Image Transform Coding With Size-Limited Non-Separable Transforms
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Solution Overview
Problem
The increasing demand for high-resolution and high-quality images/videos, including immersive media, necessitates a highly efficient image/video compression technique to reduce transmission and storage costs while effectively handling diverse image features.
Innovation Solution
An image coding method and apparatus that employs a multiple transform technique, including non-separable transforms, to optimize block sizes and enhance transform index coding efficiency, with specific conditions for applying inverse non-separable transforms based on block sizes and color formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution and high-quality images/videos are transmitted or stored, then image quality is improved, but transmission cost and storage cost increase
Solution Approach 1:
The image is divided into multiple blocks, and different transform techniques are applied to different blocks based on their characteristics. This segmentation allows selective application of computationally intensive non-separable transforms only to blocks that benefit most from them, reducing overall computational cost while maintaining high image quality.
Solution Approach 2:
Different transform techniques are applied to different regions of the image based on local characteristics. Non-separable transforms are applied to blocks with specific features (e.g., high-frequency content, specific prediction modes) while simpler transforms are used elsewhere, optimizing the balance between quality and complexity locally.
2Productivity
If non-separable transform is applied to all block sizes, then transform coding efficiency is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter of block size to determine when non-separable transform is applied. By setting a maximum block size threshold, the system adapts the transform technique based on block dimensions, achieving good coding efficiency for small blocks while avoiding excessive complexity for larger blocks.
Solution Approach 2:
Instead of applying non-separable transform to all blocks, the patent applies it partially only to blocks that meet specific size criteria. This partial application provides sufficient coding efficiency improvement without incurring the full computational cost of universal application.
3Adaptability or versatility
If transform index coding is performed without size limitation, then coding flexibility is improved, but coding overhead increases
Solution Approach 1:
The patent introduces a size parameter as a constraint on transform index coding. By limiting the maximum block size for non-separable transform application, the system reduces the number of possible transform index values that need to be coded, thereby reducing coding overhead while maintaining sufficient flexibility for blocks that benefit from the transform.
Data Source
AI summary
An image decoding method according to the present document is characterized by including: a step for receiving a bitstream including residual information; a step for deriving transform coefficients for a target block on the basis of the residual information; a step for deriving corrected transform coefficients on the basis of an inverse non-separable transform of the transform coefficients; and a step for deriving residual samples for the target block on the basis of an inverse primary transform of the corrected transform coefficients, wherein the inverse non-separable transform is performed when the size of the target block is equal to or smaller than the size of a prescribed maximum transform application block.