[FFmpeg-devel] [PATCH] ALSA for libavdevice

Michael Niedermayer michaelni
Mon Dec 29 04:03:21 CET 2008

On Mon, Dec 29, 2008 at 01:39:45AM +0100, Luca Abeni wrote:
> Hi all,
> On Sun, 2008-12-28 at 21:39 +0100, Nicolas George wrote:
> > (I was busy and not well last seek, I am a bit late in my various works.
> > Sorry.)
> > 
> > Le quintidi 5 niv?se, an CCXVII, Stefano Sabatini a ?crit :
> > I am pondering the best way to implement a robust generic timestamp filter
> > that will allow to just use av_gettime.
> I think that your current code is the best solution in the long term,
> but we really need a fallback solution until alsa lib is fixed (or we
> need to document how to use "pcm_hw" instead of "pcm_dsnoop").
> Maybe a possible solution is to have a configure check for the presence
> of snd_pcm_htimestamp(), and to provide some mechanism for allowing the
> user to disable the usage of such function (if alsalib provides it, but
> it is broken)...

I think you are missing a small detail here, V4L and OSS support in ffmpeg
currently IS broken, and can under some circumstances generate invalid
files without the users knowledge. (invalid in the sense of flaky timestamps)

the timestamp filter might fix or at least reduce this issue.
having alsalib fixed upstream is the correct thing for alsa but its not going
to help with OSS/V4L
so i think we will need that timestamp filter anyway ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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