[mythtv] Latest CVS XvMC - Nvidia Nforce2 IGP Live TV hangs

Andy Poling andy at realbig.com
Mon Feb 7 00:42:36 UTC 2005


On Sun, 6 Feb 2005, Jeremy Garff wrote:
> Has anyone else seen this problem where watching recordings with XvMC
> enabled is fine, but watching live TV results in artifacts and hangs
> immediately after going to LiveTV?
> 
> I'm currently running the latest Nvidia drivers (6629), and the stream is
> being sent to a remote client over the network (100Mb).  The linux kernel
> is 2.6.9-ac12.  The CPU is a 2000XP and the compile options include OpenGL
> XvMCNVIDIA and pentiumpro.

I have pretty severe xvmc problems with a similar setup (Sempron 2000,
GeForce4 MX builtin to the nforce2 chipset, nvidia 6629, GL sync, 2.6.9
kernel, myth code from cvs Saturday) when playing any HDTV programs.  I have
set the fade time to 0 in osd.xml, and have even switched to using blueosd to
avoid having any transparency at all.

I have virtually instant playback lockup as soon as any OSD is displayed.
mythfrontend is still running (ESC will get me out of playback) - it just
stops playing video.  I had to disable the input display OSD to be able to
watch live tv at all.

HDTV playback is otherwise fine, regardless of whether it's 480i, 720p or
1080i.  If it's 480i (e.g. an SDTV secondary subchannel like weatherplus), I
can watch, get info, fast forward, rewind and skip back and forth, but I can't
pause reliably (more correctly, I cannot un-pause reliably).  With any higher
resolution content, 99% of the time any activity that invokes an OSD display
will result in a freeze of the video play.  If it doesn't stop playing (which
happens maybe 1% of the time) it...  gets... really... intermittent until the
OSD clears.

If I disable GL sync in settings.pro (which means we fall back to RTC timing),
then it gets much better.  I get heavy intermittency of audio, and occasional
playback lockups (maybe 20% of the time).  

Surprisingly (to me, at least), it seems not to matter whether I'm using audio
or video as the timebase.

It doesn't matter whether I have de-interlacing enabled or not.

I tried regressing the nvidia driver to version 6111 with no apparent change
in this problem.

In all these situations I have at least 60% cpu idle.  That would seem to
indicate that some race condition is arising in the processing of the higher
res hdtv programs.  It wouldn't surprise me - I kind of expect hdtv to uncover
some new warts as it pushes everything alot harder.

I'm only being this verbose in hopes that this will trigger an "ah-hah" from
someone who's spent alot more time looking at this code than I have.  It only
takes me a few seconds to reproduce the problem.  :-)

Oh, and there's another strange effect that happens only when watching 720p
with xvmc.  I get what look like very slightly old frames mixed in, causing
weird jumpiness, sometimes even causing moving objects to leave (for lack of a
better description) trailing ghosts.  I'm guessing it has something to do with
it not being interlaced.

-Andy


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