[gst-devel] Lip Sync with v4l2/oss/theora/vorbis/ogg

Dave Baker dave at accidentalegg.co.uk
Wed Jul 27 03:35:04 CEST 2005


After a spot of card changing, I've managed to try capturing using v4l1 
instead, and it's still out of sync. Again, it starts in sync and the audio 
drifts behind at a rate of (very) approximately a second in ten minutes or 
so. The difference is that it seems to know that it's going out of sync 
because MPlayer soon gets confused and starts pausing, possibly to try to 
rectify the problem, or possibly because it has too much video in the buffer. 
It generally pauses the video, then the audio starts jittering as well. After 
a while it will play the video sped up, and then stop again. Once I restart 
MPlayer it's fine (but out of sync) again for a while.

This is with a different pipeline, since I can't use the same one as I can't 
specify the video input as a property with the v4l element, but it's all the 
same elements otherwise. I tried using different codecs and a different 
muxer, but couldn't get a working pipeline with a anything but the xiph.org 

So I guess the v4l element does have something to do with the problem, but 
either they are both at fault (seems unlikley as it appears to work for 
everybody else) or there's something else contributing to the issue. I'd 
really appreciate any feedback whatsoever!


> Hi,
> On Mon, 2005-07-18 at 13:53, Thomas Vander Stichele wrote:
> > "some sync patches" where really a bunch of patches over the course of a
> > few weeks, and I think it would be hard to distill a nice patch from it.
> Try it. We'll have to do something to make it work. Doing nothing won't
> fix it. Put a patch online and I'll have a try.
> Although I still think the build solution that Gerd used to use (ship
> your own header) is ugly, I can live with it, so just do that and move
> to v4l2. We've discussed this half a year ago already, and probably
> several times before. :).
> > there is currently no v4l subsystem maintainer since Gerd Knorr stopped
> > doing it in March.  Maybe Ronald can comment a little here too.
> It's been messy for a bunch of weeks, and after that, a few new people
> stepped up, teamed up to continue development and one of them got
> assigned the famous big hat. It's been working fine for quite a while
> after that already. I'm not active in that team, though, I do other
> stuff nowadays. If you want to follow v4l(2)/driver development,
> subscribe to video4linux-list at redhat.com, which has been the official
> v4l project mailinglist ever since it was started.
> Re: sync, afaik v4l and v4l2 both have perfect sync in Cupid, so I don't
> know what you guys do differently, but it sounds odd to me that v4l2src
> wouldn't be in sync and v4lsrc would be. I'll need more context here to
> make sense out of it.
> Cheers,
> Ronald
> -- 
> Ronald S. Bultje <rbultje at ronald.bitfreak.net>

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