[mythtv-users] Where's the playback bottleneck?

Jerry Rubinow jerrymr at gmail.com
Wed Jan 25 01:39:44 UTC 2006


On 1/24/06, Robert Johnston <anaerin at gmail.com> wrote:
> On 1/24/06, Jerry Rubinow <jerrymr at gmail.com> wrote:
> > If I playback an HD resolution file, I get stuttering, pick a codec, any codec.
> >
> > If I play it back with mplayer (-vo xv -vc ffmpeg12), also stuttering.
> >  If I play it back with mplayer (-vo xvmc -vc ffmpeg12mc), plays back
> > pretty much ok.
> >
> > In all cases, myth and mplayer, CPU is between 20% and 50% (this is on
> > a combined front/backend, P4 2.8 Pundit, with onboard VGA disabled,
> > using a PCI FX5200).
> >
> > The fact that I can playback the file in mplayer with xvmc, tells me
> > it's not a disk issue, and the fact that mplayer cannot play it back
> > smoothly with xv tells me it's probably not a myth issue.
> >
> > Is it a bandwidth problem in the video card or the bus?  Some BIOS
> > setting incorrect?  Does anyone have any suggestions for how to narrow
> > it down and tell for sure where the problem might be?
> >
> > Is anyone using an original (sis-based) Pundit for HD playback successfully?
>
> If you can play back using mplayer (and XvMC), it means you can enable
> XvMC in Myth and have smooth HDTV playback.
> --
> Robert "Anaerin" Johnston

Theoretically, yes, but I've tried many different combinations of
options (vsync, vblank, audio buffering, etc) and it's just not quite
good enough for useability.  Sometimes I get a lockup when starting to
play, sometimes it gets a stutter, sometimes it gets out of sync with
sound.  Nothing consistent, but perhaps indicative of getting near the
same bandwidth limit I'm hitting consistently without xvmc.

Am I correct in assuming that less data is going to the video card
when using xvmc?  Anyone know the data ratio of xvmc vs. non-xvmc?

-Jerry


More information about the mythtv-users mailing list