Implicit Transform Derivation for Intra Prediction Mode Selection
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Solution Overview
Problem
Existing video coding systems face inefficiencies in deriving inverse and transform indexes for blocks, leading to suboptimal compression and decoding performance.
Innovation Solution
A method for determining transform indexes based on intra prediction modes, utilizing a plurality of inverse or transform sets, and employing a modulo operation to select the appropriate inverse or transform, with optional lookup tables for enhanced precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transform index derivation mode is used for all intra prediction modes, then the device complexity is reduced, but the video coding efficiency deteriorates
Solution Approach 1:
The patent divides the intra prediction modes into two distinct groups: first intra prediction modes (e.g., planar, DC, and angular modes 2-30) and second intra prediction modes (e.g., matrix-based intra prediction modes 31-66). Each group uses a different transform index derivation mode, allowing optimized processing for each segment while maintaining overall system efficiency.
Solution Approach 2:
The patent implements dynamic transform index derivation where the derivation mode adapts based on the prediction mode of the current block. The system dynamically selects between first and second transform index derivation modes according to the specific intra prediction mode being used, enabling flexible optimization without fixed complexity constraints.
2Productivity
If transform index is determined using multiple inverse transform sets and modulo operations, then the compression performance is improved, but the computational complexity increases
Solution Approach 1:
The patent pre-establishes multiple inverse transform sets (first inverse transform set, second inverse transform set, etc.) with different numbers of inverse transforms. This preliminary organization allows the decoder to efficiently select and apply the appropriate transform set based on the TIDM value and block characteristics, improving compression performance without requiring complex real-time decisions.
Solution Approach 2:
The patent changes the parameter of transform set selection by using different numbers of inverse transforms in different sets (e.g., first set has 2 inverse transforms, second set has 4 inverse transforms). The modulo operation on TIDM value dynamically selects which set to use, allowing the system to adapt transform complexity to match block characteristics and improve overall compression efficiency.
3Speed
If implicit inverse transform selection is enabled for all blocks, then the decoding speed is improved, but the precision of transform selection deteriorates
Solution Approach 1:
The patent applies different transform index derivation approaches based on local block characteristics. For blocks with specific prediction modes, the system uses implicit selection with modulo operations on TIDM values. For other blocks, explicit transform index signaling is used. This localized optimization ensures high decoding speed where applicable while maintaining precision where needed.
Solution Approach 2:
The patent enables implicit inverse transform selection where the decoder independently determines the transform index using the TIDM value and pre-configured inverse transform sets. This self-service mechanism eliminates the need for explicit transform index signaling in many cases, improving decoding speed while maintaining adequate selection precision through the structured modulo-based derivation.
Data Source
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AI summary
Systems, devices, and methods are described herein for implicit transform derivation. A device (e.g., for video decoding) may obtain a block. The device may determine a prediction mode for the block. On a condition that the prediction mode is a first intra prediction mode, the device may determine a first transform index derivation mode (TIDM) value. On a condition that the prediction mode is a second intra prediction mode, the device may determine a second TIDM value. The device may determine a transform index based on the determined first or second TIDM value. The transform index may identify an inverse transform. The device may perform inverse transform for the block based on the inverse transform.