Wavelet Band Separation for Chroma Packing in Video Codecs
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Solution Overview
Problem
Current video codec technologies lack widespread support for higher-resolution chroma sampling formats like YUV 4:4:4, which are preferable for content with richer color information, due to the dominance of YUV 4:2:0 formats in hardware implementations, limiting their use in applications such as screen capture and video with artificial hard-edged boundaries.
Innovation Solution
The method involves packing frames of a higher-resolution chroma sampling format, such as YUV 4:4:4, into frames of a lower-resolution format, like YUV 4:2:0, using wavelet decomposition and reconstruction, allowing existing encoders and decoders to handle the higher-resolution format while leveraging available hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If YUV 4:2:0 chroma sampling format is used for encoding/decoding, then compression efficiency is improved and bit rate is reduced, but chroma resolution and color fidelity deteriorate
Solution Approach 1:
The patent embeds multiple chroma sampling formats within a unified encoding framework. Higher-resolution chroma data (4:4:4 or 4:2:2) is nested within the 4:2:0 encoding structure by packing multiple chroma components into the available bit stream, allowing progressive enhancement where base 4:2:0 provides compatibility while embedded higher-resolution data provides enhanced color fidelity when available
Solution Approach 2:
The patent dynamically changes chroma sampling parameters based on content characteristics and decoder capabilities. The encoder adjusts chroma subsampling ratios, bit depth, and packing density according to the importance of chroma information in different video regions and the capabilities of the target decoder, optimizing the trade-off between compression efficiency and color fidelity
2Manufacturing precision
If YUV 4:4:4 chroma sampling format is used, then chroma resolution and color fidelity are improved, but device compatibility and widespread support deteriorate
Solution Approach 1:
The patent creates a universal encoding framework that can handle multiple chroma sampling formats (4:2:0, 4:2:2, 4:4:4) within a single bit stream structure. The same encoder and decoder infrastructure can process different chroma resolutions by interpreting the packed data differently, making the system universally compatible across devices with varying capabilities while maintaining access to higher-resolution chroma data
3Loss of information
If wavelet decomposition and reconstruction is applied for frame packing/unpacking, then chroma information preservation is improved, but computational complexity increases
Solution Approach 1:
The patent applies wavelet decomposition selectively rather than to the entire frame. Only specific chroma components or regions where color fidelity is most important undergo full wavelet transformation and repacking, while other regions use simpler packing methods. This partial application maintains chroma information where needed while reducing overall computational complexity
Data Source
AI summary
When packing a video frame of a higher-resolution chroma sampling format such as YUV 4:4:4 into frames of a lower-resolution chroma sampling format such as YUV 4:2:0, a computing device performs wavelet decomposition (or other band separation filtering) on sample values of chroma components of the higher-resolution frame, producing sample values of multiple bands. The device assigns the sample values of the bands to parts of the lower-resolution frames. During corresponding unpacking operations, a computing device assigns parts of the frames of the lower-resolution chroma sampling format to sample values of multiple bands. The device performs wavelet reconstruction (or other inverse band separation filtering) on the sample values of the bands, producing sample values of chroma components of the frame of the higher-resolution chroma sampling format. Band separation filtering can help improve quality of reconstruction when distortion has been introduced during encoding of the chroma components packed into low-resolution frames.