Video Encoder Transform Basis Selection by Block Size
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Solution Overview
Problem
Conventional video encoding methods face inefficiencies in processing transform coefficients due to the application of second transforms across varying block sizes without appropriate selection of transform bases, leading to increased processing loads.
Innovation Solution
An encoder and decoder that perform a second transform on transform coefficients obtained by a first transform, selecting a transform basis from a group of candidates based on the current block size, reducing processing loads by applying a common block size and avoiding unnecessary transforms for smaller blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a second transform is applied to transform coefficients for all block sizes, then encoding completeness is maintained, but processing load increases
Solution Approach 1:
The patent applies different transform strategies based on local block size characteristics. For larger blocks (8x8 or greater), a second transform is applied to improve encoding efficiency, while for smaller blocks (4x4), only the first transform is applied. This local differentiation optimizes processing load by avoiding unnecessary transforms on small blocks while maintaining efficiency on larger blocks.
Solution Approach 2:
The system dynamically adjusts the transform process based on block size conditions. The controller selectively enables or disables the second transform operation according to the detected block size, making the encoding process adaptive rather than static. This dynamic approach allows the system to optimize between processing load and encoding completeness based on actual block characteristics.
2Manufacturing precision
If transform bases are selected from multiple candidates for each block size, then encoding precision improves, but device complexity increases
Solution Approach 1:
The patent defines different candidate sets for transform bases according to local block size requirements. For 8x8 blocks, a first candidate set is used, while for 4x4 blocks, a second candidate set is used. This local quality approach ensures that the appropriate transform bases are selected for each block size, improving encoding precision without requiring a single complex selection mechanism for all block sizes.
Data Source
AI summary
An encoder includes circuitry and memory. Using the memory, the circuitry: performs a transform process of (i) applying a first transform to a prediction residual signal indicating a difference between a current block to be encoded and a prediction image of the current block and (ii) further applying a second transform to a transform result of the first transform; and in the second transform, selects one transform basis (i) from a first group of candidates when a size of the current block is a first block size and (ii) from a second group of candidates when the size of the current block is a second block size different from the first block size, the first group including one or more candidates for a transform basis, the second group being different from the first group.