Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for reducing a quantity of buffers for a video codec. One of the methods includes determining, from a plurality of prediction modes, a prediction mode for data that represents frame data in a frame; in response to determining the prediction mode, selecting, using the prediction mode, one or more buffers from a plurality of buffers, each buffer of which is for a prediction mode from the plurality of prediction modes, a first quantity of buffers in the plurality of buffers being less than a second quantity of prediction modes in the plurality of prediction modes; retrieving, from each of the one or more buffers, historical data for the frame data; and in response to retrieving the historical data, generating, using the historical data, updated data for the frame data in the frame of the video sequence.

Abstract: Techniques are proposed to improve temporal motion projection in video coding. Candidate reference frames available for use in temporal motion projection are sorted in processing order according to scores assigned based on estimates of the reference frames' suitability for prediction. Such estimates may be based on temporal distance between each candidate reference frame and that reference frame's prediction references. Estimates may be based, for each reference frame, based on an estimate of coding quality of a reference frame from which the respective candidate reference frame makes a prediction reference. Once sorted, the candidate reference frames may be processing in the sorting order to supply prediction data to a current frame that is to be coded from the candidate reference frames. Additionally, hardware friendly designs of motion field hole filling and motion vector smoothing operations are proposed.

Abstract: In an example method, a decoder accesses a bitstream representing video content, and parses one or more flexible coefficient position (FCP) syntax from the bitstream, where the one or more FCP syntax indicate one or more index values. The decoder further determines side information representing one or more characteristics of an encoded portion of the video content. The decoder interprets the one or more FCP syntax based on the side information, including determining a coefficient position with respect to the encoded portion of the video content based on the one or more index values and the side information. The decoder decodes the encoded portion of the video content according to the coefficient position.

Abstract: The present disclosure describes techniques for efficient coding of motion vectors developed for multi-hypothesis coding applications. According to these techniques, when coding hypotheses are developed, each having a motion vector identifying a source of prediction for a current pixel block, a motion vector for a first one of the coding hypotheses may be predicted from the motion vector of a second coding hypothesis. The first motion vector may be represented by coding a motion vector residual, which represents a difference between the developed motion vector for the first coding hypothesis and the predicted motion vector for the first coding hypothesis, and outputting the coded residual to a channel. In another embodiment, a motion vector residual may be generated for a motion vector of a first coding hypothesis, and the first motion vector and the motion vector residual may be used to predict a second motion vector and a predicted motion vector residual.

Abstract: Improved lossless entropy coding techniques for coding of image data include selecting a context for entropy coding based on an ordered scan path of possible context locations. A symbol for a current location within a source image may be entropy coded based on a context of prior encoded symbols of other locations within source images, where the context is selected based on an ordered scan path enumerating a series of potential context locations within one or more source images. To select a context, a predetermined number of prior symbols may be selected by qualifying or disqualifying locations in the scan path, and then the current symbol may be encoded with a context based on prior symbols corresponding to the first qualifying context locations in the order of the scan path.

Abstract: Techniques are disclosed for improved video coding with virtual reference frames. A motion vector for prediction of a pixel block from a reference may be constrained based on the reference. In as aspect, if the reference is a temporally interpolated virtual reference frame with corresponding time close to the time of the current pixel block, the motion vector for prediction may be constrained magnitude and/or precision. In another aspect, a bitstream syntax for encoding the constrained motion vector may also be constrained. In this manner, the techniques proposed herein contribute to improved coding efficiencies.

Abstract: Disclosed is a method that includes receiving an image frame having a plurality of coded blocks, determining a prediction unit (PU) from the plurality of coded blocks, determining one or more motion compensation units arranged in an array within the PU, and applying a filter to one or more boundaries of the one or more motion compensation units. Also disclosed is a method that includes receiving a reference frame that includes a reference block, determining a timing for deblocking a current block, performing motion compensation on the reference frame to obtain a predicted frame that includes a predicted block, performing reconstruction on the predicted frame to obtain a reconstructed frame that includes a reconstructed PU, and applying, at the timing for deblocking the current block, a deblocking filter based on one or more parameters to the reference block, the predicted block, or the reconstructed PU.

Abstract: Video coders and decoders perform transform coding and decoding on blocks of video content according to an adaptively selected transform type. The transform types are organized into a hierarchy of transform sets where each transform set includes a respective number of transforms and each higher-level transform set includes the transforms of each lower-level transform set within the hierarchy. The video coders and video decoders may exchange signaling that establishes a transform set context from which a transform set that was selected for coding given block(s) may be identified. The video coders and video decoders may exchange signaling that establishes a transform decoding context from which a transform that was selected from the identified transform set to be used for decoding the transform unit. The block(s) may be coded and decoded by the selected transform.

Abstract: Techniques are described for express and implied signaling of transform mode selections in video coding. Information derived from coefficient samples in a given transform unit (TU) or prediction unit (PU) may constrain or modify signaling of certain syntax elements at the coding block (CB), TU, or PU levels. For instance, based on the spatial locations of decoded coefficients, the spatial patterns of coefficients, or the correlation with the coefficients in neighboring blocks, various syntax elements such as the transform type and related flags/indices or secondary transform modes/flags indices, a residual coding mode, intra and inter prediction modes, and scanning order may be disabled or constrained. In another case, if the coefficient samples match a desired spatial pattern or have other desired properties then a default transform type, a default secondary transform type, a default intra and inter prediction mode or other block level modes may be inferred at the decoder side.

Abstract: A flexible coefficient coding (FCC) approach is presented. In the first aspect, spatial sub-regions are defined over a transform unit (TU) or a prediction unit (PU). These sub-regions organize the coefficient samples residing inside a TU or a PU into variable coefficient groups (VCGs). Each VCG corresponds to a sub-region inside a larger TU or PU. The shape of VCGs or the boundaries between different VCGs may be irregular, determined based on the relative distance of coefficient samples with respect to each other. Alternatively, the VCG regions may be defined according to scan ordering within a TU. Each VCG can encode a 1) different number of symbols for a given syntax element, or a 2) different number of syntax elements within the same TU or PU. Whether to code more symbols or more syntax elements may depend on the type of arithmetic coding engine used in a particular coding specification. For multi-symbol arithmetic coding (MS-AC), a VCG may encode a different number of symbols for a syntax element.

Abstract: Techniques are disclosed for generating virtual reference frames that may be used for prediction of input video frames. The virtual reference frames may be derived from already-coded reference frames and thereby incur reduced signaling overhead. Moreover, signaling of virtual reference frames may be avoided until an encoder selects the virtual reference frame as a prediction reference for a current frame. In this manner, the techniques proposed herein contribute to improved coding efficiencies.

Abstract: An apparatus for video decoding includes processing circuitry. The processing circuitry decodes prediction information of a current block from a coded video bitstream. The prediction information is indicative of an intra block copy mode, the current block is one of a plurality of coding blocks in a coding tree block (CTB) with a right to left coding order being allowed within the current CTB. The processing circuitry determines a block vector that points to a reference block in a same picture as the current block. Then, the processing circuitry ensures the reference block being buffered in a reference sample memory based on at least a determination that a sample that is right of a leftmost sample of the reference block is buffered in the reference sample memory. Further, the processing circuitry reconstructs at least a sample of the current block based on reconstructed samples of the reference block.

Abstract: An apparatus includes processing circuitry, which determines a block vector that points to a reference block in a same picture as a current block in an intra block copy mode. The current block is one of a plurality of coding blocks in a coding tree block (CTB) with a right to left coding order being allowed within the CTB. The processing circuitry checks that two corner samples of the reference block have been reconstructed based on first outputs from a derivation process for block availability. The processing circuitry checks that a non corner sample of the reference block has been reconstructed based on a second output from the derivation process. The processing circuitry encodes the current block based on reconstructed samples of the reference block after a determination that the two corner samples of the reference block and the non corner sample of the reference block have been reconstructed.

Abstract: In an example method, a decoder obtains a data stream representing video content. The video content is partitioned into one or more logical units, and each of the logical units is partitioned into one or more respective logical sub-units. The decoder determines that the data stream includes first data indicating that a first logical unit has been encoded according to a flexible skip coding scheme. In response, the decoder determines a first set of decoding parameters based on the first data, and decodes each of the logical sub-units of the first logical unit according to the first set of decoding parameters.

Abstract: A cross-component based filtering system is disclosed for video coders and decoders. The filtering system may include a filter having an input for a filter offset and an input for samples reconstructed from coded video data representing a native component of source video on which the filter operates. The offset may be generated at least in part from a sample classifier that classifies samples reconstructed from coded video data representing a color component of the source video orthogonal to the native component according to sample intensity.

Abstract: A filtering system for video coders and decoders is disclosed that includes a feature detector having an input for samples reconstructed from coded video data representing a color component of source video, and having an output for data identifying a feature recognized therefrom, an offset calculator having an input for the feature identification data from the feature detector and having an output for a filter offset, and a filter having an input for the filter offset from the offset calculator and an input for the reconstructed samples, and having an output for filtered samples. The filtering system is expected to improve operations of video coder/decoder filtering systems by selecting filtering offsets from analysis of recovered video data in a common color plane as the samples that will be filtered.

Abstract: Improved neural-network-based image and video coding techniques are presented, including hybrid techniques that include both tools of a host codec and neural-network-based tools. In these improved techniques, the host coding tools may include conventional video coding standards such H.266 (VVC). In an aspects, source frames may be partitioned and either host or neural-network-based tools may be selected per partition. Coding parameter decisions for a partition may be constrained based on the partitioning and coding tool selection. Rate control for host and neural network tools may be combined. Multi-stage processing of neural network output may use a checkerboard prediction pattern.

Abstract: An encoder or decoder can perform enhanced motion vector prediction by receiving an input block of data for encoding or decoding and accessing stored motion information for at least one other block of data. Based on the stored motion information, the encoder or decoder can generate a list of one or more motion vector predictor candidates for the input block in accordance with an adaptive list construction order. The encoder or decoder can predict a motion vector for the input block based on at least one of the one or more motion vector predictor candidates.

Abstract: An apparatus includes processing circuitry, which determines a block vector that points to a reference block in a same picture as a current block in an intra block copy mode. The current block is one of a plurality of coding blocks in a coding tree block (CTB) with a right to left coding order being allowed within the CTB. The processing circuitry checks that two corner samples of the reference block have been reconstructed based on first outputs from a derivation process for block availability. The processing circuitry checks that a non corner sample of the reference block has been reconstructed based on a second output from the derivation process. The processing circuitry encodes the current block based on reconstructed samples of the reference block after a determination that the two corner samples of the reference block and the non corner sample of the reference block have been reconstructed.

Abstract: An apparatus for video decoding includes processing circuitry. The processing circuitry decodes prediction information of a current block from a coded video bitstream. The prediction information is indicative of an intra block copy mode. The current block is one of a plurality of coding blocks in a coding tree block (CTB) with a right to left coding order being allowed within the CTB. Further, the processing circuitry determines a block vector that points to a reference block in a same picture as the current block and checks that two corner samples of the reference block of the reference block have been reconstructed. In addition, the processing circuitry checks that an additional sample of the reference block has been reconstructed. Then, the processing circuitry reconstructs at least a sample of the current block based on reconstructed samples of the reference block that are retrieved from the reference sample memory.