Lip Sync Correction Using Robust Synchronization Test Signals
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Solution Overview
Problem
Existing methods for reducing lip sync errors between audio and video signals in broadcast processing are inadequate, as they often rely on manual adjustments or arbitrary delay factors, which are not precise and can be affected by unknown signal paths and processing steps, and require specialized equipment that may not survive digital broadcast signal processing.
Innovation Solution
A system using a synchronization test signal with a video signal comprising a non-black signal interrupted by blackout periods and an audio signal with tone interruptions, which is robust enough to survive digital broadcast environments, allowing for accurate measurement and correction of time differentials between video and audio signals through a multifunction broadcast signal processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual adjustment based on human-perceived delay is used, then the adjustment can be made without specialized equipment, but the measurement precision is insufficient because individuals have different perceptual thresholds
Solution Approach 1:
The system uses automatically detected lip sync test signals embedded in the broadcast content to self-measure and self-correct timing errors, eliminating the need for manual operator adjustment while achieving precise measurement through automated signal detection and timing analysis
Solution Approach 2:
The patent replaces manual human perception-based adjustment with an automated electronic detection system that analyzes embedded test signals, substituting human sensory limitations with precise electronic timing measurement capabilities
2Extent of automation
If arbitrary delay factor is used for automatic adjustment, then the system can operate automatically without specialized equipment, but the measurement precision is inadequate because the delay factor does not account for unknown signal paths and processing steps
Solution Approach 1:
The system embeds lip sync test signals in the broadcast content and automatically detects them at the receiving end, using the detected timing information as feedback to calculate and apply the appropriate delay correction factor, creating a closed-loop automatic adjustment system that adapts to actual signal path conditions
Solution Approach 2:
The system dynamically determines the delay factor based on actual measured timing differences from detected test signals rather than using a fixed arbitrary value, allowing the parameter to change according to the specific broadcast content and signal path conditions
3Extent of automation
If lip sync detection signals are inserted to detect timing errors, then automatic detection is possible, but the device complexity increases and the signals cannot survive digital broadcast signal processing
Solution Approach 1:
The patent uses universally applicable broadcast content (news footage, talk shows, sports broadcasts with visible speakers) as the carrier for lip sync test signals, allowing the same broadcast content to serve both as programming and as the test signal medium, eliminating the need for separate specialized test equipment
Solution Approach 2:
The system uses naturally occurring visual elements in broadcast content (speakers' faces and lip movements) as an intermediary to carry timing information, allowing the broadcast content itself to mediate the lip sync detection process without requiring additional specialized signal insertion equipment
Data Source
AI summary
A system and method for correcting so-called “lip sync” errors is provided, using a synchronization test signal comprising a video signal including a colorbar signal that is periodically interrupted by a series of consecutive defined black frames and an audio signal comprising a tone periodically interrupted by a period of silence beginning at the same time as the first of the series of consecutive defined black frames. The synchronization test signal is configured to survive encoding, decoding, conversion, and compressing processes used in a typical digital broadcast system environment and thus provide a means of measuring the relative audio and video timing of a processed signal. A method for correcting lip sync error receiving the synchronization test signal and comparing the relative timing of the video and audio portions of the synchronization test signal to their original relative timing, and delaying either the audio or video portions of a broadcast signal according to the timing comparison derived from the received test signal.