[mythtv-users] Experiences with XvMC

Scott catfather at donpoo.net
Mon Aug 1 18:11:03 UTC 2005

On Aug 1, 2005, at 12:52 PM, Donavan Stanley wrote:
> Your stated goal was HDTV playback.  Given that you're most likely
> going to be playing back HD content using Myth not xine then it stands
> to reason you'd actually test using Myth.

But seeing as I don't yet have a HDTV capture card yet I ended up  
using 1920x1080i samples. One was from the pchdtv.com site and the  
other was a custom made 1080i mpeg2 demo with full 5.1 sound.  A  
third sample was a LotRclip2.mpg clip which can be found via google.

>> It may be possible that the Myth Internal video player with xvmc can
>> provide better quality deinterlace and post processing than Xine +
>> xv. Obviously a deeper understanding of how Myth works with xvmc and
>> more objective tests are needed.
> There is *no* post processing using XvMC.  Not with xine nor with
> Myth.  It's decoded by the hardware and displayed (to put it simply),
> things like kerneldeint, denoise3d and the like will not work with
> XvMC.  Myth does support the use of bob under XvMC as well as a full
> OSD which is why I suggested testing with Myth not xine.

Based on available XvMC information that's what I understood the case  
to be. So really it shouldn't matter so much if I'm using Xine + XvMC  
with bob deinterlacing or Myth Internal Player with XvMC. In both  
cases the output should have very similar results. It would be nice  
to actually test this situation but from what you describe I don't  
think I should expect much difference?

As I mentioned in my first post, I wasn't worried so much about the  
lack of OSD when using Xine + XvMC. I know that Myth Internal Video  
player + XvMC works with OSD as I've heard all about the grayscale  
OSD issues. Chances are I would use Xine + xv with post processing  
for DVD playback and stick to Myth Internal Video player + XvMC for  
1080i streams

I did test Xine + XvMC with both one-field and bob deinterlace  
methods and it was clear that bob deinterlacing produced better  
results for my 1080i test clips and on 480i DVD sources. I'm glad to  
hear the Myth Internal Video player supports bob with XvMC. I also  
noted in the Xine docs that there is an apparent work around for  
grayscale OSDs with XvMC. This wasn't something I tried as I was  
mostly focused on deinterlace quality and artifacts that might be  
seen when using XvMC.

Have the Myth developers considered adding the OSD grayscale work  
around from Xine to the Myth Internal Player or is that not something  
which is feasible?

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