Lip-Sync Correction for Image Display Devices Using External Audio Delay Measurement
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Solution Overview
Problem
Image display devices experience lip-sync mismatches when outputting audio through external sound devices due to encoding and decoding delays, making it difficult to synchronize video and audio properly without increasing internal memory capacity.
Innovation Solution
An image display device with a control unit that stores a test signal, outputs it to measure audio delay, and adjusts the decoding timestamp of the video processing unit accordingly, using a lip-sync table to correct lip-sync values for various external audio sources and outputs, allowing users to easily adjust synchronization through a UI menu.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If audio is output through an external sound device, then audio quality is improved, but lip-sync matching between video and audio deteriorates due to encoding and decoding delays
Solution Approach 1:
The system performs preliminary measurement of audio delay by outputting a test signal through the external sound device and detecting it with a remote control microphone. The measured delay value is stored in advance in a lip-sync table, so that when actual video playback occurs, the pre-measured delay can be directly applied without real-time measurement, ensuring both high audio quality and proper lip-sync timing.
2Reliability
If internal memory capacity is increased to buffer video frames for lip-sync correction, then lip-sync matching is improved, but device cost and complexity increase
Solution Approach 1:
The system uses feedback by measuring the actual audio delay through the external sound device and using this measured value to adjust the video decoding timestamp. The lip-sync table stores the measured delay values, which are fed back into the video processing pipeline to correct the timing, achieving accurate lip-sync without requiring large memory buffers.
3Ease of operation
If automatic lip-sync correction is implemented, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The system enables self-service by automatically measuring the audio delay and correcting the lip-sync without requiring user intervention. The control unit autonomously outputs test signals, detects them through the remote control, calculates delay values, and applies corrections to video playback, making the device self-adjusting and easy to operate.
4Measurement precision
If a test signal is output to measure audio delay, then measurement precision is improved, but productivity is reduced due to additional processing time
Solution Approach 1:
The audio delay measurement is performed as a preliminary action during system initialization or setup phase. The test signal is output once to measure and store the delay value in the lip-sync table. During subsequent video playback, the pre-measured value is directly applied without repeating the measurement process, achieving precise audio delay measurement without recurring productivity loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively matches lip-sync between video and audio for various external audio outputs and sources without increasing internal memory, enabling simple correction of mismatches by outputting an audio and video test stream and adjusting timestamps.
Implementation Method 1
control to detect the test signal output through a connected external speaker by transmitting an audio detection command to a remote control device through a microphone of the remote control device
Data Source
AI summary
An image display device, a lip-sync correction method thereof, and an image display system thereof are proposed. The lip-sync correction method of the image display device includes: receiving an audio delay measurement command from a user; transmitting an audio detection command to a remote control device and outputting a pre-stored test signal to an external speaker; calculating an audio delay value by comparing an audio signal received from the remote control device with the test signal; and correcting a decoding time stamp of an image signal on the basis of the audio delay value. Accordingly, it is possible to match lip-synching of video and audio in response to various external audio outputs or external audio devices.