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

Isaac Richards ijr at po.cwru.edu
Mon Aug 23 13:54:19 EDT 2004

On Monday 23 August 2004 10:33 am, Damian Ivereigh wrote:
> 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
> sound.
> 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.

I don't see how this patch fixes anything.  The code in question throws out 
bad timestamps (if they're less than 0), and instead guesses the next 
timestamp from the existing data..    


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