[mythtv] XvMc-OpenGL and OpenGL-OSD

Daniel and Mary-Beth Sherwood jackanddougal at yahoo.co.uk
Wed Apr 30 10:55:25 UTC 2008


Mike

A quick follow up to my own post.  After some more digging around, I found the 'original' source for the XvMC-OpenGL stuff currently in MythTV (http://www.xfree86.org/~mvojkovi/mpeg2play_accel.tar.gz) and this exhibited the same problem (works with XvMC, same video problems with XvMC-OpenGL).  I also came accross a post (http://www.nvnews.net/vbulletin/archive/index.php/t-81943.html) describiung similar problems and suggesting that an alpha channel is essential in teh FB config (for some cards).  I hacked the mpeg2play_accell::display_gl.c file to add 'GLX_ALPHA_SIZE, 5' to the attr_fbconfig structure and recompiled and it all worked!!!

Some performance figures from various combinations... (with and without -f25)
                         CPU-Load at 25FPS   MaxFrameRate
   Standard-XvMC         13-18%            48
   XvMC-OpenGL           15-20%           113
   XvMC-OpenGL-glFenceNV 14-19%           122

Therefore I conclude that the impact of this copy is minimal (strange that the load went up when running at 25fps but the free running frame rate went up:)) and should only add 2-3% to my playback load under MythTV (which is currently 30%) so I should be good to go.

When I get home tonight, I will make the same change to MythTV and see if I get the same results.  If I do, then a patch will follow soon.

Thanks for your help.

Daniel

--- On Tue, 29/4/08, Daniel and Mary-Beth Sherwood <jackanddougal at yahoo.co.uk> wrote:

> From: Daniel and Mary-Beth Sherwood <jackanddougal at yahoo.co.uk>
> Subject: Re: [mythtv] XvMc-OpenGL and OpenGL-OSD
> To: "Development of mythtv" <mythtv-dev at mythtv.org>
> Date: Tuesday, 29 April, 2008, 10:21 PM
> Mike
> 
> Thanks for your response, your link to the original
> submission gave me the clues I needed and having read up a
> bit about what is being done, I agree that in it's
> current implementation (with the copy from the XvMC surface
> to the GLX p-buffer) ths isn't going to fly on my
> machine (ashame) however I do still have a few of follow up
> questions...
> 
> ***Q1*** Although it is slow, I would still expect it to
> work (i.e. display the video and OSD corerctly).  I suspect
> some form of mismatch between the colourspace and/or bit
> depth and/or stride of the two buffers.  I suspect the
> other ticket you linked is probably a similar issue.  Any
> thoughts where to start looking at this?
> 
> ***Q2*** The copy from XvMC to p-buffer is obviously an
> expensive operation.  Does anyone (danielk) know if it is
> possible to skip this step in any way and if so, are there
> ant plans to progress this?  
> 
> I am a very experienced software engineer and I am willing
> to put effort into looking at this is someone can a) give
> me pointers and b) indicate that I am not completely
> wasting my time given the low-power CPU I am aiming at:)
> 
> Cheers
> 
> Daniel
> 
> --- On Tue, 29/4/08, Michael T. Dean
> <mtdean at thirdcontact.com> wrote:
> 
> > From: Michael T. Dean <mtdean at thirdcontact.com>
> > Subject: Re: [mythtv] XvMc-OpenGL and OpenGL-OSD
> > To: "Development of mythtv"
> <mythtv-dev at mythtv.org>
> > Date: Tuesday, 29 April, 2008, 7:54 PM
> > On 04/29/2008 02:44 PM, Daniel and Mary-Beth Sherwood
> wrote:
> > > ***Q1*** Please can someone confirm that XvMCW
> > doesn't support XvMC-OpenGL
> > 
> >
> http://www.gossamer-threads.com/lists/mythtv/commits/202450#202450
> > 
> > Notice the name, "nVidia XvMC copy to texture
> > extension".
> > 
> > > ***Q2*** What is the current state of this
> > configuration?  Is it stable and working? or is this
> > behaviour expected?
> > >   
> > 
> > Pretty sure it's not really "supported"
> on
> > 0.21 (which is--at least part 
> > of the reason--why the packagers don't enable it).
> > 
> > > For the record, here are some other bits of
> > configuration info:
> > >
> > > CPU:     PIII 866MHz
> > >   
> > 
> > I'm pretty sure you're going to need a much
> bigger
> > processor for it to 
> > work properly.  IIRC, it's not even close to
> optimized.
> > 
> > See, also, http://svn.mythtv.org/trac/ticket/4813 .
> > 
> > Mike
> > _______________________________________________
> > mythtv-dev mailing list
> > mythtv-dev at mythtv.org
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev
> 
> 
>      
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