[mythtv-users] stuttering and loss of sync after transcoding some recordings

Peter Schachte schachte at csse.unimelb.edu.au
Mon Sep 29 11:59:14 UTC 2008

I have an intermittent problem with my myth installation (0.21-fixes, 
mythbuntu 8.04 weekly builds, AMD64).  Occasionally transcoded recordings 
(MPEG2 from DVB-T transcoded to MPEG 4) become damaged, and at some point in 
the recording, suddenly and without apparent reason, the playback becomes 
about 1.25 seconds out of sync, and I start getting a continual "WriteAudio: 
buffer underrun" messages in the frontend log.  This always appears in the 
same place in any given recording, but different places in different 
recordings.  Playback before the error, and on transcoded recordings that 
don't have the problem, is fine.  mysqlcheck says my tables are OK, and 
rebuilding the seek table with mythcommflag --rebuild makes no difference. 
When playing back the same recording with VLC, I lose all sound at the same 
place I lose sync playing back inside myth.  I can't find a log file for the 
transcoder, nor can I find a place in the settings to enable logging.

I can't remember exactly when I first had this problem, but it definitely 
didn't occur under 0.20, but it's been happening a few times a week for 
several months.  I've googled and searched gossamer threads about this; there 
are a million hits, but none with the same symptoms.

Thanks in advance for any help tracking this down.

Peter Schachte              The untrammeled intensification of laissez-faire
schachte at cs.mu.OZ.AU        capitalism ... is endangering our open and
www.cs.mu.oz.au/~schachte/  democratic society.
Phone: +61 3 8344 1338          -- George Soros

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