Color Phase Correction Logic for Video Decoder Systems
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Solution Overview
Problem
Video systems, particularly those using the PAL standard, face challenges in accurately detecting motion due to color phase errors, which can lead to false motion detection and degradation of video quality, especially when there is little or no motion in the video.
Innovation Solution
A video decoder system that demodulates composite video signals to produce sets of chroma components for multiple frames, calculates a phase correction value based on the angular differences between these components, and uses this value to correct color phase errors, thereby improving motion detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 3-D comb filtering is applied to separate luma and chroma signals, then false color and dot crawl artifacts are reduced, but motion detection accuracy degrades due to color phase error in PAL systems
Solution Approach 1:
The patent applies color phase correction before motion detection by calculating a phase correction value from chroma component angular differences and using it to adjust the phase of the chroma subcarrier. This preliminary correction eliminates the color phase error that would otherwise deceive the motion detection algorithm, allowing both accurate luma-chroma separation and reliable motion detection to coexist
Solution Approach 2:
The patent introduces chroma component angular difference analysis as an intermediary mechanism. By calculating the angular differences between chroma components of consecutive frames and deriving a phase correction value from these differences, the system creates an intermediate processing step that removes color phase error before it affects motion detection, thereby resolving the contradiction between separation accuracy and motion detection reliability
2Measurement precision
If color phase correction is applied using chroma component angular differences, then motion detection accuracy is improved, but system complexity increases
Solution Approach 1:
The patent makes the existing demodulator system multi-functional by enabling it to perform both standard video decoding and color phase correction using the same chroma component extraction and processing infrastructure. The phase correction logic reuses existing demodulation components, thereby improving motion detection accuracy without proportionally increasing system complexity
Solution Approach 2:
The patent changes the phase parameter of the chroma subcarrier based on calculated angular differences from chroma components. By adjusting this single critical parameter (phase) derived from signal analysis rather than adding complex hardware, the system achieves improved motion detection accuracy with minimal increase in overall system complexity
Data Source
AI summary
Systems and methods are provided for correcting color phase error in a video decoder system. A demodulator system demodulates the composite input signal and the at least one delayed signal to produce sets of baseband chroma components based on a phase correction value. Color phase correction logic determines the phase correction value for the demodulator system based upon characteristics of the baseband chroma components associated with a series of at least two consecutive frames.