Re: software for manipulating AVI files

[Brendan Drew]

Funny you should mention this --- I almost exclusively use Octave as a 
prototyping environment for machine vision and video processing 
algorithms ;-)

Unfortunately, the AVI file format is not quite as simple as one would 
want to believe. AVI is merely a container format, it makes no 
statements about how things are compressed or decompressed. Depending on 
the codecs you're using, things can become very complicated very quickly 
(specifying which codec and then specific parameters for that codec, 
followed by relevant sanity checking, correctly matching AVI streams to 
codecs when you have multiple versions to choose between, etc.)

Under Windows, this can very quickly become a nightmare. (DirectX is yet 
another homage to a good idea whose implementation was screwed beyond 
recognition by MS). The Unix tools aren't much better, at least in my 
experience. FFmpeg tends to be a fairly iffy proposition at best (I seem 
to have a talent for crashing it on a fairly regular basis in such a way 
as to completely lock at least X, if not portions of the kernel). That 
said, ffmpeg does have some nice advantages --- if compiled correctly, 
you can use any V4L2 or DCAM/IIDC compliant camera as a video source.

At present, I use ffmpeg to extract frames and then run my algorithms 
over the sequence of frames. This works well enough for my purposes. 
When I need to produce video files, ffmpeg can convert the frames into 
basically any format and codec I could care to use. Long story short: I 
don't know that the utility of solving this problem outweights the costs 
involved in solving it as well as Matlab has. ("as well as Matlab has" 
means no support for compressed AVIs under non-Windows platforms and 
using DirectX under Windows in this case)

Just my $0.02.

John W. Eaton wrote:

> On 29-Sep-2005, Søren Hauberg wrote:
>
> | I don't know about it's dependencies, but I think Gstreamer
> | (http://gstreamer.freedesktop.org/) would be nice for Octave. It's a
> | multi-format library, so you would get more then just avi support. It's
> | a LGPL library and it's a very active project.
>
> Yes, I suppose it might be nice to have bindings for such a general
> purpose library.  But it seems like overkill for what I want, which is
> just a simple way to read and write a particular file format.  Looking
> at the gstreamer docs does not help much for me as the unfamiliar
> jargon has my head spinning.  Perhaps there is someone on the list
> familiar with gstreamer who can point the way to implementing
> something simple like reading and writing AVI files?
>
> jwe
>
>
>
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--
Brendan Drew
Research Scientist
PercepTek, Inc.
12395 North Mead Way
Littleton, CO 80125
Tel: 720-344-1037 x 126
Fax: 720-344-2360



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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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