Chroma Prediction with Dual Models for Nonlinear Luma Correlation
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Solution Overview
Problem
Existing video coding methods using cross-component linear models (CCLM) for luma and chroma prediction suffer from low accuracy in non-linear correlations, leading to large residuals and reduced compression efficiency.
Innovation Solution
A dual-model approach is employed, utilizing a linear model for pixel points with good linear correlation and a non-linear model for those with poor correlation, determining chroma prediction values based on luma down-sampled reconstructed values to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a linear model (CCLM) is used for chroma prediction, then the device complexity is reduced and ease of operation is improved, but the manufacturing precision (prediction accuracy) deteriorates when luma-chroma correlation is non-linear
Solution Approach 1:
The patent divides the coding block into multiple sub-blocks and applies different prediction models (linear CCLM for some sub-blocks, non-linear for others) based on local luma-chroma correlation characteristics. This segmentation allows the system to maintain simplicity where linear correlation suffices while improving accuracy where non-linear relationships exist, thereby resolving the contradiction between ease of operation and prediction accuracy.
Solution Approach 2:
The patent dynamically selects between linear and non-linear prediction models based on local correlation assessment. By evaluating the luma-chroma correlation in different regions and adaptively choosing the appropriate model, the system transitions from a static single-model approach to a dynamic multi-model approach, achieving both operational efficiency and high prediction accuracy across diverse content types.
2Manufacturing precision
If a non-linear model is used for chroma prediction, then the prediction accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies non-linear prediction models only to specific sub-blocks where luma-chroma correlation is determined to be non-linear, rather than applying it universally. This selective segmentation reduces the overall computational burden and device complexity while still achieving improved prediction accuracy in the regions that benefit most from non-linear modeling.
Solution Approach 2:
The patent implements local quality by applying different prediction model complexities to different spatial regions based on their specific correlation characteristics. High-complexity non-linear models are applied only where needed (in regions with non-linear correlation), while simpler linear models are used elsewhere, thereby optimizing the balance between prediction accuracy and device complexity through localized model selection.
3Speed
If a single linear model is used for all pixel points, then the processing speed is maintained, but the measurement precision (prediction accuracy) deteriorates for pixel points with non-linear correlation
Solution Approach 1:
The patent segments the coding block into sub-blocks and processes each with appropriate model complexity. By identifying and separating regions with non-linear correlation, the system can apply enhanced prediction only where necessary, maintaining high processing speed for the majority of regions while improving overall prediction accuracy through targeted non-linear modeling in critical areas.
Solution Approach 2:
The patent applies non-linear prediction modeling partially—only to the extent necessary for regions with non-linear luma-chroma correlation—rather than applying it excessively to the entire block. This partial action approach improves measurement precision where needed while avoiding the full computational overhead that would significantly reduce processing speed, thereby achieving an optimal balance between accuracy and speed.
Data Source
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AI summary
A coding method and apparatus, a decoding method and apparatus, and a device, which facilitate an improvement in the chroma prediction precision, thereby improving the compression effect. The decoding method comprises: receiving coding information corresponding to a target coded block; determining a first model and a second model according to index information and parameter information of the first model and index information and parameter information of the second model; according to a luma down-sampling reconstruction value of a first pixel point, determining a target chroma prediction value of the first pixel point by means of the first model; according to a luma down-sampling reconstruction value of a second pixel point, determining a target chroma prediction value of the second pixel point by means of the second model; and determining a chroma reconstruction value of the target coded block according to the target chroma prediction value and a target difference value of the first pixel point and the target chroma prediction value and a target difference value of the second pixel point.