Re: Synchronizing camcorder with telemetry

From: Mike Fields (spam_me_not_mr.gadget2_at_comcast.net)
Date: 07/10/04 

Date: Sat, 10 Jul 2004 23:34:48 GMT

You're probably OK. This effect has been seen most
often when the video capture path and audio capture
path are different (some think it is drift in the clock on
the sound card). Some people have had this problem
and others have not -- one of those things that seems
to drive some people nuts !! There are probably
multiple causes (and places for it to occur), but it has
been a topic in the rec.desktop.video group (among
others) a significant number of times (with no 2
people having the same results). 

--
Mike "mikey" Fields
http://home.comcast.net/~mike.fields/
outgoing email scanned by Norton Antivirus ... is that good ?
Linux users brag on how long their system stays up,
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"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0407100650.15688271@posting.google.com...
> > The most common problem has been loss of sync between
> > speech and lip movement and you didn't say how critical your
> > timing was.  Just thought I would mention it.
>
> Actually, I did mention it briefly - I will accept 2.5 seconds drift
> over 120 minutes recording time. As you can see, I don't care about
> getting the data synced with a specific frame.
>
> The info that would be going in this track (assuming I put actual data
> in there as well as a timestamp) is sampled at all sorts of different
> rates according to the individual sensor characteristics, and the
> micro we're talking about here only gets to see an infrequent periodic
> snapshot of the sampled data anyway.
>
> As long as the data stream can be recovered reliably (which was my
> major concern), I think timing issues are not really a problem. If the
> tape speed varies, the data and video will vary at the same time,
> right? For archival purposes I'll capture in MJPEG with a 22.05kHz
> uncompressed mono audio track so there shouldn't be playback sync
> issues on that end either. Empirically, I can tell you that my capture
> card and playback software (with the aforementioned settings) keeps
> A-V sync very tight over 120 minutes continuous recording time;
> certainly close enough to keep lip sync appearing OK.

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