Adaptive Secondary Transform Signaling in Video Coding
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Solution Overview
Problem
Current video coding standards face challenges in efficiently signaling and applying secondary transforms, leading to increased latency and decoding complexity, particularly in handling large transform blocks and multiple transform units.
Innovation Solution
The proposed method adaptively signals and applies secondary transforms based on the position of the last significant coefficient within a transform block, allowing for conditional signaling and inversion, thereby reducing unnecessary transform operations and improving encoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If secondary transform is applied to all transform blocks, then coding efficiency is improved, but decoding complexity and latency increase
Solution Approach 1:
The patent applies different treatment to different transform blocks based on their characteristics. Specifically, it determines whether to apply secondary transform to each transform block individually based on whether it contains only DC coefficients, rather than uniformly applying the transform to all blocks. This local differentiation reduces unnecessary processing while maintaining coding efficiency where beneficial.
Solution Approach 2:
The patent extracts and handles special cases separately from the general case. Transform blocks containing only DC coefficients are identified as special cases and excluded from secondary transform application, while other transform blocks proceed with the full secondary transform process. This extraction of edge cases simplifies the overall decoding process.
2Productivity
If secondary transform is applied to all transform blocks, then coding efficiency is improved, but processing time increases
Solution Approach 1:
The patent determines locally for each transform block whether secondary transform is needed based on its coefficient characteristics. By skipping the secondary transform for transform blocks with only DC coefficients, the patent eliminates unnecessary processing time while preserving the efficiency benefits where transform blocks require it.
Solution Approach 2:
Instead of applying secondary transform to all transform blocks (excessive action), the patent applies it only to those that need it based on their coefficient content (partial action). This partial application approach reduces overall processing time while maintaining sufficient coding efficiency.
3Manufacturing precision
If secondary transform index is signaled for all blocks, then transform application is controlled accurately, but bitstream complexity increases
Solution Approach 1:
The patent extracts transform blocks with only DC coefficients from the general set and excludes them from requiring secondary transform index signaling. This selective signaling approach reduces bitstream complexity while maintaining accurate transform control for blocks that actually need the secondary transform.
Solution Approach 2:
Transform blocks with only DC coefficients self-identify as not requiring secondary transform, eliminating the need for explicit signaling. The decoder can automatically determine whether to apply secondary transform based on the block's coefficient characteristics, reducing signaling overhead.
Data Source
AI summary
Video processing methods and apparatuses implemented in a video encoding or decoding system with conditional secondary transform signaling. The video encoding system determines and applies a transform operation to residuals of a transform block to generate final transform coefficients, and adaptively signals a secondary transform index according to a position of a last significant coefficient in the transform block. A value of the secondary transform index is determined according to the transform operation. The video decoding system parses last significant coefficient position syntax of each transform block in the current block from a video bitstream to determine a position of a last significant coefficient for each transform block, and infers inverse secondary transform is not applied to the current block according to the positions of the last significant coefficients; otherwise, the video decoding system determines an inverse transform operation by parsing a secondary transform index from the video bitstream.