RU2787810C1 - Method and apparatus for colour conversion in versatile video coding (vvc) - Google Patents

Abstract

FIELD: video encoding.

SUBSTANCE: in the method for video decoding, wherein a bit stream of the encoded video including the current image is received, reverse quantisation is executed for the current block of the current image, and reverse colour conversion is executed for the current block after reverse quantisation; herein, reverse colour conversion for the current block is executed in response to determining that different colour components of the reverse colour conversion are encoded using the same coding unit division tree, and reverse colour conversion is applied for intra-coded blocks.

EFFECT: higher accuracy of signal encoding.

21 cl, 21 dwg

Description

INCLUSION BY LINK

[0001] The present invention claims priority in U.S. Ordinary Application No. 16/817,028, "METHOD AND APPARATUS FOR COLOR TRANSFORM IN VVC", filed March 12, 2020, which claims priority in U.S. Provisional Application No. 62/817,500, "COLOR TRANSFORM IN VVC" filed March 12, 2019. The contents of the previous applications are hereby incorporated by reference in their entirety.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0002] This application describes embodiments generally related to video coding.

BACKGROUND OF THE INVENTION

[0003] The description of the background of the invention is provided herein to provide a general context for the invention. The work of the authors of the invention, to the extent that it is described in this section, as well as aspects of the description that cannot be qualified as state of the art at the time of filing, neither expressly nor impliedly recognized as the state of the art underlying the present invention.

[0004] Encoding and decoding of the video signal may be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a sequence of images, each of which has a spatial size of, for example, 1920 x 1080 luma samples and associated chrominance samples. The image sequence may have a fixed or variable image rate (informally also referred to as frame rate), such as 60 images per second, or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video with 8 bits per sample (resolution of 1920x1080 luminance samples at 60Hz frame rate) requires about 1.5Gbps of bandwidth. An hour of such video requires more than 600 GB of storage.

[0005] One goal of video encoding and decoding may be to reduce redundancy in the input video signal by compressing. Compression can help to alleviate the aforementioned bandwidth or storage requirements, in some cases by two orders of magnitude or more. You can use both lossless and lossy compression, as well as a combination of both. Lossless compression refers to techniques for reconstructing an exact copy of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may not be identical to the original signal, but the discrepancy between the original and reconstructed signals is small enough that the reconstructed signal can be used for the intended application. Lossy compression is widely used for video. The amount of distortion allowed depends on the application; for example, users of some custom streaming applications can tolerate higher distortion than users of broadcast TV applications. With an achievable compression ratio, a higher allowed/allowable distortion may result in a higher compression ratio.

[0006] The video encoder and decoder may use techniques from several broad categories including, for example, motion compensation, transformation, quantization, and entropy coding.

[0007] Video codec technologies may include techniques known as intra-coding. With internal (intra-) coding, sample values are represented without reference to samples or other data from previously reconstructed reference pictures. In some video codecs, the image is spatially divided into blocks of samples. When all blocks of samples are encoded in intra-mode, the picture is called an intra-picture. Intra-pictures and their derivatives, such as pictures obtained in the decoder independent update mode, can be used to reset the decoder state, allowing them to be used as the first picture in the encoded video bitstream and video session, or as a still picture. The intra-block samples may be transformed and the transform coefficients may be quantized prior to entropy coding. Intra-prediction may be a technique for minimizing sample values in the pre-transform region. In some cases, the smaller the value of DC (constant component) after the transformation, and the smaller the AC (variable components) coefficients, the fewer bits are required for a given quantization step size to represent a block after entropy coding.

[0008] Conventional intra coding known, for example, from MPEG-2 generation coding technologies, does not use intra prediction. However, some more recent video compression technologies include techniques that attempt to do this from, for example, ambient sample data and/or metadata obtained during encoding/decoding of spatially adjacent and preceding, in decoding order, data blocks. Such methods are hereinafter referred to as "internal prediction" methods. Note that, in at least some cases, intra prediction is only performed using reference data from the current image to be reconstructed, and not from reference images.

[0009] There may be many different forms of intra prediction. When more than one of these methods can be used in a given video coding technology, the method used can be encoded in intra prediction mode. In some cases, modes may have sub-modes and/or parameters that may be encoded separately or included in the mode codeword. The use of a particular codeword for a given combination of modes/submodes/parameters can affect the gain in coding efficiency through intra prediction and hence the entropy coding technology used to translate the codewords into the bitstream.

[0010] A certain mode of intra prediction was first specified in H.264, refined in H.265, and further refined in more modern coding technologies, for example, the joint exploration model (JEM, joint exploration model), universal video coding (VVC, versatile video coding) and a set of standards (BMS, benchmark set). The predictor block can be formed using the values of neighboring samples belonging to already available samples. The values of neighboring samples are copied into the predictor block according to the direction. The reference to the direction to be used may be encoded in the bitstream, or may be self-predictable.

[0011] In the lower right corner of FIG. 1A shows a subset of the nine predictor directions of the set known from 33 possible H.265 predictor directions (corresponding to 33 angular modes out of 35 intra modes). The point (101) where the arrows converge represents the predicted count. The arrows represent the direction from which the reading is predicted. For example, an arrow (102) indicates that the reading (101) is predicted from the reading or readings located at the upper right, at an angle of 45 degrees to the horizontal. Likewise, arrow (103) indicates that sample (101) is predicted from the sample(s) located down to the left of sample (101), at an angle of 22.5 degrees to the horizontal.

[0012] In the upper left corner of FIG. 1A depicts a square block (104) of 4x4 samples (indicated by the heavy dotted line). The square block (104) includes 16 samples, each of which is denoted by the letter "S", a y-axis position (eg, row index) and an x-axis position (eg, column index). For example, sample S21 is the second sample on the Y axis (top) and the first sample (left) on the X axis. Similarly, sample S44 is the fourth sample in block (104) on both the Y and X axes. Since the block has a size of 4x4 samples, S44 located at the bottom right. Additionally, reference readings are shown that follow a similar numbering scheme. The reference sample is denoted by the letter R, its Y-position (eg, row index) and X-position (column index) relative to the block (104). In both H.264 and H.265, the predicted samples are adjacent to the block to be reconstructed; so there is no need to use negative values.

[0013] Intra-picture prediction may work by copying sample reference values from neighboring samples indicated by the signaled prediction direction. For example, suppose the coded video bitstream includes signaling that, for this block, indicates the direction of prediction indicated by the arrow (102) i.e. the samples are predicted from the predicted sample(s) located at the top right, below 45 degree angle to the horizontal. In this case, samples S41, S32, S23 and S14 are predicted from the same reference sample R05. Then, the sample S44 is predicted from the reference sample R08.

[0014] In some cases, the values of multiple reference samples can be combined, for example, by interpolation to calculate the reference sample; especially when the directions are not multiples of 45 degrees.

[0015] The number of possible directions increases as video coding technologies develop. In H.264 (2003), nine different directions could be represented. In H.265 this has increased to 33 (2013), and JEM/VVC/BMS can support up to 65 destinations at the time of writing this description. Experiments have been made to identify the most likely directions, and some entropy encoding techniques are used to represent these likely directions with a small number of bits, at the cost of losing some of the less likely directions. Additionally, the directions themselves can sometimes be predicted from adjacent directions used in adjacent already decoded blocks.

[0016] Intra prediction modes used in high performance video coding are shown in FIG. 1B. High-performance video coding has 35 intra prediction modes. In this case, mode 10 is horizontal, and mode 26 is vertical. Modes 2, 18 and 34 are diagonal modes. The intra prediction modes are signaled by the three highest probability modes and 32 other modes.

[0017] FIG. 1C depicts intra prediction modes used in high performance video coding. According to FIG. 1C, there are 95 intra prediction modes in high performance video coding. Mode 18 is horizontal, mode 50 is vertical, and modes 2, 34 and 66 are diagonal. Modes -1~-14 as well as modes 67~80 are called Wide-Angle Intra Prediction (WAIP) modes.

[0018] The mapping of intra prediction direction bits in the encoded video bitstream that represent the direction may differ from one video coding technology to another video coding technology; and may cover, for example, from simple forward prediction direction mapping to intra prediction mode, code words, complex adaptive schemes involving most likely modes, and similar techniques. However, in all cases, there may be some trends that are statistically less likely to occur in video content than for some other trends. Because the goal of video compression is to reduce redundancy, these less likely directions will, in a well-performing video coding technology, be represented by more bits than more likely directions.

[0019] Video encoding and decoding may be performed using inter-picture prediction with motion compensation. Uncompressed digital video may include a sequence of images, each of which has a spatial size of, for example, 1920 x 1080 luma samples and associated chrominance samples. The image sequence may have a fixed or variable image rate (informally also referred to as frame rate), such as 60 images per second, or 60 Hz. Uncompressed video has significant bitrate requirements. For example, 1080p60 4:2:0 video with 8 bits per sample (resolution of 1920x1080 luminance samples at 60Hz frame rate) requires about 1.5Gbps of bandwidth. An hour of such video requires more than 600 GB of storage.

[0020] Motion compensation can be a lossy compression method, as well as a method in which a block of sample data from a previous reconstructed image or part thereof (reference image) after it has been moved in the direction indicated by the motion vector (hereinafter MV (MV, motion vector) ) is used to predict the newly reconstructed image or part of it. In some cases, the reference image may correspond to the reconstructed image. A VD can have two dimensions, X and Y, or three dimensions. The third dimension is an indicator of the reference image used (the latter can indirectly be a temporal dimension).

[0021] In some video compression techniques, the VD applied in a certain sample data region can be predicted from other VDs, for example, those belonging to another sample data region adjacent to the one being reconstructed and preceding that VD in decoding order. This approach can significantly reduce the amount of data needed to encode the VD, thereby reducing redundancy and increasing compression. PD prediction can be effective. For example, when encoding a video input signal from a camera (uncompressed video), there is a statistical probability that areas (that exceed the scope of a single VD) move in the same direction, and thus, in some cases, prediction with an identical motion vector from an adjacent VD area is possible. As a result, the VD detected in the given area is similar or similar to the VD predicted from neighboring VDs, which, in turn, can be represented after entropy coding in fewer bits than with direct coding of the VD. In some cases, TD prediction may be an example of lossless compression of a signal (SR) obtained from the original signal (sample stream). In other cases, PD prediction may be lossy, for example, due to rounding errors when the predictor is calculated over several adjacent PDs.

[0022] Various VD prediction mechanisms are described in H.265/HEVC (ITU-T Rec. H.265, "High Efficiency Video Coding", December 2016). Of the many VD prediction mechanisms offered by H.265, this document introduces a "spatial fusion" technique.

[0023] FIG. 1D, the current block (101) includes samples detected by the encoder while searching for motion predicted from a previous block of identical size with partial offset. Instead of encoding this VD directly, it can be obtained from the metadata of one or more reference pictures using the VD of one of the five neighboring samples - A0, A1 and B0, B1, B2 (102 - 106 respectively). VD prediction by H.265 may use predictors of the same reference picture used by an adjacent block. The order of compilation of the list of candidates can be as follows: A0 → B0 → B1 → A1 → B2.

SUMMARY OF THE INVENTION

[0024] According to an exemplary embodiment, the video decoding method is performed by a video encoder. The method includes receiving an encoded video bitstream including a current picture. Next, inverse quantization is performed on the current block included in the current image. After inverse quantization, an inverse transform is performed on the current block. Further, after the inverse transformation on the current block, prediction is carried out with the establishment of the fulfillment or non-fulfillment of a predetermined condition. When a predetermined condition is met, a reverse color transformation is performed on the current block.

[0025] According to an exemplary embodiment, a video decoder for video decoding, including a processing circuit, is configured to receive an encoded video stream including a current picture. Next, the processing circuit is configured to perform inverse quantization on the current block of the current image. After inverse quantization on the current block, the processing circuit is tuned to inverse transform on the current block. After the inverse transformation on the current block, the processing scheme is tuned to the prediction on the current block. After the prediction on the current block, the processing scheme is set to establish the fulfillment (non-fulfillment) of the predetermined condition. Upon establishing the fulfillment of a predetermined condition, the processing scheme is adjusted to the inverse color transformation on the current block.

[0026] According to an exemplary embodiment, the computer-readable storage medium stores instructions that, when executed by the video encoder processor, cause the video encoder to perform a procedure for obtaining an encoded video stream involving the current picture. Next, inverse quantization is performed on the current block of the current image. After inverse quantization, an inverse transform is performed on the current block. After the inverse transformation, prediction is performed on the current block. After the prediction on the current block, the determination of the fulfillment or non-fulfillment of the predetermined condition is performed. Upon establishing the fulfillment of a predetermined condition on the current block, an inverse color transformation is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Additional features, nature and various advantages of the disclosed invention will be apparent from the following detailed description and the accompanying drawings, in which:

[0028] FIG. 1A is a diagram of an exemplary subset of intra prediction modes;

[0029] FIG. 1B is a diagram of intra prediction directions.

[0030] FIG. 1C is a diagram of intra prediction directions.

[0031] FIG. 1D is a diagram of the current block and its surrounding candidates for spatial merging in one example.

[0032] FIG. 2 is a simplified block diagram of a communications system (200) in accordance with an embodiment.

[0033] FIG. 3 is a simplified block diagram of a communications system (300) in accordance with an embodiment.

[0034] FIG. 4 is a simplified block diagram of a decoder according to an embodiment.

[0035] FIG. 5 is a simplified block diagram of an encoder according to an embodiment.

[0036] FIG. 6 is a block diagram of an encoder in accordance with another embodiment.

[0037] FIG. 7 is a block diagram of a decoder according to another embodiment.

[0038] FIG. 8A shows block division according to an embodiment.

[0039] FIG. 8B is a block division tree according to an embodiment.

[0040] FIG. 9A is a division of a vertical center-side ternary tree according to an embodiment.

[0041] FIG. 9B is a division of a horizontal center-side ternary tree according to an embodiment.

[0042] FIG. 10A-10D show various color formats according to embodiments.

[0043] FIG. 11 is an example of an encoder according to an embodiment.

[0044] FIG. 12 is an example of a decoder according to an embodiment.

[0045] FIG. 13 is a straight line between the minimum and maximum brightness value according to the embodiment.

[0046] FIG. 14A and 14B show sample positions for obtaining α and β in LT_CCLM according to an embodiment.

[0047] FIG. 15A and 15B show sample positions for obtaining α and β in T_CCLM according to an embodiment.

[0048] FIG. 16A and 16B show sample positions for obtaining α and β in L_CCLM according to an embodiment.

[0049] FIG. 17 is an example of classifying adjacent samples into two groups according to an embodiment.

[0050] FIG. 18 is a diagram of an encoder and decoder according to the embodiment.

[0051] FIG. 19 is a diagram of an embodiment of the encoder.

[0052] FIG. 20 is a diagram of an embodiment of a decoder.

[0053] FIG. 21 is a diagram of a computer system in accordance with an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0054] FIG. 2 shows a simplified block diagram of a communication system (200) according to an embodiment of the present invention. The communication system (200) includes a plurality of terminal devices that can communicate with each other, for example, through a network (250). For example, the communication system (200) includes a first pair of terminals (210) and (220) interconnected via a network (250). In the example shown in FIG. 2, the first pair of terminals (210) and (220) performs a unidirectional data transfer. For example, a terminal device (210) may encode video data (eg, a video stream captured by a terminal device (210)) for transmission to another terminal device (220) via a network (250). The encoded video data may be transmitted in the form of one or more encoded video bitstreams. The terminal device (220) may receive the encoded video data from the network (250), decode the encoded video data to recover the video images, and display the video images according to the recovered video data. One-way communication may be inherent in media service applications and the like.

[0055] In another example, the communication system (200) includes a second pair of terminals (230) and (240) that carry out bi-directional transmission of encoded video data that may occur, for example, during a video conference. For bidirectional data communication, by way of example, each terminal of terminals (230) and (240) may encode video data (eg, a video stream captured by the terminal) for transmission to the other terminal of terminals (230) and (240). ) through the network (250). Each terminal of terminals (230) and (240) may also receive encoded video data transmitted by another terminal from terminals (230) and (240) and may decode the encoded video data to reconstruct video images and display video images on an available display device according to recovered video data.

[0056] In the example shown in FIG. 2, terminal devices (210), (220), (230), and (240) can be illustrated as servers, personal computers, and smartphones, but this does not limit the principles of the present invention. Embodiments of the present invention find application in laptop computers, tablet computers, media players and/or dedicated video conferencing equipment. Network (250) represents any number of networks that carry encoded video data between terminals (210), (220), (230) and (240), including, for example, wired and/or wireless communication networks. The communication network (250) allows data to be exchanged in a circuit switched and/or packet switched mode. Exemplary networks include telecommunications networks, local area networks, wide area networks, and/or the Internet. For the purposes of this discussion, the architecture and topology of the network (250) may not be relevant to the present invention unless specifically noted below.

[0057] FIG. 3 shows, as an example of the application of the disclosed invention, the placement of a video encoder and a video decoder in a streaming environment. The disclosed invention may be equally applicable to other video processing applications, including, for example, videoconferencing, digital television, storage of compressed video on digital media, including CD, DVD, memory card, etc., etc.

[0058] The streaming system may include a capture subsystem (313), which may include a video signal source (301), such as a digital camera, creating, for example, an uncompressed video stream (302). For example, the video stream (302) includes samples taken by a digital camera. The video stream (302), shown in bold to highlight the large amount of data compared to the encoded video data (304) (or encoded video bitstreams), may be processed by an electronic device (320) that includes a video encoder (303) connected to video source (301). The video encoder (303) may include hardware, software, or a combination thereof for providing or implementing aspects of the disclosed invention, as described in more detail below. The encoded video data (304) (or the encoded video bitstream (304)), depicted with a thin line to emphasize the smaller amount of data compared to the video stream (302), may be stored on the streaming server (305) for future use. One or more streaming client subsystems, such as client subsystems (306) and (308) in FIG. 3 may access the streaming server (305) to retrieve copies (307) and (309) of the encoded video data (304). The client subsystem (306) may include a video decoder (310), such as in an electronic device (330). The video decoder (310) decodes the incoming copy (307) of the encoded video data and creates an outgoing video stream (311) that can be rendered on a display (412) (eg, a display screen) or other rendering device (not shown). In some streaming systems, the encoded video data (304), (307), and (309) (eg, video bitstreams) may be encoded according to one or another video coding/compression standard. Examples of these standards include ITU-T Recommendation H.265. For example, a video coding standard is being developed under the official name "universal video coding" (VVC, Versatile Video Coding). The disclosed invention may be used in the context of VVC.

[0059] Note that the electronic devices (320) and (330) may include other components (not shown). For example, electronic device (320) may include a video decoder (not shown), and electronic device (330) may also include a video encoder (not shown).

[0060] FIG. 4 shows a block diagram of a video decoder (410) according to an embodiment of the present invention. The video decoder (410) may be included in the electronic device (430). The electronic device (430) may include a receiver (431) (eg, receiver circuits). Video decoder (410) may be used instead of video decoder (310) in the example shown in FIG. 3.

[0061] The receiver (431) may receive one or more encoded video sequences for decoding by the video decoder (410); in the same or another embodiment, one coded video sequence at a time, where the decoding of each coded video sequence is independent of other coded video sequences. The encoded video sequence may be received from a channel (401), which may be a hardware/software link to a storage device where the encoded video data is stored. The receiver (431) may receive the encoded video data with other data, such as encoded audio data and/or auxiliary data streams, which may be relayed to their respective utilizing entities (not shown). The receiver (431) may separate the encoded video sequence from other data. To combat network jitter, a buffer memory (415) may be connected between the receiver (431) and the entropy decoder/analyzer (420) (hereinafter "analyzer (420)"). In some applications, the buffer memory (415) is included in the video decoder (410). In others, it may not be part of the video decoder (410) (not shown). In other embodiments, there may be a buffer memory (not shown) outside the video decoder (410), for example, to combat network jitter, in addition to another buffer memory (415) within the video decoder (410), for example, to control playback timing. When the receiver (431) receives data from a storage/relay device with sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (415) may not be needed or may be small. For use in best attempt packet networks, such as the Internet, buffer memory (415) may be required, may be relatively large, and may have a predominantly adaptive size, and may at least partially be implemented in an operating system or similar elements (not shown) outside video decoder (410).

[0062] The video decoder (410) may include an analyzer (420) for reconstructing the symbols (421) from the encoded video sequence. The categories of these symbols include information used to control the operation of the video decoder (410) and possibly information to control a visualization device such as a visualization device (412) (for example, a display screen) that is not part of the electronic device (430), but may be connected to an electronic device (430) as shown in FIG. 4. The control information for the rendering device(s) may be Supplemental Enhancement Information (SEI) messages or Video Usability Information (VUI) parameter set fragments (not shown). The analyzer (420) may analyze/entropy decode the received encoded video sequence. Encoding of the encoded video sequence may follow a video coding technology or standard and may follow various principles, including variable run length coding, Huffman coding, arithmetic coding with or without context sensitivity, and so on. The analyzer (420) can extract from the encoded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. Subgroups may include groups of pictures (GOP, Groups of Pictures), images, tiles, slices, macroblocks, coding units (CU, Coding Units), blocks, transformation units (TU, Transform Units), prediction units (PU, Prediction Units ) etc. The analyzer (420) can also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter values, motion vectors, and so on.

[0063] The analyzer (420) may perform an entropy decoding/analysis operation of the video sequence received from the buffer memory (415) to create symbols (421).

[0064] Several different modules may be used for symbol reconstruction (421) depending on the type of encoded video image or parts thereof (eg: inter- and intra-pictures, inter- and intra-block) and other factors. Which modules are used, and how, may be determined by the subgroup management information extracted from the encoded video sequence by the analyzer (420). The flow of such subgroup management information between the analyzer (420) and multiple modules is not shown hereinafter for simplicity.

[0065] In addition to the previously mentioned functional blocks, the video decoder (410) can be fundamentally divided into several functional modules, as described below. In a practical implementation operating under commercial constraints, many of these modules interact closely with one another and can, at least partially, be nested within one another. However, for the purposes of describing the disclosed invention, a fundamental subdivision into the following functional modules is appropriate.

[0066] The first module is the scaling/inverse transform module (451). The scaling/inverse transform module (451) receives the quantized transform coefficient as well as control information including the transform used, block size, quantization factor, quantization scaling matrices, and so on. as character(s) (421) from the analyzer (420). The scaling/inverse transform module (451) can output blocks containing sample values that can be input to the aggregator (455).

[0067] In some cases, the output samples of the scaling/inverse transform block (451) may refer to an intra-coded block; that is, to a block that does not use predicted information from previously reconstructed images, but may use predicted information from previously reconstructed portions of the current image. Such predicted information may be provided by an intra-picture prediction module (452). In some cases, the intra-image prediction module (452) generates a block of the same size and shape as the block to be reconstructed using the previously reconstructed environment information retrieved from the current image buffer (458). The current picture buffer (458) buffers, for example, a partially reconstructed current picture and/or a fully reconstructed current picture. The aggregator (455) in some cases adds, for each sample, the prediction information generated by the intra prediction module (452) to the output sample information provided by the scaling/inverse transform module (451).

[0068] In other cases, the output samples of the scaler / demapper (451) may refer to an intra-coded block, possibly with motion compensation. In such a case, the motion compensation prediction module (453) may access the reference picture memory (457) to retrieve samples used for prediction. After motion compensation is applied to the extracted samples according to the symbols (421) associated with the block, these samples can be added by the aggregator (455) to the output signal of the scaler / inverse transform module (451) (in this case referred to as residual samples or residual signal) for generation of output sample information. The addresses in the reference picture memory (457) from where the motion compensation prediction module (453) retrieves the predicted samples may be governed by the motion vectors available to the motion compensation prediction module (453) in the form of symbols (421), which may have, for example, X, Y components and reference image. Motion compensation may also include interpolation of sample values retrieved from reference picture memory (457) when accurate sub-sample motion vectors, motion vector prediction mechanisms, etc. are used.

[0069] Various loop filtering methods can be applied to the output samples of the aggregator (455) in the loop filter module (456). The video compression technologies may include deblocking filter technologies driven by parameters included in the encoded video sequence (also referred to as the encoded video bitstream) and made available to the loop filter module (456) as symbols (421) from the analyzer (420), but may also respond to meta-information obtained during the decoding of the previous (in the order of decoding) parts of the encoded image or encoded video sequence, as well as respond to previously reconstructed and loop-filtered sample values.

[0070] The loop filter module (456) may provide a stream of samples that may be fed to the renderer (412) and also stored in reference picture memory (457) for use in future inter-picture prediction.

[0071] Some encoded pictures, when fully reconstructed, can be used as reference pictures for future prediction. For example, when the encoded picture corresponding to the current picture is completely reconstructed and the encoded picture is identified as a reference picture (eg, by the analyzer (420)), the current picture buffer (458) may become part of the reference picture memory (457), and a fresh current picture buffer may be re-allocated before the reconstruction of the next encoded picture starts.

[0072] The video decoder (410) may perform decoding operations according to a predetermined video compression technology, such as the ITU-T Rec. H.265. The encoded video sequence may conform to the syntax defined by the used video compression technology or standard, in the sense that the encoded video sequence may adhere to both the syntax of the video compression technology or standard and the profiles documented in the video compression technology or standard. In particular, a profile may select certain tools as tools available for use only under that profile, from among all the tools available in a video compression technology or standard. It may also be necessary for consistency that the complexity of the encoded video sequence remain within the boundaries set by the video compression technology level or standard. In some cases, the levels limit the maximum image size, the maximum frame rate, the maximum sampling rate for reconstruction (measured in megasamples per second, for example), the maximum reference image size, and so on. The limits set by the levels, in some cases, may be further limited by the specifications of the Hypothetical Reference Decoder (HRD) and the metadata for managing the HRD buffer signaled in the encoded video sequence.

[0073] According to an embodiment, the receiver (431) may receive additional (redundant) data with encoded video. Additional data may be included as part of the encoded video sequence(s). The additional data may be used by the video decoder (410) to correctly decode the data and/or more accurately reconstruct the original video data. The additional data may be, for example, enhancement layers in time, space, or signal-to-noise ratio (SNR), redundant slices, redundant images, forward error correction codes, and so on.

[0074] FIG. 5 shows a block diagram of a video encoder (503) according to an embodiment of the present invention. The video encoder (503) is included in the electronic device (520). The electronic device (520) includes a transmitter (540) (eg, a transmission circuit). Video encoder (503) may be used instead of video encoder (303) in the example shown in FIG. 3.

[0075] The video encoder (503) may receive video samples from a video source (501) (which is not part of the electronic device (520) in the example shown in FIG. 5) that may capture the video image(s) to be encoding with a video encoder (503). In another example, the video signal source (501) is included in the electronic device (520).

[0076] The video source (501) may provide the source video sequence to be encoded by the video encoder (503) in the form of a digital video sample stream of any suitable bit depth (eg: 8 bit, 10 bit, 12 bit, ...), any color space (eg, BT.601 Y CrCB, RGB, ...) and any suitable sampling structure (eg Y CrCb 4:2:0, Y CrCb 4:4:4). In a media service system, the video source (501) may be a storage device where previously prepared video is stored. In a videoconferencing system, the video source (501) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of individual images that give a sense of movement when viewed in sequence. The images themselves may be organized as a spatial array of pixels, where each pixel may contain one or more samples depending on the sampling structure, color space, etc. used. It is not difficult for a person skilled in the art to understand the relationship between pixels and samples. The following description is about readings.

[0077] According to an embodiment, the video encoder (503) can encode and compress images of the original video sequence into the encoded video sequence (543) in real time or subject to any other time constraints imposed by the application. Establishing a proper coding rate is one of the functions of the controller (550). In some embodiments, the controller (550) controls other functional modules, as described below, and is operatively connected to other functional modules. The connection is not shown for simplicity. The parameters set by the controller (550) may include parameters related to frequency adjustment (picture skip, quantizer, lambda value applied in rate-distortion optimization, ...), picture size, group of pictures scheme (GOP, group of pictures) , maximum motion vector search area, etc. The controller (550) may be configured to have other suitable functions related to the video encoder (503) optimized for a given system design.

[0078] In some embodiments, the video encoder (503) is configured to operate in a coding loop. As a very simplified description, by way of example, an encoding loop may include a source encoder (530) (e.g., responsible for generating symbols, e.g., a stream of symbols, based on the input image to be encoded and the reference image(s) )) and a (local) decoder (533) built into the video encoder (503). The decoder (533) reconstructs the symbols to create sample data, in a similar manner as a (remote) decoder would (because any compression between the symbols and the encoded video bitstream is lossless in the video compression technologies of the disclosed invention). The reconstructed sample stream (sample data) enters the reference picture memory (534). Since the decoding of the symbol stream results in bit-accurate results independent of the position of the decoder (local or remote), the contents of the reference picture memory (534) will also be the same bit-accurate for the local and remote encoder. In other words, the predicted portion of the encoder "sees" as reference picture samples exactly the same sample values as the decoder would "see" if using prediction during decoding. This fundamental principle of reference picture synchronism (and eventually drift if synchronism cannot be maintained, for example due to channel errors) is also used in some related fields of technology.

[0079] A "local" decoder (533) may operate in the same manner as a "remote" decoder, such as the video decoder (410) detailed above with reference to FIG. 4. However, again, referring to FIG. 4, since the symbols are available and the entropy encoder (545) and analyzer (420) can be losslessly encoded/decoded into the encoded video sequence, the entropy decoding parts of the video decoder (410) including the buffer memory (415) and the analyzer (420) , may not be fully implemented in the local decoder (533).

[0080] It can thus be concluded that any decoding technology present in a decoder, with the exception of analysis/entropy decoding, must also be present, in substantially identical functional form, in the corresponding encoder. For this reason, the disclosed invention is focused on the operation of the decoder. The description of encoding technologies can be abbreviated as they are the inverse of the decoded technologies described in detail. Only in some areas a more detailed description is required, which is given below.

[0081] According to some examples, in operation, source encoder (530) may perform motion-compensated predictive coding, in which an input picture is predictively encoded based on one or more previously encoded pictures from a video sequence, referred to as "reference pictures". Thus, the encoding engine (532) encodes the differences between the pixel blocks of the input image and the pixel blocks of the reference image(s) that can be selected as the predicted reference(s) to the input image.

[0082] The local video decoder (533) may decode the encoded video data of pictures that can be specified as reference pictures based on the symbols generated by the source encoder (530). The operations of the encoding engine (532) may be predominantly lossy processes. When the encoded video data can be decoded in a video decoder (not shown in FIG. 5), the reconstructed video sequence can typically be a copy of the original video sequence with some errors. The local video decoder (533) duplicates the decoding processes that may be performed by the video decoder on the reference pictures and may cause the reconstructed reference pictures to be stored in the reference picture cache (534). Thus, the video encoder (503) can locally store copies of the reconstructed reference pictures having the same content as the reconstructed reference pictures to be received by the video decoder at the receiver side (in the absence of transmission errors).

[0083] The predictor (535) may perform prediction searches for the encoding engine (532). Thus, for a new picture to be encoded, the predictor (535) can search the reference picture memory (534) for sample data (as candidates for the role of reference pixel blocks) or some metadata, for example, motion vectors of the reference picture, block shapes etc., which can serve as a proper reference for predicting new images. The predictor (535) may operate on a sample-block-pixel-block basis to find the proper references for prediction. In some cases, according to the search results obtained by the predictor (535), the input picture may have prediction references extracted from the plurality of reference pictures stored in the reference picture memory (534).

[0084] The controller (550) may control the encoding operations of the source encoder (530), including, for example, setting parameters and subgroup parameters used to encode video data.

[0085] The output signal of all the above functional modules can be entropy encoded in an entropy encoder (545). An entropy encoder (545) converts the symbols generated by the various functional units into an encoded video sequence by lossless symbol compression according to techniques such as Huffman coding, variable run length coding, arithmetic coding, and so on.

[0086] The transmitter (540) may buffer the encoded video sequence(s) created by the entropy encoder (545) in preparation for transmission over a communication channel (560), which may be a hardware/software link to a storage device where encoded video data. The transmitter (540) may combine the encoded video data from the video encoder (503) with other data to be transmitted, such as encoded audio data and/or auxiliary data streams (sources not shown).

[0087] The controller (550) may control the operation of the video encoder (503). During encoding, the controller (550) may assign to each encoded picture an encoded picture type, which may determine the encoding methods applicable to the corresponding picture. For example, images can often be assigned the following image types:

[0088] An intra-picture (I-picture) that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow different types of intra-pictures, including, for example, pictures in the Independent Decoder Refresh ("IDR" format). One skilled in the art will be aware of the 1-image varieties and their respective uses and features.

[0089] A predicted picture (P-picture) that can be encoded and decoded using intra prediction or inter prediction using at most one motion vector and reference index to predict sample values of each block.

[0090] A bi-directionally predicted picture (B-picture) that can be encoded and decoded using intra prediction or inter prediction with no more than two motion vectors and reference indices to predict sample values of each block. Likewise, multi-predicted pictures may use more than two reference pictures and associated metadata to reconstruct a single block.

[0091] Source images typically allow for spatial division into multiple blocks of samples (eg, blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and coding on a block-by-block basis. The blocks may be predictively encoded with reference to other (previously encoded) blocks determined by the coding assignment applied to the respective images of those blocks. For example, blocks of I-pictures may be encoded without prediction or predictively with reference to previously coded blocks of the same picture (spatial prediction or intra prediction). The pixel blocks of P-pictures may be predictively encoded by spatial prediction or temporal prediction with reference to one previously encoded reference picture. Blocks of B-pictures may be predictively encoded by spatial prediction or temporal prediction with reference to one or two previously encoded reference pictures.

[0092] The video encoder (503) may perform encoding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. H.265. In operation, the video encoder (503) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. Therefore, the encoded video data may conform to the syntax given by the video coding technology or standard being used.

[0093] According to an embodiment, the transmitter (540) may transmit additional data with encoded video. The source encoder (530) may include such data as part of the encoded video sequence. The additional data may include temporal/spatial/SNR enhancement layers, other forms of redundant data such as redundant images and slices, SEI messages, VUI parameter set fragments, and so on.

[0094] The video may be captured as a plurality of source images (video images) in time sequence. Intra-image prediction (often abbreviated as intra-image prediction) uses spatial correlation within a given image, and inter-image prediction uses (temporal or otherwise) correlation between images. For example, a specific image to be encoded/decoded, which is called the current image, is divided into blocks. When a block in the current picture is similar to a reference block in a previously encoded and still buffered reference picture in a video, the block in the current picture may be encoded with a vector, which is referred to as a motion vector. The motion vector points to a reference block in the reference picture and may have a third dimension identifying the reference picture in case multiple reference pictures are used.

[0095] In some embodiments, a dual prediction technique may be used in inter-picture prediction. According to the double prediction method, two reference pictures are used, for example, a first reference picture and a second reference picture, both of which precede the current picture in the video in decoding order (but may be in the past and future, respectively, in display order). A block in the current picture may be encoded by a first motion vector that points to a first reference block in the first reference picture and a second motion vector that points to a second reference block in the second reference picture. The block may be predicted by a combination of the first and second reference blocks.

[0096] Additionally, a combining mode technique may be used in inter-picture prediction to improve coding efficiency.

[0097] According to some embodiments of the invention, predictions, such as inter-picture predictions and intra-picture predictions, are performed block by block. For example, according to the HEVC standard, an image in a video sequence is divided into coding tree units (CTUs) for compression, CTUs in an image are the same size, such as 64x64 pixels, 32x32 pixels, or 16x16 pixels. In general, the CTU includes three coding tree blocks (CTBs), namely one luma CTB and two chrominance CTBs. Each CTU may recursively divide the quadtree into one or more coding units (CUs). For example, a 64x64 pixel CTU can be divided into one 64x64 pixel CU or 4 32x32 pixel CUs or 16 16x16 pixel CUs. For example, each CU is analyzed to determine a prediction type for the CU, such as an inter prediction type or an intra prediction type. The CU is divided into one or more prediction units (PU) depending on the temporal and/or spatial prediction. In general, each PU includes a luma prediction block (PB) and two chrominance PBs. According to an embodiment, an encoding (encoding/decoding) prediction operation is performed in a prediction block unit. If using the luminance prediction block as an example of the prediction block, the prediction block includes a matrix of values (e.g., luminance values) for pixels, e.g., 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, and the like.

[0098] FIG. 6 shows a diagram of a video encoder (603) according to another embodiment of the invention. The video encoder (603) is configured to receive a processing unit (eg, a prediction unit) of sample values in the current video image in the video sequence and encoding the processing unit into an encoded image that is part of the encoded video sequence. For example, video encoder (603) is used instead of video encoder (303) in the example shown in FIG. 3.

[0099] In the HEVC example, video encoder (603) receives a matrix of sample values for a processing block, such as an 8x8 sample prediction block, or the like. The video encoder (603) determines whether the processing block is best encoded in intra mode, inter mode, or dual prediction mode using, for example, rate-distortion optimization. When the processing block is to be encoded in intra mode, the video encoder (603) may use an intra prediction technique to encode the processing block into an encoded picture; and when the processing unit is to be encoded in inter mode or dual prediction mode, the video encoder (603) may use an inter prediction or dual prediction technique, respectively, to encode the processing unit into an encoded picture. In some video coding technologies, the combining mode may be a sub-mode of inter-picture prediction where a motion vector is derived from one or more motion vector predictors without involving the encoded motion vector component outside of the predictors. In some other video coding technologies, there may be a motion vector component applicable to a given block. By way of example, the video encoder (603) includes other components, such as a mode determination module (not shown) for determining the mode of the processing units.

[0100] In the example shown in FIG. 6, the video encoder (603) includes an inter encoder (630), an intra encoder (622), a residual calculator (623), a switch (626), a residual encoder (624), a common controller (621), and an entropy encoder (625). ) connected to each other as shown in Fig. 6.

[0101] The inter-encoder (630) is configured to receive samples of the current block (e.g., processing block), compare the block with one or more reference blocks in reference pictures (e.g., blocks in previous pictures and later pictures), generate information inter prediction (eg, describing redundant information according to the intra coding method, motion vectors, combining mode information), and calculating inter prediction results (eg, prediction block) based on the inter prediction information using any suitable method. In some examples, reference pictures are decoded reference pictures that are decoded based on encoded video information.

[0102] The intra-encoder (622) is configured to receive samples of the current block (e.g., processing block), in some cases comparing the block with blocks previously encoded in the same picture, generating quantized coefficients after the transform, and in some cases also information intra prediction (eg, intra prediction direction information according to one or more intra coding methods). By way of example, the intra encoder 622 also calculates intra prediction results (eg, prediction block) based on intra prediction information and reference blocks in the same picture.

[0103] The common controller (621) is configured to determine common control data and control other components of the video encoder (703) based on the common control data. For example, the common controller (621) determines the mode of the block and outputs a control signal to the switch (626) based on the mode. For example, when the mode is the intra mode, the common controller (621) controls the switch (626) to select the result of the intra mode in order to use the residual calculator (623), and the entropy encoder (625) to select the intra prediction information and turn on the intra prediction information into the bitstream; and when the mode is inter mode, the common controller (621) controls a switch (626) to select an inter prediction result to use a residual calculator (623), and an entropy encoder (625) to select and include inter prediction information in the bitstream.

[0104] The residual calculator (623) is configured to calculate the difference (residual data) between the received block and the prediction results selected from the intra-coder (622) or inter-coder (630). The residual encoder (624) is configured to operate on the residual data to encode the residual data in order to generate transform coefficients. For example, the residual encoder (624) is configured to transform residual data from the spatial domain to the frequency domain and generate transform coefficients. Then, the transform coefficients are subjected to quantization processing to obtain quantized transform coefficients. In various embodiments, the video encoder (603) also includes a residual decoder (628). The residual decoder (628) is configured to perform inverse transformation and generate decoded residual data. The decoded residual data may be appropriately used by the intra-coder (622) and the inter-coder (630). For example, the inter-coder (630) may generate decoded blocks based on the decoded residual data and inter prediction information, and the intra-coder (622) may generate decoded blocks based on the decoded residual data and intra prediction information. The decoded blocks are properly processed to generate decoded pictures, and the decoded pictures can be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

[0105] The entropy encoder (625) is configured to format the bitstream so that it includes a coded block. The entropy encoder (625) is configured to include various information according to a suitable standard, such as the HEVC standard. For example, the entropy encoder (625) is configured to include common control data, selected prediction information (eg, intra prediction information or inter prediction information), residual information, and other appropriate information in the bitstream. Note that, according to the disclosed invention, when encoding a block in the combining submode of the inter mode or dual prediction mode, there is no residual information.

[0106] In FIG. 7 shows a diagram of a video decoder (710) according to another embodiment of the invention. The video decoder (710) is configured to receive encoded pictures that are part of the encoded video sequence and decode the encoded pictures to generate reconstructed pictures. For example, video decoder (710) is used instead of video decoder (310) in the example shown in FIG. 3.

[0107] In the example shown in FIG. 7, the video decoder (710) includes an entropy decoder (771), an inter decoder (780), a residual decoder (773), a reconstruction unit (774), and an intra decoder (772) connected to each other as shown in FIG. 7.

[0108] The entropy decoder (771) may be configured to reconstruct, from the encoded image, some symbols that represent the syntax elements that form the encoded image. Such symbols may include, for example, a block coding mode (e.g., intra mode, inter mode, dual prediction mode, the latter two being in a pooling submode or other submode), prediction information (e.g., intra prediction information, or inter prediction information ) that can identify a specific sample or metadata used for prediction by the intra-decoder (772) or inter-decoder (780), respectively, residual information in the form of, for example, quantized transform coefficients, and the like. For example, when the prediction mode is an intra or dual prediction mode, the inter prediction information is input to the inter decoder (780); and when the prediction type is an intra prediction type, the intra prediction information is input to the intra decoder (772). The residual information may be inverse quantized and fed to a residual decoder (773).

[0109] The inter decoder (780) is configured to receive inter prediction information and generate inter prediction results based on the inter prediction information.

[0110] The intra decoder (772) is configured to receive intra prediction information and generate prediction results based on the intra prediction information.

[0111] The residual decoder (773) is configured to perform inverse quantization to extract the dequantized transform coefficients and process the dequantized transform coefficients to transform the residual from the frequency domain to the spatial domain. The residual decoder (773) may also require some control information (include a quantizer parameter (QP, Quantizer Parameter)), and this information may be provided by the entropy decoder (771) (the data path is not shown since this may only be small volume control information).

[0112] The reconstruction module (774) is configured to combine in the spatial domain the residual at the output of the residual decoder (773) and prediction results (at the output of the inter or intra prediction modules, as appropriate) to form a reconstructed block that may be included in reconstructed image, which, in turn, can be part of the reconstructed video. Note that other suitable operations, such as a release operation and the like, may be performed to improve the visual quality.

[0113] Note that video encoders (303), (503) and (603) and video decoders (310), (410) and (710) may be implemented using any suitable technique. According to an embodiment, video encoders (303), (503) and (603) and video decoders (310), (410) and (710) may be implemented using one or more integrated circuits. In another embodiment, video encoders (303), (503) and (603) and video decoders (310), (410) and (710) may be implemented using one or more processors that execute program instructions.

[0114] According to some embodiments, the coding tree unit is partitioned into coding units by a quad tree binary tree (QTBT) structure known as the coding tree to adapt various local characteristics of the individual blocks included in the coding units. The decision to encode an image region by temporal or spatial image prediction may be made at the coding unit level. Each coding unit can be divided into one, two, or four prediction units, according to the division type of prediction units. According to some embodiments, within one prediction unit, an identical prediction process is performed and the necessary information is transmitted to the decoder based on the prediction unit. When obtaining a residual block by a prediction process based on a division type of prediction units, a coding unit can be divided into transformation units according to another quadtree structure similar to the quadtree structure applied to the coding tree and its units. In some other embodiments, the prediction unit contains only one transformation unit, of the same form as the prediction unit.

[0115] The coding tree for coding tree units may include various partitions, including coding units, prediction units, and transform units. In some embodiments, the coding or transform unit is represented solely by a square shape, and the prediction unit may be square or rectangular for an intra prediction block. In other embodiments, rectangular coding, prediction, and transform units are allowed. An implicit quadtree can be applied at the image boundary so that the block continues to split the quadtree until the size of the separated block is adjusted to fit the image boundary. In some embodiments, an implicit split means hiding the split flag. For example, implicit quadtree (QT) means permission to split QT for a border block of an image. The split flag is not signaled at the image boundary. Another example: when allowing a binary tree (BT) split at an image boundary, the implicit split is a binary split. In some embodiments, when QT and BT are allowed at the image boundary, there is no implicit separation, and the separation method is signaled explicitly.

[0116] According to some embodiments, the Quadtree Binary Tree (QTBT) structure does not include multiple split types (eg, QTBT does not include coding, prediction, and transform unit splits) and is more flexible for coding unit splitting forms. For example, in the QTBT block structure, the coding unit may be square or rectangular. Fig. 8A illustrates an example coding tree unit (800) separated by a QTBT structure. For example, the coding tree unit (800) is divided into 4 coding subunits (A), (B), (C), and (D). Fig. 8B shows the corresponding coding tree with branches corresponding to coding subunits (A), (B), (C), and (D). The solid lines represent the quadtree split, and the dotted lines represent the binary tree split. The binary tree structure may include two types of partitioning: (i) symmetrical horizontal partitioning and (ii) symmetrical vertical partitioning. At each partitioned (i.e., non-leaf) node of the binary tree, one flag may be signaled to indicate the type of partitioning applied (eg, horizontal or vertical), where 0 denotes a horizontal partition and 1 a vertical partition, or vice versa. For quadtree splitting, the type of splitting is not specified because the corresponding splitting splits the block horizontally and vertically simultaneously to produce four sub-blocks of the same size.

[0117] According to the images of FIG. 8A and 8B, the coding subunit (A) is first divided into two subblocks by vertical division followed by vertical division of the left subblock. Next, the coding subunit (B) goes through a horizontal division. Further, the coding subunit (C) is divided by a quadruple division. The upper left subunit of the coding subunit (C) is divided vertically followed by a horizontal division. Further, the lower right subunit of the coding subunit (C) is divided horizontally. The upper right and lower left subunits of the coding subunit (C) are not subject to further division. The encoding subunit (D) is not subject to further subdivision and thus does not include additional leaf nodes of the encoding tree below branch "D".

[0118] The leaf nodes of a binary tree may refer to coding units, where binary division can be used to process prediction and transformation without subsequent division. This means that the coding, prediction, and transform units have the same block size in the QTBT block coding structure. A coding unit may include coding units of various color components. For example, one coding unit may contain one luminance coding unit and two chrominance coding units in the case of slices P and B of the 4:2:0 color format, and sometimes may contain a single component coding unit (for example, one coding unit contains only one luminance coding unit or just two chroma coding units in the case of intra-coded images or slices). In some embodiments, intra-coded images or slices have a transform unit width or height constrained (eg, 64 for luma and 32 for chrominance). If the width or height of the coding block exceeds the limit, then the transformation unit is divided until the size does not exceed the specified limit.

[0119] According to some embodiments, the QTBT partitioning scheme includes the following parameters: CTU size: quadtree root node size MinQTSize: minimum allowed quadtree leaf node size MaxBTSize: maximum allowed binary tree root node size MaxBTDepth: maximum allowed binary tree depth MinBTSize: the minimum allowable size of a leaf node in a binary tree.

[0120] In one example of the QTBT division structure, the coding tree unit size is 128×128 luma samples with corresponding chroma sample blocks of 64×64, MinQTSize is 16×16, MaxBTSize is 64×64, MinBTSize (width and height) is 4 ×4, MaxBTDepth - 4. The QTBT division structure is applied to the coding tree unit to form the leaf nodes of the quadtree. Quadtree leaf node sizes: from 16x16 (i.e. MinQTSize) to 128x128 (i.e. coding tree unit size). If the size of the quadtree leaf node is 128x128, the quadtree leaf node will not further divide the binary tree because its size is larger than MaxBTSize (64x64). Otherwise, the leaf node of the quadtree can again be divided into a binary tree. Thus, the leaf node of the quadtree is also the root node of the binary tree, and the leaf of the quadtree has zero depth of the binary tree. When the maximum depth of the binary tree MaxBTDepth (for example, 4) is reached, no further division is performed. If the width of a binary tree node is MinBTSize (eg 4), no further horizontal division is made. Similarly, if the height of a binary tree node is MinBTSize, no further vertical division is made. Next, the leaf nodes of the binary tree are processed by prediction and transformation without further division. In some embodiments, the maximum size of coding tree units is 256×256 luminance samples.

[0121] Also, the QTBT division structure may support the ability of the luma and chrominance components to have separate QTBT structures. For example, for P and B slices, coding tree luma and chrominance blocks in the same coding tree unit may have the same QTBT structure. However, for I-slices, the luminance of a coding tree block is divided into coding units by one QTBT structure, and the chrominance blocks of the coding tree are divided into chroma coding units by another QTBT structure. Thus, in this example, a coding unit in an I-slice contains a luma component coding block or coding blocks of two chrominance components, and a coding unit in a P or B slice contains coding blocks of all three color components.

[0122] In some embodiments, inter prediction for small blocks is limited in order to reduce memory access requirements for motion compensation so that bidirectional prediction is not supported for 4x8 and 8x4 blocks, and inter prediction is not supported for 4x4 blocks. In other embodiments, the QTBT division scheme does not include these restrictions.

[0123] According to some embodiments, a multi-type tree (MTT) structure includes (i) quad-tree splitting, (ii) binary tree splitting, and (iii) horizontal and vertical ternary center-side trees. In FIG. 9A shows an embodiment of a vertical ternary center-side tree, and FIG. 9B is an example of a horizontal ternary center-side tree. Compared to the QTBT structure, the multitype tree structure can be more flexible because additional structures are allowed.

[0124] Ternary tree splitting includes significantly useful features, such as providing a complement to quadtree/binary tree splitting, whereby ternary tree splitting is able to capture objects located in the center of a block while splitting the quadtree and binary tree at the center of the block. Another advantage of ternary tree divisions is that the width and height of the proposed ternary tree divisions are multiplied by 2, so no additional transformations are required. The advantage of a two-level tree is to reduce complexity. For example, the complexity of traversing a tree is T ^D , where T is the number of division types, and D is the depth of the tree.

[0125] There are various YUV formats, or chrominance formats, shown in FIG. 10A-10D. Each color format defines its own downsampling grid for various color components.

[0126] The color of video samples can be represented in various color formats (eg, YCbCr or RGB format). In RGB format, the three components have strong correlations (ie, R, G, and B), leading to statistical redundancy of the three color components. The color representation of video samples can be converted to another color space using linear transformations. The conversion of the RGB color space to the YUV color space is as follows:

[0127] The conversion of the RGB color space to the YUV color space can occur as follows:

[0128] For efficient coding of RGB video content, a contour adaptive color transform (ACT, Adaptive Color Transform) method has been developed that works in the residual region. A coding unit level flag may be signaled to indicate the use of ACT. A direct color conversion using the ACT method (for example, the conversion performed by the encoder) can be performed as follows:

[0129] An inverse color transform ACT (eg, an inverse transform performed by a decoder) can be performed as follows:

[0130] In FIG. 11 shows an example of an encoder 1100 for performing color space conversion. In FIG. 11, the prediction is performed before the color space conversion is performed. For example, intra or inter prediction is performed on the current block to generate a residual signal. The residual signal is generated by the color space conversion block (1102) to perform direct conversion as in Eq. (7). The result of the direct conversion of the color space is transmitted to the block (1102) the formation of cross-components (CCP, cross component production). The output from the CCP (1102) is passed to a transform (T, transform) block (1106) to perform discrete cosine transform (DCT) type transformations. The result of the transform (1106) is transmitted to the quantizer (Q) (1108) to obtain the coefficients. The coefficients are passed to an entropy encoder (1110) to provide a bit stream. The entropy encoder (1110) may receive a mode signal/mv to select a specific mode of operation of the entropy encoder.

[0131] The encoder (1100) may also include components for converting the bitstream into a residual signal. For example, the bitstream produced by the entropy encoder (1110) may be transmitted to an inverse quantizer (IQ) (1112). The result of the inverse quantizer (IQ) may be transmitted to an inverse transform (IT) (1114). The result of the inverse transform (IT) (1114) may be passed to the inverse CPP block (1116). The output signal of the inverse CPP block (1116) may be transmitted to a color space inverse transform (1118) performing the conversion according to Eq. (8).

[0132] FIG. 12 shows an exemplary decoder (1200) for converting a bit stream into a residual signal. The bit stream shown in FIG. 12 may be generated by the entropy encoder (1110) (FIG. 11). The bit stream may be transmitted to an entropy encoder (1200). The result of the entropy encoder (1202) may be transmitted to an inverse quantizer (IQ) (1202). The result of the inverse quantizer (IQ) may be transmitted to an inverse transform (IT) (1204). The result of the inverse transform (IT) (1204) may be passed to the inverse CPP block (1206). The result of the inverse CPP (1206) may be transmitted to the color space inverse mapper (1208) shown in Eq. (8) which can generate residual signal. Intra or inter prediction may be performed on the residual signal to decode the current block. The devices in FIG. 11 and 12 can be applied through programs through a processor or through circuits, for example through a special integrated circuit designed to perform the function of each device.

[0133] For the internal prediction unit (PU) color component, the encoder can select the best color prediction modes out of 8, including planar, direct coding, DC, horizontal, vertical, intra prediction mode (DM) direct copy from luma component, left and top linear cross-component mode (LT_CCLM), left linear cross-component mode (L_CCLM), and upper linear cross-component mode (T_CCLM). The LT_CCLM, L_CCLM, and T_CCLM modes can be included in a Linear Cross-Component Mode (CCLM) group. The difference between these three modes lies in the possibility of using different areas of neighboring samples to obtain the parameters α and β. For LT_CCLM, the left and top adjacent samples may be used to obtain the parameters α and β. For L_CCLM, in some examples, only left adjacent samples are used to obtain the parameters α and β. For T_CCLM, in some examples only the upper adjacent samples are used to obtain the parameters α and β.

[0134] Linear cross-component model (CCLM) prediction modes can be applied to reduce cross-component redundancy in which chrominance samples are predicted from reconstructed luma samples of the same CU by applying a linear model quantizer as follows:

where pred _c (i,j) are the predicted chrominance samples in a coding unit and rec _L (i,j) are the reconstructed reduced resolution luma samples of the same coding unit CU. The parameters α and β can be obtained from the straight line equation, which may also be called the maximum-minimum method. Since this calculation process may be performed as part of the decoding process and not simply as a lookup operation by the encoder, the syntax for passing the values of α and β may not be used.

[0135] For a 4:2:0 chrominance format, CCLM prediction may apply a six-tap interpolation filter to obtain a reduced resolution luminance sample corresponding to the chroma sample in FIG. 13. The reduced resolution luminance reading Rec'L[x, y] is calculated from the reconstructed luminance readings using the formula.

[0136] Reduced resolution luminance samples may be used to find the maximum and minimum sample points. The two points (luma and chrominance pair) (A, B) may be the minimum and maximum values within a set of adjacent luminance samples, as shown in FIG. 13.

[0137] The linear model parameters α and β can be obtained from the following equations:

[0138] Division operations can be effectively avoided by shift and multiplication operations. A single look-up table (LUT) may be used to store the precomputed values, and the absolute difference between the minimum and maximum brightness samples may be used to designate the LUT record pointer. The LUT size can be 512.

[0139] FIG. 14A and 14B depict exemplary sample positions used to obtain α and β in LT_CCLM. In T_CCLM mode, some examples use only the above adjacent samples (including 2*W samples) to calculate the linear model coefficients. In FIG. 15A and 15B depict exemplary sample positions used to obtain α and β in T_CCLM.

[0140] In the L_CCLM mode, in some examples, only left adjacent samples (including 2*H samples) are used to calculate the linear model coefficients. In FIG. 16A and 16B depict exemplary sample positions used to obtain α and β in L_CCLM.

[0141] The CCLM prediction mode may also include prediction between two chrominance components (eg, the Cr component is predicted from the Cb component). Instead of using the recovered sample signal, CCLM Cb-Cr prediction in the residual region can be used. The CCLM Cb-Cr prediction can be applied by adding the weighted reconstructed residual prediction Cb to the original intra prediction Cr to form the final prediction Cr:

[0142] The CCLM luminance-chrominance prediction mode can be added as an additional intra chroma prediction mode. On the part of the encoder, an additional cost-distortion-rate (RD) check is made for the chrominance components in order to select the intra chrominance prediction mode. When applying an intra prediction mode for the chrominance components of a coding unit other than the CCLM luminance-chrominance prediction mode, Cb-Cr CCLM prediction is applied to the Cr component.

[0143] Multiple CCLM Model (MMLM) is another extension of CCLM with the possibility of having multiple models (eg, 2 or more models). In MMLM, adjacent luminance and chrominance samples of the current block can be classified into two groups, and each of the groups can be used as a training set to obtain a linear model (ie, certain α and β are obtained for a certain group). Further, the samples of the current luminance block can also be classified based on the same classification rule for adjacent luma samples.

[0144] FIG. 17 shows an example of classifying adjacent samples into two groups. The threshold shown in Fig. 17 can be calculated as the average of adjacent reconstructed brightness samples. If Rec'L[x,y] <= Threshold, the adjacent sample is defined in group 1, and if Rec'L[x,y] > Threshold, the adjacent sample is defined in group 2.

[0145] In order to perform a color contour transform in universal video coding in order to efficiently encode an input video signal in RGB format, it is necessary to adjust the interaction between the chrominance transform and several encoding tools (for example, cross-component linear model and dual tree splitting method) in universal video coding. Embodiments of the present invention provide highly efficient chroma transform adjustment functions by the universal video coding tool.

[0146] Embodiments of the present invention may be applied separately or together in any order. Also, each of the methods, encoder and decoder, according to embodiments of the present invention, may be implemented by a processing circuit (eg, one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored on a computer-readable storage medium. According to embodiments of the present invention, the term "block" may refer to a prediction block, a coding block, or a coding unit (ie, CU). According to embodiments of the present invention, the term "luminance component" may refer to any color component encoded as the first component in coding order (eg, red (R) or green (G) color component). Further, according to embodiments of the present invention, the term "chrominance component" can be understood to mean any color component that is not encoded as the first component in the coding order.

[0147] According to some embodiments of the present invention, a color transform such as ACT? is applied before the encoder's prediction, and after the encoder performs the recovery. At the encoder, ACT may be performed prior to prediction (eg, intra or inter prediction), and reference samples and incoming seed samples may be displayed in a different color space if ACT is applied to the current coding unit. In pixel reconstruction by the decoder, if ACT is applied to the block being restored, the reference samples may be displayed in an alternate color space before they are used for prediction, and the reconstructed samples may again be displayed in the original color space.

[0148] In FIG. 18 shows embodiments of ACT encoding and decoding processes. The blocks shown in Fig. 18 may be implemented in programs by a processor or a circuit, such as an ASIC, designed to perform the function of each block shown in FIG. 18. ACT blocks (1800) and (1804) perform an ACT transform on the reference and input signal, respectively. The ACT transform performed by the ACT encoder units (1800) and (1804) may be the ACT transform disclosed in Eq. (7). The result of the ACT (1800) is provided to the prediction block (1802). The reference signal is then passed to a prediction block (1806). Predictors (1802) and (1806) may perform intra or inter prediction. Transform block 1808 receives (i) the difference between the result (output) of the prediction block (1802) and the result of the ACT block (1804), or (ii) the difference between the result of the prediction block (1806) and the input signal. The transform block (1808) may perform a transform operation, such as a discrete cosine transform (DCT). The result of the transform block (1808) is passed to the quantizer (Q) (1810) for quantization, followed by a series of coefficients.

[0149] The inverse quantizer (IQ) of the decoder (1812) obtains coefficients to perform inverse quantization. The result of the inverse quantizer (IQ) (1812) is passed to the inverse transform (IT) (1814) for inverse transformation. The ACT block (1820) receives the final result of the prediction block (1818) as well as the result of the inverse transform (IT) block (1814). The ACT block (1816) receives the result of the prediction block (1818). Blocks ACT (1816) and (1820) can perform the inverse color transformation as in Eq. (8). Transform blocks (1818) and (1822) may perform inter or intra prediction. The restored reference signal is provided by the result of the ACT block (1816) and the restored original signal is provided by the result of the ACT block (1820).

[0150] According to some embodiments, during the ACT process, the 2nd and 3rd color components are shifted by a constant "c" after and before the color transform for forward and reverse transform, respectively. Lv. (14) depicts a modified direct transformation, and Eq. (15) - modified inverse transformation.

[0151] In some embodiments, the constant c is defined as 1<<(bitDepth-1), where bitDepth is the bit depth of the input sample.

[0152] According to some embodiments, color transformation is only applied when encoding different color components with a transformation unit tree. In one embodiment, when using a DualTree on an intra-slice, the color transform is only applied to the inter-slice.

[0153] According to some embodiments, when color transform is used, the CCLM mode is not applied or signaled because the generation of residual samples from one component depends on the reconstruction of another component. In another embodiment, no color conversion is applied or signaled when using the CCLM mode. In one embodiment, when color transform is used on the intra-coding residual samples, the CCLM mode is not applied or signaled because the generation of residual samples from one component depends on the reconstruction of another component. In one embodiment, when using a color transform on the residual sample and applying the CCLM mode, no color transform is applied or signaled.

[0154] According to some embodiments, a color transform is signaled for each coding tree unit that is the largest coding unit.

[0155] In some embodiments, a color transform is signaled and applied only to intra coding blocks or only to outer coding blocks. In some embodiments, no dual tree is applied when applying a color transform (ie, different color components use the same division of transform units).

[0156] FIG. 19 shows an embodiment of the process performed by the encoder (603). The process may start at the step (S1900) of determining whether the color conversion condition is met. For example, the color transform condition may be a flag indicating whether the color transform is enabled for the current block. As another example, the color transform condition could be a flag indicating that color transform is enabled for each block in the CTU. When the color conversion condition is met, the process proceeds to a step (S1902) in which color conversion is performed on the current block. For example, the color transform may be the ACT operation presented in Eq. (7).

[0157] The process proceeds from step (S1902) to step (S1904) to perform prediction for the current color transform block. Prediction can be internal or external. If the color conversion condition is not met in step (S1900), the process proceeds to step (S1904). The process proceeds from step (S1904) to step (S1906) to perform, for example, discrete cosine transform (DCT) on the predicted current block. The process proceeds to step (S1908) to perform quantization on the transformed current block. The result of the quantization may be a set of coefficients included in the bitstream transmitted to the decoder. The process shown in fig. 19 can be ended after step (S1908) is completed.

[0158] FIG. 20 shows an embodiment of the process performed by the decoder (710). The process may be started in step (S2000) when an encoded video bitstream is received. This bitstream includes the coefficients generated in step (S1908) (FIG. 19). The process proceeds to the step (S2002) of performing inverse quantization on a number of coefficients corresponding to the current block. The process proceeds to a step (S2004) of performing an inverse transform on the inverse quantization result for the current block. The process proceeds to a step (S2006) where intra or inter prediction is performed on the inverse transform result corresponding to the current block. In step (S2008), the fulfillment of the color conversion condition for the current block is determined. For example, the color transform condition may be a flag indicating that a color transform is allowed for the current block. As another example, a color transform condition could be a flag indicating that a color transform is allowed for each block in the CTU. When the color conversion condition is met, the process proceeds to the step (S2010) of performing an inverse color conversion on the current block. For example, the inverse color transform may be the ACT operation presented in Eq. (8). If the color conversion condition is not met, the process shown in FIG. 20. The process depicted in FIG. 20 may also be executed upon completion of the step (S2010).

[0159] The above methods may be implemented in computer software using computer-readable instructions and physically stored on one or more computer-readable media. For example, in FIG. 21 shows a computer system (2100) suitable for implementing some embodiments of the disclosed invention.

[0160] Computer software may be coded using any suitable machine code or computer language that may be assembled, compiled, linked, or similarly processed to create code containing instructions that can be executed directly, or through interpretation, execution of microcode, etc. .p., one or more computer central processing units (CPU, central processing units), graphic processors (GPU, Graphics Processing Units), etc.

[0161] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, IoT devices, and the like.

[0162] The computer system components (2100) shown in FIG. 21 are illustrative in nature and are not intended to impose any limitation on the scope of application or functionality of computer software implementing embodiments of the present invention. The configuration of the components should also not be interpreted as having any dependency or requirement in connection with any one or combination of the components shown in the illustrative embodiment of the computer system (2100).

[0163] The computer system (2100) may include some human interface input devices. Such an input device may be responsible for input by one or more users through, for example, tactile input (e.g., keystrokes, waving, glove movements), audio input (e.g., voice, claps), visual input (e.g., gestures), olfactory input (not shown). Interface devices may also be used to capture certain media not necessarily directly related to conscious human input, e.g. sound (e.g. speech, music, external sound), images (e.g. scanned images, photographic images received from a still camera) , video (eg, 2D video, 3D video including stereoscopic video).

[0164] Input interface devices can be represented by one or more devices (one of each shown): keyboard (2101), mouse (2102), touch pad (2103), touch screen (2110), information glove (not shown), joystick (2105), microphone (2106), scanner (2107), camera (2108).

[0165] The computer system (2100) may also include some human interface output devices. Such output devices may stimulate the senses of one or more users through, for example, tactile output, sound, light, and smell/taste. Such output devices may include tactile output devices (e.g., haptic feedback via touch screen (2110), data glove (not shown), or joystick (2105), but may also be tactile feedback devices that do not serve as input devices) , audio output devices (for example: speakers (2109), headphones (not shown)), visual output devices (for example, screens (2110), including CRT screens, LCD screens, plasma screens, OLED screens, each with touchscreen input capabilities, each with or without tactile feedback capabilities, some of which are capable of 2D visual output or more than 3D output through, for example, stereographic output; virtual reality glasses (not shown), holographic displays, smoke tanks (not shown) and printers (not shown).

[0166] The computer system (2100) may also include human accessible storage devices and associated media, such as optical media including CD/DVD ROM/RW (2120) with CD/DVD media (2121), etc. .p., flash memory cards (2122), removable hard drive or solid state drive (2123), conventional magnetic media such as tape and floppy disk (not shown), dedicated ROM/ASIC/PLD based devices such as security hardware keys (not shown) and the like.

[0167] Those skilled in the art should also understand that the term "computer-readable media" as used in connection with the invention disclosed herein does not encompass transmission media, carrier waves, or other short-term signals.

[0168] The computer system (2100) may also include an interface to one or more communication networks. Networks can be, for example, wireless, wired, optical. Networks may additionally be local, wide area, metropolitan, transport and industrial, real-time, latency, etc. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., digital wide area networks for wired or wireless television, including cable television, satellite TV and terrestrial TV, transport and industrial include CANBus, etc. Some networks typically require external network interface adapters that are connected to some general purpose data ports or peripheral buses (2149) (for example, computer system USB ports (2100)); others are typically built into the core of the computer system (2100) by connecting to a system bus as described below (eg, an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks, the computer system (2100) can communicate with other entities. Such communication may be unidirectional with receive-only capability (eg broadcast), unidirectional with transmit-only capability (eg CANbus to some CANbus devices), or bidirectional, eg to other computer systems using a local area network or a wide area digital network. Several protocols and protocol stacks may be used on each of these networks and the network interfaces described above.

[0169] The aforementioned human interface devices, human accessible storage devices, and network interfaces can be connected to the core (2140) of the computer system (2100).

[0170] The core (2140) may include one or more central processing units (CPUs) (2141), graphics processing units (GPUs) (2142), specialized programmable processing modules in the form of Field Programmable Gate Areas (FPGAs). ) (1543), hardware accelerators (2144) for some tasks, etc. These devices, together with read-only memory (ROM) (2145), random access memory (2146), high-capacity internal storage such as user-inaccessible internal hard drives, SSDs, etc. (2147), can be connected via a system bus (2148). In some computer systems, the system bus (2148) may be available in the form of one or more physical connectors to allow for expansions with additional CPUs, GPUs, and the like. Peripherals can be connected either directly to the kernel system bus (2148) or via a peripheral bus (1549). Peripheral bus architectures include PCI, USB, and the like.

[0171] CPUs (2141), GPUs (2142), FPGAs (2143), and accelerators (2144) may execute some instructions that together may constitute the aforementioned computer code. This computer code may be stored in ROM (2145) or RAM (2146). Transient data may also be stored in RAM (2146), while persistent data may be stored, for example, in an internal mass storage (2147). Fast storage and retrieval from any storage device can be achieved through the use of cache memory, which can be closely associated with one or more CPU (1541), GPU (1542), mass storage (2147), ROM (2145), RAM (2146) etc.

[0172] Computer-readable media may store computer code for performing various computer-implemented operations. The media and computer code may be specially created for the purposes of the present invention or may be well known and available to those skilled in the art of computer software.

[0173] By way of example, and not limitation, a computer system having an architecture (2100), and in particular a core (2140), can provide functionality through execution by processor(s) (including(and) CPU, GPU, FPGAs, accelerators, etc.) software embodied in one or more tangible computer-readable media. Such computer-readable media can be media associated with the user-accessible bulk data storage described above, as well as some long-term core storage (2140), such as internal bulk data storage (2147) or ROM (2145). Software implementing various embodiments of the present invention may be stored on such devices and executed by the core (2140). The computer-readable medium may include one or more memory devices or chips, in accordance with specific needs. The software may cause the core (2140) and in particular its processors (including CPUs, GPUs, FPGAs, etc.) to execute specific processes or specific parts of the specific processes described herein, including setting data structures stored in RAM (2146) , and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality through logic hardwired or otherwise embodied in circuitry (e.g., an accelerator (2144)) that may operate in place of or in conjunction with software to perform specific processes or specific portions of the specific processes described herein. A reference to software may cover logic, and vice versa when appropriate. Reference to computer-readable media may encompass a circuit (eg, an integrated circuit (IC)) where software is stored for execution, a circuit embodying logic for execution, or both, as appropriate. The present invention encompasses any suitable combination of hardware and software.

Appendix A: Abbreviations

JEM: collaborative research model

VVC: Universal Video Coding

BMS: a set of standards

MV: motion vector

HEVC: High Performance Video Coding

SEI: Additional Improvement Information

VUI: video suitability information

GOP: group of images

TU: conversion unit

PU: prediction unit

CTU: coding tree unit

CTB: coding tree block

RW: prediction block

HRD: Hypothetical Reference Decoder

SNR: signal to noise ratio

CPU: central processing unit

GPU: GPU

CRT: kinescope

LCD: liquid crystal display

OLED: organic light emitting diode

CD: CD

DVD: Digital Video Disc

ROM: Read Only Memory

RAM: random access memory

ASIC: Application Specific Integrated Circuit

PLD: Programmable Logic Device

LAN: local area network

GSM: Global System for Mobile Communications

LTE: a project for the long-term development of communication systems

CANBus: controller network bus

USB: Universal Serial Bus

PCI: Peripheral Component Interconnect

FPGA: Field Programmable Gate Arrays

SSD: solid state drive

IC: integrated circuit

CU: coding unit.

[0174] Although several illustrative embodiments are described here, changes, permutations, and various replacement equivalents are possible that fall within the scope of the invention. Thus, those skilled in the art can provide numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the invention and thus fall within its spirit and scope.

[0175] (1) A video decoding method performed by a video decoder is to obtain an encoded video bitstream including a current picture; in performing inverse quantization on the current block of the current image; after inverse quantization in performing an inverse transform on the current block; in performing the prediction on the current block after the inverse transformation; after prediction on the current block in determining whether a predetermined condition is met; and in performing an inverse color transformation on the current block after determining whether the predetermined condition is met.

[0176] (2) The method according to (1), wherein the inverse color transform is an inverse adaptive color transform (ACT), and performing the inverse color transform converts the reconstructed current block from color-spatial transform to RGB format.

[0177] (3) The method according to (1) or (2), wherein performing an inverse color transform includes subtracting a constant from one or more inverse color transform color components.

[0178] (4) The method according to (3), in which the constant is obtained by a left shift operation for the input sample bit depth minus one.

[0179] (5) The method according to one of (1) to (4), wherein the predetermined condition is executed in response to determining the color conversion signaling for the current block.

[0180] (6) The method according to (5), in which a color transform is signaled for each coding tree unit (CTU) with the largest coding unit.

[0181] (7) The method according to one of (1) to (6), wherein the predetermined condition is met in response to determining that different inverse color transform color components are encoded with the same unit division tree transformations.

[0182] (8) The method according to (7), wherein the inverse color transform is applied only on the inter-slice in response to determining the application of the dual tree on the intra-slice.

[0183] (9) The method according to one of (1) to (8), wherein, in response to determining whether a predetermined condition is met, cross-component linear mode (CCLM) is not applied to chrominance blocks of the current block.

[0184] (10) The video decoding method according to one of the features (1) to (9), wherein the prediction process is inter prediction or intra prediction.

[0185] (11) A video decoder for decoding video, including a processing circuit configured to receive an encoded video bitstream including a current picture, perform inverse quantization on the current block of the current picture, perform inverse transformation after performing inverse quantization on the current block, perform a prediction process on the current block after performing the inverse transformation, determining whether the predetermined condition is satisfied after performing the prediction on the current block, and performing the inverse color transformation on the current block in response to determining whether the predetermined condition is satisfied.

[0186] (12) The video decoder according to (11), wherein the inverse color transform is an inverse adaptive color transform (ACT), and performing the inverse color transform converts the reconstructed current block from color-spatial transform to RGB format.

[0187] (13) The video decoder according to (11) or (12), wherein performing the inverse color transform includes a processing circuit configured to subtract a constant from one or more color inverse transform components.

[0188] (14) A video decoder according to (13), in which a constant is obtained by a left shift operation by the input sample bit depth minus one.

[0189] (15) The video decoder according to one of the features (11) to (14), in which the predetermined condition is met in response to determining the color conversion signaling for the current block.

[0190] (16) A video decoder according to (15) in which a color transform is signaled for each coding tree unit (CTU) with the largest coding unit (CU).

[0191] (17) A video decoder according to one of the features (11) to (16), wherein a predetermined condition is met in response to determining the encoding of different inverse transform color components with the same transform unit division tree.

[0192] (18) The video decoder according to (17), in which an inverse color transform is applied only to the intra-slice in response to determining whether the dual tree is applied to the intra-slice.

[0193] (19) The feature video decoder (11) in which, in response to determining whether a predetermined condition is met, cross-component linear mode (CCLM) is not applied to the chroma blocks of the current block.

[0194] (20) A computer-readable storage medium with instructions whereby the video decoder processor performs the following: receiving an encoded video bitstream including the current picture, performing inverse quantization on the current block of the current picture, performing inverse transformation after performing inverse quantization on the current block, performing a prediction process on the current block after performing the inverse transformation, determining whether the predetermined condition is satisfied after performing the prediction on the current block, and performing an inverse color transformation on the current block in response to determining whether the predetermined condition is satisfied.

Claims (42)

1. A video decoding method, in which: receiving an encoded video bitstream including the current picture; perform inverse quantization for the current block of the current image; and perform an inverse color transformation for the current block after inverse quantization; wherein the inverse color transform for the current block is performed in response to determining that the different color components of the inverse color transform are encoded with the same division tree of coding units, and the inverse color transform is applied to intra-coded blocks. 2. The method of claim 1, wherein the inverse color transform is an inverse adaptive color transform (ACT) and performing the inverse color transform converts the reconstructed current block from a color space transform to an RGB format. 3. The method of claim 1, wherein performing the inverse color transform comprises subtracting a constant value from one or more color components of the inverse color transform. 4. The method of claim 3, wherein said constant value is obtained by performing a left shift operation on the bit depth of the input sample minus one. 5. The method of claim. 1, wherein before performing the inverse color transformation for the current block, the method also includes: determining whether a predetermined condition is met; wherein the predetermined condition is met if it is determined that a color conversion is signaled for the current block. 6. The method of claim 5, wherein the color transform is signaled for each coding tree unit (CTU) that has the largest coding unit (CU). 7. The method according to claim 5, in which the dual tree (DualTree) is not used when applying the color transformation. 8. The method of claim. 1, in which before performing the inverse color transformation for the current block, the method also includes: determining whether a predetermined condition is met; wherein the predetermined condition is met if it is determined that different inverse color transform color components are encoded with the same transform unit division tree. 9. The method of claim 8, wherein if it is determined that the DualTree is applied to the intra-slice, then the inverse color transform is applied to the inter-slice only. 10. The method according to p. 1, including: determining whether a predetermined condition is met; while not applying the cross-component linear mode (CCLM) to the chrominance blocks of the current block in response to determining whether a predetermined condition is met. 11. Video decoder for video decoding, comprising: a processing scheme configured to: receiving an encoded video bitstream including the current picture, performing inverse quantization on the current block of the current picture; and performing an inverse color transform on the current block after performing inverse quantization, wherein the inverse color transform is performed on the current block in response to determining that different inverse color transform color components are encoded with the same coding unit division tree, and inverse color transform used for blocks with intra coding. 12. The video decoder of claim 11, wherein the inverse color transform is an inverse adaptive color transform (ACT), and performing the inverse color transform converts the reconstructed current block from a color space transform to an RGB format. 13. The video decoder of claim 11, which, in order to perform a color inverse transform, includes a processing circuit configured to subtract a constant value from one or more color inverse transform color components. 14. The video decoder of claim 13, wherein the constant value is obtained by a shift left operation for the bit depth of the input sample minus one. 15. The video decoder of claim. 11, wherein the processing circuit is also configured to determine whether a predetermined condition is met before performing an inverse color transformation for the current block, wherein the predetermined condition is met if it is determined that a color conversion is signaled for the current block. 16. The video decoder of claim 15, wherein the color transform is signaled for each coding tree unit (CTU) that has the largest coding unit (CU). 17. The video decoder of claim 15, wherein the DualTree is not applied when applying the color transform. 18. The video decoder of claim 11, wherein the processing circuitry is also configured to determine whether a predetermined condition is met before performing an inverse color transformation for the current block, wherein the predetermined condition is met if it is determined that different inverse color transform color components are encoded with the same transform unit division tree. 19. The video decoder of claim 18, wherein the inverse color transform is applied only to the inter-slice in response to determining whether a DualTree is applied to the intra-slice. 20. Video decoder according to claim 11, in which the processing circuit is also configured to determine whether a predetermined condition is met; wherein, in response to determining whether the predetermined condition is met, the cross-component linear mode (CCLM) is not applied to the chrominance blocks of the current block. 21. A computer-readable storage medium with instructions, when executed by the video decoder processor, the video decoder performs a method, comprising: receiving an encoded video bitstream including the current picture; performing inverse quantization on the current block of the current picture; and performing an inverse color transform on the current block after performing the inverse quantization; wherein the inverse color transform for the current block is performed in response to determining that the different color components of the inverse color transform are encoded with the same coding unit division tree, and the inverse color transform is applied to the intra-coded blocks.

Images