Secondary Transform Selection in Video Coding
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Solution Overview
Problem
Current video coding technologies face challenges in efficiently reducing redundancy in video signals, particularly in handling intra prediction directions and motion vectors, which affects compression ratios and bandwidth requirements.
Innovation Solution
The implementation of a method for video encoding and decoding that determines the necessity of a secondary transform based on the position of non-zero transform coefficients and CU size, allowing for adaptive transform selection to optimize coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a secondary transform is applied to all coding blocks, then coding efficiency is improved, but computational complexity and processing overhead increase
Solution Approach 1:
The patent applies secondary transforms selectively based on local characteristics of coding blocks. Specifically, it uses the position of non-zero transform coefficients and CU size as criteria to determine which blocks receive secondary transforms, rather than applying them uniformly across all blocks. This localized approach maintains coding efficiency for blocks that benefit from secondary transforms while avoiding unnecessary processing for blocks where they provide minimal benefit.
Solution Approach 2:
The patent implements partial action by applying secondary transforms only to a subset of coding blocks that meet specific criteria (non-zero coefficient position and CU size thresholds). This partial application strategy achieves sufficient compression performance without the excessive computational cost of universal application, resolving the contradiction between coding efficiency and computational complexity.
2Quantity of substance
If adaptive transform selection is implemented, then compression ratio is improved, but decision complexity increases
Solution Approach 1:
The patent changes the parameters used for transform selection by incorporating specific criteria: the position of non-zero transform coefficients (using thresholds like lastPosX < 2 and lastPosY < 2) and CU size (using thresholds like tuSize >= 8). These parameter-based decisions simplify the adaptive selection process compared to more complex methods, while still achieving improved compression ratios through selective secondary transform application.
Data Source
AI summary
In a method for video decoding in a decoder, coded information of a coding unit (CU) is decoded from a coded video bitstream. The coded information indicating a last position of non-zero transform coefficients of a first coding block (CB) of the CU. Whether a secondary transform index is signaled in the coded information is determined based on whether the last position of non-zero transform coefficients indicates that the first CB of the CU has only zero coefficients or only one nonzero coefficient at the last coefficient position, wherein the secondary transform index is determined to be not signaled in the coded information when the last position of non-zero transform coefficients indicates that the first CB of the CU has only zero coefficients or only one nonzero coefficient at the last coefficient position. Whether to perform a secondary transform on a second CB of the CU is determined.