Chroma Mode Coding With Luma-Derived Delta Angles
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Solution Overview
Problem
In AV1 video coding format, all 56 directional angles, including both nominal and delta angles, are signaled for the chroma component regardless of the collocated luma prediction modes, neglecting the correlation between luma and chroma components, which leads to inefficient encoding and decoding processes.
Innovation Solution
Derive delta angle values 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
1Loss of information
If all 56 directional angles are signaled for chroma component, then complete angle information is available, but encoding efficiency deteriorates due to redundant signaling
Solution Approach 1:
The patent extracts only the necessary angle information for chroma prediction by deriving delta angles from luma component data. Instead of signaling all 56 chroma directional angles, the system extracts angle information from the luma component (which has stronger correlation with prediction patterns) and derives the corresponding chroma angles, thereby removing redundant signaling while preserving essential prediction accuracy.
Solution Approach 2:
The patent makes the luma component's angle information serve dual purposes: it is used for luma prediction directly and also serves as the basis for deriving chroma prediction angles. This multi-functional use of luma angle data eliminates the need for separate chroma angle signaling, improving encoding efficiency while maintaining prediction capability.
2Measurement precision
If all 56 directional angles are signaled for chroma component, then accurate prediction is achieved, but decoding complexity increases
Solution Approach 1:
The patent extracts angle information from the already-decoded luma component and uses it to derive chroma prediction angles. This extraction approach avoids the complexity of processing and storing all 56 chroma angles separately, reducing decoding complexity while maintaining prediction accuracy through the use of correlated luma angle data.
Solution Approach 2:
The chroma component's angle information is generated self-service by deriving it from the luma component's angle data. Instead of requiring the decoder to process and interpret separate chroma angle parameters, the system allows chroma angles to be automatically derived from luma angles, reducing decoding complexity and eliminating redundant processing steps.
3Loss of substance
If delta angles are derived from luma nominal angles, then redundant signaling is reduced, but encoding complexity increases
Solution Approach 1:
The patent performs preliminary derivation of chroma delta angles from luma nominal angles during the encoding process. By pre-calculating these derived angles and storing them in a lookup table or cache, the encoder avoids complex real-time calculations during actual encoding, thus reducing redundant signaling while managing encoding complexity through advance preparation.
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.