[mythtv-users] Garbled sound on channel with mono audio

Rene H. Larsen rhl at izzlazz.dk
Wed Dec 29 18:04:14 UTC 2010

ons, 29 12 2010 kl. 01:32 +0100, skrev Rene H. Larsen:
> Hi,
> On one on my channels I get very strange sounding audio.  It sounds a
> bit like the people speaking have all been inhaling helium.  Mplayer and
> VLC plays back recordings from this channel correctly.  My Samsung TV
> also has no problem with this channel.
> The channel in question has dual mono audio.  Other channels with stereo
> or ac3 audio play back fine.
> A 20MB sample of a recording is available here:
> http://izzlazz.dk/myth/sample.mpg
> My setup:
> Ubuntu 10.10
> MythTV 0.24-fixes (latest JYA release build)
> Audio via HDMI (nVidia GT220)
> Signal via DVB-C
> I hope someone more knowledgeable than me will look into this problem. 
> Thanks,
> Rene

I've investigated a bit further, and found out that the problem only
occurs when outputting audio over HDMI.  If I use the on-board Intel HDA
sound, the clip plays back just fine.

Enabling playback logging, I get:

2010-12-29 18:43:33.659 ALSA: WriteAudio: buffer underrun

And later a bunch of these:

2010-12-29 18:43:34.037 Player(0): Video is 3.67027 frames ahead of audio,
			doubling video frame interval to slow down.
2010-12-29 18:43:34.117 Player(0): Video is 4.65895 frames ahead of audio,
			doubling video frame interval to slow down.

This might be related to the garbled audio I'm experiencing. I've
attached the full log from mythavtest obtained with -v

Any ideas?
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