Video Block Decoding With Channel-Specific Transform Kernels
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Solution Overview
Problem
Existing video coding standards face challenges in efficiently handling the varying requirements of different sections of a video frame, particularly in terms of block partitioning and quantisation parameters, leading to suboptimal compression and decoding performance.
Innovation Solution
The method involves independently selecting kernels for the primary and secondary color channels based on decoded split flags and applying non-separable transforms to residual coefficients, along with adjusting quantisation parameters at a finer granularity based on subdivision levels for each section of the frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If video frames are divided into sections with uniform block partitioning and quantisation parameters, then the encoding process is simple and fast, but the compression performance is suboptimal for sections with varying content characteristics
Solution Approach 1:
The patent applies local quality by allowing different block partitioning structures and quantisation parameters for different sections of the video frame. Each section can be independently configured based on its content characteristics, enabling optimal compression for each region while maintaining overall frame quality. This resolves the contradiction by moving from uniform global parameters to localized adaptive parameters.
Solution Approach 2:
The patent segments the video frame into multiple sections, each of which can be independently processed with its own block partitioning and quantisation settings. This segmentation allows the encoder to apply different compression strategies to different parts of the frame, improving overall compression performance without sacrificing encoding efficiency through parallel processing of sections.
2Adaptability or versatility
If separate kernels are selected for primary and secondary color channels, then the decoding flexibility and compression efficiency are improved, but the device complexity and implementation cost increase
Solution Approach 1:
The patent applies local quality by selecting different transform kernels for primary and secondary color channels based on their specific characteristics. The primary color channel (luma) and secondary color channels (chroma) can use different kernels optimized for their respective statistical properties, improving compression efficiency while maintaining manageable complexity through standardized kernel selections.
Solution Approach 2:
The patent introduces dynamics by allowing the selection of different kernels for different color channels and potentially different sections of the frame. This dynamic adaptation enables the decoding process to flexibly respond to varying content characteristics, improving compression performance while the kernel selection mechanisms keep implementation complexity controlled.
3Loss of information
If chroma channels are subsampled at lower rates, then the bitrate is reduced and compression is improved, but the video quality and resilience to editing operations deteriorate
Solution Approach 1:
The patent applies local quality by allowing different chroma subsampling rates for different sections of the video frame. Sections with simpler content can use lower subsampling (e.g., 4:2:0) to reduce bitrate, while sections with more complex chroma content can use higher subsampling (e.g., 4:2:2 or 4:4:4) to maintain quality. This resolves the contradiction by adapting subsampling to local content requirements.
Solution Approach 2:
The patent segments the chroma processing into different sections with potentially different subsampling rates. This allows the system to apply aggressive compression where acceptable and maintain higher quality where needed, optimizing the trade-off between bitrate and video quality across the entire frame.
Data Source
AI summary
A method of decoding a coding unit of a coding tree from a coding tree unit of an image frame from a video bitstream, the coding unit having a primary colour channel and at least one secondary colour channel. The method comprises determining a coding unit including the primary colour channel and the at least one secondary colour channel according to decoded split flags of the coding tree unit; decoding a first index to select a kernel for the primary colour channel and a second index to select a kernel for the at least one secondary colour channel; selecting a first kernel according to the first index and a second kernel according to the second index; and decoding the coding unit by applying the first kernel to residual coefficients of the primary colour channel and the second kernel to residual coefficients of the at least one secondary colour channel.