HDTV Sampling Clock Phase Control Using Tri-Level Sync
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Solution Overview
Problem
Existing digital display devices face challenges in accurately synchronizing the phase of the clock signal for sampling High Definition Television (HDTV) signals, leading to noise and image degradation due to the dynamic nature of HDTV content, which is more difficult to phase-lock compared to static PC graphics.
Innovation Solution
A system and method that utilize a tri-level sync pattern at the beginning of each display line in HDTV signals for accurate phase detection, ensuring consistent phase alignment of the clock signal through a phase-locked loop and controller, even during motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spatial or temporal methods are used for phase detection, then phase detection can be performed, but the method fails to provide consistent results for HDTV signals with motion content
Solution Approach 1:
The patent applies preliminary action by using the sync pulse at the beginning of each display line to pre-establish phase reference points before the actual video content is processed. This sync pulse contains known transition patterns that allow the system to prepare and lock onto the correct phase in advance, ensuring consistent phase detection regardless of subsequent motion content in the video signal.
Solution Approach 2:
The sync pulse serves as an intermediary element between the clock signal and the video content. It provides a stable, known reference pattern that mediates the phase relationship between the sampling clock and the varying video signal, allowing accurate phase detection without being affected by the dynamic nature of the actual video content.
2Ease of operation
If the clock signal phase is not properly synchronized with the HDTV signal, then the A/D converter can operate, but the sampled transitions cause serious noise and image degradation
Solution Approach 1:
The patent implements feedback by continuously monitoring the sync pulse transitions and adjusting the clock signal phase accordingly. The phase detection circuit analyzes the timing of transitions in the sync pulse and provides feedback to the phase-locked loop, which then adjusts the clock phase to maintain optimal alignment with the HDTV signal, preventing sampling of transitions and the associated noise.
3Measurement precision
If conventional phase detection methods are used, then the system can process static graphics well, but the method fails to maintain accuracy for motion picture graphics in HDTV
Solution Approach 1:
The patent applies universality by designing a phase detection method based on sync pulses that works universally for all HDTV content types, whether static or motion picture graphics. The sync pulse is a standardized feature present in all HDTV signals, allowing the same detection methodology to be applied consistently across different content types without requiring content-specific adjustments.
Data Source
AI summary
The present invention provides a system and method for automatically controlling the phase of the clock signal for sampling an HDTV signal, which implements a new and improved method for phase detection. The system and method utilize the standard format of an HDTV signal to consistently ensure accurate phase detection. Particularly, the system and method detect the target phase for the sampling clock using a tri-level sync pattern that exists at the beginning of each display line. This tri-level sync pattern or “sync pulse” is well suited for phase detection since it includes several static areas separated by substantial transitions. Furthermore, by using the sync pulse of the HDTV signal, the system and method provide consistent and accurate results, since the sync pulse will not change regardless of the whether the video data is static or in motion.