 1The system 100 shown is merely an example. Typically, any digital video encoding and / or decoding device can perform the techniques described herein for ALF and for signaling ALF coefficients. Source device 102 and destination device 116 are merely examples of such decoding devices, where source device 102 generates decoded video data for transmission to destination device 116. This disclosure refers to a “decoding” device as a device that performs the decoding (e.g., encoding and / or decoding) of data. Thus, video encoder 200 and video decoder 300 represent examples of decoding devices, specifically, a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 may operate in a substantially symmetrical manner, such that each of source device 102 and destination device 116 includes video encoding and decoding components. Therefore, system 100 may support one-way or two-way video transmission between source device 102 and destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0029] Typically, video source 104 represents the source of video data (i.e., unencoded raw video data) and provides a sequential series of pictures (also referred to as "frames") of the video data to video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include video capture devices such as cameras, video archives containing previously captured raw video, and / or video feed interfaces for receiving video from video content providers. Alternatively, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from the received order (sometimes referred to as "display order") to a decoding order for decoding. Video encoder 200 may generate a bitstream including encoded video data. Then, the source device 102 can output encoded video data to a computer-readable medium 110 via the output interface 108 for reception and / or retrieval by, for example, the input interface 122 of the destination device 116.

[0030] The memory 106 of source device 102 and the memory 120 of destination device 116 represent general-purpose memory. In some examples, memories 106 and 120 may store raw video data, such as raw video from video source 104 and raw decoded video data from video decoder 300. Additionally or alternatively, memories 106 and 120 may store software instructions executable by, for example, video encoder 200 and video decoder 300. Although memories 106 and 120 are shown separately from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Furthermore, memories 106 and 120 may store encoded video data, such as output from video encoder 200 and input to video decoder 300. In some examples, portions of memories 106 and 120 may be allocated as one or more video buffers, for example, to store raw decoded and / or encoded video data.

[0031] Computer-readable medium 110 may represent any type of medium or device capable of transmitting encoded video data from source device 102 to destination device 116. In one example, computer-readable medium 110 represents a communication medium that enables source device 102 to directly transmit encoded video data to destination device 116 in real time, for example, via a radio frequency network or a computer-based network. According to a communication standard such as a wireless communication protocol, output interface 108 may modulate the transmitted signal including the encoded video data, and input interface 122 may demodulate the received transmitted signal. The communication medium may include any wireless or wired communication medium, such as radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network such as a local area network, a wide area network, or a global network (such as the Internet). The communication medium may include a router, switch, base station, or any other equipment that may be useful for facilitating communication from source device 102 to destination device 116.

[0032] 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 may include any data storage medium of various distributed or locally accessed data storage media, such as hard disk drives, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0033] In some examples, source device 102 can output encoded video data to file server 114 or another intermediate storage device that can store the encoded video data generated by source device 102. Destination device 116 can access the stored video data from file server 114 via streaming or downloading.

[0034] File server 114 can be any type of server device capable of storing encoded video data and sending the encoded video data to destination device 116. File server 114 may represent a web server (e.g., for a website), a server configured to provide file transfer protocol services (such as File Transfer Protocol (FTP) or FLUTE-based file delivery protocol), a Content Delivery Network (CDN) device, a Hypertext Transfer Protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and / or a Network Attached Storage (NAS) device. File server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as HTTP-based Dynamic Adaptive Streaming (DASH), HTTP Live Streaming (HLS), Real-Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0035] Destination device 116 can access encoded video data from file server 114 via any standard data connection, including an internet connection. This may include a wireless channel (e.g., Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), cable modem, etc.), or a combination of both, suitable for accessing encoded video data stored on file server 114. Input interface 122 can be configured to operate according to any or more of the various protocols discussed above for retrieving or receiving media data from file server 114, or other such protocols for retrieving media data.

[0036] Output interface 108 and input interface 122 can represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 can be configured to transmit data such as encoded video data according to cellular communication standards such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 can be configured to comply with other wireless standards such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee), etc. ™),Bluetooth ™ Standards are used to transmit data such as encoded video data. In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include an SoC device for performing functions belonging to video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device for performing functions belonging to video decoder 300 and / or input interface 122.

[0037] The technology disclosed herein can be applied to video decoding to support any multimedia application in a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission (such as HTTP-based Dynamic Adaptive Streaming (DASH)), digital video encoded onto data storage media, decoding of digital video stored on data storage media, or other applications.

[0038] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, storage device 112, file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements having values ​​describing the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays a decoded picture of the decoded video data to the user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0039] Despite Figure 1Not shown, but in some examples, both the video encoder 200 and the video decoder 300 may be integrated with the audio encoder and / or audio decoder (e.g., audio codec), and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams that include both audio and video in a common data stream. Example audio codecs may include AAC, AC-3, AC-4, ALAC, ALS, AMBE, AMR, AMR-WB (G.722.2), AMR-WB+, aptX (various versions), ATRAC, BroadVoice (BV16, BV32), CELT, Enhanced AC-3 (E-AC-3), EVS, FLAC, G.711, G.722, G.722.1, G.722.2 (AMR-WB), G.723.1, G.726, G.728, G.729, G.729.1, GSM-FR, HE-AAC, iLBC, iSAC, LA Lyra, Monkey's Audio, MP1, MP2 (MPEG-1, 2 Audio Layer II), MP3, Musepack, Nellymoser Asao, OptimFROG, Opus, Sac, Satin, SBC, SILK, Siren 7, Speex, SVOPC, True Audio (TTA), TwinVQ, USAC, Vorbis (Ogg), WavPack and Windows Media Aud.

[0040] Both the video encoder 200 and the video decoder 300 can be implemented as any of a variety of suitable encoder and / or decoder circuits comprising a processing system, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is implemented in part in software, the device may 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 technology of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder / decoder (CODEC) in the respective device. Devices including the video encoder 200 and / or the video decoder 300 may implement the video encoder 200 and / or the video decoder 300 in processing circuitry such as integrated circuits and / or microprocessors. Such devices may be wireless communication devices (such as cellular phones) or any other type of device described herein.

[0041] The video encoder 200 and video decoder 300 may operate according to a video decoding standard such as ITU-T H.265 (also known as High Efficiency Video Decoding (HEVC)) or extensions thereof such as MultiView and / or Scalable Video Decoding Extensions. Alternatively, the video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards such as ITU-T H.266 (also known as Multi-Functional Video Decoding (VVC)). In other examples, the video encoder 200 and video decoder 300 may operate according to proprietary video codecs / formats such as AOMedia Video 1 (AV1), extensions to AV1, and / or subsequent versions of AV1 (e.g., AV2)). In other examples, the video encoder 200 and video decoder 300 may operate according to other proprietary formats or industry standards. However, the techniques disclosed herein are not limited to any particular decoding standard or format. In general, the video encoder 200 and video decoder 300 may be configured to perform the techniques of this disclosure in conjunction with any video decoding technology using ALF.

[0042] Typically, video encoder 200 and video decoder 300 perform block-based decoding of images. The term "block" generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used during encoding and / or decoding). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, video encoder 200 and video decoder 300 decode video data represented in YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding the red, green, and blue (RGB) data used for images, video encoder 200 and video decoder 300 decode the luminance and chrominance components, where the chrominance components may include both red hue chrominance components and blue hue chrominance components. In some examples, video encoder 200 converts the received RGB format data to a YUV representation before encoding, and video decoder 300 converts the YUV representation to RGB format. Alternatively, preprocessing and postprocessing units (not shown) may perform these conversions.

[0043] This disclosure generally relates to the decoding (e.g., encoding and decoding) of images to include processes of encoding or decoding data of the image. Similarly, this disclosure may relate to the decoding of blocks of images to include processes of encoding or decoding data used for the blocks (e.g., prediction and / or residual decoding). Encoded video bitstreams typically include a series of values ​​for syntax elements representing decoding decisions (e.g., decoding modes) and the partitioning of images into blocks. Therefore, references to the decoding of an image or block should generally be understood as the decoded values ​​of the syntax elements that form the image or block.

[0044] HEVC defines various blocks, including decoding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as a video encoder 200) divides the decoding tree unit (CTU) into CUs based on a quadtree structure. That is, the video decoder divides the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. Nodes without child nodes are called "leaf nodes," and the CU of such leaf nodes may include one or more PUs and / or one or more TUs. The video decoder may further divide the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of the TU. In HEVC, the PU represents inter-frame prediction data, while the TU represents residual data. The CU after intra-frame prediction includes intra-frame prediction information, such as intra-frame mode indication.

[0045] As another example, video encoder 200 and video decoder 300 can be configured to operate according to VVC. According to VVC, the video decoder (such as video encoder 200) partitions the image into multiple CTUs. Video encoder 200 can partition the CTUs according to a tree structure (such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels: a first level partitioned according to a quadtree and a second level partitioned according to a binary tree. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to CUs.

[0046] In the MTT partitioning structure, blocks can be divided using quadtree (QT) partitioning, binary tree (BT) partitioning, and one or more types of ternary tree (TT) partitioning (also known as triplet tree (TT)). A ternary tree or triplet tree partition is a partition in which a block is divided into three sub-blocks. In some examples, a ternary tree or triplet tree partition divides a block into three sub-blocks without dividing the original block through the center. Partition types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0047] When operating according to the AV1 codec, the video encoder 200 and video decoder 300 can be configured to decode video data in blocks. In AV1, the largest decoded block that can be processed is called a superblock. In AV1, a superblock can be 128x128 luma samples or 64x64 luma samples. However, in subsequent video decoding formats (e.g., AV2), superblocks can be defined by different (e.g., larger) luma sample sizes. In some examples, the superblock is the top level of a block quadtree. The video encoder 200 can further divide the superblock into smaller decoded blocks. The video encoder 200 can use square or non-square partitions to divide the superblock and other decoded blocks into smaller blocks. Non-square blocks can include N / 2xN blocks, NxN / 2 blocks, N / 4xN blocks, and NxN / 4 blocks. The video encoder 200 and video decoder 300 can perform separate prediction and transform processing for each decoded block.

[0048] AV1 also defines video data tiles. A tile is a rectangular array of superblocks that can be decoded independently of other tiles. That is, the video encoder 200 and video decoder 300 can encode and decode the decoding blocks within a tile separately without using video data from other tiles. However, the video encoder 200 and video decoder 300 can perform filtering across tile boundaries. The tile size can be uniform or non-uniform. Tile-based decoding enables parallel processing and / or multithreading in the encoder and decoder implementations.

[0049] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma and chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the respective chroma components).

[0050] The video encoder 200 and the video decoder 300 can be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, superblock partitioning or other partitioning structures.

[0051] In some examples, a CTU includes a decoded tree block (CTB) of luminance samples, two corresponding CTBs of chrominance samples of an image with three sample arrays, or a CTB of samples of an image decoded using three separate color planes and a syntax structure for decoding the samples. A CTB can be an NxN sample block of some value N, such that a partitioning method divides the components into CTBs. A component is an array or a single sample from one of the three arrays (luminance and two chrominance) constituting a 4:2:0, 4:2:2, or 4:4:4 color format image, or an array or a single sample constituting an array or array constituting a monochrome format image. In some examples, a decoded block is an MxN sample block of values ​​M and N, such that a partitioning method divides the CTB into decoded blocks.

[0052] Blocks (e.g., CTUs or CUs) can be grouped in various ways within an image. As an example, a brick can refer to a rectangular area of ​​a row of CTUs within a specific tile in an image. A tile can be a rectangular area of ​​CTUs within a specific tile column and a specific tile row in an image. A tile column refers to a rectangular area of ​​a CTU having a height equal to the height of the image and a width specified by syntax elements (e.g., such as in an image parameter set). A tile row refers to a rectangular area of ​​a CTU having a height specified by syntax elements (e.g., such as in an image parameter set) and a width equal to the width of the image.

[0053] In some examples, a tile can be divided into multiple bricks, each brick comprising one or more CTU rows within the tile. A tile that is not divided into multiple bricks can also be called a brick. However, bricks that are a true subset of a tile cannot be called a tile. Bricks in an image can also be arranged in slices. A slice can be an integer number of bricks in an image that can be uniquely contained within a single Network Abstraction Layer (NAL) unit. In some examples, a slice comprises multiple complete tiles or a consecutive sequence of complete bricks comprising only one tile.

[0054] This disclosure uses "NxN" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in the vertical and horizontal dimensions, for example, 16x16 samples or 16 by 16 samples. Generally, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxNCU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU can be arranged in rows and columns. Furthermore, a CU does not necessarily need to have the same number of samples in the horizontal direction as it does in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0055] The video encoder 200 encodes video data for use in predicting and / or residual information, as well as other information, for the CU. The prediction information indicates how the CU should be predicted to form a prediction block of the CU. The residual information typically represents the sample-by-sample difference between a sample of the CU before encoding and the prediction block.

[0056] To predict a CU, the video encoder 200 typically forms a predicted block of the CU through inter-frame prediction or intra-frame prediction. Inter-frame prediction typically refers to predicting the CU from data in a previously decoded image, while intra-frame prediction typically refers to predicting the CU from data in a previously decoded image within the same frame. To perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate the predicted block. The video encoder 200 can typically perform a motion search to identify a reference block that closely matches the CU, for example, based on the differences between the CU and a reference block. The video encoder 200 can use sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculations to compute a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional or bidirectional prediction to predict the current CU.

[0057] Some examples of VVC also provide an affine motion compensation mode, which can be viewed as an inter-frame prediction mode. In affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion, such as zooming in or out, rotation, perspective motion, or other irregular motion types.

[0058] To perform intra-frame prediction, the video encoder 200 can select an intra-frame prediction mode to generate prediction blocks. Some examples of VVC provide sixty-seven intra-frame prediction modes, including various directional modes, as well as planar and DC modes. Typically, the video encoder 200 selects an intra-frame prediction mode that describes the neighboring samples of the current block (e.g., the block of the CU), from which it predicts samples for the current block. Assuming the video encoder 200 decodes the CTU and CU in raster scan order (from left to right, from top to bottom), such samples are typically located above, to the upper left, or to the left of the current block within the same frame as the current block.

[0059] The video encoder 200 encodes data representing the prediction mode of the current block. For example, for inter-frame prediction modes, the video encoder 200 may encode data indicating which of the various available inter-frame prediction modes is used, as well as the motion information for the corresponding mode. For example, for unidirectional or bidirectional inter-frame prediction, the video encoder 200 may encode motion vectors using Advanced Motion Vector Prediction (AMVP) or merging modes. The video encoder 200 may use similar modes to encode motion vectors used for affine motion compensation modes.

[0060] AV1 includes two common techniques for encoding and decoding blocks of video data. These two common techniques are intra-frame prediction (e.g., intra-frame prediction or spatial prediction) and inter-frame prediction (e.g., inter-frame prediction or temporal prediction). In the context of AV1, when using intra-frame prediction modes to predict blocks of video data for the current frame, the video encoder 200 and video decoder 300 do not use video data from other frames of the video data. For most intra-frame prediction modes, the video encoder 200 encodes blocks of the current frame based on the difference between sample values ​​in the current block and predicted values ​​generated from reference samples in the same frame. The video encoder 200 determines the predicted values ​​generated from the reference samples based on the intra-frame prediction mode.

[0061] After prediction (such as intra-frame or inter-frame prediction for a block), the video encoder 200 can compute residual data for the block. The residual data (such as residual blocks) represents the sample-wise difference between predicted blocks formed using the corresponding prediction mode. The video encoder 200 can apply one or more transforms to the residual blocks to produce transformed data in the transform domain rather than the sample domain. For example, the video encoder 200 can apply Discrete Cosine Transform (DCT), integer transform, wavelet transform, or conceptually similar transforms to the residual video data. Additionally, the video encoder 200 can apply a second transform after the first transform, such as Mode Correlated Inseparable Second Transform (MDNSST), Signal Correlation Transform, Karhunen-Loeve Transform (KLT), etc. The video encoder 200 produces transform coefficients after applying one or more transforms.

[0062] As noted above, after any transform that produces the transform coefficients, the video encoder 200 may perform quantization on the transform coefficients. Quantization generally refers to a process in which the transform coefficients are quantized to reduce the amount of data used to represent them, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may round an n-bit value down to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift on the value to be quantized.

[0063] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix containing the quantized transform coefficients. The scan can be designed to place higher-energy (and therefore lower-frequency) transform coefficients before the vector and lower-energy (and therefore higher-frequency) transform coefficients after the vector. In some examples, the video encoder 200 can utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy-encode the quantized transform coefficients of that vector. In other examples, the video encoder 200 can perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy-encode the one-dimensional vector, for example, according to context-adaptive binary arithmetic decoding (CABAC). The video encoder 200 can also entropy-encode the values ​​of syntax elements describing metadata associated with the encoded video data, which is used by the video decoder 300 when decoding the video data.

[0064] To perform CABAC, the video encoder 200 can assign context within a context model to the symbols to be transmitted. Context may involve, for example, whether the neighboring values ​​of a symbol are zero. Probability determination can be based on the context assigned to the symbols.

[0065] The video encoder 200 may further generate syntax data for the video decoder 300, such as block-based syntax data, image-based syntax data, and sequence-based syntax data, for example, in image headers, block headers, and slice headers, or generate other syntax data such as sequence parameter sets (SPS), image parameter sets (PPS), or video parameter sets (VPS). The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

[0066] In this way, the video encoder 200 can generate a bitstream that includes encoded video data, such as syntax elements describing the partitioning of images into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0067] Typically, the video decoder 300 performs the reverse process of the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 can use CABAC to decode the values ​​of syntax elements used for the bitstream in a manner substantially similar to but reversed by the CABAC encoding process of the video encoder 200. Syntax elements can define partitioning information for dividing a picture into CTUs and defining the CUs of each CTU according to a corresponding partitioning structure such as a QTBT structure. Syntax elements can further define prediction and residual information for video data blocks (e.g., CUs).

[0068] The residual information can be represented, for example, by quantized transform coefficients. The video decoder 300 can inversely quantize and inverse transform the quantized transform coefficients of the block to reconstruct the residual block for the block. The video decoder 300 uses a signaling prediction mode (intra-frame prediction or inter-frame prediction) and associated prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 can then combine the prediction block and the residual block (on a sample-by-sample basis) to reconstruct the original block. The video decoder 300 can perform additional processing, such as performing a deblocking process to reduce visual artifacts along the block boundaries.

[0069] This disclosure may generally relate to "signaling" certain information (such as syntax elements). The term "signaling" can generally refer to the communication of values ​​and / or other data of syntax elements used to decode encoded video data. That is, video encoder 200 may signal the values ​​of syntax elements in the bitstream. Generally, signaling refers to generating values ​​in the bitstream. As noted above, source device 102 may transmit the bitstream to destination device 116 substantially in real time or not in real time (such as when syntax elements are stored in storage device 112 for later retrieval by destination device 116).

[0070] In a typical video encoder (such as Video Encoder 200), frames of the original video sequence are divided into rectangular regions or blocks encoded in intra-frame mode (I-mode) or inter-frame mode. These blocks are then decoded using some form of transform decoding (such as DCT decoding). However, purely transform-based decoding only reduces inter-pixel correlation within a specific block, without considering inter-block correlation, and still produces a high bit rate for transmission. Current digital image decoding standards also utilize certain processes to reduce the correlation of pixel values ​​between blocks.

[0071] Generally, blocks encoded in inter-frame mode are predicted based on several previously decoded and transmitted frames. The prediction information for a block can be represented, for example, by two-dimensional (2D) motion vectors. For blocks encoded in I-mode, spatial prediction is used to form the predicted block from adjacent blocks encoded within the same frame. The prediction error (e.g., the difference between the encoded block and the predicted block) is represented as a set of weighted basis functions of a discrete transform. Typically, this transform is performed on a block-by-block basis. The weights (e.g., transform coefficients) are then quantized. Quantization can introduce information loss, and therefore, the quantized transform coefficients generally have lower precision than the original coefficients.

[0072] The quantized transform coefficients, along with the motion vector and some control information, form a complete decoded sequence representation, known as a syntax element. Before being sent from the encoder to the decoder, the syntax element can undergo entropy decoding to further reduce the number of bits required for its representation.

[0073] At the decoder (such as video decoder 300), the blocks in the current frame are obtained by first constructing its predictions in the same way as in the encoder and then adding the compressed prediction errors (e.g., residual blocks) to the predictions (e.g., prediction blocks). The compressed prediction errors are found by weighting the transform basis functions using quantized coefficients. The difference between the reconstructed frame and the original frame is called the reconstruction error.

[0074] In video decoding, filtering is commonly used to enhance the quality of the decoded video signal. Filters can be used as post-filters (where the filtered frame is not used to predict future frames) or as in-loop filters (where the filtered frame is used to predict future frames). For example, a filter can be designed to minimize the error between the original signal and the decoded filtered signal. Similar to transform coefficients, filter coefficients... Quantified:

[0075]

[0076] The quantized coefficients are decoded and transmitted to the decoder. Usually equals . Larger values ​​typically correspond to more precise quantization and quantized filter coefficients that offer better performance. .on the other hand, Larger values ​​of this coefficient also result in a coefficient that requires more bits to be sent. .

[0077] At the decoder, the decoding filter coefficients Applied to reconstructing images ,as follows:

[0078]

[0079] in and These are the coordinates of pixels within the frame. Filter coefficients can also be applied to the samples to be filtered. Difference between its neighboring samples :

[0080]

[0081] In this example, the sample This is achieved by adding the sums obtained to the reconstructed sample. And thus obtained. For example, the difference can be modified by applying clipping. .

[0082] M. Karczewicz et al., in their paper "In-Loop Filters in VVC" (IEEE Transactions on Circuits and Systems, Vol. 31, No. 10, pp. 3907-3925, October 2021), describe a block-based adaptive ALF in VVC, which can be considered a state-of-the-art in-loop filter. Sub-block or pixel-level filter adaptation is applied. Blocks are based on their directionality and activity The quantized values ​​are divided into one category of 25 categories:

[0083] .

[0084] Each category can have an assigned filter.

[0085] A Laplacian operator-based classifier is used to derive categories from samples in the target block. A window covering the target block is used to classify the target block. Activity and directionality are derived using the values ​​of the horizontal gradient, vertical gradient, and two diagonal gradients calculated using the 1-D Laplacian operator:

[0086]

[0087] The sum of the horizontal, vertical, and two diagonal gradients within the window are respectively expressed as: , , and Directionality It is determined by comparing the following with a set of thresholds.

[0088]

[0089] Activity Through calculation and The sum is derived by comparing it with this set of thresholds.

[0090] Before filtering, geometric transformations, such as rotation, diagonalization, and vertical flipping, can be applied to pixels in the filter support region (pixels multiplied by the filtered coefficients) based on the direction of the gradient of the filtered pixels. These transformations increase the similarity between different regions within the image, such as their orientation. This reduces the number of filters that must be sent to the decoder, thereby reducing the number of bits required to represent the filters and / or reducing reconstruction errors. Applying transformations to the filter support region is equivalent to applying these transformations directly to the filter coefficients.

[0091] To support filtering across all categories, filters for all categories are signaled within a single filter bank. To reduce the number of bits required to represent filter coefficients, different categories can be combined. This is achieved by transmitting an index for each of the 25 categories. This provides information about which categories are being merged. (Categories with the same index) The categories share the same filters. Therefore, in this example, a filter bank includes a maximum of 25 filters, where 25 is the number of categories.

[0092] In VVC version 1, ALF coefficients are signaled in the ALF Adaptive Parameter Set (APS). An APS can contain a set of luma filters with up to 25 filters, up to 8 chroma filters, and up to 8 cross-component ALF (CC-ALF) filters. Each luma filter set supports applying ALF to 25 luma classes. VVC version 1 supports up to 8 ALF_APS. Each coefficient is represented by a fixed-point number, and the fractional part is represented using 8 bits. In one example, if the coefficient is 1, the numerator value 128 is sent in the bitstream, such that for a bit depth of 8 bits, 1 = 128 / 2^(bit depth - 1).

[0093]

[0094]

[0095]

[0096] The ALF coefficients of the reference image are stored and can be reused as the ALF coefficients of the current image. For the current image, the video decoder can optionally use the ALF coefficients stored for the reference image and bypass ALF coefficient signaling. In this case, only the index of one reference image is signaled, and for the current image, the stored ALF coefficients of the indicated reference image are simply inherited. In ECM, to filter samples, ALF filters are applied to several types of sample values, such as the ALF input sample values ​​of the current sample and neighboring samples, the fixed filter result of the current sample and neighboring samples, the Gaussian filter result of the current sample and neighboring samples, the reconstruction residual values ​​of the current sample and neighboring samples, and the deblocking filter input sample values ​​of the current sample and neighboring samples. For each type of sample value, a filter shape is applied, and the center coefficients are applied to that type of sample value of the current sample.

[0097] According to the techniques of this disclosure, the bit depth (e.g., the number of bits used to represent the denominator portion of a coefficient) can be adaptive. In some examples, the video encoder 200 may signal the bit depth of each coefficient to the video decoder 300. In some examples, the video encoder 200 may signal the bit depth of each filter to the video decoder 300, such that the signaled bit depth is applied to all coefficients in that filter. In some examples, the video encoder 200 may signal the bit depth of a filter group to the video decoder 300, such that the signaled bit depth is applied to all coefficients in all filters of that filter group. In some examples, for a filter group, the video encoder 200 may signal the first bit depth of a first filter group to the video decoder 300, such that the first signaled bit depth is applied to all coefficients in those filters of the first group. The video encoder 200 may signal the second bit depth of a second filter group to the video decoder, such that the second signaled bit depth is applied to all coefficients in those filters of the second group.

[0098] In some examples, the video encoder 200 may signal the bit depth of each color component to the video decoder 300, such that the signaled bit depth is applied to the coefficients in a filter that is applied to that color component.

[0099] In some examples, the video encoder 200 may signal the bit depth of each APS to the video decoder 300, such that the signaled bit depth is applied to coefficients in a filter within the APS. In some examples, the video encoder 200 may signal the bit depth of a picture sequence or group, or picture, or slice, or block group, or block, or sub-block level to the video decoder 300, such that the signaled bit depth is applied to coefficients in a filter applied to that picture sequence or group, picture, or slice, or block group, or block, or sub-block level.

[0100] To signal the bit depth, the video encoder 200 can signal indices to the video decoder 300, where each index is mapped to a bit depth. In another example, the video encoder 200 can signal offsets to the video decoder 300, such that the bit depth can be derived by adding the offsets to the base bit depth.

[0101] In some examples, the bit depth may depend on whether a non-linear (clipping) ALF is applied. In some examples, the bit depth can be inferred from the clipping flag.

[0102] The coefficients in a filter can be divided into several groups, and the bit depth can be signaled and / or applied to the coefficients in each group. The bit depth of the coefficients can depend on the position of the coefficients in the filter shape. For example, the video encoder 200 can signal the bit depth of coefficients located at the center of each filter shape (center coefficients are applied to intermediate results of the current sample, such as the fixed filter result of the current sample, the Gaussian filter result of the current sample, the deblocking filter input sample value of the current sample, or the reconstruction residual value of the current sample) to the video decoder 300. The video encoder 200 can signal another bit depth of coefficients not located at the center of each filter shape to the video decoder 300.

[0103] The order of the Golomb code used for signaling coefficients can depend on the bit depth and / or position of the coefficients. In one example, when the bit depth of all coefficients is equal to the first bit depth in the first filter bank, the Golomb code order is determined by adding the first fundamental order to the offset of the first signaling to signal non-center coefficients. The second Golomb decoder order is determined by adding the second fundamental order to the offset of the second signaling to signal center coefficients. When the bit depth of all coefficients is equal to the second bit depth in the second filter bank, the third Golomb code order is determined by adding the third fundamental order to the offset of the third signaling to signal non-center coefficients. The fourth Golomb decoder order is determined by adding the fourth fundamental order to the offset of the fourth signaling to signal center coefficients.

[0104] The bit depth of a coefficient can depend on the decoding method used for that coefficient. For example, when using Golomb codes to signal coefficients, the bit depth of the coefficients can depend on the order of the Golomb codes.

[0105] In some examples, the video encoder 200 may signal a flag for the coefficient to the video decoder 300. If the flag equals one value, the coefficient is inferred to be zero. On the other hand, if the flag equals another value, the coefficient is inferred to be non-zero. A second value is then derived, and the absolute value of this coefficient can then be derived by adding one to the second value.

[0106] Figure 2 This is a block diagram illustrating an example video encoder 200 that can perform the techniques of this disclosure. Figure 2 This disclosure is provided for illustrative purposes and should not be construed as a limitation on the techniques extensively illustrated and described herein. For illustrative purposes, this disclosure describes the video encoder 200 in accordance with the techniques of VVC and HEVC. However, the techniques of this disclosure can be performed by video encoding devices configured for other video decoding standards and video decoding formats, such as AV1 and subsequent formats of AV1 video decoding.

[0107] exist Figure 2 In the example, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any or all of the video data memory 230, mode selection 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 coding unit 220 may be implemented in one or more processors or in processing circuitry. For example, the units of the video encoder 200 may be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0108] Video data storage 230 is an example of a storage system capable of storing video data to be encoded by components of video encoder 200. Video encoder 200 can receive data from, for example, video source 104 (…). Figure 1 The video data memory 230 receives video data stored in the video data memory 230. The DPB 218 is an example of a memory system that can act as a reference picture memory, storing reference video data for use when the video encoder 200 predicts subsequent video data. The video data memory 230 and DPB 218 can each be formed from any of one or more memory devices or memory cells, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 can be on-chip (as illustrated) with other components of the video encoder 200, or off-chip relative to those components.

[0109] In this disclosure, references to video data memory 230 should not be construed as limited to memory inside video encoder 200 (unless specifically described) or memory outside video encoder 200 (unless specifically described). Rather, references to video data memory 230 should be understood as a reference memory that stores video data received by video encoder 200 for encoding (e.g., video data for the current block to be encoded). Figure 1The memory 106 can also provide temporary storage for the outputs from various units of the video encoder 200.

[0110] Examples Figure 2 Various units help understand the operations performed by the video encoder 200. Units can be implemented as fixed-function circuits, programmable circuits, or combinations thereof. Fixed-function circuits are circuits that provide specific functionality and are pre-configured for the operations that can be performed. Programmable circuits are circuits that can be programmed to perform various tasks and provide flexible functionality for the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is generally immutable. In some examples, one or more units in the unit may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units in the unit may be integrated circuits.

[0111] The video encoder 200 may include an arithmetic logic unit (ALU), an essential function unit (EFU), digital circuitry, analog circuitry, and / or a programmable core, all formed by programmable circuitry. In an example where the operation of the video encoder 200 is performed using software executed by programmable circuitry, memory 106 ( Figure 1 The video encoder 200 may store instructions (e.g., target code) of the software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0112] The video data storage unit 230 is configured to store received video data. The video encoder 200 can retrieve images of the video data from the video data storage unit 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data storage unit 230 can be raw video data to be encoded.

[0113] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra-frame prediction unit 226. The mode selection unit 202 may include additional functional units for performing video prediction based on other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-frame block copying unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0114] Mode selection unit 202 typically coordinates multiple coding channels to test combinations of coding parameters and the resulting rate-distortion values ​​for such combinations. Coding parameters may include the CTU-CU partitioning, the prediction mode for the CU, the transformation type of the residual data for the CU, the quantization parameters of the residual data for the CU, etc. Mode selection unit 202 can ultimately select a combination of coding parameters that has a better rate-distortion value compared to other tested combinations.

[0115] The video encoder 200 can divide an image retrieved from the video data storage 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 can divide the image's CTUs according to the tree structure described above (such as an MTT structure, QTBT structure, superblock structure, or the quadtree structure described above). As described above, the video encoder 200 can form one or more CUs by dividing the CTUs according to the tree structure. Such CUs are also commonly referred to as "video blocks" or "blocks".

[0116] Typically, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra-frame prediction unit 226) to generate predicted blocks for the current block (e.g., the current CU, or, in HEVC, the overlapping portion of PU and TU). To perform inter-frame prediction for the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate values ​​representing the similarity between a potential reference block and the current block, for example, based on sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. Motion estimation unit 222 may typically perform these calculations using sample-by-sample differences between the current block and the reference blocks under consideration. Motion estimation unit 222 may identify reference blocks with the lowest values ​​produced by these calculations to indicate the reference block that best matches the current block.

[0117] Motion estimation unit 222 can generate one or more motion vectors (MVs) that define the location of a reference block in a reference image relative to the location of the current block in the current image. Motion estimation unit 222 can then provide the motion vectors to motion compensation unit 224. For example, for unidirectional inter-frame prediction, motion estimation unit 222 can provide a single motion vector, while for bidirectional inter-frame prediction, motion estimation unit 222 can provide two motion vectors. Motion compensation unit 224 can then use the motion vectors to generate a prediction block. For example, motion compensation unit 224 can use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional-sample accuracy, motion compensation unit 224 can interpolate the values ​​of the prediction block according to one or more interpolation filters. Furthermore, for bidirectional inter-frame prediction, motion compensation unit 224 can retrieve data for two reference blocks identified by corresponding motion vectors and combine the retrieved data, for example, by per-sample averaging or weighted averaging.

[0118] When operating according to the AV1 video decoding format, the motion estimation unit 222 and the motion compensation unit 224 can be configured to encode the decoded blocks of video data (e.g., both luma and chroma decoded blocks) using translational motion compensation, affine motion compensation, overlap block motion compensation (OBMC), and / or composite inter-intra-frame prediction.

[0119] As another example, for intra-prediction or intra-prediction decoding, intra-prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, for directional mode, intra-prediction unit 226 may typically mathematically combine the values ​​of adjacent samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for DC mode, intra-prediction unit 226 may calculate the average of the adjacent samples of the current block and generate a prediction block to include the resulting average for each sample of the prediction block.

[0120] When operating according to the AV1 video decoding format, the intra-frame prediction unit 226 can be configured to encode decoded blocks of video data (e.g., both luma and chroma decoded blocks) using directional intra-frame prediction, non-directional intra-frame prediction, recursive filter intra-frame prediction, luma-chroma (CFL) prediction, intra-block copying (IBC), and / or palette modes. The mode selection unit 202 may include additional functional units for performing video prediction based on other prediction modes.

[0121] Mode selection unit 202 provides a prediction block to residual generation unit 204. Residual generation unit 204 receives an uncoded raw version of the current block from video data memory 230 and a prediction block from mode selection unit 202. 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 the residual block for the current block. In some examples, residual generation unit 204 may also determine the differences between sample values ​​in the residual block to generate the residual block using residual differential pulse decoding modulation (RDPCM). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits performing binary subtraction.

[0122] In the example where mode selection unit 202 divides a CU into PUs, each PU can be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and video decoder 300 can support PUs of various sizes. As noted above, the size of a CU can refer to the size of the luma decoding block of the CU, while the size of a PU can refer to the size of the luma prediction unit of the PU. Assuming a particular CU size is 2Nx2N, video encoder 200 can support PU sizes of 2Nx2N or NxN for intra-frame prediction, and symmetric PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar for inter-frame prediction. Video encoder 200 and video decoder 300 can also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0123] In an example where mode selection unit 202 does not further divide the CU into PUs, each CU can be associated with a luminance decoding block and a corresponding chrominance decoding block. As mentioned above, the size of the CU can refer to the size of the luminance decoding block of the CU. The video encoder 200 and the video decoder 300 can support CU sizes of 2Nx2N, 2NxN, or Nx2N.

[0124] For other video decoding techniques, such as intra-block copy mode decoding, affine mode decoding, and linear model (LM) mode decoding, as some examples, mode selection unit 202 generates a prediction block of the current block being encoded via a corresponding unit associated with the decoding technique. In some examples (such as palette mode decoding), mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how the block is reconstructed based on a selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy coding unit 220 for encoding.

[0125] As described above, the residual generation unit 204 receives video data for the current block and the corresponding prediction block. Then, the residual generation unit 204 generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0126] Transform processing unit 206 applies one or more transformations to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 may apply various transformations to the residual block to form the transform coefficient block. For example, transform processing unit 206 may apply a discrete cosine transform (DCT), direction transform, Karhunen-Loeve transform (KLT), or conceptually similar transformations to the residual block. In some examples, transform processing unit 206 may perform multiple transformations on the residual block, such as primary and secondary transformations (e.g., rotation transformations). In some examples, transform processing unit 206 does not apply any transformations to the residual block.

[0127] When operating according to AV1, transform processing unit 206 may apply one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). Transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, transform processing unit 206 may apply a combination of horizontal / vertical transforms, which may include the Discrete Cosine Transform (DCT), the Asymmetric Discrete Sine Transform (ADST), the Reversed ADST (e.g., ADST in reverse order), and the Identity Transform (IDTX). When using the Identity Transform, the transform is skipped in either the vertical or horizontal direction. In some examples, transform processing may be skipped entirely.

[0128] Quantization unit 208 quantizes the transform coefficients in a transform coefficient block to produce a quantized transform coefficient block. Quantization unit 208 quantizes the transform coefficients of the transform coefficient block according to the quantization parameter (QP) value associated with the current block. Video encoder 200 (e.g., via 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 may cause information loss, and therefore, the quantized transform coefficients may have lower accuracy compared to the original transform coefficients produced by transform processing unit 206.

[0129] The inverse quantization unit 210 and the inverse transform processing unit 212 can apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block based on the transform coefficient block. The reconstruction unit 214 can generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 can add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate the reconstructed block.

[0130] Filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce block artifacts along the edges of the CU. In some examples, the operation of filter unit 216 may be skipped.

[0131] When operating according to AV1, filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce block artifacts along the edges of the CU. In other examples, filter unit 216 may apply a constrained direction enhancement filter (CDEF) after deblocking and may include the application of a non-separable, nonlinear, low-pass directional filter based on the estimated edge direction. Filter unit 216 may also include a loop recovery filter applied after CDEF and may include a separable symmetric normalized Wiener filter or a dual-guided filter.

[0132] Filter unit 216 may additionally or alternatively perform SAO and / or ALF. When performing ALF, filter unit 216 may determine the bit depth of the coefficients used for ALF. Filter unit 216 may determine the values ​​of syntax elements to indicate the bit depth, and entropy coding unit 220 encodes these values ​​of syntax elements into the coded bitstream of video data.

[0133] The video encoder 200 stores reconstructed blocks in the DPB 218. For example, in an example where the filter unit 216 is not operated, the reconstruction unit 214 may store the reconstructed blocks in the DPB 218. In an example where the filter unit 216 is operated, the filter unit 216 may store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve a reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction of blocks in subsequent encoded pictures. Additionally, the intra-frame prediction unit 226 may use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction of other blocks in the current picture.

[0134] Typically, entropy coding unit 220 can entropy-encode syntax elements received from other functional components of video encoder 200. For example, entropy coding unit 220 can entropy-encode quantized transform coefficient blocks from quantization unit 208. As another example, entropy coding unit 220 can entropy-encode predictive syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from mode selection unit 202. Entropy coding unit 220 can perform one or more entropy coding operations on syntax elements (another example of video data) to generate entropy-coded data. For example, entropy coding unit 220 can perform context-adaptive variable-length decoding (CAVLC), CABAC, variable-to-variable (V2V) length decoding, syntax-based context-adaptive binary arithmetic decoding (SBAC), probability interval partitioning entropy (PIPE) decoding, exponential Golomb coding, or another type of entropy coding operation on the data. In some examples, entropy coding unit 220 can operate in a bypass mode where syntax elements are not entropy-encoded.

[0135] The video encoder 200 can output a bitstream that includes the entropy coding syntax elements required to reconstruct slices or blocks of images. Specifically, the entropy coding unit 220 can output a bitstream.

[0136] According to AV1, entropy coding unit 220 can be configured as a symbol-to-symbol adaptive multi-symbol arithmetic decoder. The syntax elements in AV1 consist of an N-element alphabet, and the context (e.g., a probability model) consists of a set of N probabilities. Entropy coding unit 220 can store the probabilities as an n-bit (e.g., 15-bit) cumulative distribution function (CDF). Entropy coding unit 220 can perform recursive scaling using an update factor based on the alphabet size to update the context.

[0137] The operations described above are relative to blocks. This description should be understood as operations applied to luma decoding blocks and / or chroma decoding blocks. As described above, in some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the CU. In some examples, the luma decoding block and chroma decoding block are the luma and chroma components of the PU.

[0138] In some examples, it is not necessary to repeat the operations performed relative to the luma decoder for the chroma decoder block. As an example, the operations for identifying the motion vector (MV) and reference image of the luma decoder block do not need to repeat the MV and reference image used to identify the chroma block. Instead, the MV used for the luma decoder block can be scaled to determine the MV used for the chroma block, and the reference image can be the same. As another example, the intra-frame prediction process can be the same for both the luma and chroma decoders.

[0139] Video encoder 200 represents an example of a device configured to encode video data, the device including a memory configured to store the video data and one or more processing units implemented in circuitry and configured to determine the bit depth of one or more coefficients for ALF.

[0140] Figure 3 This is a block diagram illustrating an example video decoder 300 that can perform the techniques of this disclosure. Figure 3 This disclosure is provided for illustrative purposes and not for limiting the techniques extensively illustrated and described herein. For illustrative purposes, the video decoder 300 is described in accordance with VVC and HEVC techniques. However, the techniques of this disclosure can be implemented by video decoding devices configured for other video decoding standards.

[0141] exist Figure 3 In the example, the video decoder 300 includes a 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 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 can be implemented in one or more processors or in processing circuitry. For example, the units of the video decoder 300 can be implemented as one or more circuit or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0142] 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.

[0143] When operating according to AV1, motion compensation unit 316 can be configured to decode video data blocks (e.g., both luma and chroma blocks) using translational motion compensation, affine motion compensation, OBMC, and / or composite inter-intra-frame prediction, as described above. Intra-frame prediction unit 318 can be configured to decode video data blocks (e.g., both luma and chroma blocks) using directional intra-frame prediction, non-directional intra-frame prediction, recursive filter intra-frame prediction, CFL, IBC, and / or palette mode, as described above.

[0144] CPB memory 320 is an example of a memory system capable of storing video data (such as encoded video bitstreams) to be decoded by components of video decoder 300. For example, it can be stored from computer-readable medium 110 ( Figure 1 The video data stored in the CPB memory 320 is obtained. The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. Furthermore, the CPB memory 320 may store video data other than the syntax elements of the decoded picture, such as temporary data representing the output from various units of the video decoder 300. The DPB 314 is an example of a memory system that typically stores a decoded picture, which the video decoder 300 may output, and / or uses as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and the DPB 314 may each be formed from any of various memory devices or memory cells, such as DRAM (including SDRAM), MRAM, RRAM, or other types of memory devices. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300, or off-chip relative to those components.

[0145] Additionally or alternatively, in some examples, the video decoder 300 may be from the memory 120 ( Figure 1 Decoded video data can be retrieved from the memory. That is, memory 120 can utilize CPB memory 320 to store data, as discussed above. Similarly, when some or all of the functionality of video decoder 300 is implemented in software to be executed by the processing circuitry of video decoder 300, memory 120 can store instructions to be executed by video decoder 300.

[0146] Examples Figure 3 The various units shown help to understand the operations performed by the video decoder 300. The units can be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Similar to... Figure 2Fixed-function circuits are circuits that provide specific functionality and are pre-configured for the operations they can perform. Programmable circuits are circuits that can be programmed to perform various tasks and provide flexible functionality for the operations they can perform. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive or output parameters), but the type of operation performed by a fixed-function circuit is typically immutable. In some examples, one or more units in a cell may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units in a cell may be integrated circuits.

[0147] The video decoder 300 may include an ALU, EFU, digital circuitry, analog circuitry, and / or a programmable core formed by programmable circuitry. In an example where the operation of the video decoder 300 is performed by software executed on programmable circuitry, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0148] The entropy decoding unit 302 can receive encoded video data from the CPB and perform entropy decoding on the video data to reproduce the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 can generate decoded video data based on the syntax elements extracted from the bitstream.

[0149] Typically, the video decoder 300 reconstructs the image block by block. The video decoder 300 can perform the reconstruction operation on each block individually (where the block currently being reconstructed (i.e., decoded) can be referred to as the "current block").

[0150] Entropy decoding unit 302 can entropy decode the syntax elements of the quantized transform coefficients defining the quantized transform coefficient block, as well as transform information (such as quantization parameters (QP) and / or transform mode indications). Inverse quantization unit 306 can use the QP associated with the quantized transform coefficient block to determine the degree of quantization, and similarly, determine the degree of inverse quantization to be applied by inverse quantization unit 306. Inverse quantization unit 306 can, for example, perform a bit-by-bit left shift operation to inverse quantize the quantized transform coefficients. Inverse quantization unit 306 can thereby form a transform coefficient block including the transform coefficients.

[0151] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse direction transform, or another inverse transform to the transform coefficient block.

[0152] Furthermore, the prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy-decoded by the entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is an inter-frame prediction, the motion compensation unit 316 can generate the prediction block. In this case, the prediction information syntax elements may indicate the reference picture from which the reference block is to be retrieved in the DPB 314, and a motion vector identifying the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion compensation unit 316 can generally be configured according to the parameters relative to the motion compensation unit 224 ( Figure 2 The method described is essentially the same as the method used to perform the inter-frame prediction process.

[0153] As another example, when the prediction information syntax element indicates that the current block is intra-predictive, the intra-predictive unit 318 can generate a prediction block according to the intra-predictive mode indicated by the prediction information syntax element. Similarly, the intra-predictive unit 318 can generally be configured according to the intra-predictive unit 226 ( Figure 2 The intra-prediction process is performed in a manner substantially similar to that described above. The intra-prediction unit 318 can retrieve data of neighboring samples of the current block from the DPB 314.

[0154] Reconstruction unit 310 can use the prediction block and the residual block to reconstruct the current block. For example, reconstruction unit 310 can add samples from the residual block to the corresponding samples from the prediction block to reconstruct the current block.

[0155] Filter unit 312 may perform one or more filtering operations on the reconstructed block. For example, filter unit 312 may perform a deblocking operation to reduce block artifacts along the edges of the reconstructed block. The operation of filter unit 312 is not necessarily performed in all examples. Filter unit 312 may, for example, apply an ALF with adaptive bit depth coefficients, as described herein.

[0156] The video decoder 300 can store reconstructed blocks in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 can store the reconstructed blocks in the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 can store the filtered reconstructed blocks in the DPB 314. As discussed above, the DPB 314 can provide reference information (such as samples of the current image for intra-frame prediction and samples of previously decoded images for subsequent motion compensation) to the prediction processing unit 304. Furthermore, the video decoder 300 can output decoded images (e.g., decoded video) from the DPB 314 for use in applications such as... Figure 1 The subsequent presentation on display devices such as display device 118.

[0157] In this manner, video decoder 300 represents an example of a video decoding device, which includes a memory configured to store video data and one or more processing units implemented in a circuit and configured to perform the following operations: determining blocks of video data; determining an ALF for the block of video data, including determining the bit depth of the coefficients for the ALF; applying the ALF to the block of video data to determine a filtered block of video data; and outputting a decoded picture of video data including the filtered block of video data.

[0158] Figure 4 This is a flowchart illustrating an example method for encoding the current block according to the technology of this disclosure. The current block may be or may include the current CU. Although it is relative to video encoder 200 ( Figure 1 and Figure 2 This is a description, but it should be understood that other devices can be configured to perform similar actions. Figure 4 Similar to the method.

[0159] In this example, the video encoder 200 initially predicts the current block (400). For example, the video encoder 200 may form a prediction block for the current block. Then, the video encoder 200 may compute a residual block for the current block (402). To compute the residual block, the video encoder 200 may compute the difference between the unencoded original block of the current block and the prediction block. Then, the video encoder 200 may transform the residual block and quantize the transform coefficients of the residual block (404). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (406). During or after the scan, the video encoder 200 may entropy encode the transform coefficients (408). For example, the video encoder 200 may use CAVLC or CABAC to encode the transform coefficients. Then, the video encoder 200 may output the entropy-encoded data of the block (410).

[0160] Figure 5 This is a flowchart illustrating an example method for decoding a current block of video data according to the technology of this disclosure. The current block may be or may include the current CU. Although it is relative to video decoder 300 ( Figure 1 and Figure 3 This is a description, but it should be understood that other devices can be configured to perform similar actions. Figure 5 Similar to the method.

[0161] The video decoder 300 may receive entropy-coded data for the current block, such as entropy-coded prediction information and entropy-coded data for the transform coefficients of the residual block corresponding to the current block (500). The video decoder 300 may entropy decode the entropy-coded data to determine prediction information for the current block and reproduce the transform coefficients of the residual block (502). The video decoder 300 may predict the current block (504) for example using an intra-frame prediction mode or inter-frame prediction mode indicated by the prediction information of the current block to compute a prediction block for the current block. The video decoder 300 may then perform an inverse scan (506) on the reproduced transform coefficients to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (508). The video decoder 300 may form a reconstructed block (510) by combining the prediction block and the residual block (e.g., by addition). The video decoder 300 may apply one or more filters to the reconstructed block to determine a filtered block of video data (512). Then, the video decoder 300 outputs a decoded image of the video data, which includes the filtered blocks of video data.

[0162] Figure 6 This is a flowchart illustrating an example method for encoding the current block according to the technology of this disclosure. The current block may be or may include the current CU. Although it is relative to video encoder 200 ( Figure 1 and Figure 2 This is a description, but it should be understood that other devices can be configured to perform similar actions. Figure 6 Similar to the method.

[0163] according to Figure 6 In this technique, video encoder 200 determines the coefficient values ​​of a set of one or more filters for encoding a block group of video data, wherein the set of filters is used in an adaptive loop filtering process (600). To determine the actual decimal coefficient values ​​of the set of one or more filters, video encoder 200 may determine the fractional part of the coefficient values ​​based on the bit depth and also determine the numerator part of the coefficient values. The fractional or denominator part of the coefficient value may be equal to 2^(bit depth - 1), and the numerator may be a value signaled by the bit depth. Therefore, a coefficient can be considered as the numerator divided by the denominator.

[0164] The video encoder 200 determines the bit depth (602) used to signal the coefficient values. The video encoder 200 outputs encoded video data, wherein the encoded video data includes an indication of the bit depth (604). The indication of the bit depth can, for example, be an index value mapped from multiple available bit depths used for the adaptive loop filter to the bit depth. The encoded video data may also include indications of coefficient values, such as the values ​​of alf_chroma_coeff_abs and alf_chroma_coeff_sign.

[0165] Figure 7 This is a flowchart illustrating an example method for decoding a current block of video data according to the technology of this disclosure. The current block may be or may include the current CU. Although it is relative to video decoder 300 ( Figure 1 and Figure 3 This is a description, but it should be understood that other devices can be configured to perform similar actions. Figure 7 Similar to the method.

[0166] exist Figure 7 In the example, video decoder 300 determines blocks (700) from encoded video data. Video decoder 300 may, for example, add predicted blocks to residual blocks to determine reconstructed blocks.

[0167] The video decoder 300 determines the bit depth for the adaptive loop filter from a plurality of available bit depths (702). To determine the bit depth for the adaptive loop filter from the plurality of available bit depths, the video decoder 300 may, for example, receive an index value in the encoded video data and map the index value to a bit depth. To determine the bit depth for the adaptive loop filter from the plurality of available bit depths, the video decoder 300 may, for example, determine the bit depth for a set of adaptive loop filters, which includes adaptive loop filters, and all coefficients of all adaptive loop filters in the set are available at the bit depth.

[0168] The video decoder 300 determines the coefficient values ​​(704) of a set of filter coefficients for an adaptive loop filter based on the bit depth. To determine the coefficient values ​​of this set of filter coefficients for the adaptive loop filter based on the bit depth, the video decoder 300 may, for example, determine the fractional part of the coefficient value based on the bit depth. The actual decimal value of the coefficient value may be equal to the signaled coefficient value divided by 2^(bd-1), where the value of bd is equal to the bit depth. To determine the decimal value of the coefficients for this set of filter coefficients for the adaptive loop filter based on the bit depth, the video decoder 300 may, for example, receive the numerator value in the encoded video data and determine that the decimal value of the set of filter coefficients is equal to the numerator value divided by 2^(bd-1), where the value of bd is equal to the bit depth.

[0169] The video decoder 300 applies an adaptive loop filter to the block to determine the filtered block of the video data (706). The video decoder 300 determines the decoded version of the block of video data based on the filtered block of the video data (708). In some examples, the decoded version of the block may be the same as the filtered block of the video data. In other examples, the video decoder 300 may apply additional processing to the filtered block to determine the decoded version of the block.

[0170] The video decoder 300 outputs a decoded image (710) of the video data, comprising a decoded version of the video data blocks. The video decoder 300 may, for example, output the decoded image for display or for storage or transmission. The video decoder 300 may store the decoded image in a decoded image buffer for use in decoding other images of the encoded video data.

[0171] The following numbered clauses illustrate one or more aspects of the devices and technologies described in this disclosure.

[0172] Clause 1A: A method for decoding video data, the method comprising: determining blocks of video data; determining an adaptive loop filter (ALF) for the blocks of video data, wherein determining the ALF includes determining a bit depth of coefficients for the ALF; applying the ALF to the blocks of video data to determine filtered blocks of video data; and outputting a decoded picture of video data including the filtered blocks of video data.

[0173] Clause 2A: The method according to Clause 1A, wherein determining the bit depth for the coefficients of the ALF comprises: receiving one or more syntax elements; and determining the bit depth based on the values ​​of the one or more syntax elements.

[0174] Clause 3A: The method according to Clause 1A or 2A, wherein determining the block of video data comprises: determining a prediction block for the block of video data; determining a residual block for the block of video data; and combining the prediction block and the residual block to determine a reconstruction block of video data.

[0175] Clause 4A: The method according to Clause 3A, wherein determining the block of video data further comprises: applying one or more filters to the reconstructed block of video data.

[0176] Clause 5A: An apparatus for decoding video data, the apparatus comprising one or more components for performing a method according to any one of Clauses 1A to 4A.

[0177] Clause 6A: The device according to Clause 5A, wherein the one or more components include one or more processors implemented in a circuit.

[0178] Clause 7A: The device pursuant to any one of Clauses 5A and 6A further includes a memory for storing the video data.

[0179] Clause 8A: The device according to any one of Clauses 5A to 7A further includes a display configured to display decoded video data.

[0180] Clause 9A: The device pursuant to any one of Clauses 5A to 8A, wherein the device includes one or more of a camera, computer, mobile device, broadcast receiver device or set-top box.

[0181] Clause 10A: A device pursuant to any one of Clauses 5A to 9A, wherein the device includes a video decoder.

[0182] Clause 11A: A device pursuant to any one of Clauses 5A to 10A, wherein said device includes a video encoder.

[0183] Clause 12A: A computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform a method according to any one of Clauses 1A to 4A.

[0184] Clause 1B: A method for decoding coded video data, the method comprising: determining a block from the coded video data; determining a bit depth for an adaptive loop filter from a plurality of available bit depths for the adaptive loop filter; determining coefficient values ​​of a set of filter coefficients for the adaptive loop filter based on the bit depth; applying the adaptive loop filter to the block to determine a filtered block of video data; determining a decoded version of the block of video data based on the filtered block of video data; and outputting a decoded picture of video data including the decoded version of the block of video data.

[0185] Clause 2B: The method according to Clause 1B, wherein determining the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter comprises: receiving an index value in the coded video data; and mapping the index value to the bit depth.

[0186] Clause 3B: The method according to Clause 1B or 2B, wherein determining the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth includes a denominator portion for determining the coefficient values ​​based on the bit depth.

[0187] Clause 4B: The method according to Clause 3B, wherein the denominator portion of the coefficient value is equal to 2^(bd-1), wherein the value of bd is equal to the bit depth.

[0188] Clause 5B: The method according to any one of Clauses 1B to 4B, wherein determining the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter includes determining the bit depth for a set of adaptive loop filters, wherein the set of adaptive loop filters includes the adaptive loop filter, and all coefficients of all the adaptive loop filters in the set use the bit depth.

[0189] Clause 6B: The method according to any one of Clauses 1B to 5B, wherein determining the coefficient value of the set of filter coefficients for the adaptive loop filter based on the bit depth comprises: receiving a numerator value in the coded video data; and determining that the coefficient value of the set of filter coefficients is equal to the numerator value divided by 2^(bd-1), wherein the value of bd is equal to the bit depth.

[0190] Clause 7B: The method according to any one of Clauses 1B to 6B, the method further comprising: determining the order of the Golomb code based on the bit depth; and determining the coefficient values ​​for the set of filters based on the order of the Golomb code.

[0191] Clause 8B: An apparatus for decoding encoded video data, the apparatus comprising: a memory; and one or more processors implemented in circuitry, coupled to the memory, and configured to: determine blocks from the encoded video data; determine a bit depth for an adaptive loop filter from a plurality of available bit depths for the adaptive loop filter; determine coefficient values ​​for a set of filter coefficients for the adaptive loop filter based on the bit depth; apply the adaptive loop filter to the blocks to determine a filtered block of video data; determine a decoded version of the block of video data based on the filtered block of video data; and output a decoded picture of video data including the decoded version of the block of video data.

[0192] Clause 9B: The apparatus according to Clause 8B, wherein, in order to determine the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter, the one or more processors are further configured to: receive an index value in the coded video data; and map the index value to the bit depth.

[0193] Clause 10B: The apparatus according to Clause 8B or 9B, wherein, in order to determine the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth, the one or more processors are further configured to determine the denominator portion of the coefficient values ​​based on the bit depth.

[0194] Clause 11B: The device according to Clause 10B, wherein the denominator portion of the coefficient value is equal to 2^(bd-1), wherein the value of bd is equal to the bit depth.

[0195] Clause 12B: An apparatus according to any one of Clauses 8B to 11B, wherein, in order to determine the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter, the one or more processors are further configured to determine the bit depth for a set of adaptive loop filters, wherein the set of adaptive loop filters includes the adaptive loop filter, and all coefficients of all the adaptive loop filters in the set use the bit depth.

[0196] Clause 13B: The apparatus according to any one of Clauses 8B to 12B, wherein, in order to determine the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth, the one or more processors are further configured to: receive a numerator value in the coded video data; and determine that the coefficient values ​​of the set of filter coefficients are equal to the numerator value divided by 2^(bd-1), wherein the value of bd is equal to the bit depth.

[0197] Clause 14B: A device pursuant to any one of Clauses 8B to 13B, wherein the device includes a wireless communication device and the device further includes a receiver configured to receive the encoded video data.

[0198] Clause 15B: The device according to any one of Clauses 8B to 14B, the device further comprising: a display configured to display the decoded image of the video data.

[0199] Clause 16B: A method for encoding video data, the method comprising: determining coefficient values ​​of one or more filters for encoding a block group of video data, wherein the set of filters is used for an adaptive loop filtering process; determining a bit depth for signaling the coefficient values; and outputting encoded video data, wherein the encoded video data includes an indication of the bit depth.

[0200] Clause 17B: The method according to Clause 16B, wherein the indication of the bit depth includes an index value that maps from a plurality of available bit depths for the adaptive loop filtering process to the bit depth.

[0201] Clause 18B: The method according to Clause 16B or 17B, wherein determining the coefficient value for the set of one or more filters includes determining the denominator portion of the coefficient value based on the bit depth, wherein the denominator portion of the coefficient value is equal to 2^(bd-1), where the value of bd is equal to the bit depth.

[0202] Clause 19B: The method according to any one of Clauses 16B to 18B, wherein the encoded video data includes an indication of the coefficient values.

[0203] Clause 20B: The method according to any one of Clauses 16B to 19B, wherein determining the coefficient values ​​of the set of filter coefficients for the adaptive loop filtering process comprises: determining a numerator value; and determining that a coefficient value among the coefficient values ​​is equal to the numerator value divided by 2^(bd-1), wherein the value of bd is equal to the bit depth.

[0204] It should be recognized that, based on the examples, certain actions or events of any technique described herein may be performed in a different sequence, and may be added, combined, or omitted entirely (e.g., not all actions or events described are necessary for implementing the technique). Furthermore, in some examples, actions or events may be performed concurrently (e.g., through multithreading, interrupt handling, or multiple processors) rather than sequentially.

[0205] In one or more examples, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium or transmitted via a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium (which corresponds to a tangible medium such as a data storage medium) or a communication medium, including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. Thus, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. Computer program products may include computer-readable media.

[0206] By way of example, and not limitation, such computer-readable storage media may include one or more of RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or any other medium capable of storing desired program code in the form of instructions or data structures and accessible by a computer. Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared, radio, and microwave), then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (such as infrared, radio, and microwave) is included in the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but instead refer to non-transient tangible storage media. As used herein, disks and optical discs include compact optical discs (CDs), laser optical discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs use lasers to reproduce data optically. Combinations of these should also be included within the scope of computer-readable media.

[0207] Instructions can be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuit" as used herein can refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into combined codecs. Furthermore, these techniques can be fully implemented in one or more circuit or logic elements.

[0208] The techniques disclosed herein can be implemented in a wide variety of devices or apparatuses, including wireless mobile phones, integrated circuits (ICs), or IC sets (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but implementation by different hardware units is not necessarily required. Specifically, as described above, various units may be combined within a codec hardware unit, or may be provided by a collection of interoperable hardware units (including one or more processors as described above) combined with appropriate software and / or firmware.

[0209] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding encoded video data, the method comprising: Determine blocks from the encoded video data; The bit depth for the adaptive loop filter is determined from a plurality of available bit depths for the adaptive loop filter; The coefficient values ​​of a set of filter coefficients for the adaptive loop filter are determined based on the bit depth. The adaptive loop filter is applied to the block to determine the filtering block for the video data; The decoding version of the video data block is determined based on the filtered block of the video data; as well as The output is a decoded image of the video data, which includes the decoded version of the video data block.

2. The method of claim 1, wherein determining the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter comprises: Receive the index value from the encoded video data; as well as Map the index value to the bit depth.

3. The method of claim 1, wherein determining the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth includes determining the denominator portion of the coefficient values ​​based on the bit depth.

4. The method of claim 3, wherein the denominator portion of the coefficient value is equal to 2^(bd-1), wherein the value of bd is equal to the bit depth.

5. The method of claim 1, wherein determining the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter comprises determining the bit depth for a set of adaptive loop filters, wherein the set of adaptive loop filters includes the adaptive loop filter, and all coefficients of all the adaptive loop filters in the set use the bit depth.

6. The method of claim 1, wherein determining the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth comprises: Receive the molecular values ​​from the encoded video data; as well as The coefficient values ​​of the set of filter coefficients are determined to be equal to the numerator value divided by 2^(bd-1), where the value of bd is equal to the bit depth.

7. The method according to claim 1, further comprising: The order of the Columbus code is determined based on the bit depth. as well as The coefficient values ​​for the set of filters are determined based on the order of the Golomb code.

8. An apparatus for decoding encoded video data, the apparatus comprising: Memory; and One or more processors, implemented in a circuit, coupled to the memory, and configured to: Determine blocks from the encoded video data; The bit depth for the adaptive loop filter is determined from a plurality of available bit depths for the adaptive loop filter; The coefficient values ​​of a set of filter coefficients for the adaptive loop filter are determined based on the bit depth. The adaptive loop filter is applied to the block to determine the filtering block for the video data; The decoding version of the video data block is determined based on the filtered block of the video data; as well as The output is a decoded image of the video data, which includes the decoded version of the video data block.

9. The apparatus of claim 8, wherein, in order to determine the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter, the one or more processors are further configured to: Receive the index value from the encoded video data; and Map the index value to the bit depth.

10. The apparatus of claim 8, wherein, in order to determine the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth, the one or more processors are further configured to determine the denominator portion of the coefficient values ​​based on the bit depth.

11. The device of claim 10, wherein the denominator portion of the coefficient value is equal to 2^(bd-1), wherein the value of bd is equal to the bit depth.

12. The apparatus of claim 8, wherein, in order to determine the bit depth for the adaptive loop filter from the plurality of available bit depths for the adaptive loop filter, the one or more processors are further configured to determine the bit depth for a set of adaptive loop filters, wherein the set of adaptive loop filters includes the adaptive loop filter, and all coefficients of all the adaptive loop filters in the set use the bit depth.

13. The device of claim 8, wherein, in order to determine the coefficient values ​​of the set of filter coefficients for the adaptive loop filter based on the bit depth, the one or more processors are further configured to: Receive the molecular values ​​from the encoded video data; and The coefficient values ​​of the set of filter coefficients are determined to be equal to the numerator value divided by 2^(bd-1), where the value of bd is equal to the bit depth.

14. The device of claim 8, wherein the device includes a wireless communication device, and the device further includes a receiver configured to receive the encoded video data.

15. The apparatus according to claim 8, further comprising: A display configured to display the decoded image of video data.

16. A method for encoding video data, the method comprising: Determine the coefficient values ​​of one or more filters for a block group used to encode video data, wherein the set of filters is used for an adaptive loop filtering process; Determine the bit depth used to signal the coefficient value; and Output encoded video data, wherein the encoded video data includes an indication of the bit depth.

17. The method of claim 16, wherein the indication of the bit depth comprises an index value mapped from a plurality of available bit depths for the adaptive loop filtering process to the bit depth.

18. The method of claim 16, wherein determining the coefficient values ​​for the set of one or more filters includes determining a denominator portion of the coefficient values ​​based on the bit depth, wherein the denominator portion of the coefficient values ​​is equal to 2^(bd-1), where the value of bd is equal to the bit depth.

19. The method of claim 16, wherein the encoded video data includes an indication of the coefficient values.

20. The method of claim 16, wherein determining the coefficient values ​​of the set of filter coefficients used in the adaptive loop filtering process comprises: Determine the molecule value; as well as The coefficient value is determined to be equal to the molecule value divided by 2^(bd-1), where the value of bd is equal to the bit depth.

Images