[mythtv-users] My Perennial Problems with XvMC

Steven Adeff adeffs.mythtv at gmail.com
Thu Sep 14 14:24:34 UTC 2006

On 9/13/06, Dylan Semler <dylan.semler at gmail.com> wrote:
> Once upon a time, I thought it would be cool to watch HDTV on my computer.
> So I bought an HD-3000 and installed myth on to my FC4 box and hoped for the
> best.  It soon became apparent that my P4 2.26 GHz was too weak to handle
> all of this content, and I was resigned to watching SD content only.  Then I
> heard about this wonderful mechanism called XvMC that offloads the video
> decoding processes from the processor to the video card.  Perhaps watching
> HD was indeed possible with my current equipment.  But alas, the fine print
> says that the nvidia driver fully supports XvMC on 5000 series cards and
> above, and only partially supports it on some 4000 series cards.  Well since
> I had a 4200 I figured I'd give it a try anyways.  Needless to say, the
> results were not very good.  Whereas with no XvMC at all, I was getting a
> few prebuffering pauses every second and very jerky playback.  With XvMC
> enabled, the prebuffering pauses were happening very rapidly (and of very
> short duration) offering an overall smoother playback, but still
> un-watchable.  Oh well, I say to myself, perhaps someday I'll upgrade my
> system.
> Enter GeForce 6200.  Nvidia claims XvMC is fully supported on this model so
> I should see some serious improvement.  I replace the old 4200 in the FC4
> box and fire up Myth.  I enter live TV and go to my favorite HD channel and
> BAM!  Reacts exactly the same as before--for about 3 seconds.  Then the
> picture starts deteriorating in what some people may have described as
> "tearing."  A few sections of the picture change to a different color (or
> scene maybe--it's hard to tell).  The sections grow until the entire screen
> is covered in garbage, and I think the system crashes/stalls, I haven't
> really let it go this far lately, but I'm pretty sure something bad happens.
> So still no dice, I figure I'll test to see if it's a Myth problem or an
> XvMC problem.  I try to fire up mplayer with -vo xvmc -vc <ffmpeg12mc>  but
> I guess it wasn't compiled in.  I figured I'd recompile mplayer with xvmc
> support but when I go to look for it I can't find it.  It wasn't in
> /usr/local and rpm -qa | grep mplayer returned nothing.  Long story short, I
> decided to reinstall to FC6T3 (I really wanted to see aiglx in action
> anyways).  So I go a head and do the install and I get everything with
> mplayer setup and test a Conan recording that I had made before. For the
> first time, it actually played smoothly with XvMC!  Processor load is down
> to 50% - 60%. Optimistically, I install and setup Myth, try to watch an HD
> channel of live tv... but alas, I witness the same response that I had on
> FC4.


So, in Myth after a few seconds you get weird coloration and major pixelation?
This is a new one for me. Since it seems to be fine in mplayer, I
would agree that it must be some way in which Myth is working with
XvMC. Have you tried disabling/enabling OpenGL Vsync? What about some
of the options in "nv-settings"?

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