Image Coding Mode Selection for Flat-Area Quality Consistency
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Solution Overview
Problem
Existing image coding methods, such as H.264/AVC, H.265/HEVC, and emerging H.266/VVC, fail to completely prevent blocks of intra-prediction and inter-prediction from being adjacent in flat areas of an image, leading to noticeable image quality differences and deterioration.
Innovation Solution
An image coding apparatus and method that employs a multi-reference prediction mode to combine intra-predicted and inter-predicted images, using a weighting coefficient to reduce image quality differences by blending pixel values, and a prediction mode selection unit to determine the optimal coding mode based on coding costs and flatness analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intra-prediction and inter-prediction are used to code adjacent blocks, then coding efficiency is improved through cost function optimization, but image quality deterioration occurs due to visible differences in predicted images in flat areas
Solution Approach 1:
The patent introduces a cost correction value that modifies the cost function parameters based on block flatness characteristics. By adjusting the cost function with this correction value, the system optimizes the balance between coding efficiency and image quality, preventing visible differences in predicted images while maintaining good compression performance.
Solution Approach 2:
The patent applies different prediction mode selection strategies based on the local flatness characteristics of each block. By determining whether a block is flat or complex and applying appropriate cost corrections accordingly, the system achieves optimal performance locally in different regions, preventing image quality deterioration in flat areas while maintaining coding efficiency overall.
2Productivity
If cost function optimization is used to select prediction modes, then coding efficiency is improved, but blocks of intra-prediction and inter-prediction may still be adjacent in flat areas causing noticeable quality differences
Solution Approach 1:
The patent modifies the cost function parameters by introducing a cost correction value that depends on block flatness. This parameter change ensures that prediction mode selection not only optimizes coding efficiency but also maintains image quality consistency by preventing adjacent blocks with different prediction modes in flat areas.
Solution Approach 2:
The system uses feedback from flatness detection to adjust the cost function. By detecting whether a block is flat and using this information to correct the cost value, the system continuously optimizes prediction mode selection to maintain both coding efficiency and image quality consistency.
Data Source
AI summary
A coding apparatus that performs coding processing on each block of an input image comprises a coding unit that executes coding processing using an inter-prediction mode, an intra-prediction mode or a multi-reference prediction mode, an output unit that outputs a result of the coding processing as coded data; and a calculation unit that calculates a first coding cost if the block is coded in the inter-prediction mode and a second coding cost if the block is coded in the intra-prediction mode using a predetermined function. The coding unit executes the coding processing using the multi-reference prediction mode if a difference between the first coding cost and the second coding cost is equal to or less than a threshold, and using the prediction mode with a smaller one of the first coding cost and the second coding cost if the difference is larger than the threshold.