[gst-devel] A/V sync issues with multiple dv1394src sources

Jerome Alet alet at librelogiciel.com
Thu Apr 5 17:22:52 CEST 2007


On Thu, Apr 05, 2007 at 01:09:39AM +0200, daniel fischer wrote:
> Jerome,
> Jerome Alet <alet at librelogiciel.com> (on Tue, 3 Apr 2007 14:02:20 +0200):
>   > as part of my Boxtream project (http://cortex.unice.fr/~jerome/boxtream/)
>   > I've encountered an A/V sync problem which happens in some cases only,
>   > but is easily reproductible.
> it's a while back that i've had a hack on dv1394src and it changed 
> since. one thing i remembered though was that my pcmcia firewire 
> card would sometimes/often produce incomplete frames when i put my 
> camera to play a tape fast-forward, or pause and such, so i would 
> drop those frames with dv1394src. 
> try setting drop_incomplete=false on your dv1394src. maybe the 
> missing frames are the cause of your sync trouble... 

Very good idea !

Unfortunately this didn't help.

I've now checked again with a different analog-to-dv converter
placed between the switcher and the gstreamer PC, and result
is far better : not a single A/V sync problem after having
switched hundreds of times. Of course the switch is not smooth,
but at least there's not A/V sync issues anymore.

What is strange is that the other day I've done the very same test 
with this equipment (Canopus ADVC700) and it was better but not 
perfect, today it's perfect, so maybe I changed some hardware 
settings on it... So the sync problem might have come from
the Canopus ADVC55 I used before, which probably disturbed
GStreamer when it was missing some frames.

In any case I've now ordered a multi-channel TBC to put in from of 
the video switchers (because some of our potential sources are 
unknown and can't be genlocked : it's mobile equipment we plan to 
move everywhere and use whichever sources are available), and I
think this will definitely fix the problem.

Thanks for your help.

Jerome Alet

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