Professional Audio & Video Solutions

Lip-Sync The time alignment of the audio relative to the video

Lip-Sync The time alignment of the audio relative to the video

I think you know the problems when audio and video are not in sync, what to do?

We can give you the figure when you are out of sync to get it back easy.

In both professional and consumer television and A/V systems, divergent audio and video signal paths and the delay inherent in digital processing provide many opportunities for the program sound and picture to fall out of synchronization

    LTV-1 the tool

  • LTV-1 We needed a method to satisfy the A/V synchronization tests that are part of both the Dolby and DTS licensee compliance requirements. Dolby and DTS each provide test streams and discs to their licensees that include an A/V sync test, which consists of an audio pulse or “beep” that is synchronized to a white flash in the video. The LTV-1 (Figure 1) uses a light-to-voltage converter mounted in the center of a suction cup, connected to a coaxial cable terminated in a BNC connector. The LTV-1 converts the white flash on the video screen to a voltage pulse that can be acquired by an audio analyzer or oscilloscope. A second input on the analyzer or scope is connected to the device’s audio output to acquire the beep. The arrival of the two pulses are plotted against time, and the synchronization offset is easily viewed and measured.

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Related Blog messages

  • What is new in APx software 4-4

    The latest release of APx500 audio measurement software, version 4.4, is available for download at

    The release includes minor feature improvements, including regulation enhancements and the option to maintain Bluetooth® connection even when Bluetooth is not selected as output or input.

    APx500 Measurement Software
    (Must be a registered user of
    and logged in to download)

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    Pulse Density Modulation (PDM) is a one-bit, high rate data stream that conveys a signal by modulating the density of the pulses. A typical application for PDM is the Micro-Electrical-Mechanical System (MEMS) microphone found on smartphones.

    The APx PDM option provides direct connectivity for audio devices that have a PDM output (such as a MEMS microphone) or input (such as the decimator on a smartphone chip). In addition to all the standard audio measurements, APx provides variable DC voltage, variable sample rate, and a PSR (power supply rejection) measurement to test the device’s full operating parameters. No other analyzer combines direct PDM connectivity with APx’s best in class speed, ease-of-use, and performance.