Chroma-From-Luma Filter Signaling for Accurate Intra Prediction
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Solution Overview
Problem
Existing video coding technologies, such as AV1 and HEVC, face challenges in efficiently signaling and implementing downsampling filters for cross-component intra prediction modes, particularly in chroma from luma, which can lead to suboptimal performance and decoder complexity.
Innovation Solution
A method and device for performing cross-component intra prediction that involves receiving a chroma block from a coded bitstream, obtaining a syntax element indicating a downsampling filter, selecting an appropriate filter from a set of filters, determining luma sample positions, downsampling luma samples, and reconstructing the chroma block based on these samples, with support for multiple downsampling filters to improve accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple downsampling filters are supported for chroma from luma prediction mode, then prediction accuracy is improved, but decoder complexity increases due to additional signaling requirements
Solution Approach 1:
The patent applies parameter changes by introducing a syntax element that signals which downsampling filter to use for chroma from luma prediction. This allows the system to dynamically select between different filter configurations (e.g., different tap counts or kernel types) based on the specific coding context, thereby optimizing prediction accuracy while managing decoder complexity through standardized parameter signaling.
Solution Approach 2:
The patent implements dynamics by making the downsampling filter selection adaptive rather than fixed. The syntax element enables the filter choice to vary across different blocks, prediction modes, or coding conditions, allowing the system to dynamically adjust the filtering characteristics to match the local image content requirements while maintaining a manageable set of predefined filter options.
2Productivity
If downsampling filters are optimized for chroma prediction, then video coding performance improves, but signaling overhead increases
Solution Approach 1:
The patent applies universality by designing a syntax element that serves multiple functions: it not only selects the downsampling filter type but also potentially indicates associated parameters such as filter strength, application scope, or interaction with other prediction modes. This multi-functional signaling approach improves video coding performance while minimizing the increase in signaling overhead by consolidating multiple control functions into a single syntax structure.
Data Source
AI summary
Methods and apparatuses for performing cross-component intra prediction, including: receiving a coded bitstream; obtaining, from the coded bitstream, a syntax element indicating a downsampling filter used for a cross-component intra prediction mode; obtaining a plurality of reconstructed sample values of a first component which are associated with a pixel of a second component based on the downsampling filter; determining a pixel value of a downsampled pixel of the first component, based on the plurality of reconstructed sample values; determining a pixel value of the pixel of the second component based on the pixel value of the downsampled pixel of the first component; and reconstructing a picture based on the pixel value of the pixel of the second component.