Image Decoding with Chroma-Scaled Intra Prediction Modes
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Solution Overview
Problem
The existing MPEG-4 AVC/H.264 coding system faces inefficiencies in coding and decoding processes due to the lack of direct consideration for color-difference formats, particularly in intra-prediction mode coding, which affects the process efficiency when not aligned with the color-difference format.
Innovation Solution
A picture coding device and method that sets prediction blocks for both brightness and color-difference signals, using intra-brightness and intra-color-difference prediction modes to efficiently code and decode signals based on the color-difference format, allowing for optimized bitstream management and prediction within conversion blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intra-prediction mode coding is performed without considering color-difference format, then the coding process is simplified, but process efficiency is degraded
Solution Approach 1:
The patent applies local quality by adapting the intra-prediction mode coding process to different color-difference formats (4:2:0, 4:2:2, 4:4:4). Specifically, the intra-color-difference prediction mode is adjusted according to the chroma subsampling format, allowing the coding process to be optimized for each local format requirement rather than using a uniform approach, thereby resolving the contradiction between simplicity and efficiency.
2Measurement precision
If separate intra-prediction modes are used for brightness and color-difference signals, then prediction accuracy is improved, but coding complexity increases
Solution Approach 1:
The patent segments the intra-prediction process into separate modes for brightness signal and color-difference signal. The intra-brightness prediction mode and intra-color-difference prediction mode are independently coded, allowing each to be optimized for its specific signal type. This segmentation improves prediction accuracy while the independent coding structure manages the complexity through modular organization.
Solution Approach 2:
The patent changes the parameter of prediction mode selection based on the signal type. Different intra-prediction mode values are used for brightness versus color-difference signals, and these parameters are adapted according to the color-difference format. This parameter differentiation enables accurate prediction for each signal type while the systematic parameter management keeps coding complexity controlled.
Data Source
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Figure 3A~3E
AI summary
In a picture coding device for coding picture signals including a brightness signal and a color-difference signal in a block unit using intra-prediction and coding information regarding an intra-prediction mode, when aspect ratios of pixels of the brightness signal and the color-difference signal are different from each other, a bitstream generator 113 converts a mode number of a first intra-color-difference prediction mode used when the aspect ratios are equal to each other into a scaled mode number and derives a second intra-color-difference prediction mode used when the aspect ratios are different from each other.