[FFmpeg-devel] [PATCH] ALSA for libavdevice

Michael Niedermayer michaelni
Sun Dec 21 21:12:35 CET 2008

On Sun, Dec 21, 2008 at 08:10:37PM +0100, Luca wrote:
> Hi,
> 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
> hangs.
> >  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
> compilation.
> A fallback solution based on gettime+compensation would be even
> better...
> > 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.

if its possible to test if snd_pcm_htimestamp() is working in configure
(that would require detecting that it hanged ...)
alternatively if someone happens to know which version/driver/hw works ...
if neither of these then i dont see how we could add snd_pcm_htimestamp()
based input support

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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