Selective Chroma Resolution Encoding for Video Compression
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Solution Overview
Problem
Current video codec standards, such as H.264 and H.265, primarily support YUV 4:2:0 chroma sampling formats, limiting the ability to efficiently encode and decode high-resolution chroma information, which is necessary for applications like screen capture content with rich color details, leading to suboptimal rate-distortion efficiency and increased computational complexity.
Innovation Solution
A method is introduced to selectively encode high chroma resolution details on a region-by-region basis and separate them into distinct sub-sequences within a single coded picture sequence, allowing existing encoders and decoders operating on YUV 4:2:0 formats to provide high chroma resolution, while avoiding unnecessary bit rate increases in regions where quality improvements are not noticeable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If YUV 4:2:0 chroma sampling format is used for encoding, then bit rate is reduced and storage cost decreases, but chroma resolution is limited and color fidelity deteriorates
Solution Approach 1:
The patent segments the video content into different regions based on chroma complexity characteristics. Regions with high chroma detail (such as text or graphics) are identified and processed differently from regions with low chroma detail (such as natural video). This segmentation allows the encoder to apply higher chroma sampling (4:4:4) only where necessary while using lower sampling (4:2:0) elsewhere, thus maintaining chroma resolution where needed while controlling overall bit rate.
Solution Approach 2:
The patent applies different chroma sampling qualities to different regions of the video frame. Instead of uniformly applying 4:2:0 sampling across the entire frame, the encoder dynamically adjusts chroma sampling resolution based on local content characteristics. Regions containing important chroma information (like text edges or color boundaries) receive full-resolution chroma sampling, while other regions use subsampled chroma, optimizing the balance between quality and bit rate.
2Manufacturing precision
If YUV 4:4:4 chroma sampling format is used for encoding, then chroma resolution and color fidelity are improved, but bit rate increases and compression efficiency deteriorates
Solution Approach 1:
The patent divides the video frame into multiple regions and applies 4:4:4 chroma sampling only to specific regions where high chroma resolution is beneficial (such as regions containing text, graphics, or color boundaries). Other regions use 4:2:0 sampling. This selective application dramatically reduces the overall bit rate requirement compared to applying 4:4:4 uniformly across the entire frame, while still preserving chroma resolution where it matters most.
Solution Approach 2:
The encoder dynamically adjusts chroma sampling quality on a region-by-region basis. Regions with high chroma activity (detected through edge detection or variance analysis) receive full 4:4:4 sampling to maintain color fidelity, while regions with low chroma activity use 4:2:0 sampling to reduce bit rate. This local adaptation optimizes the trade-off between chroma resolution and bit rate for the specific content being encoded.
3Productivity
If chroma subsampling is applied to reduce bit rate, then compression efficiency improves, but rate-distortion performance deteriorates for content with rich color details
Solution Approach 1:
The patent segments video content based on chroma complexity metrics and applies different compression strategies to different segments. Regions with rich chroma information (such as text overlays, graphics, or colorful scenes) are identified and encoded with higher chroma sampling rates to preserve chroma information. Regions with simple chroma content use standard subsampling. This selective approach maintains rate-distortion performance for important content while preserving overall compression efficiency.
Solution Approach 2:
The encoder applies local quality adaptation by adjusting chroma sampling resolution based on regional content characteristics. Regions containing important chroma information (detected through gradient analysis or variance measurement) receive enhanced chroma sampling to minimize information loss. Other regions use conventional subsampling. This ensures that chroma information is preserved where it contributes most to perceived quality while maintaining compression efficiency overall.
Data Source
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AI summary
Encoding and decoding operations of video pictures in a high- resolution chroma sampling format (such as YUV 4:4:4) using a video encoder and decoder operating on coded pictures in a low-resolution chroma sampling format (such as YUV 4:2:0) are presented. For example, high chroma resolution details are selectively encoded on a region-by-region basis. Or, as another example, coded pictures that contain sample values for low chroma resolution versions of input pictures and coded pictures that contain sample values for high chroma resolution details of the input pictures are encoded as separate sub-sequences of a single sequence of coded pictures, which can facilitate effective motion compensation. In this way, available encoders and decoders operating on coded pictures in the low- resolution chroma sampling format can be effectively used to provide high chroma resolution details.