Chroma Block Encoding Mode Selection in HEVC Video Coding
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Solution Overview
Problem
The existing High Efficiency Video Coding (HEVC) standard's Transform Skip mode is inefficient due to unnecessary flag coding and complexity in determining the encoding mode for chroma blocks, which increases bandwidth usage and processing time.
Innovation Solution
The proposed solution eliminates the need to code flags for Transform Skip mode in specific configurations, allowing the encoder to implicitly choose the Normal mode based on rate-distortion criteria, reducing unnecessary checks and flag transmission, thereby speeding up the encoding process and improving coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Transform Skip mode is implemented with flag coding for chroma blocks, then the encoding flexibility is improved, but the bandwidth usage and processing complexity increase
Solution Approach 1:
The patent applies different encoding treatments to different chroma block types: for CbCr blocks, the Transform Skip mode is excluded and Normal mode is used, while for CrCb blocks, the Transform Skip mode may be used. This local differentiation resolves the contradiction by optimizing each chroma block type according to its specific characteristics, reducing unnecessary complexity while maintaining necessary flexibility where beneficial.
Solution Approach 2:
Instead of allowing Transform Skip mode for all chroma blocks and then using flags to control it, the patent inverts the approach by excluding Transform Skip mode for CbCr blocks by default and only allowing it for CrCb blocks. This inversion eliminates the need for flag coding in the predominant case, reducing bandwidth and processing complexity while preserving flexibility where it matters most.
2Manufacturing precision
If flags are coded for every chroma block to indicate Transform Skip mode, then the encoding precision is improved, but the bandwidth usage increases
Solution Approach 1:
The patent extracts and removes the flag coding requirement for CbCr chroma blocks, taking out the unnecessary bandwidth consumption. By determining through analysis that CbCr blocks benefit from Normal mode only, the flag mechanism is completely removed for this block type, reducing bandwidth usage while maintaining sufficient encoding precision through the default mode selection.
3Productivity
If the encoder checks both Normal mode and Transform Skip mode for chroma blocks, then the coding efficiency is improved, but the processing time increases
Solution Approach 1:
The patent performs preliminary analysis during standard encoding to identify that CbCr chroma blocks consistently achieve better rate-distortion performance with Normal mode. This preliminary finding is then used to pre-determine the encoding mode for CbCr blocks, eliminating the need for subsequent Transform Skip mode checks and reducing processing time while maintaining coding efficiency.
Data Source
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AI summary
A video signal has at least a first signal component corresponding to a first color, and a second signal component, associated with the first signal component and corresponding to a second color. Each signal component is divided into blocks, and each block has one or more encodable units. The encoding of at least one encodable unit of the second signal component is switchable between first and second modes. A method of encoding the signal comprises excluding,for at least one encodable unit of the second signal component, use of the second mode for the encoding of the second- signal-component encodable unit concerned when at least one predetermined condition is satisfied relating to an encoded block or encodable unit of the first signal component that corresponds to the second-signal-component encodable unit concerned.