BDPCM Image Coding Without Inverse Non-Separable Transform
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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.
Innovation Solution
An image coding method based on BDPCM (block differential pulse coded modulation) that applies BDPCM to luma and chroma components, infers transform index and skip flag values, and performs intra prediction based on direction, without applying inverse non-separable transforms, to enhance coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional image coding techniques are used for high-resolution images/videos, then image quality is maintained, but transmission cost and storage cost increase
Solution Approach 1:
The patent applies BDPCM (Block Differential Pulse Code Modulation) to change the coding parameters from conventional transform-based methods to differential coding in the spatial domain. This parameter change enables more efficient compression for specific block types (luma and chroma components) while maintaining image quality, thereby reducing transmission and storage costs for high-resolution images and videos
2Productivity
If transform coding is applied to all blocks, then compression efficiency is improved, but coding complexity increases
Solution Approach 1:
The patent segments the image data into different component types (luma and chroma blocks) and applies different coding strategies to each. By identifying specific block characteristics and applying BDPCM selectively to certain blocks while using conventional transform coding for others, the patent reduces overall coding complexity while maintaining compression efficiency through differentiated processing
3Measurement precision
If inverse non-separable transform is applied, then transform accuracy is improved, but processing time increases
Solution Approach 1:
The patent applies inverse non-separable transform selectively only to blocks where it provides significant accuracy improvement, rather than uniformly to all blocks. By using BDPCM as an alternative for blocks where simple differential coding suffices, the patent reduces overall processing time while maintaining transform accuracy where truly needed
4Loss of information
If transform skip flag coding is used, then signaling overhead is reduced, but coding flexibility decreases
Solution Approach 1:
The patent implements transform skip flag coding with different inference rules for different block types and positions. By inferring transform skip flag values based on block characteristics (such as block size, component type, and neighboring block properties), the patent reduces signaling overhead for common cases while preserving coding flexibility for exceptional cases where explicit signaling is needed
Data Source
AI summary
An image decoding method according to the present document comprises the steps of: deriving a quantized transform coefficient for a current block on the basis of BDPCM; deriving a transform coefficient by performing dequantization on the quantized transform coefficient; and deriving a residual sample on the basis of the transform coefficient, wherein, when the BDPCM is applied to the current block, inverse non-separable transform is not applied to the transform coefficient.