[MPlayer-users] one dvd -> two burned dvds

[Aaron Peterson]

I've been working on a reasonable way to take dvd video off a dvd, and
re-author it to two burned dvds (if it's a very large video at least)
while keeping the chapter information.

I've been using mplayer to dump out the video and audio of the main
title without changing the original format (no re-encoding).  At first I
tried with:

mplayer dvd://1 -dvd-device /mirrored/dvd -dumpvideo -dumpfile video.m2v

mplayer dvd://1 -dvd-device /mirrored/dvd -dumpaudio -dumpfile audio.mpa

which loses all the chapter information, but I figured I could 

mplex -f 8 -M -o movie_%d.mpg audio.mpa video.m2v

then cat the resulting mpg files together into one, grab chapter
boundary times from one of the transcode tools (tcprobe) and present
them to dvdauthor to recreate the chapters. This didn't actually turn
out too badly, except the chapter boundaries were early by a second or
two.  Not the end of the world, but I am compulsive :)

After pondering a little more, I decided to try another tactic and run
mplayer in a loop to create files for each chapter.  dvdauthor, by
default, creates a chapter per mpg you feed to it.  So I ran a loop with
commands like above, but with the options -chapter 1-1, -chapter 2-2,
-chapter 3-3, and mplexed each one as part of the loop to get
chapter_1.mpg, chapter_2.mpg, chapter_3.mpg, etc...

I'm rolling now.  This actually turned out to be much easier than trying
to grab the chapter times and feed them to dvdauthor.  Especially when
splitting the movie across two discs so that the first chapter of the
second disc started at 00:00:00 and the others were offset
appropriately, etc...

So I run things through dvdauthor, the chapter boundaries come out right
and everything is great except...  at the end of dvdauthor output I get
messages like the following for every chapter except the first chapter
on the first disc:

WARN: GOP is not closed on cell 1 of source chapter_31.mpg of pgc 1
WARN: GOP is not closed on cell 1 of source chapter_32.mpg of pgc 1
WARN: GOP is not closed on cell 1 of source chapter_33.mpg of pgc 1
WARN: GOP is not closed on cell 1 of source chapter_34.mpg of pgc 1
WARN: GOP is not closed on cell 1 of source chapter_35.mpg of pgc 1

And when I play the video on from my newly authored dvd, ugly blocky
things happen at the beginning of each chapter for about a second, that
I'm guessing are related.  Unfortunately I'm not enough of a mpeg guru
to know exactly what "GOP is not closed on cell" means.  I think I
remember it having to do with key frames.  My guess is that the mpegs
have to have a keyframe at the first cell and the way I dumped them out
of mplayer didn't break the video at keyframes but rather at chapter
boundaries, but I'll just let the experts inform me since I'm really
shooting in the dark here.

whew, now my questions:

1) Is there some procedure that makes all this easier that I've
obviously missed?

2) How can I fix my chapter.mpg files without re-encoding (losing
quality) so as not to cause this ugly blocky thing to happen at the
beginning of each chapter?

3) would it have solved these problems to have used a different method
to dump out the original files? What?
-- 
Aaron Peterson <aaron at alpete.com>
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