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

[Phil Ehrens]

Corey Hickey wrote:
> D Richard Felker III wrote:
> >On Tue, Mar 15, 2005 at 12:41:48PM -0800, Corey Hickey wrote:
> >
> >>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.
> >
> >
> >Interesting. Can you tell me if strange frame skips or duplicates
> >happen at the beginning (with or without pullup loaded). Unfortunately
> >mencoder doesn't like filters that buffer a few frames ahead, so
> >pullup has to do a nasty hack to hide that it's doing this.. If the
> >first few frames are supposed to be skipped it could mess things up
> >rather badly, perhaps...?
> >
> 
> I don't know exactly what you mean by strange, but there certainly are a
> lot more of them when I use pullup. I just made a couple logs of the
> first part of the movie:
> 
> mencoder starwars.vob -v -aid 128 \
> -vf pullup,softskip,crop=714:352:2:62,scale=688:288 \
> -ovc lavc -oac copy -ofps 24000/1001 -endpos 530
> 
> ...with and without pullup,softskip.
> 
> bugfood at bugfood:~/mpbug$ grep 'Skipping frame!' big-nopullup.log | wc -l
> 2
> bugfood at bugfood:~/mpbug$ grep 'duplicate frame(s)' big-nopullup.log | wc -l
> 3
> bugfood at bugfood:~/mpbug$ grep 'Skipping frame!' big-pullup.log | wc -l
> 1
> bugfood at bugfood:~/mpbug$ grep 'duplicate frame(s)' big-pullup.log | wc -l
> 115
> 
> big-pullup.log and big-nopullup.log are uploaded:
> mpqh incoming/desync2/
> http://fatooh.org/files/mpbug/desync2/
> 
> I also just noticed something I hadn't before: when using pullup
> mencoder reports "Could not get buffer from pullup!" four times. I just
> checked the logs of the cut section I uploaded earlier, though, and I
> don't see that message (even though the cut section has the same desync).
> 
> The messages appear after a long series of duplicate frames, between
> about 84 and 88 MB into the file. I tried encoding just that portion,
> and pullup doesn't give me an error - just lots of duplicate frames. If
> you're interested, you can download just that portion:

I just wanted to step in here and say that if this is a
U.S. release dvd, these things typically change frame rate
at strange times and for no apparent reason. Hardware players,
mplayer, and mencoder seem to be able to deal with this
in all the cases I have seen, but maybe some filter or
plugin is incompatible with the "handling"? Just an idea.

-- 
Phil Ehrens <phil at slug.org>      | Fun stuff:
The SilverLake Linux Users Group | http://www.ralphmag.org
3428 Winslow Drive               | http://www.yellow5.com
Silverlake, CA 90026             | http://www.slug.org