[vdr] How to get a synced demux from vdr recordings

C.Y.M syphir at syphir.sytes.net
Thu Mar 31 17:13:38 CEST 2005


It appears to me that depending on the broadcast quality of the stream, some
demuxers do the job better than others.  Sometimes I have to use vdrsync, and
sometimes its project-x, but I have never been able to find a demuxer that works
all the time on every recording.  Vdrsync will most often drop the audio stream
if it finds many audio gaps in the recording (most certainly related to cutting
and editing within vdr). It is safe to assume that about 100ms of audio is lost
per cut in vdr.  After some testing, I have been able to use
lve-050112.src.tar.bz2 to demux and create perfect A/V sync in mpg vobs for DVD
creation.  The combination of libdvbmegtools (0.5.5.1) used to convert VDRs PES
to a PS stream is also a critical step.

mkfifo file.m2v file.mpa
cat 00*.vdr|pes2ts2 100 101|ts2ps 100 101 > file.ps
lvedemux file.ps | lvemux -p -1 -r -sh -400 -v file.m2v -a file.mpa -o file.mpg


The following command gets perfect sync on a recording with 4 cuts (note the
400ms timeshift to compensate for the lost audio frames.  What would be cool is
to have the ability to detect the number of cuts in a recording to automatically
adjust for the audio loss to create better A/V sync (if we can agree on an
average frame loss per cut).  Some other methods of demuxing, including mencoder
and vlc, seem to do the job as well, but the A/V sync is off when several cuts
have been made (and transcoding does not help).  It seems the only method that
really works all the time is to count the cutmarks and adjust the timeshift
accordingly (~100ms per cut).

Best Regards,
C.Y.M.



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