Chroma-From-Luma Prediction with Adaptive Downsampling Filters
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Solution Overview
Problem
Existing video coding technologies, such as AV1 and HEVC, lack efficient methods for cross-component intra prediction, particularly in chroma from luma modes, leading to suboptimal chroma prediction and increased computational complexity.
Innovation Solution
Implementing a method for cross-component intra prediction that involves receiving a chroma block from a coded bitstream, selecting a downsampling filter, determining luma sample positions, and reconstructing the chroma block based on downsampled luma samples, using multiple downsampling filters to improve prediction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple downsampling filters are implemented for chroma from luma prediction, then chroma prediction accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic filter selection where the decoder adaptsively chooses from multiple downsampling filters (e.g., 2-tap, 4-tap, 6-tap filters) based on the specific chroma block characteristics and prediction mode. This dynamic approach allows the system to optimize prediction accuracy for different content types while maintaining manageable complexity through conditional logic rather than exhaustive processing of all filters for every block.
Solution Approach 2:
The patent changes the parameter of filter tap count (2-tap, 4-tap, 6-tap) to adapt to different prediction scenarios. By varying the filter parameters based on chroma block size, prediction mode, and content characteristics, the system achieves improved prediction accuracy without requiring a fixed complex structure for all cases.
2Manufacturing precision
If luma samples are downsampled to align with chroma block positions, then reconstruction precision is improved, but computational complexity increases
Solution Approach 1:
The patent segments the downsampling process into distinct phases: first determining which luma samples are needed based on chroma block position, then applying the selected filter only to those specific samples. This segmentation avoids unnecessary computation on all luma samples and focuses processing only where needed for chroma reconstruction.
Solution Approach 2:
The patent performs preliminary determination of luma sample positions and filter selection before actually executing the downsampling computation. By pre-calculating which luma samples require processing and which filter to apply based on chroma block characteristics, the system minimizes actual computational workload during the reconstruction phase.
3Reliability
If chroma blocks are reconstructed using downsampled luma samples, then video quality is improved, but processing time increases
Solution Approach 1:
The patent applies partial downsampling action by selectively processing only the necessary luma samples for each chroma block rather than downsampling entire luma frames. This partial approach achieves sufficient video quality improvement for chroma components while minimizing processing time by avoiding excessive computation on unnecessary data.
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.