[mythtv-users] WriteAudio: buffer underrun with kernel upgrade

Jeff Piazza jeff at jeffpiazza.org
Sat Jul 10 15:23:30 UTC 2010

I recently bought an HD-PVR, so I'm trying to upgrade my kernel, from  
the 2.6.26 that ships with Debian lenny, to a 2.6.34 kernel I'm  
compiling from sources.  I'm able to boot the new kernel and configure  
the HD-PVR device -- so far, so good.

Trouble is, playback of HD recordings that played just fine under  
2.6.26 now stutter horribly, with "WriteAudio: buffer underrun"  
messages from mythfrontend.  I don't see any "prebuffering pause"  
messages.  The audio problem goes away if I reboot back to the old  
kernel.  I've tried compiling the 2.6.34 kernel with several different  
configurations trying to make the problem go away, but I'm really just  
guessing, and nothing I've tried has had any effect.

I'm using an AMD 4400+ CPU, NVIDIA GeForce 6600 LE video card, and XvMC.

I'm trying to compare the kernel config settings, but not having much  
luck -- I don't know what most of the config symbols mean, and the set  
of symbols changes between kernel releases.

Are there any known performance/configuration issues with the newer  
kernels that anyone knows about, or other directions to look?

Thanks in advance for any suggestions.


2010-07-08 07:45:21.717 TV: Attempting to change from None to  
2010-07-08 07:45:22.151 AFD: Opened codec 0xad9cf30,  
id(MPEG2VIDEO_XVMC) type(Video)
2010-07-08 07:45:22.151 AFD: codec AC3 has 2 channels
2010-07-08 07:45:22.151 AFD: Opened codec 0xad9a720, id(AC3) type(Audio)
2010-07-08 07:45:22.158 Opening audio device 'hw:2,0'. ch 2(2) sr  
48000 (reenc 0)
2010-07-08 07:45:22.159 Opening ALSA audio device 'hw:2,0'.
2010-07-08 07:45:22.193 VideoOutputXv: XvMC Adaptor Name: 'NV17 Video  
2010-07-08 07:45:22.205 WriteAudio: buffer underrun
2010-07-08 07:45:22.219 NVP(0): Forcing decode extra audio option on  
(Video method requires it).
2010-07-08 07:45:22.220 OSD Theme Dimensions W: 640 H: 480
2010-07-08 07:45:22.228 WriteAudio: buffer underrun
2010-07-08 07:45:22.251 WriteAudio: buffer underrun
2010-07-08 07:45:22.274 WriteAudio: buffer underrun
2010-07-08 07:45:22.297 WriteAudio: buffer underrun
2010-07-08 07:45:22.311 TV: Changing from None to WatchingPreRecorded
2010-07-08 07:45:22.313 Using realtime priority.
2010-07-08 07:45:22.315 OpenGLVideoSync()
2010-07-08 07:45:22.320 WriteAudio: buffer underrun
2010-07-08 07:45:22.343 WriteAudio: buffer underrun
2010-07-08 07:45:22.357 ScreenSaverX11Private: DPMS Deactivated 1
2010-07-08 07:45:22.365 Video timing method: SGI OpenGL
2010-07-08 07:45:22.367 WriteAudio: buffer underrun
2010-07-08 07:45:22.390 WriteAudio: buffer underrun
2010-07-08 07:45:22.413 WriteAudio: buffer underrun
2010-07-08 07:45:22.415 VideoOutputXv: ProcessFrameXvMC: Tried to  
reuse frame but failed
2010-07-08 07:45:22.415 VideoOutputXv: ProcessFrameXvMC: Called  
without frame
2010-07-08 07:45:22.415 VideoOutputXv Error: Child     A        was  
already marked as available.
2010-07-08 07:45:22.415 VideoOutputXv Error: Child     A        was  
already marked as available.
2010-07-08 07:45:22.435 WriteAudio: buffer underrun

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