[MPlayer-dev-eng] XviD

[Christoph Lampert]

Hi all,

sorry, I changed the list to "daily digest" (which arrives every
few hours now), so I can't quote correctly... I hope I'll remember
to answer everything:

1) Many bugs in XviD were fixed, one is not, because it wasn't a bug
in XviD but a bug with MPEG-quantization in DivX4 (and of course it's
still there in DivX5). If you have anything specific, please write
bugreports to team at xvid.org 

2) B-frames are coming. It's possible to implement them, but it's not
easy to do the encoding in a clever way. E.g. DivX5 creates AVIs with
audio lag and the first frame is shown twice as long than normal :-( We
don't want to use the same method. Also, we want possibility of a
IBBPBBPBB GOP (like normal MPEG2), not only IBPBPBP like DivX5. 

3) We had a version including quartel-pel ME, but it was slow and did 
not give much improvement. Maybe it was buggy, anyhow it did not make it
into CVS. When B-frames are in, we'll come back to that. Any other
features new of DivX5 are unknown to me at the moment, if you know 
exactly what elements of MPEG4 they are using, please inform everyone.

4) XviD is FAST for encoding, much faster than DivX4 and still faster
than DivX5. It's somewhat slower for decoding than ffodivx, true. 
But that's no reason to not make it DivX5 compatible, is it? 
I looked into ffmpeg code because I know it's heavily optimized, but 
saw no easy way of including ffmpeg's routines into XviD or vice versa. 
Actually I liked XviD decoder source better...

5) XviD plays ALL MPEG-4 simple profile contents (+ larger dimensions). 
Actually it's more compatible than DivX4 when it comes to MPEG-4.
It does not play DivX3.11 at the moment, it's not the top priority to
us, although there is some working code for it including one-the-fly DivX3
to MPEG4 conversion. Pete who did that just found a new job, so he's a 
little busy doing other things at the moment.

6) XviD switched from inline assembler to NASM, because it's a Windows and
Linux application and we needed a tool that is accepted on both
plattforms. However, there is not very much work going on at nasm at the
moment (there is P4 support now, but no 64-bit etc.). The latest release
if from '99 and has several problems, e.g. with P4.  
In the long range, XviD might have to switch to YASM instead. I doubt
that GAS is an alternative for the Windows people, which is the majority
of XviD users! 

7) There hasn't been a release of XviD, because there are still a few
code lines from OpenDivX (or that from MoMuSys reference code, as it's
only in the encoder's part). Also, code changes very often, not always
staying comaptible. We still consider it alpha code. 
For the moment, it's more about the developers' fun than about spreading
it out to as many users as possible. But when GPL is reached (soon), there
will be a first release, I'm quite sure about that. 

8) Since Pete has less time now and I'm busy with my PhD, we are 
looking for skilled people to help a little. At the moment, our target
is rather quality than speed, but also many things have to be optimized. 
If you have any spare time, have a look at the forum at 
http://www.xvid.org or write "hello" to team at xvid.org ;-)

Christoph

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