[MEncoder-users] [BUG] a-v sync problems with pullup, softskip (only on some DVDs)

[Corey Hickey]

I've been seeing an elusive a-v sync problem recently with a few DVDs
and have finally tracked it down to a reproducible test case.

Using pullup,softskip on the (recently released) Star Wars DVD results
in audio that plays about 0.3 seconds early.

mencoder starwars.vob -aid 128 \
-vf pullup,softskip,crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001

--> Out of sync

mencoder starwars.vob -aid 128 \
-vf crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001

--> Perfect sync

mencoder starwars.vob -aid 128 \
-vf softpulldown,ivtc=1,crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001

--> Also perfect sync


There seem to be some data early in the movie that throw pullup off; if
I use dd to cut to a dialog section before encoding, the desync goes
away. I did some experimentation and determined that I can cut 20 MB
from near the beginning, and then append any section from later in the
DVD. Thus, with dd and cat I can end up with a much smaller download for
Rich to test. :) I'd try for an even smaller file but when I cut more
out the desync is reduced.

dd if=starwars.vob of=part1.vob bs=8192 count=2560 skip=8192
dd if=starwars.vob of=part2.vob bs=8192 count=8192 skip=50000
cat part1.vob part2.vob > combined.vob

The first part is the problematic section; the second part has speaking
and the desync is visible. The mencoder lines above have the same
results when tested with combined.vob, so I'm using it to make the
sample avi files and mencoder logs.

mencoder combined.vob -v -aid 128 \
-vf pullup,softskip,crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001 -o pullup.avi &> pullup.log

mencoder combined.vob -v -aid 128 \
-vf crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001 -o none.avi &> none.log

mencoder combined.vob -v -aid 128 \
-vf softpulldown,ivtc=1,crop=714:352:2:62,scale=688:288 \
-ovc lavc -oac copy -ofps 24000/1001 -o ivtc.avi &> ivtc.log


Sample source files:
part1.vob
    --> Partial dump from the dvd, as shown above.
part2.vob
    --> Same as part 2; you don't need to download the whole file - the
        first 10000000 bytes illustrate the problem, and the rest has more
        speaking. Cat the two parts together for encoding.
bigpart.vob
    --> In case you want an uninterrupted section. This is about 450 MB so
        I'll upload it to mphq last and send this email before the
        transfer finishes.

Sample encodes and logs:
pullup.avi, pullup.log.bz2
none.avi, none.log.bz2
ivtc.avi, ivtc.log.bz2

All files are available at mphq ftp in incoming/desync2, and at
http://fatooh.org/files/mpbug/desync2/

System info:
Debian-amd64 Sid
MEncoder dev-CVS-050313-19:29-3.4.4 (C) 2000-2005 MPlayer Team
Linux bugfood 2.6.11 #1 Fri Mar 4 14:46:19 PST 2005 x86_64 GNU/Linux
Libc6 version 2.3.2
gcc version 3.4.4 20050305 (prerelease) (Debian 3.4.3-11.0.0.1.gcc4)
GNU ld version 2.15
GNU assembler 2.15

Also verified on:
i386 Ubuntu 4.1 (a different machine)
MEncoder dev-CVS-050313-19:40-3.3.4 (C) 2000-2005 MPlayer Team
Linux ganon 2.6.8.1-5-686 #1 Sat Feb 12 00:50:37 UTC 2005 i686 GNU/Linux
Libc6 version 2.3.2
gcc version 3.4.2 (Debian 3.4.2-2ubuntu1)
GNU ld version 2.14.90.0.7 20031029 Debian GNU/Linux
GNU assembler 2.14.90.0.7 20031029 Debian GNU/Linux


Thank you as always,
Corey