[mythtv-users] XvMC and high CPU usage

[Jesse Guardiani]

Tom Dombrosky wrote:
>
>
> On 3/21/06, *Kevin Kuphal* <kuphal at dls.net <mailto:kuphal at dls.net>> 
> wrote:
>
>     Jerry Rubinow wrote:
>     > On 3/21/06, Kevin Kuphal <kuphal at dls.net
>     <mailto:kuphal at dls.net>> wrote:
>     >
>     >> On FC4, I get the grey OSD and the logs report XvMC is being
>     used but my
>     >> CPU usage is high.  I can *barely* get the video to play
>     properly using
>     >> libmpeg2 but the picture seems a little jumpy.  My configure
>     script says
>     >> I'm linking with libXvMCNVIDIA as expected.  My OpenGL Vsync is
>     working
>     >> as I'm using the 7676 nvidia driver (changing it makes things
>     worse for
>     >> libmpeg2 performance).
>     >>
>     >
>     > Did you try turning off OpenGL Vsync?  It may make libmpeg2
>     worse, but
>     > it improved XvMC for me.
>     >
>     >
>     Yes.  I have no problem with OpenGL Vsync as I'm using 7676 which
>     has no
>     problems.   Is your CPU dramatically reduced with XvMC?  What xorg
>     version are you running?
>
>     Kevin
>
>
> Definitely don't use the 8xxx series drivers.  I'm using 7676 with the 
> only problem being skipping when the osd appears.  I have a nforce4 MX 
> AGP card running on a gentoo system.

I'm not so sure about that. I have an FX 5200 and I'm running 8178 
without problems. You just have to disable OpenGL VSync.
I had to upgrade because 7676 was causing consistent, reproducible 
2.6.15 kernel panics when I ran mupen64.

XvMC seems to work the same with 8178 as with 7676. The problem I have 
is that I can't run Bob deinterlacing anymore
because I output to a 1360x768 size screen. If I run Bob and pause, or 
change channels then the screen starts skipping every
other frame and bouncing a bit. It didn't do that before I upgraded from 
the nvidia's TVOUT to DVI, and others have confirmed
that it has something to do with TVOUT vs DVI or screen res.

But even back then, when I was running TVOUT, 7676, XvMC and Bob, I 
still had minor issues with Prebuffering pauses.
They were worse with LiveTV, but they occasionally occurred when playing 
a recording too. The pauses were very subtle,
which is why I didn't notice them at first and I wrote on the XvMC wiki 
page that my SD playback was "Perfect" (I really
need to change that), but once I noticed them I couldn't stand it so I 
just turned XvMC off.

However, I still use XvMC with DVD playback via xine, and it does appear 
to be "perfect". So I strongly suspect the prebuffering
pauses are a problem with the MythTV code. Perhaps a threading issue 
where a lock is held too long or something. I suspect it
could be tracked down, fixed, and all of our problems would go away.

My problem is that my MythTV box isn't a devel machine. It's production, 
so I find it difficult to do more than just sys admin
work on it.


-- 
Jesse Guardiani
Programmer/Sys Admin
jesse at wingnet.net