[vlc-devel] [RFC] V4L2 caching

Marian Ďurkovič md at bts.sk
Fri Oct 16 09:22:33 CEST 2009

On Thu, 15 Oct 2009 12:10:54 +0200, Rémi Denis-Courmont wrote
> On Mon, 12 Oct 2009 19:06:33 +0300, "Rémi Denis-Courmont"
> <remi at remlab.net> wrote:
> > V4L2 default caching seems quite big to me, considering that V4L2
> > shouldn't 
> > have much delay variance. Is there any reason for using the common
> default
> > 
> > there? OTOH, it seems VLC can never recover if the PTS delay value is too
> > small (it keeps on increasing the PTS delay, but I never see any new
> > frame).

IIRC, in the past the value of DEFAULT_PTS_DELAY was the lowest sane value where
VLC was working reliably. VLC decoders are not "zero-delay" as the spec assumes,
so while on fast machine 100 msec might be pretty sufficient, on slower you
might need 200 or more.

Not sure if that's still the case after Laurent reworked the way how PTS_DELAY

Anyway, we should probably review the caching values for all inputs, as there
are differences which definitely don't make sense to me, e.g.

FTP 600 msec
HTTP 1200 msec

Both are using TCP, which can stall the same way...

   With kind regards,


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