[mythtv-users] lossless cut and audio sync drift?

[Doug Vaughan]

Ian,
     I have, but rarely, noticed some audio drift. I am fairly sure, as 
so many of the other issues are, that mkvmerge finds some problem with 
the original recorded mpg file. Here is a reference to mkvmerge 
parameters that you can use from the commandline on an out of sync mkv 
file post lossless cut.

From: https://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge.html

Some movies start synced correctly but slowly drift out of sync. For 
these kind of movies you can specify a delay factor that is applied to 
all timestamps -- no data is added or removed. So if you make that 
factor too big or too small you'll get bad results. An example is that 
an episode I transcoded was 0.2 seconds out of sync at the end of the 
movie which was 77340 frames long. At 29.97fps 0.2 seconds correspond to 
approx. 6 frames. So I did:

$ mkvmerge -o goodsync.mkv -y 23456:0,77346/77340 outofsync.mkv

I hope this helps.

Doug