In-band A/V Timing Measurement via VANC Checksums
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Solution Overview
Problem
Conventional methods for characterizing the relative offset between audio and video signals require expensive equipment and bi-directional communication, or necessitate the television facility to be out of service, making them inefficient for real-time synchronization.
Innovation Solution
In-band signaling is used to encode characterization data, such as checksums for video and audio signals, within the vertical ancillary (VANC) space of HDTV signals, allowing receivers to dynamically measure and synchronize audio and video signals without requiring the television facility to be out of service or using expensive hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional characterization techniques are used to measure relative offset, then measurement accuracy is achieved, but the television facility must be out of service and expensive equipment is required
Solution Approach 1:
The patent embeds characterization data (checksums) into the video signal in advance at the television facility. This preliminary action allows the receiver to perform measurements without requiring the facility to be out of service, as the measurement references are already present in the transmitted signal.
Solution Approach 2:
The patent uses checksums embedded in the VANC space as an intermediary carrier. These checksums serve as a mediator between the television facility and the receiver, enabling offset measurement through the transmitted signal itself rather than requiring direct facility access or expensive test equipment.
2Loss of time
If conventional techniques with bi-directional communication are used, then real-time synchronization is achieved, but expensive equipment and complex communication infrastructure are required
Solution Approach 1:
The receiver performs self-service synchronization by extracting and processing the checksums already embedded in the received video signal. The system uses its own processing capabilities to compare received checksums with locally generated checksums, eliminating the need for complex bi-directional communication infrastructure or expensive specialized equipment.
Solution Approach 2:
The patent extracts the essential measurement information (checksums) from the complex communication infrastructure and embeds them directly in the video signal. This extraction simplifies the system by removing the need for separate communication channels, leaving only the standard video signal transmission path.
3Device complexity
If in-band signaling is used to encode characterization data, then hardware complexity and cost are reduced, but the VANC space must be efficiently utilized
Solution Approach 1:
The patent places checksums for different components (video scanlines, audio channels) in specific locations within the VANC space structure. Each region of the VANC space is assigned a specific function, efficiently utilizing the available space without requiring additional bandwidth or complex encoding schemes.
Data Source
AI summary
A system and method for characterizing the relative offset in time between audio and video signals and enables the receiver of the audio and video signals to resynchronize the audio and video signals. Signal characterization data is dynamically captured and encoded into frames of video and audio data that is output by a television origination facility. The signal characterization data is extracted by the receiver and signal characterization data is captured for the received frames. The extracted signal characterization data is compared with the captured signal characterization data to compute the relative offset in time between the video and one or more audio signals for a frame. The receiver may then resynchronize the video and audio signals using the computed relative offset.