Re: [SLUG] preserving a full DVD w/ compression

From: Levi Bard (taktaktaktaktaktaktaktaktaktak@gmail.com)
Date: Wed Sep 05 2007 - 07:47:13 EDT


> > > What would happen if you copied the DVD onto a blank dvd disk and used the
> > > original as the reference copy? Then if you damage the copy you are out a
> > > buck or so? Just wondering.
> >
> > I do this with ALL of my dvds. Burn a copy, play the copy, when/if it
> > gets scratched, burn another copy. I'm sure the MPAA would like to
> > think I've stolen billions of dollars from it by doing so.
> >
> > As for the original question, I'm pretty sure there's not a
> > straightforward way to do it. For one thing, most menus aren't
> > straightforward video streams, so transcoding them would result in
> > nothing usable.
>
> So basically every DVD::rip is a hack of a DVD. I mean, if one isn't
> preserving all of the content, it's a hack. I guess I don't
> understand what a DVD menu really is. I thought it was something like
> a .mov that has functional targets that result in playing another
> video sequence. I thought MPEG2 did this. I guess I'm totally wrong.
> In fact, I was under the impression that MPEG4 went one step further
> to offer better quality and the same functionality.

It's not really a hack; it's *ripping* the movie itself out of the dvd
and transcoding it. If you want to look at it like that, *all*
transcoding is a hack, since encoding to a(nother) lossy format loses
you some of the content.

A DVD menu is generally an image or an MPEG2 stream with buttons
overlaid using a hack of standard subtitle formatting. It has
metadata embedded that associate certain buttons with certain actions
(e.g. selecting button N should result in a jump to title 4 chapter
6). Most video formats, generally being linear video streams are not
set up to deal with this.

> I would even be fine with a hybrid, such as the menu in MPEG2 and the
> rest of the sequences (longer ones) in MPEG4 or another sexy
> compression scheme. However, you're saying it's not even a
> transcoding issue. I guess there are some other factors in there
> besides audiovisual tracks. I still find it hard to believe this is
> impossible or someone hasn't already devised something.

This is not impossible. It's very possible to create some software
that detects menus, preserves them intact, transcodes feature content
to some high-compression format like MPEG4, and alters the menu
metadata to point to the newly transcoded content in the appropriate
places. This, of course, would break the DVD standard, and the
resulting content would only be playable in a custom player that has
been designed specifically to handle this.

Some software may already exist that does this. However, I know of none.

-- 
"Tak does not require that we think of Him, only that we think."
--Grag Bashfullsson
http://www.gnu.org/philosophy/shouldbefree.html
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