Patent Application
20250234033
The present disclosure describes aspects generally related to video coding.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Image/video compression can help transmit image/video data across different devices, storage and networks with minimal quality degradation. In some examples, video codec technology can compress video based on spatial and temporal redundancy. In an example, a video codec can use techniques referred to as intra prediction that can compress an image based on spatial redundancy. For example, the intra prediction can use reference data from the current picture under reconstruction for sample prediction. In another example, a video codec can use techniques referred to as inter prediction that can compress an image based on temporal redundancy. For example, the inter prediction can predict samples in a current picture from a previously reconstructed picture with motion compensation. The motion compensation can be indicated by a motion vector (MV).
Aspects of the disclosure include bitstreams, methods and apparatuses for video encoding/decoding. In some examples, an apparatus for video encoding/decoding includes processing circuitry.
Some aspects of the disclosure provide a method of video decoding. In some examples, a coded video bitstream is received. The coded video bitstream includes at least coded information of a block in a picture of a video. Transform coefficients are extracted from the coded information of the block. For example, the coded information of the block is parsed and decoded to extract the transform coefficients. An inverse transform is applied on the transform coefficients to generate scaled residual values. An inverse scaling operation is applied on the scaled residual values based on one or more scaling values to generate restored residual values. The block is reconstructed according to the restored residual values. In an example, the restored residual values are combined with prediction of samples of the block to generate the reconstructed samples of the block.
Some aspects of the disclosure provide a method of video encoding. In some examples, to scale residual values of a block in a picture of a video is determined. A scaling operation is applied on the residual values of the block according to one or more scaling values to generate scaled residual values. A transform operation is applied on the scaled residual values to generate transform coefficients. Coded information of the block is generated according to the transform coefficients. The coded information of the block is included into a coded video bitstream for the video.
According to an aspect of the disclosure, a method of processing visual media data is provided. In the method, a conversion between a visual media file and a bitstream of visual media data is performed according to a format rule. In an example, the bitstream includes coded information of a block in a picture of a video. The format rule specifies that: transform coefficients are extracted from the coded information; an inverse transform is applied on the transform coefficients to generate scaled residual values; an inverse scaling operation is applied on the scaled residual values based on one or more scaling values to generate restored residual values; and the block is reconstructed according to the restored residual values.
Aspects of the disclosure also provide an apparatus for video encoding. The apparatus for video encoding including processing circuitry configured to implement any of the described methods for video encoding.
Aspects of the disclosure also provide a method for video decoding. The method including any of the methods implemented by the apparatus for video decoding.
Aspects of the disclosure also provide a non-transitory computer-readable medium storing instructions which, when executed by a computer, cause the computer to perform any of the described methods for video decoding/encoding.
Further features, the nature, and various advantages of the disclosed subject matter will be more apparent from the following detailed description and the accompanying drawings in which:
The video processing system (100) includes a capture subsystem (113), that can include a video source (101), for example a digital camera, creating for example a stream of video pictures (102) that are uncompressed. In an example, the stream of video pictures (102) includes samples that are taken by the digital camera. The stream of video pictures (102), depicted as a bold line to emphasize a high data volume when compared to encoded video data (104) (or coded video bitstreams), can be processed by an electronic device (120) that includes a video encoder (103) coupled to the video source (101). The video encoder (103) can include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter as described in more detail below. The encoded video data (104) (or encoded video bitstream), depicted as a thin line to emphasize the lower data volume when compared to the stream of video pictures (102), can be stored on a streaming server (105) for future use. One or more streaming client subsystems, such as client subsystems (106) and (108) in
It is noted that the electronic devices (120) and (130) can include other components (not shown). For example, the electronic device (120) can include a video decoder (not shown) and the electronic device (130) can include a video encoder (not shown) as well.
The receiver (231) may receive one or more coded video sequences, included in a bitstream for example, to be decoded by the video decoder (210). In an aspect, one coded video sequence is received at a time, where the decoding of each coded video sequence is independent from the decoding of other coded video sequences. The coded video sequence may be received from a channel (201), which may be a hardware/software link to a storage device which stores the encoded video data. The receiver (231) may receive the encoded video data with other data, for example, coded audio data and/or ancillary data streams, that may be forwarded to their respective using entities (not depicted). The receiver (231) may separate the coded video sequence from the other data. To combat network jitter, a buffer memory (215) may be coupled in between the receiver (231) and an entropy decoder/parser (220) (“parser (220)” henceforth). In certain applications, the buffer memory (215) is part of the video decoder (210). In others, it can be outside of the video decoder (210) (not depicted). In still others, there can be a buffer memory (not depicted) outside of the video decoder (210), for example to combat network jitter, and in addition another buffer memory (215) inside the video decoder (210), for example to handle playout timing. When the receiver (231) is receiving data from a store/forward device of sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (215) may not be needed, or can be small. For use on best effort packet networks such as the Internet, the buffer memory (215) may be required, can be comparatively large and can be advantageously of adaptive size, and may at least partially be implemented in an operating system or similar elements (not depicted) outside of the video decoder (210).
The video decoder (210) may include the parser (220) to reconstruct symbols (221) from the coded video sequence. Categories of those symbols include information used to manage operation of the video decoder (210), and potentially information to control a rendering device such as a render device (212) (e.g., a display screen) that is not an integral part of the electronic device (230) but can be coupled to the electronic device (230), as shown in
The parser (220) may perform an entropy decoding/parsing operation on the video sequence received from the buffer memory (215), so as to create symbols (221).
Reconstruction of the symbols (221) can involve multiple different units depending on the type of the coded video picture or parts thereof (such as: inter and intra picture, inter and intra block), and other factors. Which units are involved, and how, can be controlled by subgroup control information parsed from the coded video sequence by the parser (220). The flow of such subgroup control information between the parser (220) and the multiple units below is not depicted for clarity.
Beyond the functional blocks already mentioned, the video decoder (210) can be conceptually subdivided into a number of functional units as described below. In a practical implementation operating under commercial constraints, many of these units interact closely with each other and can, at least partly, be integrated into each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the functional units below is appropriate.
A first unit is the scaler/inverse transform unit (251). The scaler/inverse transform unit (251) receives a quantized transform coefficient as well as control information, including which transform to use, block size, quantization factor, quantization scaling matrices, etc. as symbol(s) (221) from the parser (220). The scaler/inverse transform unit (251) can output blocks comprising sample values, that can be input into aggregator (255).
In some cases, the output samples of the scaler/inverse transform unit (251) can pertain to an intra coded block. The intra coded block is a block that is not using predictive information from previously reconstructed pictures, but can use predictive information from previously reconstructed parts of the current picture. Such predictive information can be provided by an intra picture prediction unit (252). In some cases, the intra picture prediction unit (252) generates a block of the same size and shape of the block under reconstruction, using surrounding already reconstructed information fetched from the current picture buffer (258). The current picture buffer (258) buffers, for example, partly reconstructed current picture and/or fully reconstructed current picture. The aggregator (255), in some cases, adds, on a per sample basis, the prediction information the intra prediction unit (252) has generated to the output sample information as provided by the scaler/inverse transform unit (251).
In other cases, the output samples of the scaler/inverse transform unit (251) can pertain to an inter coded, and potentially motion compensated, block. In such a case, a motion compensation prediction unit (253) can access reference picture memory (257) to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols (221) pertaining to the block, these samples can be added by the aggregator (255) to the output of the scaler/inverse transform unit (251) (in this case called the residual samples or residual signal) so as to generate output sample information. The addresses within the reference picture memory (257) from where the motion compensation prediction unit (253) fetches prediction samples can be controlled by motion vectors, available to the motion compensation prediction unit (253) in the form of symbols (221) that can have, for example X, Y, and reference picture components. Motion compensation also can include interpolation of sample values as fetched from the reference picture memory (257) when sub-sample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.
The output samples of the aggregator (255) can be subject to various loop filtering techniques in the loop filter unit (256). Video compression technologies can include in-loop filter technologies that are controlled by parameters included in the coded video sequence (also referred to as coded video bitstream) and made available to the loop filter unit (256) as symbols (221) from the parser (220). Video compression can also be responsive to meta-information obtained during the decoding of previous (in decoding order) parts of the coded picture or coded video sequence, as well as responsive to previously reconstructed and loop-filtered sample values.
The output of the loop filter unit (256) can be a sample stream that can be output to the render device (212) as well as stored in the reference picture memory (257) for use in future inter-picture prediction.
Certain coded pictures, once fully reconstructed, can be used as reference pictures for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture has been identified as a reference picture (by, for example, the parser (220)), the current picture buffer (258) can become a part of the reference picture memory (257), and a fresh current picture buffer can be reallocated before commencing the reconstruction of the following coded picture.
The video decoder (210) may perform decoding operations according to a predetermined video compression technology or a standard, such as ITU-T Rec. H.265. The coded video sequence may conform to a syntax specified by the video compression technology or standard being used, in the sense that the coded video sequence adheres to both the syntax of the video compression technology or standard and the profiles as documented in the video compression technology or standard. Specifically, a profile can select certain tools as the only tools available for use under that profile from all the tools available in the video compression technology or standard. Also necessary for compliance can be that the complexity of the coded video sequence is within bounds as defined by the level of the video compression technology or standard. In some cases, levels restrict the maximum picture size, maximum frame rate, maximum reconstruction sample rate (measured in, for example megasamples per second), maximum reference picture size, and so on. Limits set by levels can, in some cases, be further restricted through Hypothetical Reference Decoder (HRD) specifications and metadata for HRD buffer management signaled in the coded video sequence.
In an aspect, the receiver (231) may receive additional (redundant) data with the encoded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder (210) to properly decode the data and/or to more accurately reconstruct the original video data. Additional data can be in the form of, for example, temporal, spatial, or signal noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and so on.
The video encoder (303) may receive video samples from a video source (301) (that is not part of the electronic device (320) in the
The video source (301) may provide the source video sequence to be coded by the video encoder (303) in the form of a digital video sample stream that can be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ), and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (301) may be a storage device storing previously prepared video. In a videoconferencing system, the video source (301) may be a camera that captures local image information as a video sequence. Video data may be provided as a plurality of individual pictures that impart motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, wherein each pixel can comprise one or more samples depending on the sampling structure, color space, etc. in use. The description below focuses on samples.
According to an aspect, the video encoder (303) may code and compress the pictures of the source video sequence into a coded video sequence (343) in real time or under any other time constraints as required. Enforcing appropriate coding speed is one function of a controller (350). In some aspects, the controller (350) controls other functional units as described below and is functionally coupled to the other functional units. The coupling is not depicted for clarity. Parameters set by the controller (350) can include rate control related parameters (picture skip, quantizer, lambda value of rate-distortion optimization techniques, . . . ), picture size, group of pictures (GOP) layout, maximum motion vector search range, and so forth. The controller (350) can be configured to have other suitable functions that pertain to the video encoder (303) optimized for a certain system design.
In some aspects, the video encoder (303) is configured to operate in a coding loop. As an oversimplified description, in an example, the coding loop can include a source coder (330) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded, and a reference picture(s)), and a (local) decoder (333) embedded in the video encoder (303). The decoder (333) reconstructs the symbols to create the sample data in a similar manner as a (remote) decoder also would create. The reconstructed sample stream (sample data) is input to the reference picture memory (334). As the decoding of a symbol stream leads to bit-exact results independent of decoder location (local or remote), the content in the reference picture memory (334) is also bit exact between the local encoder and remote encoder. In other words, the prediction part of an encoder “sees” as reference picture samples exactly the same sample values as a decoder would “see” when using prediction during decoding. This fundamental principle of reference picture synchronicity (and resulting drift, if synchronicity cannot be maintained, for example because of channel errors) is used in some related arts as well.
The operation of the “local” decoder (333) can be the same as a “remote” decoder, such as the video decoder (210), which has already been described in detail above in conjunction with
In an aspect, a decoder technology except the parsing/entropy decoding that is present in a decoder is present, in an identical or a substantially identical functional form, in a corresponding encoder. Accordingly, the disclosed subject matter focuses on decoder operation. The description of encoder technologies can be abbreviated as they are the inverse of the comprehensively described decoder technologies. In certain areas a more detail description is provided below.
During operation, in some examples, the source coder (330) may perform motion compensated predictive coding, which codes an input picture predictively with reference to one or more previously coded picture from the video sequence that were designated as “reference pictures.” In this manner, the coding engine (332) codes differences between pixel blocks of an input picture and pixel blocks of reference picture(s) that may be selected as prediction reference(s) to the input picture.
The local video decoder (333) may decode coded video data of pictures that may be designated as reference pictures, based on symbols created by the source coder (330). Operations of the coding engine (332) may advantageously be lossy processes. When the coded video data may be decoded at a video decoder (not shown in
The predictor (335) may perform prediction searches for the coding engine (332). That is, for a new picture to be coded, the predictor (335) may search the reference picture memory (334) for sample data (as candidate reference pixel blocks) or certain metadata such as reference picture motion vectors, block shapes, and so on, that may serve as an appropriate prediction reference for the new pictures. The predictor (335) may operate on a sample block-by-pixel block basis to find appropriate prediction references. In some cases, as determined by search results obtained by the predictor (335), an input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (334).
The controller (350) may manage coding operations of the source coder (330), including, for example, setting of parameters and subgroup parameters used for encoding the video data.
Output of all aforementioned functional units may be subjected to entropy coding in the entropy coder (345). The entropy coder (345) translates the symbols as generated by the various functional units into a coded video sequence, by applying lossless compression to the symbols according to technologies such as Huffman coding, variable length coding, arithmetic coding, and so forth.
The transmitter (340) may buffer the coded video sequence(s) as created by the entropy coder (345) to prepare for transmission via a communication channel (360), which may be a hardware/software link to a storage device which would store the encoded video data. The transmitter (340) may merge coded video data from the video encoder (303) with other data to be transmitted, for example, coded audio data and/or ancillary data streams (sources not shown).
The controller (350) may manage operation of the video encoder (303). During coding, the controller (350) may assign to each coded picture a certain coded picture type, which may affect the coding techniques that may be applied to the respective picture. For example, pictures often may be assigned as one of the following picture types:
An Intra Picture (I picture) may be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow for different types of intra pictures, including, for example Independent Decoder Refresh (“IDR”) Pictures.
A predictive picture (P picture) may be coded and decoded using intra prediction or inter prediction using a motion vector and reference index to predict the sample values of each block.
A bi-directionally predictive picture (B Picture) may be coded and decoded using intra prediction or inter prediction using two motion vectors and reference indices to predict the sample values of each block. Similarly, multiple-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.
Source pictures commonly may be subdivided spatially into a plurality of sample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 samples each) and coded on a block-by-block basis. Blocks may be coded predictively with reference to other (already coded) blocks as determined by the coding assignment applied to the blocks' respective pictures. For example, blocks of I pictures may be coded non-predictively or they may be coded predictively with reference to already coded blocks of the same picture (spatial prediction or intra prediction). Pixel blocks of P pictures may be coded predictively, via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of B pictures may be coded predictively, via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.
The video encoder (303) may perform coding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. H.265. In its operation, the video encoder (303) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. The coded video data, therefore, may conform to a syntax specified by the video coding technology or standard being used.
In an aspect, the transmitter (340) may transmit additional data with the encoded video. The source coder (330) may include such data as part of the coded video sequence. Additional data may comprise temporal/spatial/SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, and so on.
A video may be captured as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated to intra prediction) makes use of spatial correlation in a given picture, and inter-picture prediction makes uses of the (temporal or other) correlation between the pictures. In an example, a specific picture under encoding/decoding, which is referred to as a current picture, is partitioned into blocks. When a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture can be coded by a vector that is referred to as a motion vector. The motion vector points to the reference block in the reference picture, and can have a third dimension identifying the reference picture, in case multiple reference pictures are in use.
In some aspects, a bi-prediction technique can be used in the inter-picture prediction. According to the bi-prediction technique, two reference pictures, such as a first reference picture and a second reference picture that are both prior in decoding order to the current picture in the video (but may be in the past and future, respectively, in display order) are used. A block in the current picture can be coded 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 can be predicted by a combination of the first reference block and the second reference block.
Further, a merge mode technique can be used in the inter-picture prediction to improve coding efficiency.
According to some aspects of the disclosure, predictions, such as inter-picture predictions and intra-picture predictions, are performed in the unit of blocks. For example, according to the HEVC standard, a picture in a sequence of video pictures is partitioned into coding tree units (CTU) for compression, the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree split into one or multiple coding units (CUs). For example, a CTU of 64×64 pixels can be split into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUs of 16×16 pixels. In an 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 split into one or more prediction units (PUs) depending on the temporal and/or spatial predictability. Generally, each PU includes a luma prediction block (PB), and two chroma PBs. In an aspect, a prediction operation in coding (encoding/decoding) is performed in the unit of a prediction block. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of values (e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.
It is noted that the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using any suitable technique. In an aspect, the video encoders (103) and (303) and the video decoders (110) and (210) can be implemented using one or more integrated circuits. In another aspect, the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using one or more processors that execute software instructions.
According to some aspects of the disclosure, video coding can be used in machine scenarios.
In some examples, an encoder can be optimized for machine consumption. For example, the encoder device (402) is optimized for encoding bitstreams for machine consumption. For example, the encoder device (402) is coupled, via a network (403), to a decoder device (404), and the decoder device (404) is coupled to a machine (405) that consumes the decoded video (e.g., perform further analysis, detection, and the like on the video). Thus, an encoded bitstream can be provided from the encoder device (402) to the decoder device (404) via the network (403), and the encoded bitstream can be decoded by the decoder device (404), and the decoded video data can be further processed by the machine (405).
In certain environments, such as in video coding for consumption by machines (in contrast to humans), the requirement for a bitstream to pass a quality threshold based on human perception are not required in some examples. Instead, the quality can be sufficient for machine consumption even if not adequate for human consumption.
Video compression can be used for not only human but also machine consumptions. In some examples, video compression for machine consumption can be based on traditional video codecs as the core codec. However, traditional video codecs are primarily standardized for video application served for human vision, and additional coding tools or pre-/post-processing methods can be applied on top of a traditional video codec to achieve a higher coding efficiency for machine consumptions, measured by bitrate and machine task scores, e.g., object detection accuracy rates.
Some aspects of the disclosure provide a set of video coding methods for optimizing, transforming, signaling residual data of video frames in video coding systems. The methods can be used separately or combined in any order. Further, each of the techniques (or embodiments), methods, encoders, and decoders can be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program that is stored in a non-transitory computer-readable medium.
It is noted that the methods provided in the present disclosure can be used in video coding for machines (VCM) as well as in general video coding systems that are served for human consumptions.
Some aspects of the disclosure provide techniques for flexible scaling of residual values of blocks, such as inter (prediction) blocks, intra (prediction) blocks and the like. In some examples, the encoder can scale the residual values before further processing, and the decoder can inverse scale the obtained residual values decoded from a bitstream to restore the residue values for reconstruction.
In some aspects, a scaling operation can be applied to one or more residual samples. For example, at the encoder side, after residual samples are obtained (for example, differences of original samples to prediction samples are calculated), the scaling operation is applied on the residual samples to obtained scaled residual samples. The scaled residual samples can be further encoded (e.g., transformed, entropy coded, and the like) into coded information in a bitstream. At the decoder side, the scaled residual samples can be obtained (e.g., parsed, inverse transformed and the like) from the coded information of the bitstream. The scaled residual samples can be scaled (e.g., inverse scaled with respect to the scaling at the encoder side) to generate the restored residual samples. The restored residual samples are added to the prediction samples to generate the reconstruction samples. In some examples, the scaling operation on a residual sample is defined as a multiplication operation of a residual sample and a multiplier (also referred to as a scaler, a scaling value, a scaling factor, and the like). For case of description, scaling operation at the decoder side is referred to as inverse scaling operation. In some examples, the scaling value at the decoder side can be an inverse number of the scaling number at the encoder side.
It is noted that the scaler (also referred to as scaling value, a scaling factor and the like) can be implicitly derived or can be explicitly signaled.
In some examples, the value of the scaling factor is a constant for all residual sample values. Example values of scaling factors include, but not limited to 0.8, 0.6, 0.4.
In some examples, the values of the scaling factor can be derived from a function. Examples of the function include, but not limited to a polynomial function, a Gaussian function, an exponential function, and the like. The inputs to the function can be any suitable parameter. In an example, the block size can be the input of a function to derive the scaling factor. In another example, at the encoder side, the residual values can be the input of a function to derive the scaling factor, and at the decoder side, the scaled residual values can be the input of a function to derive the scaling factor.
In some examples, scaling factor is dependent on the relative sample position inside a coding block. For different samples inside a residual block, different scaling factors can be applied. For example, the scaling factor at the block boundary of a block can be 1, and the scaling factor decreases toward center of the block to a constant value, such as 0.75, 0.5, 0.25. In an example, block boundary can provide more useful information to a machine task, and with different scaling factors at the block boundary and the center can keep the useful information and improve coding efficiency.
In some examples, the scaling factor is derived according to context adaptive function. A context adaptive function is a function where the scale factor values depend on the values of decoded sample values, and also the context of the decoded samples values (e.g., the sequence of the decoded samples values).
In some examples, during the encoding and/or decoding process, the scaling factor can be dynamically adjusted based on specific characteristics of the content. In an example, the scaling factor changes based on motion vectors of coded blocks. In another example, the scaling factor changes based on texture of the coded blocks.
In some examples, the scaling factors are derived using a machine learning/deep learning to restore the residual values at decoder side. In an example, at the decoder side, the scaled residual values obtained from the coded information can be input to a neural network that is pre-trained, and the neural network can output the scaling factors. The scaling factors can be further used to calculate the restored residual values. In another example, at the decoder side, the scaled residual values obtained from the coded information can be input to a neural network that is pre-trained, and the neural network can output the restored residual values.
In some aspects, various approaches can be used on the scaling operations (including the scaling operation at the encoder side and/or the inverse scaling operation at the decoder side).
In some examples, a scaling operation is performed by a multiplication with a first integer value and then right or left shift by a second integer value. In some examples, the values of the multiplier and shifting bits can be signaled in the bitstream, such as a high-level syntax or a block-level syntax. In some examples, the values of the multiplier and shifting bits can be implicitly derived using coded information that is known to both encoder and decoder, such as the size or shape of the block.
In some examples, the scaler values can be a fixed factor (e.g., a power of two) to maintain precision without the need for floating-point calculations.
In some examples, lookup tables (LUTs) can be used in the scaling operations. For example, at the decoder side, a lookup table can store restored residual sample values corresponding to scaled residual sample values. When a parsed residual sample is obtained from the bitstream (e.g., after inverse transform), the value of the parsed residual sample can be input to the lookup table, and the lookup table can output the corresponding value of the restored residual sample corresponding to the value of the parsed residual sample. At the encoder side, for scaling, a LUT can include the scaled values for a range of input sample values in some examples. The LUT allows quick retrieval instead of real-time calculation.
In some aspects, the scaling operation can be conditionally applied.
In some examples, the scaling operation is performed for given block sizes or shapes.
In some examples, the scaling operation is performed for given prediction mode (e.g., intra prediction mode or inter prediction mode). In an example, the scaling operation is performed for blocks of intra prediction mode. In another example, the scaling operation is performed for blocks of inter prediction mode.
In some aspects, the enabling of the scaling operation, and the parameters used in scaling operation (e.g., which scaling value, which approach, which processing stage, and the like) is signaled in a high-level syntax, including but not limited to a sequence level flag, a picture level flag, a slice level flag, a tile level flag and the like. In some examples, a multi-level scaling process where different scaling factors are applied at various levels of the video data, such as the block level, the slice level, or frame level.
In some aspects, the enabling of the scaling operation can be signaled at block level.
In some aspects, the scaling operation can be performed at different processing stages in the decoding process.
In some examples, at the decoder side, the scaling (inverse scaling) is applied to the decoded residual samples to obtain the intermediate restored residual samples, and then DC component is added back to the intermediate restored residual samples to obtain the final residual samples. At the encoder side, the DC component is removed from the residual block before doing scaling operation.
In some examples, the scaling (inverse scaling) is applied to decoded residual blocks that already include DC component.
In some examples, the scaling (inverse scaling) is applied to the decoded residual samples and a value is added to scaled residual block (restored residual block). In an example, this value is signaled to the decoder, e.g., in high-level syntax or block-level syntax. In another example, this value is implicitly derived.
At (S510), a coded video bitstream is received. The coded video bitstream includes at least coded information of a block in a picture of a video.
At (S520), when applicable in some examples, transform coefficients are extracted from the coded information of the block. For example, the coded information of the block is parsed and decoded to extract the transform coefficients.
At (S530), when applicable in some examples, an inverse transform is applied on the transform coefficients to generate scaled residual values.
At (S540), an inverse scaling operation is applied on the scaled residual values based on one or more scaling values to generate restored residual values.
At (S550), the block is reconstructed according to the restored residual values. In an example, the restored residual values are combined (e.g., added) with prediction of samples of the block to generate the reconstructed samples of the block.
The one or more scaling values can be explicitly signaled or can be implicitly derived. In some examples, the one or more scaling values includes at least a constant value.
In an example, a scaling value is derived based on a function. In another example, a scaling value is derived based on a relative position of a sample in the block. In another example, a scaling value is derived based on a context adaptive function with the scaled residual values being input to the context adaptive function. In another example, a scaling value is derived based on a content characteristic of the block. In another example, a scaling value is derived based on a motion vector of the block. In another example, a scaling value is derived based on a texture of the block. In another example, a scaling value is derived using a neural network that is pretrained.
In some examples, to apply the inverse scaling operation, a multiplication of a scaled residual value with a first integer value is performed to calculate an intermediate residual value, and the intermediate residual value is shifted (left shifted or right shifted) by a second integer value of bits to obtain a restored residual value. In an example, the first integer value and the second integer value are determined according to one or more syntax elements in the coded video bitstream. In another example, the first integer value and the second integer value are derived according to the coded information of the block.
In some examples, a scaling value in the one or more scaling values is a fixed factor corresponding to a power of two. Thus, the inverse scaling operation can be performed with efficiently.
In some examples, to apply the inverse scaling operation, a restored residual value corresponding to a scaled residual value can be determined according to a lookup table (LUT). For example, the LUT stores restored values corresponding to scaled values.
In some examples, the inverse scaling operation is applied when a block size and/or a block shape satisfies a requirement. In some examples, the inverse scaling operation is performed when the block is coded with a specific prediction mode, such as an intra prediction mode, an inter prediction mode and the like.
In some examples, a first syntax element of a specific level is parsed from the coded video bitstream, the first syntax element indicates whether a scaling is enabled at the specific level. Also, one or more second syntax elements of the specific level are parsed from the coded video bitstream, the one or more second syntax elements indicate scaling parameters for the scaling at the specific level. Inverse scaling operations can be applied on blocks of the specific level according to the scaling parameters when the scaling is enabled.
In some examples, the specific level includes at least one of a sequence level, a picture level, a slice level, a tile level and a block level.
In some examples, a scaled residual value generated by the inverse transform corresponds to a scaled non-DC portion. To apply the inverse scaling operation, in some examples, the inverse scaling operation is applied on the scaled non-DC portion to generate a restored non-DC portion, and the restored non-DC portion is combined (e.g., added) with a DC component to obtain a restored residual value.
In some examples, a scaled residual value generated by the inverse transform includes already includes a non-DC portion and a DC portion. The inverse scaling operation is applied on the scaled residual value to generate a restored residual value.
In some examples, the inverse scaling operation is applied on a scaled residual value to generate an intermediate restored residual value, and the intermediate restored residual value is combined (e.g., added) with a value to obtain a restored residual value. In an example, a syntax element that indicates the value is signaled in the coded video bitstream and can be parsed and extracted from the coded video bitstream. In another example, the value is not signaled in the coded video bitstream and can be derived from the coded information of the block.
Then, the process proceeds to (S599) and terminates.
The process (500) can be suitably adapted. Step(s) in the process (500) can be modified and/or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.
At (S610), to scale residual values of a block in a picture of a video is determined.
At (S620), a scaling operation is applied on the residual values of the block according to one or more scaling values to generate scaled residual values.
At (S630), when applicable in some examples, a transform operation is applied on the scaled residual values to generate transform coefficients.
At (S640), coded information of the block is generated according to the transform coefficients.
At (S650), the coded information of the block is included into a coded video bitstream for the video.
The one or more scaling values can be explicitly signaled or can be derived based on information available at the encoder and the decoder. In some examples, the one or more scaling values includes at least a constant value.
In an example, a scaling value is derived based on a function. In another example, a scaling value is derived based on a relative position of a sample in the block. In another example, a scaling value is derived based on a context adaptive function with the scaled residual values being input to the context adaptive function. In another example, a scaling value is derived based on a content characteristic of the block. In another example, a scaling value is derived based on a motion vector of the block. In another example, a scaling value is derived based on a texture of the block. In another example, a scaling value is derived using a neural network that is pretrained.
In some examples, to apply the scaling operations, a multiplication of a residual value with a first integer value is performed to calculate an intermediate scaled residual value, and the intermediate scaled residual value is shifted (left shifted or right shifted) by a second integer value of bits to obtain a scaled residual value. In an example, the first integer value and the second integer value are encoded as one or more syntax elements in the coded video bitstream. In another examples, the first integer value and the second integer value can be derived based on information available at the encoder and decoder, such as according to the coded information of the block.
In some examples, a scaling value in the one or more scaling values is a fixed factor corresponding to a power of two. Thus, the scaling operation can be performed with efficiently.
In some examples, to apply the scaling operation, a scaled residual value corresponding to a residual value can be determined according to a lookup table (LUT). For example, the LUT stores scaled values corresponding to residual values.
In some examples, when a block size and/or a block shape satisfies a requirement, to scale the residual values is determined. In some examples, when the block is coded with a specific prediction mode, to scale the residual values is determined.
In some examples, a first syntax element of a specific level is included into the coded video bitstream, the first syntax element indicates a scaling is enabled at the specific level. Also, one or more second syntax elements of the specific level are included into the coded video bitstream, the one or more second syntax elements indicate scaling parameters at the specific level. The specific level can be at least one of a sequence level, a picture level, a slice level, a tile level and a block level.
In some examples, a DC component of the residual values is subtracted respectively from the residual values to generate intermediate residual values. The scaling operations are applied on the intermediate residual values to generate scaled residual values.
In some examples, the scaling operations are applied on the residual values that include a DC component and non-DC components to generate the scaled residual values
In some examples, a value is respectively subtracted from the residual values to generate intermediate residual values, and the scaling operations on the intermediate residual values to generate scaled residual values. In an example, a syntax element that indicates the value is included into the coded video bitstream. In another example, the value can be derived based on information that is available at both the encoder and the decoder.
Then, the process proceeds to (S699) and terminates.
The process (600) can be suitably adapted. Step(s) in the process (600) can be modified and/or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.
According to an aspect of the disclosure, a method of processing visual media data is provided. In the method, a conversion between a visual media file and a bitstream of visual media data is performed according to a format rule. For example, the bitstream may be a bitstream that is decoded/encoded in any of the decoding and/or encoding methods described herein. The format rule may specify one or more constraints of the bitstream and/or one or more processes to be performed by the decoder and/or encoder.
In an example, the bitstream includes coded information of a block in a picture of a video. The format rule specifies that: transform coefficients are extracted from the coded information; an inverse transform is applied on the transform coefficients to generate scaled residual values; an inverse scaling operation is applied on the scaled residual values based on one or more scaling values to generate restored residual values; and the block is reconstructed according to the restored residual values.
The techniques described above, can be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. For example,
The computer software can be coded using any suitable machine code or computer language, that may be subject to assembly, compilation, linking, or like mechanisms to create code comprising instructions that can be executed directly, or through interpretation, micro-code execution, and the like, by one or more computer central processing units (CPUs), Graphics Processing Units (GPUs), and the like.
The instructions can be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, internet of things devices, and the like.
The components shown in
Computer system (700) may include certain human interface input devices. Such a human interface input device may be responsive to input by one or more human users through, for example, tactile input (such as: keystrokes, swipes, data glove movements), audio input (such as: voice, clapping), visual input (such as: gestures), olfactory input (not depicted). The human interface devices can also be used to capture certain media not necessarily directly related to conscious input by a human, such as audio (such as: speech, music, ambient sound), images (such as: scanned images, photographic images obtain from a still image camera), video (such as two-dimensional video, three-dimensional video including stereoscopic video).
Input human interface devices may include one or more of (only one of each depicted): keyboard (701), mouse (702), trackpad (703), touch screen (710), data-glove (not shown), joystick (705), microphone (706), scanner (707), camera (708).
Computer system (700) may also include certain human interface output devices. Such human interface output devices may be stimulating the senses of one or more human users through, for example, tactile output, sound, light, and smell/taste. Such human interface output devices may include tactile output devices (for example tactile feedback by the touch-screen (710), data-glove (not shown), or joystick (705), but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers (709), headphones (not depicted)), visual output devices (such as screens (710) to include CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch-screen input capability, each with or without tactile feedback capability-some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual-reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted).
Computer system (700) can also include human accessible storage devices and their associated media such as optical media including CD/DVD ROM/RW (720) with CD/DVD or the like media (721), thumb-drive (722), removable hard drive or solid state drive (723), legacy magnetic media such as tape and floppy disc (not depicted), specialized ROM/ASIC/PLD based devices such as security dongles (not depicted), and the like.
Those skilled in the art should also understand that term “computer readable media” as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.
Computer system (700) can also include an interface (754) to one or more communication networks (755). Networks can for example be wireless, wireline, optical. Networks can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, and so on. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain networks commonly require external network interface adapters that attached to certain general purpose data ports or peripheral buses (749) (such as, for example USB ports of the computer system (700)); others are commonly integrated into the core of the computer system (700) by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface into a smartphone computer system). Using any of these networks, computer system (700) can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbus to certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks and network interfaces as described above.
Aforementioned human interface devices, human-accessible storage devices, and network interfaces can be attached to a core (740) of the computer system (700).
The core (740) can include one or more Central Processing Units (CPU) (741), Graphics Processing Units (GPU) (742), specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) (743), hardware accelerators for certain tasks (744), graphics adapters (750), and so forth. These devices, along with Read-only memory (ROM) (745), Random-access memory (746), internal mass storage such as internal non-user accessible hard drives, SSDs, and the like (747), may be connected through a system bus (748). In some computer systems, the system bus (748) can be accessible in the form of one or more physical plugs to enable extensions by additional CPUs, GPU, and the like. The peripheral devices can be attached either directly to the core's system bus (748), or through a peripheral bus (749). In an example, the screen (710) can be connected to the graphics adapter (750). Architectures for a peripheral bus include PCI, USB, and the like.
CPUs (741), GPUs (742), FPGAs (743), and accelerators (744) can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM (745) or RAM (746). Transitional data can also be stored in RAM (746), whereas permanent data can be stored for example, in the internal mass storage (747). Fast storage and retrieve to any of the memory devices can be enabled through the use of cache memory, that can be closely associated with one or more CPU (741), GPU (742), mass storage (747), ROM (745), RAM (746), and the like.
The computer readable media can have computer code thereon for performing various computer-implemented operations. The media and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those having skill in the computer software arts.
As an example and not by way of limitation, the computer system having architecture (700), and specifically the core (740) can provide functionality as a result of processor(s) (including CPUs, GPUs, FPGA, accelerators, and the like) executing software embodied in one or more tangible, computer-readable media. Such computer-readable media can be media associated with user-accessible mass storage as introduced above, as well as certain storage of the core (740) that are of non-transitory nature, such as core-internal mass storage (747) or ROM (745). The software implementing various aspects of the present disclosure can be stored in such devices and executed by core (740). A computer-readable medium can include one or more memory devices or chips, according to particular needs. The software can cause the core (740) and specifically the processors therein (including CPU, GPU, FPGA, and the like) to execute particular processes or particular parts of particular processes described herein, including defining data structures stored in RAM (746) and modifying such data structures according to the processes defined by the software. In addition or as an alternative, the computer system can provide functionality as a result of logic hardwired or otherwise embodied in a circuit (for example: accelerator (744)), which can operate in place of or together with software to execute particular processes or particular parts of particular processes described herein. Reference to software can encompass logic, and vice versa, where appropriate. Reference to a computer-readable media can encompass a circuit (such as an integrated circuit (IC)) storing software for execution, a circuit embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.
The use of “at least one of” or “one of” in the disclosure is intended to include any one or a combination of the recited elements. For example, references to at least one of A, B, or C; at least one of A, B, and C; at least one of A, B, and/or C; and at least one of A to C are intended to include only A, only B, only C or any combination thereof. References to one of A or B and one of A and B are intended to include A or B or (A and B). The use of “one of” does not preclude any combination of the recited elements when applicable, such as when the elements are not mutually exclusive.
While this disclosure has described several examples of aspects, there are alterations, permutations, and various substitute equivalents, which fall within the scope of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the disclosure and are thus within the spirit and scope thereof.
The above disclosure also encompasses the features noted below. The features may be combined in various manners and are not limited to the combinations noted below.
(1). A method of video decoding, including: receiving a coded video bitstream including coded information of a block; extracting transform coefficients from the coded information; applying an inverse transform on the transform coefficients to generate scaled residual values; applying an inverse scaling operation on the scaled residual values based on one or more scaling values to generate restored residual values; and reconstructing the block according to the restored residual values.
(2). The method of feature (1), in which the one or more scaling values include a constant value.
(3). The method of any of features (1) to (2), further including at least one of: deriving a scaling value based on a function; deriving a scaling value based on a relative position of a sample in the block; deriving a scaling value based on a context adaptive function with the scaled residual values being input to the context adaptive function; deriving a scaling value based on a content characteristic of the block; deriving a scaling value based on a motion vector of the block; deriving a scaling value based on a texture of the block; and/or deriving a scaling value using a neural network that is pretrained.
(4). The method of any of features (1) to (3), in which the applying the inverse scaling operation includes: performing a multiplication of a scaled residual value with a first integer value to calculate an intermediate residual value; and shifting the intermediate residual value by a second integer value of bits to obtain a restored residual value.
(5). The method of any of features (1) to (4), further including at least one of: determining the first integer value and the second integer value according to one or more syntax elements in the coded video bitstream; and deriving the first integer value and the second integer value according to the coded information of the block.
(6). The method of any of features (1) to (5), in which a scaling value in the one or more scaling values is a fixed factor corresponding to a power of two.
(7). The method of any of features (1) to (6), in which the applying the inverse scaling operation includes: determining a restored residual value corresponding to a scaled residual value according to a lookup table (LUT).
(8). The method of any of features (1) to (7), in which the applying the inverse scaling operation includes at least one of: applying the inverse scaling operation when a block size and/or a block shape satisfies a requirement; and/or applying the inverse scaling operation when the block is coded with a specific prediction mode.
(9). The method of any of features (1) to (8), further including: parsing a first syntax element of a specific level from the coded video bitstream, the first syntax element indicating whether a scaling is enabled at the specific level; parsing one or more second syntax elements of the specific level from the coded video bitstream, the one or more second syntax elements indicating scaling parameters for the scaling at the specific level; and applying inverse scaling operations on blocks of the specific level according to the scaling parameters when the scaling is enabled.
(10). The method of any of features (1) to (9), in which the specific level includes at least one of a sequence level, a picture level, a slice level, a tile level and a block level.
(11). The method of any of features (1) to (10), in which a scaled residual value generated by the inverse transform corresponds to a scaled non-DC portion, and the applying the inverse scaling operation further includes: applying the inverse scaling operation on the scaled non-DC portion to generate a restored non-DC portion; combining the restored non-DC portion with a DC component to obtain a restored residual value.
(12). The method of any of features (1) to (11), in which a scaled residual value generated by the inverse transform includes a non-DC portion and a DC portion, and the applying the inverse scaling operation further includes: applying the inverse scaling operation on the scaled residual value to generate a restored residual value.
(13). The method of any of features (1) to (12), in which the applying the inverse scaling operation includes: applying the inverse scaling operation on a scaled residual value to generate an intermediate restored residual value; and combining the intermediate restored residual value with a value to obtain a restored residual value.
(14). The method of any of features (1) to (13), further including at least one of: parsing a syntax element that indicates the value; and deriving the value from the coded information.
(15). A method of video encoding, including: determining to scale residual values of a block in a picture of a video; applying scaling operations on the residual values of the block according to one or more scaling values to generate scaled residual values; applying a transform operation on the scaled residual values to generate transform coefficients; generating coded information of the block according to the transform coefficients; and including the coded information of the block into a coded video bitstream for the video.
(16). The method of feature (15), in which the one or more scaling values include at least a constant value.
(17). The method of any of features (15) to (16), further including at least one of: deriving a scaling value based on a function; deriving a scaling value based on a relative position of a sample in the block; deriving a scaling value based on a context adaptive function;
(18). The method of any of features (15) to (17), in which the applying the scaling operations includes: performing a multiplication of a residual value with a first integer value to calculate an intermediate scaled residual value; and shifting the intermediate scaled residual value by a second integer value of bits to obtain a scaled residual value.
(19). The method of any of features (15) to (18), further including at least one of: encoding the first integer value and the second integer value as one or more syntax elements in the coded video bitstream; and deriving the first integer value and the second integer value according to the coded information of the block.
(20). The method of any of features (15) to (19), in which a scaling value in the one or more scaling values is a fixed factor corresponding to a power of two.
(21). The method of any of features (15) to (20), in which the applying the scaling operations includes: determining a scaled residual value corresponding to a residual value according to a lookup table (LUT).
(22). The method of any of features (15) to (21), in which the applying the scaling operations includes at least one of: applying the scaling operations when a block size and/or a block shape satisfies a requirement; and/or applying the scaling operations when the block is coded with a specific prediction mode.
(23). The method of any of features (15) to (22), further including: including a first syntax element of a specific level into the coded video bitstream, the first syntax element indicating a scaling is enabled at the specific level; and including one or more second syntax elements of the specific level into the coded video bitstream, the one or more second syntax elements indicating scaling parameters at the specific level.
(24). The method of any of features (15) to (23), in which the specific level includes at least one of a sequence level, a picture level, a slice level, a tile level and a block level.
(25). The method of any of features (15) to (24), further including: subtracting a DC component of the residual values respectively from the residual values to generate intermediate residual values; and applying the scaling operations on the intermediate residual values to generate scaled residual values.
(26). The method of any of features (15) to (25), in which the applying the scaling operations further includes: applying the scaling operations on the residual values that include a DC component to generate the scaled residual values.
(27). The method of any of features (15) to (26), in which the applying the scaling operations further includes: subtracting a value respectively from the residual values to generate intermediate residual values; and applying the scaling operations on the intermediate residual values to generate scaled residual values.
(28). The method of any of features (15) to (27), further including: including a syntax element that indicates the value into the coded video bitstream.
(29). A method of video processing, the method including: processing a bitstream of video data according to a format rule, in which: the bitstream includes coded information of a block; and the format rule specifies that: transform coefficients are extracted from the coded information; an inverse transform is applied on the transform coefficients to generate scaled residual values; an inverse scaling operation is applied on the scaled residual values based on one or more scaling values to generate restored residual values; and the block is reconstructed according to the restored residual values.
(30). An apparatus for video decoding, including processing circuitry that is configured to perform the method of any of features (1) to (14).
(31). An apparatus for video encoding, including processing circuitry that is configured to perform the method of any of features (15) to (28).
(32). A non-transitory computer-readable storage medium storing instructions which when executed by at least one processor cause the at least one processor to perform the method of any of features (1) to (29).
The present application claims the benefit of priority to U.S. Provisional Application No. 63/621,098, “FLEXIBLE SCALING OF RESIDUAL SAMPLES” filed on Jan. 15, 2024. The entire disclosure of the prior application is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63621098 | Jan 2024 | US |
