[mythtv-users] More XvMC data points

Michael Tiller michael.tiller at gmail.com
Fri Dec 1 17:07:11 UTC 2006

On 12/1/06, Patrick Ouellette <pat at flying-gecko.net> wrote:
> On Wed, Nov 29, 2006 at 11:22:07AM -0500, Michael Tiller wrote:
> >
> > Just out of curiosity...when you say 65-75% CPU utilization, how is that
> > partitioned between the X server and the frontend?  I ask because if I
> try
> > and watch without XvMC on my system, the X server is something like 30%
> and
> > the frontend is like 70%.  I'm wondering if this load on the X server
> can be
> > avoided somehow.  Then I might have a chance to watch HD natively.
> >
> > It seems crazy to me that with such fast CPUs, HD playback is not a
> given.
> > My Windows machine (2.4GHz P4) can process HD streams from my HDHomerun
> > without a hiccup?!?  Why should a 2.8 GHz (granted, it is a Celeron)
> have so
> > much trouble?!?
> >
> I don't recall which video card you are using, but you will want to
> check the OpenGL vblank sync settings.

Everybody keeps mentioning this, but isn't this off by default anyway?  I
built MythTV from SVN recently and specifically looked and it said something
like "OpenGL Sync: Disabled" or some such thing.  That is the correct
setting right?  (i.e. the default setting)

using the latest NVidia driver

I've got a 440 MX using the 8776 driver.

and playing with the vblank settings

By this do you mean the instructions on the Wiki that say:

Try using the 'nvidia-settings' control panel to disable Video Texture
> Adapter and/or Video Blitter Adapter "Sync to VBlank" checkboxes (on the "X
> Server XVideo Settings" page)

I've done that.

soundcard buffer settings

By this do you mean turn on extra audio buffering during playback? (in the
Playback settings on the front end)

and dot clock in my modeline have significantly improved my XvMC output.

I'm lost here.  I've tried adding my own modelines but it always complains
they aren't valid, e.g.

        ModeLine "NTSC_60i" 14.318 768 784 848 910 483 484 492 525 Interlace
        Modeline "720x480_60" 26.72  720 736 808 896  480 481 484 497
-HSync +Vsync

Leads to this in Xorg.0.log:

(WW) NVIDIA(0): No valid modes for "720x480_60"; removing.
(WW) NVIDIA(0): No valid modes for "NTSC_60i"; removing.
(II) NVIDIA(0): Validated modes:
(II) NVIDIA(0):     "1024x768"
(II) NVIDIA(0):     "720x480"

I'm running and AMD Athlon64 3000+ and a 6600 based PCIe video card.

Thanks for the suggestions.  If I understand all of them, I think I'm close
to exhausting them all. :-(

I wish there were better diagnostics.  It seems like the current situation
with XvMC is that about the only thing you can say for sure is whether it is
"on" or not (i.e. gray background OSD or not).  Apart from that, there don't
seem to be any good diagnostic clues when you have problems.

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