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audio-video asynchrony with a USB soundcard
Dear list members,
I measured yesterday the audio-video asynchrony with an USB sound card
(M-AUDIO Fast Track Pro).
In practice, I was running a visual display and, in correspondence of
one particular video-target-frame, I was switching on a 1-cycle sine
wave (1000 Hz). I checked whether the video-frame and the audio signal
In general, the video preceded always the audio (although, if any, I had
to expect the opposite result because in the program the soundplay
command preceded the play the video-target-frame command). The average
video-anticipation was of 6.3-ms (SD=3.0, maximal video anticipation
12-ms, min=2-ms). I forgot: the video was running at 100-Hz refresh rate.
1) audio and video signals are often asynchronous;
2) the asynchrony (unfortunately) does not have a fixed value but
changes within a certain range.
It is not as bad as I was expecting but with a PCI sound card (a very
cheap one) and identical set-up I observed an average asynchrony of 2-ms
All the best,