[maemo-developers] opencv for arm WAS: signedness of char on ARM vs x86

[From: Jesus A. Baro]

Hello, Andrew.
Thanks for the information, really helpful.
Does anybody have any experience on using the n8x0's camera from opencv?

Bad news come from maemo's How to use the Camera API :
"*Since the maemo Platform delegates all multimedia handling to the
GStreamer framework, applications that need access to the built-in camera
should employ GStreamer for this instead of directly acessing Video4Linux
devices, via the v4l2src GStreamer module.*"

My attempts involved:

CvCapture * cap;
...
cap= cvCaptureFromCAM (-1);
and I get:
HIGHGUI ERROR: V4L: device /dev/video0: Unable to query number of channels

BTW, a very interesting tutorial, albeit in spanish, may be found at "
http://dis.um.es/~ginesgm/files/doc/pav/guion3.pdf"

Thank you,

Jesus A. Baro
Universidad de Valladolid

On Fri, Apr 11, 2008 at 8:33 PM, Andrew Daviel <advax at triumf.ca> wrote:

> On Sun, 6 Apr 2008, Jesus A. Baro wrote:
>
>  Hy Andrew,
> > It just may be that fun with char arithmetics is not at the root of the
> > trouble.
> > Opencv compiles ok for me under both arm and x86. The trick came form
> > ArnimS
> > at internettabletalk: change -03 to -02.
> >
>
> I had to recompile cvpyrsegmentation with -O2; did that by hand and
> restarted make, but otherwise used -O3
> Also did export PYTHON=/usr/bin/python2.5 ; ./configure as I recall.
> I'm not using Python; just to get the build to run.
>
> I see it's trivial to make an image converter from e.g. JPEG to PNG with
> opencv, e.g.
>
> http://www.cs.iit.edu/~agam/cs512/lect-notes/opencv-intro/opencv-intro.html<http://www.cs.iit.edu/%7Eagam/cs512/lect-notes/opencv-intro/opencv-intro.html>
>
> My real problem is that libdecodeqr I'm trying to use fails on 10% of
> codes for no obvious reason, and qrcode in jaimo is way too slow :-(
>
> Andrew
>
>
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