Re: Choosing a sound card for video playback

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In <20060126094721.GA25389@sofa>, Tim Orford wrote:

> On Wed, Jan 25, 2006 at 09:34:24PM +0000, Tony Houghton wrote:
> > I've got two PCs which I use mainly for watching video with MPlayer (for
> > various reasons Xine isn't so practical) and it has A/V sync problems on
> > them. I think it may be because my cheap & nasty sound cards lack some
> > feature that MPlayer relies on to sync properly:
> 
> Strange, I've been using both the CMI8738 (an excellent chipset for some
> applications) and Via Ac97 for years without any sync problems in Mplayer.

It's probably not so much the chipset as the cheap card it's on, which
could compromise the accuracy of its clock and have poor quality
analogue components. So I think getting a better card may improve things
anyway. Worth a try.

> What problems are you having? Sync slowly drifting out?

I'm outputting to a TV from a Matrox G450 with DirectFB so MPlayer can't
simply adjust the framerate. It used to drift until I tweaked MPlayer's
options. I think these fixed that problem:

framedrop=1
autosync=30

But I was left with a fixed A-V delay that would tend to differ from
file to file, but if I adjusted MPlayer's A-V delay it would usually
stay OK all the way through that file. But sometimes each time I tried
to adjust the delay, the discrepancy would change with it, so I could
never get it right.

Someone on another list pointed out to me that MPlayer's alsa driver is
buggy so I switched to -ao oss and that seems to have just about cured
it. NB -ao sdl has the same problem as alsa, at least if SDL is using
alsa.

I also have the fixed A-V delay problem with vdr-softdevice though,
which lacks any of MPlayer's flexibility to fix or work around it.

-- 
TH * http://www.realh.co.uk

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