Tencent America LLC

Madhu Peringassery Krishnan

Shan Liu

Xin Zhao

Liang Zhao

Yixin Du

Xiang Li

Han Gao

Samruddhi Yashwant Kahu

Xiang Yang Li

Xiaozhong Xu

Jing Ye

Sehoon Yea

Roman Chernyak

Biao Wang

Yushin Cho

Lien-Fei Chen

A method performed by at least one processor of a video decoder includes receiving a coded video bitstream including at least one picture and one or more syntax elements encoded in accordance with multi-hypothesis arithmetic coding. The method further includes decoding each syntax element from the one or more syntax elements based on the multi-hypothesis arithmetic coding. The method further includes selecting a probability update rate from a plurality of probability update rates based on a predetermined condition, the plurality of probability update rates including a first probability update rate that is higher than a second probability update rate. The method further includes updating at least one probability model utilized in the multi-hypothesis arithmetic coding based on the selected probability update rate. The method further includes decoding at least one block in the at least one picture based on the decoded one or more syntax elements.

Method and apparatus for adaptive multi-hypothesis probability model for arithmetic coding

An example method of video coding includes receiving a video bitstream that includes a plurality of blocks and a plurality of quantized transform coefficients. The method includes deriving a dequantized transform coefficient for a first quantized transform coefficient of the plurality of quantized transform coefficients. The method also includes obtaining an adjusted transform value by applying an offset value to the dequantized transform coefficient, the adjusted transform value based on a quantized transform coefficient level and a current state of dequantization. The method further includes reconstructing a first block using the adjusted transform value.

Systems and methods for dependent quantization based on current dequantization states

Aspects of the disclosure provide a method and an apparatus including processing circuitry for video decoding. The processing circuitry can decode coding information of a transform block (TB) from a coded video bitstream. The coding information can indicate a transform skip in one direction for the TB. The processing circuitry can decode a sign value of a current transform coefficient in the TB based on a previously decoded sign value of a previous transform coefficient. The current transform coefficient and the previous transform coefficient can be in one of a same row and a same column in the TB. The one of the same row and the same column can be along the one direction of the transform skip. The processing circuitry can determine the current transform coefficient in the TB based on the decoded sign value of the current transform coefficient.

Sign coding for one-dimensional transform skip

This disclosure relates generally to video coding/decoding and particularly for a transform dictionary. A method includes receiving the coded video bitstream; determining, based on the coded video bitstream, a transform pile for the current block, the transform pile being one transform pile in a transform dictionary, the transform dictionary comprising a plurality of transform piles, and the transform pile comprising a plurality of transform sets; determining a transform set in the transform pile; determining a transform kernel in the transform set; performing an inverse transform for the current block based on the transform kernel for obtaining a residual block for the current block; and reconstructing the current block based on the residual block.

Dictionary of transforms

This disclosure relates to adaptive loop filtering (ALF) for cross-component sample offset (CCSO), local sample offset (LSO), and generalized sample offset (GSO). ALF uses reconstructed samples of a first color component as input (e.g., Y or Cb or Cr). At least one of the GSO, LSO, or CCSO is determined to be enabled for a frame based on a syntax value in a coded video stream. The coded video stream is decoded by applying the at least one of the GSO, the LSO, or the CCSO at a block level.

Adaptive application of generalized sample offset

A method, computer program, and computer system for video coding is provided. Video data including one or more quantized coefficients is received. One or more index values associated with the quantized coefficients are mapped to one or more step values based on an exponential mapping. The video data is decoded based on the one or more step values.

Quantizer design

A method for coding video data, executable by a processor, includes receiving video data; entropy-parsing the received video data into one or more components; de-quantizing the one or more entropy-parsed components; performing a joint component secondary transformation (JCST) on the one or more components in accordance with a JCST kernel selected based on one of (i) a prediction mode corresponding to the video data, (ii) a primary transform type of a current block, and (iii) a secondary transform kernel selected for the current block; and decoding the video data based on one or more residual components corresponding to the joint component secondary transformed components.

Mode-dependent joint component transform

This disclosure relates to video coding with a block-level window size update for arithmetic coding. A probability update rate may be a function of count of appearances for the associated syntax/context when parsing a bitstream. It may also be a function of a number of different symbol values for the associated syntax/context. The value of the count is restarted with a pre-defined value at block-level. The probability or cumulative distribution function (CDF) update rate for a particular syntax/context may be reinitialized with a pre-defined value at block level.

Block-level window size update for arithmetic coding

A method and apparatus for performing a frequency-dependent joint component secondary transform (FD-JCST). The method includes obtaining a plurality of transform coefficients in a transform coefficient block; determining whether at least one of the plurality of transform coefficients is a low-frequency coefficient; based on determining that the at least one of the plurality of transform coefficients is the low-frequency coefficient, determining whether the low-frequency coefficient is a non-zero value; and based on determining that the low-frequency coefficient is the non-zero value, performing a joint component secondary transform (JCST) on the low-frequency coefficient and signaling a related syntax to indicate that the JCST is performed.

Frequency-dependent joint component secondary transform

This disclosure relates to a transform kernel sharing in video encoding and decoding. For example, a method is disclosed for such transform kernel sharing. The method may include identifying a plurality of transform kernels, wherein each of the plurality of transform kernels comprises a set of basis vectors from low to high frequencies; N high-frequency basis vectors of two or more of the plurality of transform kernels are shared, N being a positive integer; and low-frequency basis vectors of the two or more of the plurality of the transform kernels other than the N high-frequency basis vectors are individualized. The method may further include extracting a data block from a video bitstream; selecting a transform kernel from the plurality of transform kernels based on information associated with the data block; and applying the transform kernel to at least a portion of the data block to generate a transformed block.

Orthogonal transform generation with subspace constraint

Methods, apparatus, and computer readable storage medium for processing video data. The method includes extracting a data block from the video data; scanning a first number of data items in the data block following a first scan order to generate a first data sequence; performing a non-separable transform to the first data sequence to obtain a second data sequence having a second number of data items; and replacing at least a portion of the first number of data items in the data block with a portion or all of the second data sequence following a second scan order.

Scan order of secondary transform coefficients

Methods, apparatus, and computer readable storage medium for encoding/decoding video data in a decoder. The method includes receiving a coded bitstream comprising a luma transform skip flag associated with a luma coded block, the luma coded block comprising n transform blocks, n being a positive integer; receiving, via the coded bitstream, at least one chroma transform skip flag associated with at least one chroma coded block co-located with the luma coded block, the at least one chroma coded block comprising m transform blocks, m being a positive integer, wherein co-located refers to two coded blocks in different channels being located in a same spatial position; decoding the n transform blocks of the luma coded block based on the luma transform skip flag; and decoding the m transform blocks of the at least one chroma coded block based on the at least one chroma transform skip flag.

Skip transform flag coding

Methods, apparatus, and computer readable storage medium for encoding/decoding video data in a decoder. The method includes receiving a coded video bitstream for a data block; extracting, from the coded video bitstream, a transform partition type associated with the data block; and in response to the transform partition type belonging to a subset of a predefined set of transform partition types each specifying a split pattern for dividing the data block into transform blocks: extracting, as signaled in coded video bitstream, a transform type of a transform associated with a transform block split from the data block, wherein the transform type belongs to a first predefined set of transform types; and performing inverse transform on the transform block according to the transform type.

Interaction between transform partitioning and primary/secondary transform type selection

Methods, apparatus, and computer readable storage medium for multi-symbol arithmetic coding in video decoding. The method includes receiving a coded video bitstream; obtaining an array of cumulative distribution functions and corresponding M symbols, wherein M is an integer larger than 1; and performing, based on the array of cumulative distribution functions, arithmetic decoding on the coded video bitstream to extract at least one symbol by: for each extracted symbol, updating the array of cumulative distribution functions according to the extracted symbol based on at least one probability update rate, and continuing, based on the updated array of cumulative distribution functions, arithmetic decoding on the coded video bitstream to extract next symbol.

Methods, devices, and storage medium for multi-symbol arithmetic coding

A system includes code configured to cause a processor to obtain a video bitstream, the video bitstream including: a first quantization index value for a coefficient of a coded image; an offset value; a quantization step size that corresponds to the first quantization index value; a second quantization index value for another coefficient of the coded image, the second quantization index value being based on both the first quantization index value and the offset value and being greater than or equal to a predetermined threshold value; and a mode indicating whether the coded image is to be decoded in a lossy mode or a lossless mode, the mode being determined based on whether the first quantization index value is equal to a quantization index value associated with lossless coding, and whether the offset value is less than or equal to the quantization index value associated with the lossless coding.

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Mountain View, CA, United States of America

Madhu Peringassery Krishnan