[mythtv-users] Video/Deinterlacing/Sound problems (XvMC)

Tj htpc at treblid.dyndns.org
Tue Dec 21 22:28:10 UTC 2004

Brian Bartlow wrote:

> Anyhow, my main question is, how can I confirm that xvmc is being used
> by MythTV?  And if it isn't being used, how do I turn it on?  I've
> already compiled Myth with xvmc turned on the in settings.  Everywhere I
> read that with XvMC turned on, the overlays go to B&W, and mine are
> color.  Does that mean XvMC isn't being used?
Setup->TV Settings->Playback
Click on next until u see Hardware Decoding Settings at the top, below 
there's a tick box that says "Use hardware XvMC MPEG Decoding.

Yeah. i think with XvMC OSD will be in b/w.. not sure why though..

> My second questions is, is my hardware powerful enough to decode the
> HDTV MPEG stream, deinterlace it, and decode the AC3 audio?  One more
> thing, I'm using a projector so I'm not using the TV-out, just the VGA.
Dunno about that one.. :) For my case using only XvMC sorta makes me 
"seasick" when the camera pans horizontally, and PiP doesn't work with 
XvMC, it also filckers if I have some de-interlace filters on. So I 
stopped using XvMC altogether. For my setup I find Bob works best for me.

If you find your cpu couldn't keep up, maybe add some compile options to 
gcc when building myth may help? There are options you can set in 
config.mak and settings.pro - OPTFLAGS option and 

"man gcc" and experiment..

I didn't test it much, I used a Pentium, so I just use  "-O 
-mcpupentium4 -march-pentium4 -mtune=pentium4" and 
"QMAKE_CXX_FLAGS_RELEASE=-O3 -mcpupentium4 -march-pentium4 
-mtune=pentium4". It takes longer to compile though. It sorta works for 
me so I didn't touch it since. For my machine, Bob with myth 
optimizations roughly matches normal myth with XvMC.

Play around with the options and see whether it really helps you or not, 
I think you may even slow down Myth if you use the wrong combinations. 
For my case I belive just -mtune=pentium4 is fine. but I havn't tested 
that yet.


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