[mythtv-users] Audio Buffer Underruns with XvMC and HD in 0.20

[Harley Peters]

Ben Curtis wrote:
>> I have had those errors before as well.
>> I have no idea why xvmc works in some cases and not in others.
>> I wish i new what video cards worked and what doesn't as i don't really
>> want to keep the FX5900 card in my system. It is over kill for mythtv
>> and takes up two slots.
>> I will be able to try an FX5200 sometime next week and will see if it
> works.
>> I am running the svn version 11295 but there hasn't been any changes to
>> the xvmc code since the .20 release.
>> I am running Gentoo and i am renicing (-5) the X process to fix another
>> problem i have had with mythtv.
>> I have opengl vsync on , real time priority off, and extra audio
>> buffering on. Nothing special about the setup.
>>
> 
> I would be very interested to know if the FX5200 works for you.  I have
> basically the same set up without the renicing.  I have a spare partition
> on the drive so I'm considering a fresh start with FC5 to see if it fixes
> it.  Luckily my backend is a seperate system and it's not really an issue,
> just the single frontend in my media room.
> 
> Thanks,
> Ben
> 
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Well i have tested using the FX5200 in my system. It is much better than
the Geforce 4 MX 440 i used to use but not as good as the FX5900.
Playing 1080i live tv results in a few audio drop outs and write audio 
buffer underrun errors. Where with the FX5900 there where none.
Turning off sync to vblank under the Video Texture Adaptor setting in 
the nvidia-settings program seems to eliminate the drop outs but then 
there is screen tearing.
Playing back 1080i recorded video seems to play back with no problems at 
all. X cpu usage is .3 % to 1.3% playing back both live tv and recorded 
video compared to 0 % on the FX5900.
If i turn off XvmcUsesTextures in xorg.conf it then behaves like the 
other two cards with write audio buffer underruns, audio drop outs and X 
cpu usage all over the place.
Also while upgrading to the latest svn version i found out that the svn 
commit 11327 broke xvmc when using XvmcUsesTextures true in the 
xorg.conf file. It works fine until the osd fades and then you get 
choppy video and audio with write audio buffer underruns.
It is a simple one line fix to get it working.

  Index: libs/libmythtv/osd.cpp
  ===================================================================
  --- libs/libmythtv/osd.cpp (revision 11327)
  +++ libs/libmythtv/osd.cpp (revision 11416)
  @@ -2551,5 +2556,5 @@
       m_setsvisible = anytodisplay;

  -    if (m_setsvisible && !drawSurface->IsClear())
  +    if (m_setsvisible)

           return drawSurface;

Which just sets if (m_setsvisible && !drawSurface->IsClear()) back to
if (m_setsvisible) in osd.cpp which is what it was before the commit.

 From the tests i performed i would say the FX5200 is on the ragged edge 
of being able to handle 1080i video when using the XvmcUsesTextures 
setting in xorg.conf.

Harley