Re: image/data acquisition toolbox

[Brendan Drew]

I can't say much for the DAQ side, but for the image acquisition side, I 
can say this:

DirectX under Windows is a nightmare to work with. It has some 
interesting design philosophies, but the whole COM/DCOM/ActiveX/whatever 
they're calling it this week aspect is hellish to work with. Robert 
Laganiere has a good tutorial on some of the basics of talking to an 
image source (be it a camera or a video stored as an mpeg), but it is 
not for the feint of heart. You're going to be fighting a number of 
things: hooking up the right codecs in the right order, making sure that 
all the data agress on what format it should be used in (e.g: YUV4:2:2 
packed versus RGB planar versus RGB16 versus YUV4:1:1, etc.) Unless you 
do something like Intel did in OpenCV with their ProxyFilter (it takes a 
user supplied callback which operates on IplImage* structures, the 
filter itself takes care of making sure everything is in the correct 
format, etc.), this problem is going to be largely not worth solving 
under Windows.

The story under Linux is quite a bit different. While interfacing with 
Ffmpeg is... "non-trivial" (to say the least, the documentation is 
largely non-existent), using the same libraries that Ffmpeg does to do 
its raw acquisition is pretty easy. If you've got a V4L device, the 
kernel interface is pretty reasonable (all you would need to keep track 
of in your program is the file handle you're talking to the device 
with). If you want DCAM or DV, these are also doable, but require that 
you keep around pretty large data structures. I'm not quite sure how one 
would go about doing this in Octave, but if you can have Octave manage 
your handles and what not in a form that you can return to users, you're 
good to go.

Making this work on a Mac is... an interesting challenge. The only way I 
am aware of getting access to video sources (be it a live camera or a 
stored video) on a Mac is via QuickTime (or doing things the hard way 
via Ffmpeg).

Long story short, I don't believe that there is any cross platform way 
to do the image acquisition side of things. That said, I will gladly eat 
my words if I'm wrong (and buy at least one round at the pub for 
whomever shows me a better way to do things!)

Claudia Calcagno wrote:

> Hi Andrey,
>
> that sounds like a good idea: thank you for the suggestion, I didn't 
> know about that project.
> The drivers shouldn't be a problem, since I only want to use the audio 
> card
> (and it works under linux).
> Basically I think I am interested in what daqplay demo should do (I 
> only want
> to output an analog signal through the audio card and ): I didn't have 
> the chance to try
> that yet, since it is on windows only.
>
> For John : More generally I think that would be an interesting 
> project, which I will be totally happy to work on.
>
> Thanks to everybody,
>
> Claudia
>
> > Can't say anything about image processing, but as for DAQ, you may 
> > try to throw together an Octave binding  to COMEDI (www.comedi.org). 
> > Does your DAQ hardware have Linux drivers?
> >
> > Andrey
> >
> >
> >
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>
>
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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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