GPU Chroma Resampling for Accurate Video Color Rendering
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Solution Overview
Problem
Current computer display technologies fail to accurately reproduce chroma values in compressed video streams due to subsampling, leading to reduced image clarity and distorted color rendition, as they simply duplicate chroma information across multiple pixels rather than accurately resampling it.
Innovation Solution
A system utilizing a programmable graphics processing unit (GPU) decodes each frame of a video stream, separates it into luminance and chroma images, and resamples chroma values to their proper locations, combining them into a 4:4:4 image in real-time, effectively improving color accuracy by using fragment programs for chroma resampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chroma values are subsampled in compressed video formats (4:2:2, 4:1:1, 4:2:0), then data transmission efficiency is improved, but color accuracy and image clarity deteriorate due to smearing chroma information across multiple pixels
Solution Approach 1:
The patent applies preliminary action by performing chroma resampling during the video decoding process before the image is displayed. The GPU intercepts the decoded video data, identifies subsampled chroma values, and resamples them to their proper pixel locations before combining with luminance values. This preliminary correction prevents the smearing effect from occurring in the final displayed image.
Solution Approach 2:
The patent introduces an intermediary component - a programmable GPU with custom shader code - that acts as a mediator between the decoded video data and the final display output. This intermediary resamples the chroma values during the composition process, accurately placing them at their intended pixel locations rather than simply duplicating them across multiple pixels.
2Device complexity
If digital graphics units duplicate chroma values into missing locations, then processing complexity is reduced, but image clarity and color rendition are reduced by smearing chroma information
Solution Approach 1:
The system performs preliminary chroma resampling during video decoding, calculating and placing chroma values at their correct pixel locations before the final image composition. This preliminary action ensures that each pixel receives the correct chroma information without smearing, while the computational complexity is managed through efficient GPU implementation.
3Adaptability or versatility
If different video formats use different sampling locations for luminance and chroma values, then format compatibility is improved, but color rendition accuracy deteriorates due to inconsistent chroma placement
Solution Approach 1:
The patent applies local quality by implementing format-specific resampling logic that adapts to the sampling characteristics of different video formats (4:2:2, 4:1:1, 4:2:0, MPEG1, MPEG2, H.264). The custom shader code identifies the input format and applies the appropriate resampling algorithm, ensuring that chroma values are accurately placed according to each format's specific sampling pattern rather than using a generic duplication approach.
Data Source
AI summary
A system which utilizes the processing capabilities of the graphics processing unit (GPU) in the graphics controller. Each frame of each video stream is decoded. After decoding the compressed image is separated into an image representing the luminance and an image representing the chroma. The chroma image is resampled as appropriate using the GPU to provide chroma values corresponding to each luminance value at the proper locations. The resampled chroma image and the luminance image are properly combined to produce a 4:4:4 image, preferably in the RGB color space, and provided to the frame buffer for final display. Each of these operations is done in real time for each frame of the video.