Joint Transform Coding of Chroma Residuals
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Solution Overview
Problem
Current video coding technologies, such as AV1 and VVC, do not effectively utilize the correlation between chroma channels for improved compression efficiency, as they primarily focus on co-located chroma samples, neglecting the redundancy between different chroma channels.
Innovation Solution
A transform scheme is introduced for joint coding of residuals from multiple color components, specifically using a 2×N1×N2 by L×M matrix transformation to dequantize and decode chroma prediction-residual signal blocks, allowing for the reconstruction of Cb and Cr residual blocks from a combined 3D cubic structure, which includes primary and secondary transformations to set coefficients to zero based on threshold conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separate coding is used for Cb and Cr chroma channels, then coding simplicity is maintained, but compression efficiency is reduced due to unexploited inter-channel correlation
Solution Approach 1:
The patent combines Cb and Cr chroma residual blocks into a single 3D cubic structure of size 2×N1×N2, merging two separate coding processes into one unified transform operation. This allows the exploitation of correlations between different chroma channels while maintaining manageable complexity through a structured approach.
Solution Approach 2:
The patent introduces a third dimension to the transform by stacking Cb and Cr blocks to form a 3D cubic structure. The transform operates on this 3D structure with size 2×N1×N2, adding a channel dimension to the traditional 2D transform and enabling inter-channel correlation exploitation.
2Measurement precision
If all delta angles are signaled explicitly, then prediction precision is improved, but bitstream overhead increases
Solution Approach 1:
The patent extracts only the necessary angle information by deriving delta angles from nominal angles rather than signaling all delta angles explicitly. This selective approach retains prediction precision by preserving the essential angular relationships while removing redundant information from the bitstream.
Solution Approach 2:
The decoder performs on-the-fly calculations to reconstruct the full angle information from the signaled nominal angles and derived delta angles. This self-service approach allows the decoder to generate precise prediction angles without requiring all angle values to be transmitted, reducing bitstream overhead.
Data Source
AI summary
There is included a method and apparatus comprising computer code configured to cause a processor or processors to perform receiving video data in an AOMedia Video 1 (AV1) format comprising data of at least two chroma prediction-residual signal blocks, a transformation between at least one signal block, having a size less than or equal to a combination of the chroma prediction-residual signal blocks, and the chroma prediction-residual signal blocks, and decoding the video data based on an output of the transformation comprising the at least one signal block having the size less than or equal to the combination of the chroma prediction-residual blocks.