[vorbis-dev] video codec

[Kenneth Arnold]

On Wed, Feb 07, 2001 at 07:37:59PM -0800, Ralph Giles wrote:
> On Thu, 8 Feb 2001, Lourens Veen wrote:
> 
> > Okay, now the only problem is that I don't have any video4linux hardware
> > so I can't test your program...I imagine I'm not the only one.
> 
> To answer the other possible meaning of that, you can get some reasonable
> test video by rendering animations. Povray and BMRT are two good examples.
> There are some reasonable scenes available for download; you may have to
> dig a bit to find things complex enough to make good 'video' tests. (BMRT
> is better in this respect, but the images it produces are non-free.)
> 
> Another big one is you can rip from dvd (assuming you have a drive of
> course) If you downsample the encoding artifacts shouldn't be too bad.
> Same goes for vcd, I suppose, but that doesn't leave much room to see
> anything.
> 
> There's a 32-image sequence in jack's tarkin-experimental release.
> (on vorbis.com/~jack)

Unless he's changed it, those images all have an ugly bar through the
middle that the encoder is probably having a hard time with. Hack
avifile for AVI->pnm or whatever you use.

> Collecting a free set of test clips has been on my todo list for a while.
> If there's demand I can step that up a bit. Subject suggestions welcome,
> but I imagine we won't know what's hard to encode until we start trying.

I have a lot of copyrighted material (too bad I couldn't rip the
Superbowl; I had a studio HDTV receiver but no cables and inputs to
rip the MPEG2), but that won't help, and I'm behind a slow modem so it
wouldn't help anyway. There might be some video at US Government web
sites, or various archive footage or whatnot (anyone have the
Challenger launch?).

If you're totally starved for video, a regular snapshot of your
desktop moving windows around should provide something to play with
motion compensation with. Or take a whole roll of pictures with a
camera that can do that, and if 35mm camera, scan them all; if digital
camera, just link them all in. It's not going to be over about 15 frames per
second with a good camera, but you'll still get something to play
with. Or find a good friend with a (a) webcam or (b) iMac or G4 and a
newer Sony camera.

I'm similarly without vidcap cards. Well I borrowed one once and stuck
it in my computer, but it was broken already so that doesn't count.

If you give me something to try out, I have a Matrix DivX rip here, as
well as two DVDs still in MPEG2 (but I had to return the drive to its
owner so I can't rip any more). That should provide for ample material
to play with I would think. I'd like to try out a few things on my
own; the one video compression subject that I don't know and can't
readily find out about is wavelets. Can anyone suggest a good
(Internet preferrable) resource for the ins and outs of wavelets? And
is there better (I've seen chirplets)? My work at the moment is more
on the framework level; I want to mess around with a codec inside
also. I was planning on trying to encapsulate OpenDivX, but the
library is turning out to be a paininthebutt, and the encoder isn't
ported to Linux yet either. So I'll have a whack at this
integer-wavelet codec.

Thanks,

-- 
Kenneth Arnold <ken at arnoldnet.net> / kcarnold / Linux user #180115
http://arnoldnet.net/~kcarnold/



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