[FFmpeg-devel] [PATCH] ALSA for libavdevice

Luca lucabe72
Sun Dec 21 20:10:37 CET 2008


sorry for the delayed response

On Fri, 2008-12-19 at 10:59 +0100, Nicolas George wrote:
> L'octidi 28 frimaire, an CCXVII, Luca Abeni a ?crit :
> > So, it seems to me that the alsa library is still not stable enough for
> > what concerns the snd_pcm_htimestamp() function. :(
> All I can say is that it works at home (Debian Testing).

Well, I tested various ubuntu installations, but none of them provides
snd_pcm_htimestamp(). I've been able to compile the new alsa code only
on debian unstable... I tested it on various different machines with
different audio cards, but snd_pcm_htimestamp() always blocks and ffmpeg

>  Remotely testing ALSA programs is not easy.

I know... I suppose this problem depends on the ALSA library version,
but also on the driver (and on the hardware). 

> I guess that means we will have to fall back to the av_gettime-based
> timestamp, probably with a call to know the delay to ensure A-V sync.

Well, I think that a configure test for snd_pcm_htimestamp() (or for the
proper libasound2 version) is surely needed to avoid breaking
A fallback solution based on gettime+compensation would be even

> Shall I work on a filtering function and submit it as a prerequisite patch?
I do not know... I hope a alsa input with proper checking for the right
alsa version can be accepted first, but this is up to Michael.


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