CN117044203A - Signaling of EOB for one-dimensional transform skipping - Google Patents

Abstract

Methods, apparatus, and computer readable storage media for implementing signaling EOC/EOR. The method comprises the following steps: receiving a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and performing entropy coding on the transformation block; determining whether to apply one-dimensional transform skipping to the transform block based on syntax elements in the video bitstream; obtaining, from the video bitstream, an end position value associated with the transform block in response to applying the one-dimensional transform skip to the transform block, the end position value indicating only one of a horizontal coordinate end position and a vertical coordinate end position in the transform block; and retrieving the transformed block from the video bitstream according to the end position value.

Description

Signaling of EOB for one-dimensional transform skipping

Cross reference

The present application is based on and claims priority of U.S. non-provisional application No. 17/991,206, "signaling for one-dimensional transform skipped EOB (Signalling of EOB for One Dimensional Transform Skip)" filed on month 11 of 2022, which is based on and claims priority of U.S. provisional application No. 63/300,427, "signaling for one-dimensional transform skipped EOB (Signalling of EOB for One Dimensional Transform Skip)" filed on month 1 of 2022, which is incorporated herein by reference in its entirety.

Technical Field

This disclosure describes a set of advanced video codec techniques for efficient compression and signaling of video data. More particularly, the disclosed techniques relate to signaling and/or derivation of End of Block (EOB) when applying one-dimensional transform skip mode.

Background

The background description provided herein is intended to generally represent the background of the application. Work of the presently named inventors, to the extent it is described in this background section as well as aspects of the description, as it may not otherwise qualify as prior art at the time of filing, and are neither expressly nor impliedly admitted as prior art against the present disclosure.

Video encoding and decoding can be performed by inter picture prediction techniques with motion compensation. The uncompressed digital video may include a series of pictures, each having a spatial dimension of, for example, 1920 x 1080 luma samples and associated full or sub-sampled chroma samples. The series of pictures has a fixed or variable picture rate (alternatively referred to as a frame rate), such as 60 pictures per second or 60 frames per second. Uncompressed video has specific bit rate requirements for streaming or data processing. For example, video with a pixel resolution of 1920×1080, a frame rate of 60 frames/second, and chroma subsampling of 4:2:0 at 8 bits per pixel per color channel require approximately 1.5Gbit/s bandwidth. One hour of such video requires more than 600GB of memory space.

One purpose of video encoding and decoding is to reduce redundant information of an uncompressed input video signal by compression. Video compression may help reduce the bandwidth and/or storage requirements described above, in some cases by two or more orders of magnitude. Lossless and lossy compression, as well as combinations of both, may be employed. Lossless compression refers to a technique of reconstructing an exact copy of the original signal from the compressed original signal through a decoding process. Lossy compression refers to an encoding/decoding process in which the original video information is not fully preserved during encoding and not fully recovered during decoding. When lossy compression is used, the reconstructed signal may not be exactly the same as the original signal, but the distortion between the original signal and the reconstructed signal is small enough that the reconstructed signal is usable for the intended application, despite some information loss. In many applications, lossy compression is widely used for video. The amount of distortion allowed depends on the application. For example, some users consuming video streaming applications may tolerate higher distortion than users of movie or television broadcast applications. The compression ratio achievable by a particular codec algorithm reflects: higher allowable distortion generally allows for codec algorithms that can produce higher losses and higher compression ratios.

Video encoders and decoders may utilize techniques and steps from a number of broad categories, including, for example, motion compensation, fourier transforms, quantization, and entropy coding.

Video codec technology may include a technology known as intra-frame codec. In intra-coding, sample values are represented without reference to samples or other data from a previously reconstructed reference picture. In some video codecs, a picture is spatially subdivided into blocks of samples. When all sample blocks are encoded in intra mode, the picture may be referred to as an intra picture. Intra pictures and their derivatives (such as independent decoder refresh pictures) can be used to reset the decoder state and thus can be used as the first picture in an encoded video bitstream and video session, or as a still image. Samples of the intra-predicted block may be transformed into the frequency domain and the transform coefficients thus generated may be quantized prior to entropy encoding. Intra prediction may be a technique that minimizes sample values in the pre-transform domain. In some cases, the smaller the transformed DC value and the smaller the AC coefficient, the fewer bits are required to represent the entropy-encoded block at a given quantization step.

Conventional intra-frame codecs such as those known from e.g. MPEG-2 generation codec techniques do not use intra-frame prediction. However, some newer video compression techniques include techniques that attempt to encode/decode a block based on, for example, surrounding sample data and/or metadata that is obtained during encoding and/or decoding of spatially adjacent data blocks and that precedes the data block being intra-encoded or decoded in decoding order. This technique is hereinafter referred to as the "intra prediction" technique. Note that in at least some cases, intra prediction uses only reference data from the current picture in reconstruction, and not reference data from other reference pictures.

There may be many different forms of intra prediction. When more than one such technique can be used in a given video codec technique, the technique used may be referred to as intra-prediction mode. One or more intra prediction modes may be provided in a particular codec. In some cases, the modes may have sub-modes and/or may be associated with various parameters, and mode/sub-mode information and intra-coding parameters of blocks of video may be encoded separately or jointly included in a mode codeword. The codewords to be used for a given mode, sub-mode and/or parameter combination may have an impact on the coding efficiency gain through intra-prediction, as may entropy coding techniques that convert codewords into a bitstream

Some mode of intra prediction was introduced along with h.264, improved in h.265, and further improved in newer codec techniques such as joint exploration mode (JEM, joint exploration model), general video coding (VVC, versatile video coding), and reference set (BMS). In general, for intra prediction, a predictor block may be formed using neighboring sample values that become available. For example, the available values of a particular set of neighboring samples along a particular direction and/or line may be copied into a predictor block. The reference to the in-use direction may be encoded in the code stream or may be predictive of itself.

Referring to fig. 1A, the bottom right depicts a subset of nine prediction directions known from the 33 possible intra prediction directions specified in h.265 (33 angle modes corresponding to the 35 intra modes specified in h.265). The point (101) where the arrows converge represents the sample being predicted. The arrow indicates the use of neighboring samples to predict the direction of the sample at 101. For example, arrow (102) represents predicting a sample (101) from adjacent one or more samples at an upper right angle of 45 degrees to the horizontal. Similarly, arrow (103) represents predicting a sample (101) from adjacent sample or samples at an angle of 22.5 degrees from horizontal at the lower left.

Still referring to fig. 1A, a square block (104) comprising 4 x 4 samples (indicated by the thick dashed line) is shown at the top left. The square block (104) includes 16 samples, each marked with an "S", and its position in the Y dimension (e.g., row index) and its position in the X latitude (e.g., column index). For example, sample S21 is the second sample in the Y dimension (from the top) and the first sample in the X dimension (from the left). Similarly, sample S44 is the fourth sample in the block (104) in both the X and Y dimensions. Since the block is a 4×4-sized sample, S44 is located in the lower right corner. Exemplary reference samples following a similar numbering scheme are also shown. The reference samples are marked with an "R" and their Y position (e.g., row index) and X position (e.g., column index) relative to the block (104). In h.264 and h.265, prediction samples adjacent to a block under reconstruction are used.

Intra prediction of block 104 may begin by copying reference sample values from neighboring samples according to a signaled prediction direction. For example, assume that the encoded video bitstream includes signaling indicating, for this block 104, the prediction direction of arrow (102), i.e., predicting samples from one or more prediction samples at a 45 degree angle to horizontal above right. In this case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. From the reference sample R08, a sample S44 is predicted. Intra prediction of block 104 may begin by copying reference sample values from neighboring samples according to a signaled prediction direction.

In some cases, the values of multiple reference samples may be combined, for example by interpolation, to calculate the reference samples, especially when the direction is not exactly divisible by 45 degrees.

As video coding technology continues to evolve, the number of possible directions has increased. In h.264 (2003), for example, there are nine different directions that can be used for intra prediction. There are 33 more in h.265 (2013) and JEM/VVC/BMS, while at this time up to 65 directions can be supported. Experimental studies have been conducted to help identify the most appropriate directions of intra prediction, and some techniques in entropy coding are used to encode those most appropriate directions using a small number of bits, with some bit costs being accepted for some directions. In addition, it is sometimes possible to predict the direction itself from the neighboring direction used in intra prediction of neighboring, already decoded blocks

Fig. 1B shows a schematic diagram (105) depicting 65 intra-prediction directions according to JEM to show the increasing number of prediction directions in various coding techniques over time.

The manner in which bits representing the intra-prediction direction are mapped to the prediction direction in the codec video bitstream may vary from video coding technique, and may be, for example, from prediction direction to simple direct mapping to codewords of intra-prediction modes, to complex adaptation schemes involving the most probable modes, and the like. In all cases, however, there may be some intra-predicted directions in the video content that are statistically less likely to occur than some other directions. Since the goal of video compression is to reduce redundancy, in well-designed video codec techniques, those directions that are unlikely will be represented by a greater number of bits than the more likely directions.

Inter-picture prediction or inter-frame prediction may be based on motion compensation. In motion compensation, blocks of sample data from a previously reconstructed picture or a portion of a reconstructed picture (reference picture) are spatially shifted in a direction indicated by a motion vector (hereinafter MV) for prediction of a newly reconstructed picture or picture portion (e.g., block). In some cases, the reference picture may be the same as the picture currently being reconstructed. MV may have two dimensions X and Y, or three dimensions, with the third dimension representing a reference picture in use (similar to the temporal dimension).

In some video compression techniques, the current MV applied to a certain sample data region may be predicted from other MVs, for example from those other MVs that are related to other regions of sample data spatially adjacent to the region being reconstructed and that precede the current MV in decoding order. This can greatly reduce the total amount of data required to encode MVs by relying on eliminating redundant information in the associated MVs, thereby increasing compression efficiency. MV prediction can be efficiently performed, for example, when encoding an input video signal derived from a camera (referred to as natural video), there is a statistical possibility that an area larger than a single MV-applicable area will move in a similar direction in a video sequence, and thus, in some cases, prediction can be performed using similar motion vectors derived from MVs of neighboring areas. This results in the actual MVs for a given region being similar or identical to MVs predicted from surrounding MVs. After entropy coding, such MVs may in turn be represented with a smaller number of bits than the number of bits used to directly encode the MVs instead of predict from neighboring MVs. In some cases, MV prediction may be an example of lossless compression of a signal (i.e., MV) derived from an original signal (i.e., a sample stream). In other cases, MV prediction itself may be lossy, for example due to rounding errors that occur when calculating the prediction value from several surrounding MVs.

h.265/HEVC (ITU-T rec.h.265, "efficient video coding", month 12 of 2016) describes various MV prediction mechanisms. Among the various MV prediction mechanisms specified in h.265, described herein below is a technique hereinafter referred to as "spatial merging".

In particular, referring to fig. 2, a current block (201) includes samples found by an encoder during a motion search, which can be predicted from a previous block spatially shifted by the same size. The MV is not directly encoded, but is derived from metadata associated with one or more reference pictures, e.g., from the nearest (in decoding order) reference picture, by using the MV associated with any one of the five surrounding samples. Wherein five surrounding samples are denoted by A0, A1 and B0, B1, B2 (from 202 to 206), respectively. In h.265, MV prediction may use the prediction value of the same reference picture used by neighboring blocks.

Disclosure of Invention

Various aspects of the present disclosure provide methods and apparatus for video encoding and decoding, particularly for signaling and/or deriving an end of block EOB when a one-dimensional transform skip mode is applied. In some example embodiments, a method for video processing is disclosed. The method can receive a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and entropy coding is carried out on the transformation block; determining whether to apply one-dimensional transform skipping to the transform block based on syntax elements in the video bitstream; obtaining, from the video bitstream, an end position value associated with the transform block in response to applying the one-dimensional transform skip to the transform block, the end position value indicating only one of a horizontal coordinate end position and a vertical coordinate end position in the transform block; the transform block is retrieved from the video bitstream according to the end position value.

Various aspects of the present disclosure also provide a device or apparatus for video encoding or decoding, including circuitry configured to perform any of the above-described implementation methods.

Aspects of the present disclosure also provide a non-transitory computer-readable storage medium storing computer instructions that, when executed by a computer for video decoding and/or encoding, may cause the computer to be used in a method of video decoding and/or encoding.

Drawings

Further features, properties and various advantages of the disclosed subject matter will become more apparent from the following detailed description and drawings in which:

fig. 1A shows a schematic illustration of an exemplary subset of intra prediction direction modes.

Fig. 1B shows a diagram of an exemplary intra prediction direction.

Fig. 2 shows a schematic illustration of a current block and its surrounding spatial merging candidates for motion vector prediction in one example.

Fig. 3 shows a schematic illustration of a simplified block diagram of a communication system (300) according to an example embodiment.

Fig. 4 shows a schematic illustration of a simplified block diagram of a communication system (400) according to an example embodiment.

Fig. 5 shows a schematic illustration of a simplified block diagram of a video decoder according to an example embodiment.

Fig. 6 shows a schematic illustration of a simplified block diagram of a video encoder according to an example embodiment.

Fig. 7 shows a block diagram of a video encoder according to another example embodiment.

Fig. 8 shows a block diagram of a video decoder according to another example embodiment.

Fig. 9 illustrates a directional intra-prediction mode according to an example embodiment of the present disclosure.

Fig. 10 illustrates a non-directional intra-prediction mode according to an example embodiment of the present disclosure.

Fig. 11 illustrates a recursive intra prediction mode according to an example embodiment of the present disclosure.

Fig. 12 illustrates transform block partitioning and scanning of intra-prediction blocks according to an example embodiment of the present disclosure.

Fig. 13 illustrates transform block partitioning and scanning of inter prediction blocks according to an example embodiment of the present disclosure.

Fig. 14 shows an example one-dimensional transform skip and associated transform coefficient blocks in the horizontal direction.

Fig. 15 shows an exemplary one-dimensional transform skip and associated transform coefficient blocks in the vertical direction.

Fig. 16 illustrates an exemplary line graph transformation (LGT, line Graph Transforms) according to an example embodiment of the present disclosure.

Fig. 17 shows a flowchart of a method according to an example embodiment of the present disclosure.

Fig. 18 shows a schematic diagram of a computer system according to an example embodiment of the present disclosure.

Detailed Description

Fig. 3 is a simplified block diagram of a communication system (300) according to an embodiment of the present disclosure. The communication system (300) comprises a plurality of terminal devices which can communicate with each other via, for example, a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and terminal devices (320) interconnected by a network (350). In the embodiment of fig. 3, the terminal device (310) and the terminal device (320) perform unidirectional data transmission. For example, a terminal device (310) may encode video data, such as a video picture stream acquired by the terminal device (310), for transmission over a network (350) to another terminal device (320). The encoded video data is transmitted in one or more encoded video code streams. The terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to recover the video data, and display the video pictures according to the recovered video data. Unidirectional data transmission may be implemented in applications such as media services.

In another embodiment, the communication system (300) includes a second pair of terminal devices (330) and (340) that perform bi-directional transmission of encoded video data, which may be implemented, for example, during a video conferencing application. For bi-directional data transmission, each of the terminal device (330) and the terminal device (340) may encode video data (e.g., a video picture stream collected by the terminal device) for transmission over the network (350) to the other of the terminal device (330) and the terminal device (340). Each of the terminal device (330) and the terminal device (340) may also receive encoded video data transmitted by the other of the terminal device (330) and the terminal device (340), and may decode the encoded video data to recover the video data, and may display a video picture on an accessible display device according to the recovered video data.

In the embodiment of fig. 3, the terminal device (310), the terminal device (320), the terminal device (330), and the terminal device (340) may be servers, personal computers, and smart phones, but applicability of the basic principles of the present disclosure may not be limited thereto. Embodiments of the present disclosure may be implemented in laptop computers, tablet computers, media players, wearable computers, dedicated video conferencing equipment, and the like. The network (350) represents any number or type of networks that communicate encoded video data between the terminal devices (310), 320, 330, and 340), including, for example, wired (or connected) and/or wireless communication networks. The communication network (350) may exchange data in circuit-switched, packet-switched, and/or other types of channels. The network may include a telecommunications network, a local area network, a wide area network, and/or the internet. For purposes of this discussion, the architecture and topology of the network (350) may be irrelevant to the operation of the present disclosure unless explicitly stated herein.

As an example, fig. 4 shows the placement of a video encoder and video decoder in a video streaming environment. The presently disclosed subject matter is equally applicable to other video applications including, for example, video conferencing, digital TV, broadcasting, gaming, virtual reality, and storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

The video streaming system may include a video acquisition subsystem (413) that may include a video source (401), such as a digital camera for creating an uncompressed video picture stream or image (402). In an embodiment, the video picture stream (402) includes samples recorded by a digital camera of the video source 401. The video picture stream (402) is depicted as a bold line compared to the encoded video data (404) (or encoded video code stream) to emphasize a high data volume video picture stream, the video picture stream (402) being processable by an electronic device (420), the electronic device (420) comprising a video encoder (403) coupled to a video source (401). The video encoder (403) may include hardware, software, or a combination of hardware and software to implement or implement aspects of the disclosed subject matter as described in more detail below. Compared to the uncompressed video picture stream (402), the encoded video data (404) (or encoded video code stream (404)) is depicted as a thin line to emphasize lower data amounts of the encoded video data (404) (or encoded video code stream (404)), which may be stored on a streaming server (405) for future use, or directly to downstream video devices. One or more streaming client sub-systems, such as client sub-system (406) and client sub-system (408) in fig. 4, may access streaming server (405) to retrieve copies (407) and copies (409) of encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in an electronic device (430). A video decoder (410) decodes an incoming copy (407) of encoded video data and generates an output video picture stream (411) that is uncompressed and can be presented on a display (412) (e.g., a display screen) or another presentation device (not depicted). The video decoder 410 may be configured to perform some or all of the various functions described in this disclosure. In some streaming systems, encoded video data (404), video data (407), and video data (409) (e.g., a video bitstream) may be encoded according to some video encoding/compression standard. Examples of such standards include ITU-T H.265. In an embodiment, the video coding standard being developed is informally referred to as next generation video coding (Versatile Video Coding, VVC), and the present application may be used in the context of the VVC standard or other video codec standards.

It should be noted that the electronic device (420) and the electronic device (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

Fig. 5 is a block diagram of a video decoder (510) according to any embodiment of the present disclosure. The video decoder (510) may be disposed in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). A video decoder (510) may be used in place of the video decoder (410) in the embodiment of fig. 4.

The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510). In the same or another embodiment, one encoded video sequence may be decoded at a time, where each encoded video sequence is decoded independently of the other encoded video sequences. Each video sequence may be associated with a plurality of videos or images. The encoded video sequence may be received from a channel (501), which may be a hardware/software link to a storage device storing encoded video data or a streaming media source for transmitting encoded video data. The receiver (531) may receive encoded video data as well as other data, e.g., encoded audio data and/or auxiliary data streams, which may be forwarded to their respective processing circuits (not shown). The receiver (531) may separate the encoded video sequence from other data. To prevent network jitter, a buffer memory (515) may be placed between the receiver (531) and the entropy decoder/parser (520) (hereinafter "parser (520)"). In some applications, the buffer memory (515) may be implemented as part of the video decoder (510). In other cases, the buffer memory (515) may be disposed external (not labeled) to the video decoder (510). While in other applications a buffer memory (not shown) is provided external to the video decoder (510), for example for the purpose of preventing network jitter, and a further additional buffer memory (515) may be arranged inside the video decoder (510), for example to handle play-out timing. The buffer memory (515) may not be needed or may be made smaller when the receiver (531) receives data from a store/forward device with sufficient bandwidth and controllability or from an isochronous network. Of course, for use on a traffic packet network such as the internet, a buffer memory (515) of sufficient size may also be required, and the size of the buffer memory (515) may be relatively large. Such buffer memory may be of adaptive size and may be implemented at least in part in an operating system or similar element (not labeled) external to the video decoder 510.

The video decoder (510) may include a parser (520) to reconstruct the symbols (521) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (510), as well as potential information to control a display device, such as a display (512) (e.g., a display screen), that is not an integral part of the electronic device (530) but that may be coupled to the electronic device (530), as shown in fig. 5. The control information for the display device may be auxiliary enhancement information (Supplemental Enhancement Information, SEI message) or a parameter set fragment (not labeled) of video availability information (Video Usability Information, VUI). The parser (520) may parse/entropy decode the encoded video sequence received by the parser (520). Entropy encoding of an encoded video sequence may be performed in accordance with video encoding techniques or standards, and may follow various principles, including variable length encoding, huffman coding (Huffman coding), arithmetic coding with or without context sensitivity, and so forth. The parser (520) may extract a subgroup parameter set for at least one subgroup of pixels in the video decoder from the encoded video sequence based on the at least one parameter corresponding to the subgroup. A subgroup may include a group of pictures (Group of Pictures, GOP), pictures, tiles, slices, macroblocks, coding Units (CUs), blocks, transform Units (TUs), prediction Units (PUs), and so forth. The parser (520) may also extract information from the encoded video sequence, such as transform coefficients (fourier transform coefficients), quantizer parameter values, motion vectors, and so on.

The parser (520) may perform entropy decoding/parsing operations on the video sequence received from the buffer memory (515), thereby creating symbols (521).

Depending on the type of encoded video picture or a portion of encoded video picture (e.g., inter and intra pictures, inter and intra blocks), and other factors, the reconstruction of the symbol (521) may involve a number of different processing or functional units. The units involved and the manner of involvement may be controlled by a parser (520) from sub-group control information parsed from the encoded video sequence. For brevity, such a sub-group control information flow between the parser (520) and the various processing or functional units below is not described.

In addition to the functional blocks already mentioned, the video decoder (510) may be conceptually subdivided into several functional units as described below. In practical embodiments operating under commercial constraints, many of these functional units interact tightly with each other and may be integrated with each other. However, for the purpose of clearly describing the various functions of the disclosed subject matter, the present disclosure below employs conceptual subdivision into functional units.

The first unit may comprise a scaler/inverse transform unit (551). A scaler/inverse transform unit 551 receives quantized transform coefficients and control information from the parser 520, including information indicating which type of inverse transform is used, block size, quantization factors/parameters, quantized scaling matrix, and location (lie) as a symbol 521. The sealer/inverse transform unit (551) may output a block comprising sample values, which may be input into the aggregator (555).

In some cases, the output samples of the scaler/inverse transform unit (551) may belong to an intra-coded block; namely: the predictive information from the previously reconstructed picture is not used, but a block of predictive information from the previously reconstructed portion of the current picture may be used. Such predictive information may be provided by an intra picture prediction unit (552). In some cases, the intra picture prediction unit (552) uses block information that has been reconstructed and stored around the current picture buffer (558) to generate a surrounding block that is the same size and shape as the block being reconstructed. For example, the current picture buffer (558) buffers partially reconstructed current pictures and/or fully reconstructed current pictures. In some implementations, the aggregator (555) adds, on a per sample basis, the prediction information generated by the intra prediction unit (552) to the output sample information provided by the scaler/inverse transform unit (551).

In other cases, the output samples of the scaler/inverse transform unit (551) may belong to inter-coding and potential motion compensation blocks. In this case, the motion compensation prediction unit (553) may access the reference picture memory (557) to extract samples for inter prediction. After motion compensating the extracted samples according to the symbol (521), these samples may be added by an aggregator (555) to the output of a scaler/inverse transform unit (551) (the output of unit 551 may be referred to as residual samples or residual signals), thereby generating output sample information. The retrieval of the prediction samples by the motion compensated prediction unit (553) from an address within the reference picture memory (557) may be controlled by a motion vector, and the motion vector is used by the motion compensated prediction unit (553) in the form of the symbol (521), e.g. comprising a X, Y component (offset) and a reference picture component (time). When sub-sample accurate motion vectors are used, motion compensation may include interpolation of sample values extracted from a reference picture store (557), and associated with motion vector prediction mechanisms, and so on.

The output samples of the aggregator (555) may be employed by various loop filtering techniques in a loop filter unit (556). Video compression techniques may include in-loop filter techniques that are controlled by parameters included in an encoded video sequence (also referred to as an encoded video stream), and that are available to a loop filter unit (556) as symbols (521) from a parser (520). However, in other embodiments, the video compression techniques may also be responsive to meta information obtained during decoding of a previous (in decoding order) portion of an encoded picture or encoded video sequence, as well as to previously reconstructed and loop filtered sample values. Several types of loop filters may be part of loop filter unit 556 in different orders, as will be described in further detail below.

The output of the loop filter unit (556) may be a stream of samples, which may be output to a display device (512) and stored in a reference picture memory (557) for use in subsequent inter picture prediction.

Once fully reconstructed, some encoded pictures may be used as reference pictures for future inter-picture prediction. For example, once an encoded picture corresponding to a current picture is fully reconstructed and the encoded picture is identified (by, for example, a parser (520)) as a reference picture, the current picture buffer (558) may become part of a reference picture memory (557) and a new current picture buffer may be reallocated before starting to reconstruct a subsequent encoded picture.

The video decoder (510) may perform decoding operations according to predetermined video compression techniques employed in, for example, the ITU-T h.265 standard. The coded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the coded video sequence follows the syntax of the video compression technique or standard and the configuration files recorded in the video compression technique or standard. In particular, a profile may select some tools from all tools available in a video compression technology or standard as the only tools available under the profile. In order to meet the standard, it is also required that the complexity of the encoded video sequence is within the range defined by the level of the video compression technique or standard. In some cases, the hierarchy limits a maximum picture size, a maximum frame rate, a maximum reconstructed sample rate (measured in units of, for example, mega samples per second), a maximum reference picture size, and so on. In some cases, the limits set by the hierarchy may be further defined by hypothetical reference decoder (Hypothetical Reference Decoder, HRD) specifications and metadata managed by an HRD buffer signaled in the encoded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be part of the encoded video sequence. The additional data may be used by a video decoder (510) to properly decode the data and/or more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal, spatial, or signal-to-noise ratio (signal noise ratio, SNR) enhancement layer, redundant slices, redundant pictures, forward error correction codes, and the like.

Fig. 6 is a block diagram of a video encoder (603) according to an embodiment of the present disclosure. The video encoder (603) is disposed in the electronic device (620). The electronic device (620) may further include a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used in place of the video encoder (403) in the embodiment of fig. 4.

The video encoder (603) may receive video samples from a video source (601) (not part of the electronic device (620) in the fig. 6 embodiment) that may acquire video images to be encoded by the video encoder (603). In another embodiment, the video source (601) may be implemented as part of an electronic device (620).

The video source (601) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (603), which may have any suitable bit depth (e.g., 8 bits, 10 bits, 12 bits … …), any color space (e.g., bt.601YCrCb, RGB, XYZ … …), and any suitable sampling structure (e.g., YCrCb 4:2:0, Y CrCb 4: 4). In a media service system, a video source (601) may be a storage device capable of storing previously prepared video. In a video conferencing system, the video source (601) may be a camera that collects local image information as a video sequence. Video data may be provided as a plurality of individual pictures or images that are given motion when viewed in sequence. The picture itself may be implemented as a spatial pixel array, where each pixel may include one or more samples, depending on the sampling structure, color space, etc. being used. The relationship between pixels and samples can be readily understood by those skilled in the art. The following focuses on describing the sample.

According to some example embodiments, the video encoder (603) may encode and compress pictures of the source video sequence into an encoded video sequence (643) in real time or under any other temporal constraint required by the application. Performing the appropriate encoding speed constitutes a function of the controller (650). In some embodiments, the controller (650) may control and be functionally coupled to other functional units as described below. For simplicity, coupling is not shown. The parameters set by the controller (650) may include rate control related parameters (picture skip, quantizer, lambda value of rate distortion optimization techniques, etc.), picture size, picture group (group of pictures, GOP) layout, maximum motion vector search range, etc. The controller (650) may be used to have other suitable functions related to the video encoder (603) optimized for a certain system design.

In some exemplary embodiments, the video encoder (603) operates in a coding loop. As a simple description, in an embodiment, the encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on the input picture and reference picture to be encoded) and a (local) decoder (633) embedded in the video encoder (603). The decoder (633) reconstructs the symbols to create sample data in a manner similar to the way the (remote) decoder created the sample data, even though the embedded decoder 633 processes the video stream encoded by the source encoder 630 without entropy encoding (since in the video compression technique contemplated by the present application, any compression between the symbols in the entropy codec and the encoded video stream is lossless). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since decoding of the symbol stream produces a bit-accurate result independent of the decoder location (local or remote), the content in the reference picture memory (634) is also bit-accurate between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction portion of the encoder are exactly the same as the sample values "seen" when the decoder would use prediction during decoding. This reference picture synchronicity rationale (and drift that occurs if synchronicity cannot be maintained due to channel errors, for example) is used to improve the quality of the codec.

The operation of the "local" decoder (633) may be the same as, for example, the "remote" decoder of the video decoder (510) that has been described in detail above in connection with fig. 4. However, referring briefly to fig. 5 in addition, when a symbol is available and the entropy encoder (645) and the decoder (520) are able to losslessly encode/decode the symbol into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and the decoder (520), may not be implemented entirely in the local decoder (633) in the encoder.

It can be observed at this point that any decoder technique other than parsing/entropy decoding that exists only in the decoder must also exist in the corresponding encoder in substantially the same functional form. For this reason, the present application is sometimes focused on decoder operations, which are related to the decoding portion of the encoder. The description of the encoder technique may be simplified because the encoder technique is reciprocal to the fully described decoder technique. A more detailed description of the encoder is provided below, only in certain areas or aspects.

During operation, in some example embodiments, the source encoder (630) may perform motion compensated predictive encoding. The motion compensated predictive coding predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as "reference pictures". In this way, the encoding engine (632) encodes differences (or residuals) in the color channel between pixel blocks of an input picture and pixel blocks of a reference picture that may be selected as a prediction reference for the input picture. The term "residual" and adjective form "residual" are used interchangeably.

The local video decoder (633) may decode encoded video data of a picture, which may be designated as a reference picture, based on the symbol created by the source encoder (630). The operation of the encoding engine (632) may be a lossy process. When encoded video data may be decoded at a video decoder (not shown in fig. 6), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates the decoding process that may be performed on the reference picture by the video decoder and may cause the reconstructed reference picture to be stored in the reference picture cache (634). In this way, the video encoder (603) may locally store a copy of the reconstructed reference picture that has common content (no transmission errors) with the reconstructed reference picture to be obtained by the far-end video decoder.

The predictor (635) may perform a prediction search for the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or some metadata, such as reference picture motion vectors, block shapes, etc., that may be suitable prediction references for the new picture. The predictor (635) may operate on a block of samples by block of pixels to find a suitable prediction reference. In some cases, from the search results obtained by the predictor (635), it may be determined that the input picture may have prediction references taken from a plurality of reference pictures stored in the reference picture memory (634).

The controller (650) may manage the encoding operations of the source encoder (630) including, for example, setting parameters and subgroup parameters for encoding video data.

The outputs of all of the above functional units may be entropy encoded in an entropy encoder (645). An entropy encoder (645) losslessly compresses symbols generated by the various functional units according to techniques such as huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into an encoded video sequence.

The transmitter (640) may buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which may be a hardware/software link to a storage device that is to store encoded video data. The transmitter (640) may combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and/or an auxiliary data stream (source not shown).

The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign each encoded picture a certain encoded picture type, but this may affect the encoding techniques applicable to the respective picture. For example, a picture may generally be assigned to any one of the following picture types:

An intra picture (I picture), which may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow for different types of intra pictures, including, for example, independent decoder refresh (Independent Decoder Refresh, "IDR") pictures. Variations of the I picture and its corresponding applications and features are known to those of ordinary skill in the art.

A predictive picture (P-picture), which may be a picture that may be encoded and decoded using intra-or inter-prediction that predicts sample values for each block using at most one motion vector and a reference index.

Bi-predictive pictures (B-pictures), which may be pictures that can be encoded and decoded using intra-or inter-prediction that predicts sample values for each block using at most two motion vectors and a reference index. Similarly, multiple predictive pictures may use more than two reference pictures and associated metadata for reconstructing a single block.

A source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4 x 4, 8 x 8, 4 x 8, or 16 x 16 samples), and encoded block by block. These blocks may be predictive coded with reference to other (coded) blocks, which are determined from the coding allocation applied to the respective pictures of the blocks. For example, a block of an I picture may be non-predictive encoded, or the block may be predictive encoded (spatial prediction or intra prediction) with reference to an already encoded block of the same picture. The pixel blocks of the P picture may be prediction encoded by spatial prediction or by temporal prediction with reference to a previously encoded reference picture. A block of B pictures may be prediction encoded by spatial prediction or by temporal prediction with reference to one or two previously encoded reference pictures. For other purposes, the source picture or the inter-processed picture may be subdivided into other types of blocks. The partitioning of the encoded blocks and other types of blocks may or may not follow the same manner, as described in further detail below.

The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as the ITU-T h.265 recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. The encoded video data may accordingly conform to the syntax specified by the video encoding technique or standard used.

In some exemplary embodiments, the transmitter (640) may transmit additional data when transmitting the encoded video. The source encoder (630) may take such data as part of the encoded video sequence. The additional data may include temporal/spatial/SNR enhancement layers, redundant pictures and slices, other forms of redundant data, SEI messages, VUI parameter set slices, and the like.

The acquired video may be used as a plurality of source pictures (video pictures) in a time series. Intra picture prediction (often abbreviated as intra prediction) exploits spatial correlation in a given picture, while inter picture prediction exploits (temporal or other) correlation between pictures. In an embodiment, a specific picture being encoded/decoded is divided into blocks, and the specific picture being encoded/decoded is referred to as a current picture. When a block in a current picture is similar to a reference block in a reference picture that has been previously encoded and still buffered in video, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case of using multiple reference pictures, the motion vector may have a third dimension that identifies the reference picture.

In some example embodiments, bi-prediction techniques may be used in inter-picture prediction. According to bi-prediction techniques, two reference pictures are used, e.g., a first reference picture and a second reference picture, both preceding a current picture in video in decoding order (but possibly in the past or future, respectively, in display order). The block in the current picture may be encoded by a first motion vector pointing to a first reference block in a first reference picture and a second motion vector pointing to a second reference block in a second reference picture. In particular, the block may be jointly predicted by a combination of the first reference block and the second reference block.

Furthermore, merge mode techniques may be used in inter picture prediction to improve coding efficiency.

According to some exemplary embodiments of the present disclosure, prediction such as inter-picture prediction and intra-picture prediction is performed in units of blocks. For example, pictures in a sequence of video pictures are partitioned into Coding Tree Units (CTUs) for compression, the CTUs in the pictures having the same size, e.g., 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three parallel coding tree blocks (coding tree block, CTB), which are one luma CTB and two chroma CTBs. Still further, each CTU may be split into one or more Coding Units (CUs) in a quadtree. For example, a 64×64 pixel CTU may be split into one 64×64 pixel CU, or 4 32×32 pixel CUs. Each of the one or more 32 x 32 blocks may be further partitioned into 4 16 x 16 pixel CUs. In some embodiments, during encoding, each CU is analyzed to determine a prediction type, such as an inter prediction type or an intra prediction type, for the CU from among various prediction types. Furthermore, depending on temporal and/or spatial predictability, a CU is split into one or more Prediction Units (PUs). In general, each PU includes a luminance Prediction Block (PB) and two chrominance PB. In an embodiment, a prediction operation in encoding (encoding/decoding) is performed in units of prediction blocks. Partitioning a CU into PUs (or PBs of different color channels) may be done in various spatial modes. For example, luminance or chrominance PB may include a matrix of sample values (e.g., luminance values), such as 8 x 8 pixels, 16 x 16 pixels, 8 x 16 pixels, 16 x 8 pixel samples, and so forth.

Fig. 7 is a diagram of a video encoder (703) according to another embodiment of the present disclosure. A video encoder (703) is for receiving a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures and encoding the processing block into an encoded picture that is part of the encoded video sequence. In this embodiment, a video encoder (703) is used in place of the video encoder (403) in the embodiment of fig. 4.

For example, the video encoder (703) receives a matrix of sample values for a processing block, such as a prediction block of 8 x 8 samples, or the like. The video encoder (703) uses, for example, rate-distortion optimization (rate-distortion optimization, RDO) to determine whether to encode the processing block using intra-mode, inter-mode, or bi-prediction mode. When it is determined to encode the processing block in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into the encoded picture; and when it is determined to encode the processing block in inter mode or bi-predictive mode, the video encoder (703) may encode the processing block into the encoded picture using inter prediction or bi-predictive techniques, respectively. In some exemplary embodiments, the merge mode may be used as a sub-mode of inter picture prediction, wherein motion vectors are derived from one or more motion vector predictors without resorting to encoded motion vector components outside of the predictors. In some other embodiments, there may be motion vector components that are applicable to the subject block. Accordingly, the video encoder (703) comprises components not shown in fig. 7, such as a mode decision module for determining a prediction mode of the processing block.

In the embodiment of fig. 7, the video encoder (703) includes an inter-frame encoder (730), an intra-frame encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725) coupled together as shown in the exemplary arrangement in fig. 7.

An inter-frame encoder (730) is used to receive samples of a current block (e.g., a processed block), compare the block to one or more of the reference blocks (e.g., blocks in a previous picture and a subsequent picture in display order), generate inter-frame prediction information (e.g., redundancy information description according to inter-frame coding techniques, motion vectors, merge mode information), and calculate inter-frame prediction results (e.g., predicted blocks) based on the inter-frame prediction information using any suitable technique. In some embodiments, the reference picture is a decoded reference picture that is decoded based on the encoded video information using a decoding unit 633 (shown as residual decoder 728 in fig. 7 as described in further detail below) embedded in the exemplary encoder 620 in fig. 6.

An intra encoder (722) is used to receive samples of a current block (e.g., process the block), compare the block to blocks encoded in the same picture, generate quantization coefficients after transformation, and in some cases also generate intra prediction information (e.g., according to intra prediction direction information of one or more intra coding techniques). The intra encoder (722) also calculates an intra prediction result (e.g., a predicted block) based on the intra prediction information and a reference block in the same picture.

A general controller (721) is used to determine general control data and to control other components of the video encoder (703) based on the general control data. In an embodiment, a general purpose controller (721) determines a prediction mode of a block and provides a control signal to a switch (726) based on the prediction mode. For example, when the prediction mode is an intra mode, the general controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723) and controls the entropy encoder (725) to select intra prediction information and add the intra prediction information in a bitstream; and when the prediction mode of the block is an inter mode, the general controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select inter prediction information and add the inter prediction information in a bitstream.

A residual calculator (723) calculates a difference (residual data) between the received block and a prediction result of a block selected from an intra-frame encoder (722) or an inter-frame encoder (730). A residual encoder (724) is used to encode residual data to generate transform coefficients. In an embodiment, a residual encoder (724) is used to convert residual data from the time domain to the frequency domain and generate transform coefficients. The transform coefficients are then processed through quantization to obtain quantized transform coefficients. In various exemplary embodiments, the video encoder (703) further comprises a residual decoder (728). A residual decoder (728) is used to perform an inverse transform and generate decoded residual data. The decoded residual data may be suitably used by an intra encoder (722) and an inter encoder (730). For example, the inter-encoder (730) may generate a decoded block based on the decoded residual data and the inter-prediction information, and the intra-encoder (722) may generate a decoded block based on the decoded residual data and the intra-prediction information. The decoded blocks are processed appropriately to generate decoded pictures, and the decoded pictures may be buffered in a memory circuit (not shown) and used as reference pictures.

An entropy encoder (725) is used to format the code stream to produce encoded blocks and perform entropy encoding and decoding. The entropy encoder (725) generates various information in the code stream. In an embodiment, the entropy encoder (725) is used to obtain general control data, selected prediction information (e.g., intra prediction information or inter prediction information), residual information, and other suitable information in the bitstream. It should be noted that, in accordance with the disclosed subject matter, there is no residual information when encoding a block in either inter mode or in a merge sub-mode of bi-prediction mode.

Fig. 8 is a diagram of an exemplary video decoder (810) according to another embodiment of the present disclosure. A video decoder (810) is configured to receive encoded pictures that are part of an encoded video sequence and decode the encoded pictures to generate reconstructed pictures. In an embodiment, a video decoder (810) is used in place of the video decoder (410) in the embodiment of fig. 4.

In the fig. 8 embodiment, video decoder (810) includes an entropy decoder (871), an inter decoder (880), a residual decoder (873), a reconstruction module (874), and an intra decoder (872) coupled together in an exemplary arrangement as shown in fig. 8.

The entropy decoder (871) may be used to reconstruct certain symbols from the encoded pictures, the symbols representing syntax elements that make up the encoded pictures. Such symbols may include, for example, a mode used to encode the block (e.g., intra mode, inter mode, bi-predictive mode, merge sub-mode, or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata used by the intra decoder (872) or inter decoder (880) to predict, residual information in the form of, for example, quantized transform coefficients, and so forth. In an embodiment, when the prediction mode is an inter or bi-directional prediction mode, providing inter prediction information to an inter decoder (880); and providing intra prediction information to an intra decoder (872) when the prediction type is an intra prediction type. The residual information may be quantized via inverse quantization and provided to a residual decoder (873).

An inter decoder (880) is configured to receive inter prediction information and generate an inter prediction result based on the inter prediction information.

An intra decoder (872) is configured to receive intra-prediction information and generate a prediction result based on the intra-prediction information.

A residual decoder (873) is configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to transform a residual from a frequency domain to a spatial domain. The residual decoder (873) might also utilize certain control information (to obtain the quantizer parameter QP), and that information could be provided by the entropy decoder (871) (data path not labeled, since this is only low data volume control information).

A reconstruction module (874) is used to combine the residual output by the residual decoder (873) with the prediction result (which may be output by the inter prediction module or the intra prediction module) in the spatial domain to form a reconstructed block, which may form part of a reconstructed picture, which in turn may be part of a reconstructed video. It should be noted that other suitable operations, such as deblocking operations, may be performed to improve visual quality.

It should be noted that video encoder (403), video encoder (603) and video encoder (703) as well as video decoder (410), video decoder (510) and video decoder (810) may be implemented using any suitable technique. In some example embodiments, the video encoder (403), the video encoder (603), and the video encoder (703), and the video decoder (410), the video decoder (510), and the video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), video encoder (603) and video encoder (703), and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more processors executing software instructions.

Returning to the intra-prediction process, where samples in a block (e.g., a luma or chroma prediction block, or an encoded block that is not further partitioned into prediction blocks) are predicted by samples of neighboring, next neighboring, or other lines, or other multiple lines, or a combination thereof, to generate a prediction block. The residual between the actual coding block and the prediction block may be processed by transformation and then quantized. Various intra prediction modes may be made available and parameters related to intra mode selection and other parameters may be signaled in the bitstream. For example, various intra-prediction modes may relate to one or more line locations for prediction samples, a direction in which the prediction samples are selected from one or more prediction lines, and other special intra-prediction modes.

For example, a set of intra-prediction modes (interchangeably referred to as "intra-modes") may include a predefined number of directional intra-prediction modes. As described above with respect to the example embodiment of fig. 1, these intra-prediction modes may correspond to a predefined number of directions along which to select the out-of-block samples as predictions of the samples predicted in a particular block. In another particular example embodiment, eight (8) primary orientation modes may be supported and predefined, the eight (8) primary orientation modes corresponding to angles of 45 to 207 degrees from the horizontal axis.

In some other implementations of intra prediction, to further exploit the greater variety of spatial redundancies in directional texture, directional intra modes can be further extended to finer granularity angular sets. For example, the 8-angle embodiment described above may be configured to provide eight nominal (nominal) angles, referred to as v_pred, h_pred, d45_pred, d135_pred, d113_pred, d157_pred, d203_pred, and d67_pred, as illustrated in fig. 9, and a predetermined number (e.g., 7) of smaller angles may be added for each nominal angle. With such extensions, a larger total number (e.g., 56 in this example) of orientation angles corresponding to the same number of predefined orientation intra modes may be used for intra prediction. The predicted angle may be represented by the intra angle plus an angle delta from nominal frames. In the particular example described above, there are 7 finer angular directions per nominal angle, and the angle delta may be-3 to 3 times the step size of 3 degrees.

In some embodiments, alternatively or in addition to the directional intra-modes described above, a predefined number of non-directional intra-prediction modes may be predefined and provided. For example, 5 non-directional intra modes called smooth intra prediction modes may be specified. These non-directional intra prediction modes may be specifically referred to as DC, PAETH, SMOOTH, SMOOTH _v and smooth_h intra modes. Prediction of samples of a particular block in these exemplary non-directional modes is illustrated in fig. 10. As an example, fig. 10 shows a 4 x 4 block 1002, predicted by samples from an upper adjacent row and/or a left adjacent row. The particular sample 1010 in block 1002 may correspond directly to the upper sample 1004 of the sample 1010 in the upper adjacent row of block 1002, the upper left sample 1006 of the sample 1010 that is the intersection of the upper adjacent row and the left adjacent row, and the left sample 1008 of the sample 1010 in the left adjacent row of block 1002. For the exemplary DC intra prediction mode, the average of the left neighbor sample 1008 and the upper neighbor sample 1004 may be used as a predictor for the sample 1010. For the exemplary PAETH intra prediction mode, an upper reference sample 1004, a left reference sample 1008, and an upper left reference sample 1006 may be extracted, and any value of the three reference samples that is closest (upper + left-upper left) may then be set as the predictor of sample 1010. For the example smoothv intra prediction mode, the samples 1010 may be predicted by quadratic interpolation in the vertical direction of the upper left neighbor samples 1006 and the left neighbor samples 1008. For the example smoothh_h intra prediction mode, the samples 1010 may be predicted by quadratic interpolation in the horizontal direction of the upper left neighboring sample 1006 and the upper neighboring sample 1004. For the example smoothh intra prediction mode, the samples 1010 may be predicted by an average of quadratic interpolation in the vertical and horizontal directions. The above-described non-directional intra mode embodiments are illustrated as non-limiting examples only. Other neighboring rows and other non-directionally selected samples are also contemplated, as well as the manner in which the predicted samples of a particular sample are predicted in the prediction block.

The particular intra-prediction mode selected by the encoder from among the directional or non-directional modes at the various codec levels above (pictures, slices, blocks, units, etc.) may be signaled in the bitstream. In some example embodiments, 8 exemplary nominal orientation modes and 5 non-angular smoothing modes (13 options total) may be signaled first. Then, if the signaled mode is one of 8 nominal angle intra modes, an index is further signaled to indicate the selected angle δ as the corresponding signaled nominal angle. In some other example implementations, all intra-prediction modes may be indexed together (e.g., 56 directional modes plus 5 non-directional modes to generate 61 intra-prediction modes) for signaling.

In some example implementations, example 56 or other number of directional intra-prediction modes may be implemented with a unified directional predictor that projects each sample of the block to a reference sub-sample position and interpolates the reference sample through a 2-tap bilinear filter.

In some implementations, an additional filter mode, referred to as the filter intra (FILTER INTRA) mode, may be designed in order to capture the attenuated spatial correlation with respect to the reference samples on the edges. For these modes, in addition to the off-block samples, intra-block prediction samples may also be used as intra-prediction reference samples for some patches within the block. For example, these modes may be predefined and may be used at least for intra prediction of luminance blocks (or luminance blocks only). A predefined number (e.g., five) of filter intra modes may be pre-designed, each filter intra mode being represented by a set of n-tap filters (e.g., 7-tap filters) reflecting correlations between, for example, samples in a 4 x 2 patch and n adjacent samples adjacent thereto. In other words, the weight factor of the n-tap filter may be position dependent. Taking 8 x 8 blocks, 4 x 2 patches, and 7 tap filtering as an example, as shown in fig. 11, an 8 x 8 block 1102 may be partitioned into 8 4 x 2 patches. These patches are represented in fig. 11 by B0, B1, B2, B3, B4, B5, B6 and B7. For each patch, its 7 adjacent samples (indicated by R0 to R6 in fig. 11) may be used to predict the samples in the current patch. For patch B0, all neighboring samples may have been reconstructed. But for other patches some of the neighboring samples are in the current block and therefore may not be reconstructed and then the predicted values of the direct neighboring samples are used as references. For example, all of the neighboring samples of patch B7 illustrated in fig. 11 are not reconstructed, and thus predicted samples of the neighboring samples are used instead.

In some implementations of intra prediction, one color component may be predicted using one or more other color components. The color component may be any one of components in a color space such as YCrCb, RGB, XYZ. For example, prediction of a chrominance component (e.g., a chrominance block) from a luminance component (e.g., a luminance reference sample) may be implemented, referred to as predicting chrominance (or CfL, chroma from Luma) from luminance. In some example embodiments, cross-color prediction may only allow for luminance to chrominance. For example, chroma samples in a chroma block may be modeled as a linear function that conforms to reconstructed luma samples. CfL predictions can be implemented as follows:

CfL(α)＝α×L ^AC +DC (1)

wherein L is ^AC Represents the AC contribution of the luminance component, α represents a parameter of the linear model, and DC represents the DC contribution of the chrominance component. For example, the AC component is obtained for each sample in the block, while the DC component is obtained for the entire block. In particular, the reconstructed luma samples may be subsampled into the chroma resolution, and then the average luma value (DC of luma) may be subtracted from each luma value to form the AC contribution in the luma. The AC contribution of luminance is then used in the linear mode of equation (1) to predict the AC value of the chrominance component. To approximate or predict the chroma AC component from the luma AC contribution, the example CfL implementation may determine the parameter a based on the original chroma samples and signal them in the bitstream instead of requiring the decoder to calculate the scaling parameters. This reduces decoder complexity and results in more accurate predictions. In some example embodiments, the DC contribution of the chroma component may be calculated using an intra DC mode within the chroma component.

Transformation of the residual of the intra-or inter-prediction block may then be performed, followed by quantization of the transform coefficients. For the purpose of performing a transform, both intra-coded blocks and inter-coded blocks may be further partitioned into multiple transform blocks prior to the transform (sometimes interchangeably used as "transform units", even though the term "unit" is typically used to refer to a collection of three-color channels, e.g., a "coding unit" would include luma and chroma coded blocks). In some implementations, a maximum partition depth of the encoded block (or predicted block) may be specified (the term "encoded block" may be used interchangeably with "encoded block"). For example, such partitions may not exceed 2 levels. The prediction block may be divided into transform blocks differently between an intra prediction block and an inter prediction block. However, in some implementations, such partitioning between intra-predicted blocks and inter-predicted blocks may be similar.

In some example embodiments, and for intra-coded blocks, transform partitioning may be done in such a way that all transform blocks have the same size, and the transform blocks are coded in raster scan order. An example of such transform block partitioning of an intra-coded block is shown in fig. 12. Specifically, fig. 12 shows an encoded block 1202 partitioned into 16 transform blocks of the same block size via an intermediate level quadtree partition 1204, as shown at 1206. An example raster scan order for encoding is illustrated by the ordered arrows in fig. 12.

In some example implementations, for inter-coded blocks, transform unit partitioning may be done in a recursive manner, where the partition depth reaches a predefined number of levels (e.g., 2 levels). As shown in fig. 13, the partitioning may be stopped or continued recursively for any child partition and at any level. In particular, fig. 13 shows an example in which a block 1302 is split into four quadtree sub-blocks 1304, and one of these sub-blocks is further split into four second-level transform blocks, while the division of the other sub-blocks stops after the first level, resulting in a total of 7 two different-sized transform blocks. The ordered arrows in fig. 13 further illustrate an example raster scan order of encoding. Although fig. 13 illustrates an example embodiment of quadtree partitioning of square transform blocks up to two levels, in some generation embodiments, the transform partition may support 1:1 (square), 1:2/2:1 and 1:4/4:1, ranging from 4 x 4 to 64 x 64. In some exemplary embodiments, if the encoded block is less than or equal to 64×64, the transform block partition may be applied only to the luminance component (in other words, the chroma transform block will be the same as the encoded block under this condition). Otherwise, if the coding block width or height is greater than 64, both the luma coding block and the chroma coding block may be implicitly divided into multiples of min (W, 64) x min (H, 64) and min (W, 32) x min (H, 32) transform blocks, respectively.

Then, a main transform may be performed on each of the above transform blocks. The main transform essentially moves the residuals in the transform block from the spatial domain to the frequency domain. In some embodiments of the actual primary transform, to support the above-described exemplary extended coding block partitioning, multiple transform sizes (transform sizes from 4 points to 64 points for each of the two dimensions are unequal) and transform shapes (squares; rectangles with aspect ratios of 2:1/1:2 and 4:1/1:4) may be allowed.

Turning to the actual main transform, in some example embodiments, the two-dimensional transform process may involve the use of a hybrid transform kernel (e.g., which may be composed of different dimensional transforms for each dimension in the encoded residual transform block). Exemplary one-dimensional transformation kernels may include, but are not limited to: (a) 4-point, 8-point, 16-point, 32-point, 64-point DCT-2; (b) 4-point, 8-point, 16-point asymmetric DST (DST-4, DST-7) and flipped versions; (c) 4-point, 8-point, 16-point, 32-point identity transformation. The selection of the transform kernel for each dimension may be based on a rate-distortion (RD) standard. For example, the basis functions of DCT-2 and asymmetric DST that can be implemented are listed in Table 1.

Table 1: exemplary primary transform basis functions (DCT-2, DST-4, DST-7, and IDTX for N-point inputs).

In some example embodiments, the availability of a hybrid transform core for a particular primary transform embodiment may be based on the transform block size and the prediction mode. Example dependencies are listed in table 2. For chrominance components, the transform type selection may be performed implicitly. For example, for intra prediction residuals, a transform type may be selected according to an intra prediction mode, as specified in table 3. For inter prediction residues, the transform type of the chroma block may be selected according to the transform type selection of the co-located luma block. Thus, for the chrominance components, there is no transform type signaling in the code stream. IDTX in Table 1 represents an identity transformation.

Table 2: AV1 mixes the transform kernels and is based on the availability of prediction modes and block sizes. Here → sum ∈ represents the horizontal and vertical dimensions; and v and x denote the availability of cores for the block size and prediction mode.

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Table 3: transform type selection for chroma component intra prediction residues.

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In some example embodiments, a transform skip mode may be applied when performing a transform. The transform skip mode may include a plurality of variations.

In one embodiment, the two-dimensional transform described above may be less efficient and skipped (i.e., no transform is needed) when the residuals in the residual block are highly uncorrelated.

In one embodiment, as shown in fig. 14, the one-dimensional transform is applied only in the vertical direction, and the one-dimensional transform in the horizontal direction is skipped. This mode is called transform skipping in the horizontal direction. A 4×4 block is an exemplary block of transform coefficients (or, for simplicity, also referred to as a transform block) obtained after one-dimensional transform in the vertical direction, each unit showing a corresponding transform coefficient. It can be seen that the low frequency components of the transform coefficients obtained after one-dimensional transform are concentrated up the block, while the high frequency components are concentrated down the block. Specifically, in this exemplary block, all transform coefficients in the fourth row are zero.

In one embodiment, as shown in fig. 15, the one-dimensional transform is applied only in the horizontal direction, and the one-dimensional transform in the vertical direction is skipped. This mode is called transform skipping in the vertical direction. A 4×4 block is an exemplary transform coefficient block obtained by one-dimensional transform in the horizontal direction, and each unit shows a corresponding transform coefficient. It can be seen that the low frequency components of the transform coefficients obtained after one-dimensional transform are concentrated in the left column of the block, while the high frequency components are concentrated in the right column of the block. Specifically, in this exemplary block, all transform coefficients in the fourth column are zero.

In some example embodiments, IDTX (identification transform) may be used to skip transform coding in a certain direction (e.g., horizontal or vertical), and IDTX may be particularly advantageous for coding sharp edges.

In some example implementations, the secondary transform may be performed on the primary transform coefficients. For example, LFNST (low frequency inseparable transform), known as reduced secondary transform, may be applied between forward primary transform and quantization (at the encoder) and between dequantization and inverse primary transform (at the decoder side) to further de-correlate the primary transform coefficients.

In some example embodiments, the transformation may include a line graph transformation (LGT, line Graph Transforms), as shown in fig. 16. The graph may be a generic mathematical structure consisting of a collection of vertices and edges for modeling similarity relationships between objects of interest. In practice, a weighted graph (assigning a set of weights to edges and possibly vertices) may provide sparse representation for robust modeling of signals/data. LGT may improve coding efficiency by providing better adaptation to different block statistics. The separable LGT may be designed and optimized by learning line graphs from the data to model row-by-row and column-by-column statistics of the block residual signal, with an associated generalized graph laplacian (GGL, generalized graph Laplacian) matrix used to derive the LGT.

In one embodiment, given a weighting map G (W, V), the GGL matrix may be defined as le=d-w+v, where W may be represented by a non-negative edge weight W _c The constituent adjacency matrix, D, may be the angle matrix, and V may be the representation weighted self-loop Vc ₁ Sum Vc ₂ Is a diagonal matrix of (a). Matrix L _e Can be expressed as:

LGT can then be derived by the eigen decomposition of GGL Lc.

L _c ＝ UΦU ^T (3)

Wherein,the columns of the orthogonal matrix U are the basis vectors of LGT and Φ is the diagonal eigenvalue matrix. In effect, DCT and DST (including DCT-2, DCT-8, and DST 7) are LGTs derived from some form of GGL. Setting Vc ₁ Deriving DCT-2 =0; setting vc=w _c Deriving DST-7; setting Vc ₂ ＝w _c Deriving DCT-8; setting Vc ₁ ＝2w _c Deriving DST-4; setting Vc ₂ ＝2w _c DCT-4 is derived.

LGT may be implemented as a matrix multiplication. By setting Vc in Lc ₁ ＝2w _c To derive a 4p LGT core, meaning that it is DST-4. By setting Vc in Lc ₁ ＝1.5w _c Deriving an 8p LGT core may be performed by setting Vc in Lc ₁ ＝w _c To derive 16p, 32p and 64p LGT cores, meaning that it is DST-7.

In some implementations, for coefficient coding, the coefficients may be coded using a hierarchical mapping scheme, as compared to coding schemes that process each two-dimensional transform coefficient in sequence. For each transform unit (or transform block), the coefficient codec starts with encoding and decoding skipped symbols, followed by signaling of the main transform core type and end-of-block (EOB) position without skipping the transform codec. Thereafter, the coefficient values are encoded and decoded in a multi-level mapping manner with sign values added. The hierarchical mapping codec is three hierarchical planes, namely a low-level, a medium-level, and a high-level plane, and the symbol is encoded and decoded as another separate plane. The low, mid, and high level planes correspond to different coefficient magnitude ranges. The low-level plane corresponds to an example range of 0 to 2, the mid-level plane corresponds to an example range of 3 to 14, and the high-level plane covers a range of, for example, 15 and above. The three hierarchical planes may be encoded as follows: (a) first encoding EOB positions; (b) The low-level and mid-level planes are encoded and decoded together in a reverse scan order, which may include zig-zag scanning applied on a whole transform unit basis; (c) The symbol plane and the high-level plane are coded and decoded together according to the forward scanning sequence; (d) The remainder (coefficient level minus 14) is entropy encoded using exponential golomb coding. The context model applied to the low-level plane depends on the main transform direction (bi-directional, horizontal and vertical) and the transform size, and uses up to a predefined number (e.g., five) of neighboring (in the frequency domain) coefficients to derive the context. The mid-level plane may use a similar context model, but the number of context proximity coefficients may be reduced, e.g. from 5 to 2. The high-level planes may be encoded by exponential golomb coding without using a context model. The DC symbols are encoded and decoded using a context modeling method, wherein a weighted average of the upper and left neighboring block DC symbol values can be used to derive context information, as described in equation (4) below:

dc_sum＝∑ _{i∈neighbors} dc_sign(i)*overlap(i，curr_block) (4)

The weight depends on the length of the intersection of the neighboring transform block with the current transform block. The derived context information is used as an index to access three different contexts for DC symbol codec as shown in equation 5 below. The sign values of the other coefficients may be directly encoded and decoded without using a context model.

dc_ctx＝0 if dc_sum＝0，

＝1 if dc_sum＜0，

＝2if dc_sum＞0， (5)

In this disclosure, various embodiments for improving video encoding/decoding techniques in one-dimensional transform skip mode are disclosed. As described above, in the one-dimensional transform skip mode, the energy concentration mode is different from the two-dimensional transform mode in which the transform is performed in two dimensions. For example, in one-dimensional transform skip mode, energy is concentrated in the up-or left-column of the transform block. Whereas in two-dimensional transformation the energy is concentrated, for example, in the upper left corner. By utilizing different energy concentration modes in the one-dimensional transform skip mode, these improvements may include higher video data compression rates, higher codec efficiency, and lower signaling overhead.

In this disclosure, the term "block" may refer to a transform block, an encoded block, a prediction block, and the like.

In this disclosure, the term "chroma block" may refer to a block in any chroma (color) channel.

In this disclosure, the term "transform block" may also refer to coefficients in a transform block. The term "row" may also refer to a row of coefficients in a transform block. The term "column" may also refer to a sequence of coefficients in a transform block.

Transform skipping with EOR and/or EOC signaling

In the present disclosure, a set of transform types having transform skipping in the horizontal direction is hereinafter referred to as set a. Set a may include all combinations of one-dimensional transforms where the transform kernel is a matrix. Examples of one-dimensional transforms include, but are not limited to DCT, ADST, FLIPADST, LGT, FLIPLGT, KLT, all triangular transform types (DCT types 1-8 and DST types 1-8), and their derivatives in the vertical direction and transform skipping in the horizontal direction.

In the present disclosure, a set of transform types having transform skipping in the vertical direction is hereinafter referred to as set B. Set B may include all combinations of one-dimensional transforms where the transform kernel is a matrix. Examples of one-dimensional transforms include, but are not limited to DCT, ADST, FLIPADST, LGT, FLIPLGT, KLT, all triangular transform types (DCT types 1-8 and DST types 1-8), and their derivatives in the horizontal direction and transform skipping in the vertical direction.

Embodiments in the present disclosure may be applied to luminance and/or chrominance blocks.

In some example embodiments, when a one-dimensional (1-D) transform skip is applied, instead of signaling End of Block (EOB, end of Block) values that indicate both vertical and horizontal positions (i.e., positions in the x-axis and y-axis) in a two-dimensional Block, end of Row (EOC, end of Row) or Column (EOC, end of Column) are signaled that indicate only horizontal or vertical coordinates of a position in the two-dimensional Block.

In one embodiment, as shown in fig. 14, when a transform skip is applied in only the horizontal direction (in which case a one-dimensional transform is performed in the vertical direction), EOR values are signaled to indicate the row index of the last row of a transform block (or block of transform coefficients) having at least one non-zero coefficient value. In the example shown in fig. 14, the third row is the last row with at least one non-zero coefficient value. In this case, an EOR value of 2 will be signaled. Note that the example shown in fig. 14 uses a line index 0 as the first line index. Other row index numbers (e.g., 1) may be selected as the first row index, in which case the EOR value would be changed to 3.

In one embodiment, as shown in fig. 15, when a transform skip is applied only in the vertical direction (in which case a one-dimensional transform is performed in the horizontal direction), EOC values are signaled to indicate the column index of the last column of the transform block having at least one non-zero coefficient value. In the example shown in fig. 15, the third column is the last column with at least one non-zero coefficient value. In this case, an EOC value of 2 will be signaled. Note that the example shown in fig. 15 uses column index 0 as the first column index. Other column index numbers (e.g., 1) may be selected as the first column index, in which case the EOC value would be changed to 3.

In some example embodiments, when the EOR value is signaled, the EOB value may be derived as one of: EOR steps; EOR stride-1; (eor+1) stride; or (eor+1) stride-1, where stride is the transform block width. Note that the change of these equations depends on, for example, whether the row index starts with 0 or 1, and whether the EOB starts with 0 or 1.

In some exemplary embodiments, when the transform block width is 64 or greater, the stride may be limited to a value below 64, such as 32. In this case, the encoder may consider the limited stride value when encoding and decoding the transform coefficients.

In some exemplary embodiments, when the EOC value is signaled, the EOB value may be derived as one of: EOC stride; EOC stride-1; (eoc+1) stride; or (eoc+1) step-1, wherein step is the transform block height. Note that the change of these equations depends on, for example, whether the column index starts with 0 or 1, and whether the EOB starts with 0 or 1.

In some exemplary embodiments, when the transform block height is 64 or greater, the stride may be limited to a value below 64, such as 32. In this case, the encoder may consider the limited stride value when encoding and decoding the transform coefficients.

In some exemplary embodiments, when one-dimensional transform skipping is applied in the horizontal direction only, all coefficients in rows with index less than or equal to EOR need to be encoded, whether or not they are zero. When one-dimensional transform skip is applied in the vertical direction only, all coefficients in columns with index less than or equal to EOC need to be encoded, whether or not they are zero.

In some example embodiments, when entropy encoding is performed on EOR and/or EOC, the context of entropy encoding the value of EOR and/or EOC is different from the context of entropy encoding the value of EOB because the probability model associated with EOR and/or EOC is different from the probability model associated with EOB.

In some exemplary embodiments, when transform skipping is applied in only the horizontal direction, EOR values are signaled to indicate a row index of a last row of a transform coefficient block having at least one non-zero coefficient value. The context used to entropy encode the EOR value may depend on a number of factors, including transform block height; or only on the transform block height.

In some exemplary embodiments, when a transform skip is applied only in the vertical direction, the EOC value is signaled to indicate a column index of a last column of the transform coefficient block having at least one non-zero coefficient value. The context used to entropy encode the EOC value may depend on a number of factors, including transform block width; or only on the transform block width.

In some example implementations, when the transform coefficients are encoded and transform jumps are applied in the horizontal direction only, the current transform coefficient may be derived to be non-zero if i) the current transform coefficient is the last transform coefficient to be encoded in the row indexed by EOR, and ii) all previous transform coefficients in the same row are encoded to be zero. This is particularly useful at the decoder side, as the decoder can only derive the current transform coefficients to be non-zero without decoding this information from the original video stream. Referring to fig. 14, row 2 is a row indexed by EOR. When the current transform coefficient to be processed is the last one in the line, the decoder may directly derive the current transform coefficient as non-zero since the first 3 transform coefficients in the same line are all zero. Additionally or alternatively, in this case, a flag indicating whether the level of the current transform coefficient is greater than or equal to 1 is not signaled, but will be derived by the decoder as true (meaning that the level of the current transform coefficient is greater than or equal to 1).

In some example implementations, when the transform coefficients are encoded and the transform skip is applied only in the vertical direction, the current transform coefficient is derived to be non-zero if i) the current transform coefficient is the last transform coefficient to be encoded in the column indexed by EOC, and ii) all previous transform coefficients in the same column are encoded to be zero. The decoder may simply derive the current transform coefficient as non-zero without decoding the information from the original video stream. Referring to fig. 15, column 2 is a column indexed by EOC. When the transform coefficient to be processed is the last one in the column, the decoder can directly derive the transform coefficient to be non-zero since the first 3 transform coefficients in the same column are all zero. Additionally or alternatively, a flag indicating whether the level of the current transform coefficient is greater than or equal to 1 is not signaled, but will be derived as true by the decoder.

In some example embodiments, when transform skip is applied only in the horizontal direction, the context used to entropy encode the magnitude of the current transform coefficient may depend on a number of factors including previously encoded coefficients. In one embodiment, the previously encoded coefficients considered include only the previously encoded coefficients in the same row. For example, referring to fig. 14, the context for entropy encoding the magnitude of the last transform coefficient in line 1 may depend on the previous 3 encoded coefficients in the same line. Alternatively, in another embodiment, the previously encoded coefficients considered may include only previously encoded coefficients that are immediately adjacent coefficients to the current coefficient in the same row.

In some example embodiments, when transform skip is applied only in the horizontal direction, the context used to entropy encode the magnitude of the current transform coefficient may depend on a number of factors including previously encoded coefficients. In one embodiment, the previously encoded coefficients considered include only the previously encoded coefficients in the same column. For example, referring to fig. 15, the context for entropy encoding the magnitude of the last transform coefficient in column 1 may depend on the previous 3 encoded coefficients in the same column. Alternatively, in another embodiment, the previously encoded coefficients considered may include only previously encoded coefficients that are immediately adjacent coefficients to the current coefficient in the same column.

The various embodiments described above are generally applied to one-dimensional transform skip scenes in which one-dimensional transforms are applied in one direction only and one-dimensional transforms are skipped in the other direction. These different embodiments may also be applied to identity transformation (IDTX, identity Transform).

In the various example embodiments described above, the transform coefficients in a transform block (such as the transform blocks shown in fig. 14 and 15) may or may not need to undergo additional quantization processes. For example, the transform coefficients may be obtained immediately after one-dimensional transforming the residual block. Alternatively, the transform coefficients may further undergo a quantization process to transform into quantized transform coefficients. Embodiments in the present disclosure may be applied to both unquantized transform coefficients or quantized transform coefficients. Furthermore, in the present disclosure, transform coefficients may generally refer to unquantized transform coefficients or quantized transform coefficients.

Fig. 17 illustrates an exemplary method 1700 for decoding video data. Method 1700 may include some or all of the following steps: step 1710, receiving a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and entropy coding is performed on the transformation block; a step 1720 of determining whether to apply one-dimensional transform skipping to the transform block based on a syntax element in the video bitstream; step 1730, in response to applying the one-dimensional transform skip to the transform block, obtaining an end position value associated with the transform block from the video bitstream, the end position value indicating only one of an end position in horizontal coordinates of the transform block and an end position in vertical coordinates of the transform block; horizontal and vertical end coordinates in the transformed block, and step 1740, retrieving the transformed block from the video bitstream according to the end position value.

An end position value (such as EOR or EOC) may be signaled in the code stream. In one embodiment, the indication may also be a signal for indicating whether to signal EOR or EOC.

On the decoder side, once EOR or EOC is obtained, the decoder may derive a range of positions in the code stream allocated for the transform coefficients of the transform block. The decoder may then perform entropy decoding based on the location range to obtain transform coefficients for the transform block. Note that the transform coefficients may be in a quantized format, in which case a dequantization process is performed to transform the quantized transform coefficients into an unquantized format; or the transform coefficients may be in an unquantized format. Retrieving the transform block may include deriving and/or decoding transform coefficients of the transform block from the code stream. The retrieved transform block may then undergo an inverse transform to obtain a corresponding residual block.

The embodiments in this disclosure may be used alone or in combination in any order. Further, each of the method (or embodiment), encoder, and decoder may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-volatile computer readable medium. Embodiments in the present disclosure may be applied to a luminance block or a chrominance block.

The techniques described above may be implemented as computer software by computer readable instructions and physically stored in one or more computer readable media. For example, FIG. 18 illustrates a computer system (1800) suitable for implementing certain embodiments of the disclosed subject matter.

The computer software may be encoded in any suitable machine code or computer language, and code comprising instructions may be created by means of assembly, compilation, linking, etc. mechanisms, the instructions being executable directly by one or more computer Central Processing Units (CPUs), graphics Processing Units (GPUs), etc. or by means of decoding, microcode, etc.

The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, internet of things devices, and the like.

The components shown in fig. 18 for computer system (1800) are exemplary in nature, and are not intended to limit the scope of use or functionality of the computer software implementing embodiments of the application. Nor should the configuration of components be construed as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of the computer system (1800).

The computer system (1800) may include some form of human interface input device. Such human interface input devices may be responsive to input from one or more human users via tactile input (e.g., keyboard input, sliding, data glove movement), audio input (e.g., voice, palm sound), visual input (e.g., gestures), olfactory input (not shown). The human interface device may also be used to capture certain media, such as audio (e.g., speech, music, ambient sound), images (e.g., scanned images, photographic images obtained from still-image cameras), video (e.g., two-dimensional video, three-dimensional video including stereoscopic video), and the like, which may not necessarily be directly related to human conscious input.

The human interface input device may include one or more of the following (only one of which is depicted): a keyboard (1801), a mouse (1802), a touch pad (1803), a touch screen (1810), data gloves (not shown), a joystick (1805), a microphone (1806), a scanner (1807), a camera (1808).

The computer system (1800) may also include some human interface output devices. Such human interface output devices may stimulate the sensation of one or more human users by, for example, tactile output, sound, light, and smell/taste. Such human-machine interface output devices may include haptic output devices (e.g., haptic feedback via a touch screen (1810), data glove (not shown), or joystick (1805), but there may be haptic feedback devices that do not serve as input devices), audio output devices (e.g., speakers (1809), headphones (not shown)), visual output devices (e.g., screens (1810) including cathode ray tube screens, liquid crystal screens, plasma screens, organic light emitting diode screens), each with or without touch screen input functionality, each with or without haptic feedback functionality, some of which may output two-dimensional visual output or three-dimensional or more output via means such as stereoscopic output, virtual reality glasses (not shown), holographic displays, and smoke boxes (not shown)), and printers (not shown).

The computer system (1800) may also include human-accessible storage devices and their associated media, such as optical media including high-density read-only/rewritable compact discs (CD/DVD ROM/RW) (1820) with CD/DVD or similar media (1821), thumb drive (1922), removable hard disk drive or solid state drive (1823), conventional magnetic media such as magnetic tape and floppy disks (not shown), ROM/ASIC/PLD based specialized devices such as security software protectors (not shown), and so forth.

It should also be appreciated by those skilled in the art that the term "computer-readable medium" as used in connection with the disclosed subject matter does not include transmission media, carrier waves or other transitory signals.

The computer system (1800) may also include an interface (1855) to one or more communication networks (1854). The network may be wireless, wired, optical. The network may also be a local area network, wide area network, metropolitan area network, in-vehicle and industrial networks, real-time network, delay tolerant network, and so forth. Examples of networks may include local area networks such as ethernet, wireless local area networks, cellular networks (GSM, 3G, 4G, 5G, LTE, etc.), television cable or wireless wide area digital networks (including cable television, satellite television, and terrestrial broadcast television), vehicular and industrial networks (including CANBus), and the like. Some networks typically require an external network interface adapter for connection to some general purpose data port or peripheral bus (1849) (e.g., a USB port of computer system (1800)); other systems are typically integrated into the core of the computer system (1800) by connecting to a system bus as described below (e.g., an ethernet interface is integrated into a PC computer system or a cellular network interface is integrated into a smart phone computer system). Using any of these networks, the computer system (1800) may communicate with other entities. The communication may be unidirectional, for reception only (e.g., wireless television), unidirectional, for transmission only (e.g., CAN bus to certain CAN bus devices), or bidirectional, for example, to other computer systems via a local or wide area digital network. Each of the networks and network interfaces described above may use certain protocols and protocol stacks.

The human interface device, human accessible storage device, and network interface described above may be connected to a core (1840) of the computer system (1800).

The core (1840) may include one or more Central Processing Units (CPUs) (1841), graphics Processing Units (GPUs) (1842), special purpose programmable processing units in the form of Field Programmable Gate Arrays (FPGAs) (1843), hardware accelerators (1944) for specific tasks, and the like. These devices, as well as Read Only Memory (ROM) (1845), random access memory (1846), internal mass storage (e.g., internal non-user accessible hard disk drives, solid state drives, etc.) (1847), etc., may be connected via a system bus (1848). In some computer systems, the system bus (1848) may be accessed in the form of one or more physical plugs so as to be expandable by additional central processing units, graphics processing units, and the like. The peripheral devices may be directly attached to the system bus (1848) of the core or connected through a peripheral bus (1849). The architecture of the peripheral bus includes external controller interfaces PCI, universal serial bus USB, etc. In one example, screen (1810) may be connected with graphics adapter (1850). The architecture of the peripheral bus includes PCI, USB, etc.

The CPU (1841), GPU (1842), FPGA (1843), and accelerator (1844) may execute certain instructions that, in combination, may constitute the computer code described above. The computer code may be stored in ROM (1845) or RAM (1846). The transition data may also be stored in RAM (1846), while the permanent data may be stored in, for example, internal mass storage (1847). Fast storage and retrieval of any memory device may be achieved through the use of a cache memory, which may be closely associated with one or more CPUs (1841), GPUs (1842), mass storage (1847), ROM (1845), RAM (1846), and the like.

The computer readable medium may have computer code embodied thereon for performing various computer implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present application, or they may be of the kind well known and available to those having skill in the computer software arts.

By way of example, and not limitation, a computer system having architecture (1800), and in particular core (1840), may provide functionality as a processor (including CPU, GPU, FPGA, accelerator, etc.) to execute software embodied in one or more tangible computer readable media. Such computer readable media may be media associated with the mass storage device accessible by the user as described above, as well as specific memory having a non-volatile core (1840), such as mass storage within the core (1847) or ROM (1845). Software implementing various embodiments of the present application may be stored in such devices and executed by the core (1840). The computer-readable medium may include one or more storage devices or chips according to particular needs. The software may cause the core (1840), and in particular the processor therein (including CPU, GPU, FPGA, etc.), to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM (1846) and modifying such data structures according to software-defined processes. Additionally or alternatively, the computer system may provide functionality that is logically hardwired or otherwise contained in circuitry (e.g., the accelerator (1844)) that may operate in place of or in addition to software to perform certain processes or certain portions of certain processes described herein. References to software may include logic, and vice versa, where appropriate. References to computer readable medium may include circuitry (e.g., an Integrated Circuit (IC)) storing executable software, circuitry containing executable logic, or both, where appropriate. The present application includes any suitable combination of hardware and software.

While this application has been described in terms of several exemplary embodiments, various alterations, permutations, and various substitute equivalents of the embodiments are within the scope of this application. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the application and are thus within its spirit and scope.

Appendix: acronyms

JEM joint development model

VVC next generation video coding

BMS reference set

MV motion vector

HEVC (high efficiency video coding)

Supplemental enhancement information

VUI video availability information

GOPs (generic object oriented displays) picture group

TUs conversion unit

PUs prediction Unit

CTUs coding tree unit

CTBs coding tree blocks

PBs prediction block

HRD assume reference decoder

SNR signal to noise ratio

CPU (Central processing Unit)

GPUs graphics processing unit

CRT-cathode ray tube

LCD (liquid Crystal display)

OLED (organic light emitting diode)

CD, DVD, digital video disc

ROM-ROM

RAM (random Access memory)

ASIC (application specific integrated circuit)

PLD programmable logic device

LAN local area network

Global system for mobile communications (GSM)

LTE Long term evolution

CANBus controller area network bus

USB universal serial bus

PCI-peripheral device interconnect

FPGA field programmable gate array

SSD field programmable gate array

IC-integrated circuit

HDR high dynamic range

Standard dynamic range of SDR

JVET Joint video development team

MPM most probable mode

WAIP wide-angle intra prediction

CU coding unit

PU prediction unit

TU-transform unit

CTU coding tree unit

PDPC position-dependent predictive combining

ISP intra sub-partition

SPS sequence parameter set

PPS picture parameter set

APS adaptive parameter set

VPS video parameter set

DPS decoding parameter set

ALF adaptive loop filter

SAO sample adaptive offset

CC-ALF (component-adaptive loop filter)

CDEF (compact form factor) constraint directional enhancement filter

CCSO Cross-component sample offset

LSO local sample offset

LR loop recovery filter

AV1 AO media video 1

AV2 AO media video 2

Claims (20)

1. A method for video processing, the method comprising:

receiving a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and entropy coding is carried out on the transformation block;

determining whether to apply one-dimensional transform skipping to the transform block based on syntax elements in the video bitstream;

obtaining, from the video bitstream, an end position value associated with the transform block in response to applying the one-dimensional transform skip to the transform block, the end position value indicating only one of a horizontal coordinate end position and a vertical coordinate end position in the transform block; and

The transform block is retrieved from the video bitstream according to the end position value.

2. The method of claim 1, wherein the end position value comprises one of:

an end-of-line EOR value indicating the horizontal coordinate end position in the transform block, the horizontal coordinate end position including an end line index of a last line in the transform block, the last line having at least one non-zero transform coefficient; and

a column end EOC value indicating the vertical coordinate end position in the transform block, the vertical coordinate end position including an end column index of a last column in the transform block, the last column having at least one non-zero transform coefficient.

3. A method according to claim 2, characterized in that,

signaling the line end EOR value in the video bitstream as the end position value when a transform skip is applied only in the horizontal direction of the transform block; and

when a transform skip is applied only in the vertical direction of the transform block, the column end EOC value is signaled in the video bitstream as the end position value.

4. A method according to any of claims 2 to 3, characterized in that a context for entropy encoding the end-of-line EOR value is determined based on the height of the transform block.

5. A method according to any of claims 2 to 3, characterized in that a context for entropy encoding the EOC value is determined based on the width of the transform block.

6. A method according to any one of claims 2 to 3, wherein the end of line EOR value is signaled, wherein the method further comprises: the transform coefficients in the transform block are obtained by:

in response to the current transform coefficient being the last transform coefficient in a row indexed by the EOR row end value, and all previous transform coefficients in this same row being zero:

deriving the current transform coefficient as non-zero; and

the derived level flag is true indicating that the level of the current transform coefficient is greater than or equal to 1.

7. A method according to any of claims 2 to 3, characterized in that the EOC value is signalled, wherein the method further comprises obtaining the transform coefficients in the transform block by:

In response to the current transform coefficient being the last transform coefficient in a column indexed by the column end EOC value, and all previous transform coefficients in this same column being zero:

deriving the current transform coefficient as non-zero; and

the derived level flag is true indicating that the level of the current transform coefficient is greater than or equal to 1.

8. A method according to any one of claim 2 to 3,

signaling the end of line EOR value; and is also provided with

A context for entropy encoding the magnitude of the current transform coefficient in the transform block is determined based on one of:

previous transform coefficients in the same row as the current transform coefficient; or (b)

The directly previous transform coefficients in the same row and no other previous transform coefficients in the same row.

9. A method according to any one of claim 2 to 3,

signaling the end of column EOC value; and is also provided with

The context for entropy encoding the magnitude of the current transform coefficient in the transform block is determined based on only one of:

previous transform coefficients in the same column as the current transform coefficient; or (b)

The directly previous transform coefficients in the same column and no other previous transform coefficients in the same column.

10. A method according to claim 2, characterized in that,

the method further comprises: deriving a block end EOB value based on the row end EOR value or the column end EOC value, the block end EOB value indicating an end position of a last non-zero transform coefficient in the transform block; and

retrieving the transform block from the video bitstream according to the end position value comprises: the transformed block is retrieved from the video bitstream according to the block end EOB value.

11. The method of claim 10, wherein deriving the end-of-block EOB value comprises:

in response to the end position value being the end of line EOR value, deriving the end of block EOB value as one of:

EOR value step value;

EOR value stride value-1;

(EOR value+1) stride value; or (b)

(EOR value + 1) stride value-1,

wherein the stride value is equal to or associated with a width of the transform block.

12. The method of claim 11, wherein the step of determining the position of the probe is performed,

responsive to the width of the transform block being less than 64, the stride value is the width of the transform block; and

the stride value is 32 in response to the width of the transform block being greater than or equal to 64.

13. The method of claim 10, wherein deriving the end-of-block EOB value comprises:

in response to the end position value being the end of block EOC value, deriving the end of block EOB value as one of:

EOC value step value;

EOC value stride value-1;

(EOC value+1) stride value; or (b)

(EOC value + 1) stride value-1,

wherein the stride value is equal to or associated with a height of the transform block.

14. The method of claim 13, wherein the step of determining the position of the probe is performed,

responsive to the height of the transform block being less than 64, the stride value is the height of the transform block; and is also provided with

The stride value is 32 in response to the height of the transform block being greater than or equal to 64.

15. The method of claim 2, wherein the step of determining the position of the substrate comprises,

in response to applying transform skipping only in the horizontal direction of the transform block, encoding and transmitting each transform coefficient in the video bitstream, whether or not the each transform coefficient is zero, the each transform coefficient in a row having a row index less than or equal to the ending row index; and is also provided with

In response to applying transform skipping only in the vertical direction of the transform block, each transform coefficient is encoded and transmitted in the video bitstream, regardless of whether it is zero, with each transform coefficient having a column in a column index that is less than or equal to the ending column index.

16. The method of claim 2, wherein a context of entropy encoding the end of line EOR value or the end of column EOC value is different from a context of entropy encoding an EOB value in the video bitstream.

17. An apparatus for video processing, the apparatus comprising a memory for storing computer instructions and a processor in communication with the memory, wherein the processor, when executing the computer instructions, is configured to cause the apparatus to:

receiving a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and entropy coding is carried out on the transformation block;

determining whether to apply one-dimensional transform skipping to the transform block based on syntax elements in the video bitstream;

obtaining, from the video bitstream, an end position value associated with the transform block in response to applying the one-dimensional transform skip to the transform block, the end position value indicating only one of a horizontal coordinate end position and a vertical coordinate end position in the transform block; and

the transform block is retrieved from the video bitstream according to the end position value.

18. The apparatus of claim 17, wherein the end position value comprises one of:

An end-of-line EOR value indicating the horizontal coordinate end position in the transform block, the horizontal coordinate end position including an end line index of a last line in the transform block, the last line having at least one non-zero transform coefficient; and

a column end EOC value indicating the vertical coordinate end position in the transform block, the vertical coordinate end position including an end column index of a last column in the transform block, the last column having at least one non-zero transform coefficient.

19. The apparatus of claim 18, wherein the device comprises a plurality of sensors,

signaling the line end EOR value in the video bitstream as the end position value when a transform skip is applied only in the horizontal direction of the transform block; and is also provided with

When a transform skip is applied only in the vertical direction of the transform block, the column end EOC value is signaled in the video bitstream as the end position value.

20. A non-transitory storage medium storing computer readable instructions, which when executed by a processor, cause the processor to:

Receiving a video code stream, wherein the video code stream comprises a transformation block with two dimensions, and entropy coding is carried out on the transformation block;

determining whether to apply one-dimensional transform skipping to the transform block based on syntax elements in the video bitstream;

obtaining, from the video bitstream, an end position value associated with the transform block in response to applying the one-dimensional transform skip to the transform block, the end position value indicating only one of a horizontal coordinate end position and a vertical coordinate end position in the transform block; and

the transform block is retrieved from the video bitstream according to the end position value.