Chroma Mode Coding Using Luma-Derived Delta Angles
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Solution Overview
Problem
In AOMedia Video 1 (AV1), both nominal and delta angles for chroma and luma components are signaled, despite the correlation between them not being utilized, leading to inefficient encoding and decoding processes.
Innovation Solution
Derive delta angles for the chroma component based on nominal angles from the luma component, reducing the need to signal all 56 angle values and allowing for on-the-fly calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all 56 directional angles (nominal and delta) for chroma component are signaled, then angle precision is maintained, but encoding complexity and data transmission increase
Solution Approach 1:
The patent extracts only the necessary delta angle information from the full set of 56 directional angles. Instead of signaling all delta angles, it derives them from nominal angles and selectively signals only when needed, reducing the data burden while maintaining necessary precision.
Solution Approach 2:
The patent performs preliminary derivation of delta angles from nominal angles before encoding. By pre-calculating which delta angles can be derived and which need to be signaled, it reduces the complexity of the encoding process while ensuring angle precision is maintained where necessary.
2Loss of information
If all 56 directional angles are signaled, then complete angle information is available, but data transmission requirements increase
Solution Approach 1:
The patent extracts only the essential angle information that cannot be derived from nominal angles. By identifying and signaling only these necessary delta angles, it maintains angle information completeness while significantly reducing the volume of data transmitted.
Solution Approach 2:
The patent creates derived copies of delta angles from nominal angles through mathematical relationships. This allows the system to reconstruct complete angle information at the decoder without transmitting all original delta angle values, reducing transmission volume while preserving information completeness.
3Productivity
If delta angles are derived from luma nominal angles, then encoding efficiency improves, but calculation complexity increases
Solution Approach 1:
The patent makes the luma nominal angles serve multiple functions: they define the luma prediction directions and also serve as the basis for deriving chroma delta angles. This multi-functionality improves encoding efficiency by eliminating redundant signaling while the derivation follows systematic rules that manage calculation complexity.
4Measurement precision
If chroma delta angles are independent of luma, then chroma accuracy is maintained, but encoding redundancy increases
Solution Approach 1:
The patent implements a feedback mechanism where chroma delta angles are derived from luma nominal angles, and the system checks whether this derived information sufficiently represents chroma angle characteristics. When the correlation is sufficient, it reduces redundancy; when accuracy requirements demand, it signals additional chroma-specific delta angles, thus maintaining accuracy while minimizing redundancy.
Data Source
AI summary
A method, system, and non-transitory computer readable medium is provided for decoding video data. Video data comprising a chroma component having a first nominal angle and first delta angles and a luma component having a second nominal angle and second delta angles is received, wherein the first delta angles are dependent on the second delta angles. The first delta angle values corresponding to the first delta angles are parsed or derived based at least on second delta values corresponding to the second delta angles, wherein the first delta angle values are derived from one or more nominal angles associated with one or more sample positions corresponding to one or more luma blocks. A prediction mode associated with the chroma component based on a nominal mode of a corresponding luma block is entropy-coded. The video data is decoded based on the first delta angle values corresponding to the first delta angles.