[mythtv] [PATCH] Partial fix to intermittent AV sync problem with DVB cards

Damian Ivereigh damian at cisco.com
Mon Aug 23 10:33:24 EDT 2004

Some time back I mentioned that I had an intermittent issue when playing
live TV from my DVB Cards. Sometimes when changing channels the AV could
never get in sync and the video was stuck in slow motion with jumpy

Well I think I have found the problem. Every so often (I can't figure
out when or why) the timecodes for the video & audio would go negative
after a channel change. I actually can't figure out where those
timecodes come from - they seem to be buried in the actual mpeg/nuv file
itself (i.e. put there when recording the ring buffer). For all I know
they start off with a random value (initialised!).

Anyway this triggers what appears to be an old bit of code that should
have been removed which then messes up the audio timecode. This then
creates a ludicrous delay offset and sends the AVSync code into a spin
as it tries to sync up.

This patch removes this bit of code from all the
libmyth/audiooutput*.cpp files. Note I have only tested it with the OSS
files, but the fix seems reasonable.

If someone else wants to dig in and find out why the timecodes go
negative and if that is reasonable, I would be very interested in the

Damian Ivereigh
CEPS Team Lead
Desk: +61 2 8446 6344
Mob: +61 418 217 582

Please avoid sending me Word or PowerPoint attachments.
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