Image Coding Offset Process for Chroma Distortion Correction
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Solution Overview
Problem
Current image coding methods suffer from significant distortion in chroma signals due to quantization errors, leading to a deterioration in subjective image quality, especially when using advanced standards like HEVC.
Innovation Solution
The proposed method involves predicting input blocks, calculating residual blocks, performing transform and quantization, and then applying an offset process to correct quantization errors, which are indicated by flag information, to improve image quality during the coding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If quantization is performed on residual blocks to compress video data, then coding efficiency is improved, but chroma signal distortion increases and image quality deteriorates
Solution Approach 1:
The patent applies different quantization parameters to luma and chroma components, using a less aggressive quantization parameter for chroma signals to reduce distortion while maintaining overall coding efficiency. This parameter differentiation allows the system to preserve chroma quality without sacrificing compression performance.
Solution Approach 2:
The patent performs chroma offset correction before final encoding to preemptively compensate for quantization errors. By calculating and applying offset values to correct chroma signal distortion in advance, the system prevents quality deterioration rather than attempting to fix it after encoding.
2Productivity
If advanced coding standards like HEVC are used to improve compression, then data transmission efficiency increases, but chroma signal distortion and subjective image quality deterioration worsen
Solution Approach 1:
The patent applies local offset correction to chroma blocks based on their specific characteristics. By calculating offset values for individual chroma blocks and applying corrections where needed, the system maintains high compression efficiency while locally improving chroma quality in regions where quantization distortion is most problematic.
Solution Approach 2:
The patent introduces an intermediary offset correction step between quantization and final encoding. This intermediary process calculates correction values based on quantization parameters and applies them to chroma signals, acting as a mediator that reconciles the conflict between compression efficiency and chroma quality.
Data Source
AI summary
An image coding method includes: generating a predicted block; calculating a residual block; calculating quantized coefficients by performing transform and quantization on the residual block; calculating a coded residual block by performing inverse quantization and inverse transform on the quantized coefficients; generating a temporary coded block; determining whether or not an offset process is required, to generate first flag information indicating a result of the determination; executing the offset process on the temporary coded block when it is determined that the offset process is required; and performing variable-length coding on the quantized coefficients and the first flag information.