Mixed Secondary Transform Sets for Video Decoding Complexity Balance
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Solution Overview
Problem
Next-generation video contents with high spatial resolution, high frame rate, and high dimensionality require more efficient memory storage, memory access rate, and processing power, necessitating improved coding tools, particularly in transform efficiency and complexity.
Innovation Solution
A method for configuring a secondary transform set and encoding/decoding a secondary transform index based on intra prediction mode and coding block size, using mixed secondary transform sets with 8×8 and 4×4 transform kernels, and binarizing the transform index with a truncated unary scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If secondary transform is applied to improve coding efficiency, then compression performance is improved, but processing complexity increases
Solution Approach 1:
The transform block is divided into multiple sub-blocks, and secondary transform is selectively applied to specific sub-blocks based on their characteristics. This segmentation allows the system to improve coding efficiency for regions that benefit from secondary transform while avoiding unnecessary processing in regions where it would not provide benefit, thus balancing coding efficiency improvement with processing complexity reduction.
Solution Approach 2:
Different transform processing strategies are applied to different regions of the video block based on local characteristics such as prediction mode and block content. Regions with specific characteristics receive secondary transform processing to improve local coding efficiency, while other regions use standard transform processing, thereby optimizing the trade-off between overall coding efficiency and processing complexity.
2Adaptability or versatility
If multiple secondary transform sets are configured to handle various block sizes and prediction modes, then adaptability is improved, but device complexity increases
Solution Approach 1:
The system dynamically selects and configures secondary transform sets based on the specific prediction mode and block size being processed. Rather than maintaining all possible transform sets simultaneously, the system adapts the transform configuration to match the current processing context, improving adaptability while reducing the complexity of managing multiple transform sets.
Solution Approach 2:
The secondary transform sets are designed to handle multiple prediction modes and block sizes through a unified framework. The same transform set structure can be applied across different scenarios by adjusting parameters, reducing the need for completely separate transform configurations for each case and thereby reducing overall device complexity.
3Loss of substance
If transform index is binarized using truncated unary scheme to reduce signaling overhead, then bitrate is reduced, but decoding complexity increases
Solution Approach 1:
The transform index is encoded using a truncated unary scheme where the encoding method changes based on the maximum transform index value. When the maximum index is small, a simpler encoding is used; when it is larger, the truncated unary scheme is applied. This dynamic parameter change optimizes the balance between reducing signaling overhead and minimizing decoding complexity for different scenarios.
Data Source
AI summary
Disclosed is a method for decoding a video signal, including: generating a dequantized transform block by performing dequantization for a current block; acquiring an intra prediction mode of the current block; determining a secondary transform set applied to the current block among a plurality of secondary transform sets based on the intra prediction mode; deriving a transform kernel applied to the current block in the determined secondary transform set; and performing secondary transform for a top left specific area of the dequantized transform block by using the derived transform kernel, in which the plurality of secondary transform sets may include at least one mixed secondary transform set.