[mythtv-users] problem with audio underruns on 720p only

[Greg Zornetzer]

Hi Jeffrey et al,
Again, I apologize for what this is doing to threaded mail readers.
I hadn't thought to try the SD digital channels, since I just grab most of
those on an analog stream.  However, I can confirm that the audio underrun
problem does occur with 480i streams as well as the 720p streams.  1080i
streams are okay for me.  I don't know why 1080i doesn't work for you.

Out of curiosity, does transcoding fix the problem for you?  If you are
worried about being limited by graphics card throughput, you could play the
files directly from the storage directory using mplayer.  If that works,
you're probably not throughput limited (but that's my limited experience).
Thanks,
-Greg


On Sun, Dec 7, 2008 at 6:59 PM, Greg Zornetzer
<gzornetzer.lists at gmail.com>wrote:

> Hi all,
> I am running mythfrontend on a Core 2  6550 dual core machine with a
> motherboard Nvidia 7100 display.  Transport is xv-blit.  CPU usage doesn't
> seem to be a problem with HD content (~25-50% usage from top in 720p or
> 1080i mode)
> I am using the RPM version of mythtv-0.21 from rpmfusion.org.  This
> happens with both the released -13 RPM and the newer -14 RPM in rpmfusion's
> testing directory for fc9.  I'm running this on fedora core 9.
>
> When I play 720p, either in live tv mode, or freshly recorded, I get the
> following (recorded with -v playback):
>
> NVP: Video is X.xxxx frames ahead of audio, doubling video frame interval
> to slow down
> (repeated several times)
> WriteAudio: buffer underrun
>
> In this case, X.xxxx is somewhere between about 7 and 12.
> This is accompanied by stuttering of the audio every second or so.
>
> I noticed that there was a bug that got fixed a few months ago regarding
> audio buffering with 720p data (see http://svn.mythtv.org/trac/ticket/5749),
> but the fix for this (included with the newest testing version of the rpm
> from rpmfusion), doesn't fix the problem.
>
> I have noticed that if I transcode the 720p recording using the default
> settings, the transcode will replay flawlessly.  So, it's some kind of
> problem with mythtv interpreting the data coming right off the TV line.
> That's sort of good news - this way we can at least use the recordings that
> are made.
>
> Note that there is no problem with playback of 1080i material.
>
> I believe that some others may be seeing the same problem.  I think that
> the problem described here may be the same:
> http://mythtv.org/pipermail/mythtv-users/2008-December/240895.html
>
> I do have 'extra audio buffering' selected in the configuration for mythtv
> - I saw that asked before.
> Any suggestions?
> Thanks,
> -Greg
>
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