Video Decoder Transform Signaling for Latency Reduction
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Solution Overview
Problem
Existing video coding technologies face challenges in efficiently determining and signaling transform modes, leading to increased encoder and decoder side latencies and sub-optimal coding efficiency due to dependencies between transform blocks.
Innovation Solution
A transform signaling mechanism is introduced where the signaling of primary transform is performed based on the use of a secondary transform, allowing a video decoder to determine both the type of primary and secondary transforms before decoding coefficients in a transform block, and skip decoding areas not applicable for the selected transform modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transform mode signaling is performed with dependencies between transform blocks, then coding efficiency can be maintained, but encoder and decoder side latencies increase
Solution Approach 1:
The patent divides the transform mode signaling into independent per-transform-block units rather than requiring dependency resolution across entire coding units. Each transform block can be processed independently, eliminating the latency caused by waiting for complete coding unit analysis while maintaining efficient coding through localized optimization.
2Device complexity
If transform mode selection is restricted by coding unit dependencies, then signaling complexity is reduced, but coding efficiency becomes sub-optimal
Solution Approach 1:
The patent implements dynamic transform mode selection at the transform block level rather than being constrained by static coding unit boundaries. The system can adaptively choose between primary transform, secondary transform, or both based on local characteristics of each transform block, maximizing coding efficiency without requiring complex inter-block dependency resolution.
Data Source
AI summary
There is disclosed a method comprising obtaining a block of transform coefficients; searching a position of a last non-zero coefficient in a scan order in the block; selecting a secondary transform mode based on the position and encoding first syntax elements indicative of the selected secondary transform mode. A primary transform mode is selected based on the secondary transform mode. Second syntax elements indicative of the selected primary transform mode and third syntax elements defining the transform coefficients within the block are encoded. There is also disclosed a method comprising receiving encoded information related to a block of transform coefficients; decoding an indication of a position of a last non-zero coefficient in a scan order in the block and using the position to determine if an indication of a secondary transform mode is present in the bit stream. If so, first syntax elements indicative of the secondary transform mode are decoded and used to determine if an indication of a primary transform mode is present in the bit stream. If so, second syntax elements indicative of the primary transform mode are decoded. The transform coefficients are decoded and the determined transform modes are applied to select transforms and the transforms, if any, are applied to the transform coefficients.