OpenCV

Single image

You can use imgsrv to download a single image from the circbuf. MJPEG live stream is also available from imgsrv.

You can use wget to download the image to your computer or implement a small HTTP client in your software.

Live video

Using AVLD

AVLD stand for AVLD - Another Video Loopback Device. It's a very CPU and RAM consuming way to present an Elphel network camera as V4l device.

While it is the only solution with proprietary v4l compatible software products (such as skype), it's a total waste of resources for a free software app what can be adapted to receive an RTP stream.

Moreover, you can downloa from:

 http://allonlinux.free.fr/Projets/AVLD/src/avld_0.1.4.tar.bz2

Then:

 $ tar -jxvf avld_0.1.4.tar.bz2
 $ cd avld_0.1.4
 $ make && sudo make install

Right now you can mount your dummy device typing:

 $sudo modprobe avld width=<camera width resolution> height=<camera height resolution> fps=<camera fps>

Finally, you need to use mencoder in order to redirect the rtsp source to the dummy device:

 $ sudo mencoder rtsp://192.168.1.180 -nosound -ovc raw -vf format=bgr24 -of rawvideo -o /dev/video0

With this, you just need a simple code in order to preview the scene:

 #include "highgui.h"
 #include "cv.h"
 #include "cvaux.h"
 #include <ml.h>
 
 int main(int argc,char *argv[])
 {
   IplImage* pCurrentFrame = NULL;
   CvSize frame_size;
   CvCapture* capture = cvCaptureFromCAM ( 0 ); //the dummy device make the job :)
   char c;
   while ( 1 )
     {
       //Request frame from Camera

pCurrentFrame = cvQueryFrame ( capture ); //video input file finished if( !pCurrentFrame ) break;

       cvShowImage( "Current Frame", pCurrentFrame );
       c = cvWaitKey(10);
       if ( c == 27 ) break;
     }
   cvReleaseImage ( &pCurrentFrame );
   cvDestroyAllWindows ();
   return 0;
 }

Using v4lsink GStreamer plugin and v4l2loopback

This is basically an AVLD fork that now evolved into v4l2loopback and a special gstreamer sink to the loopback device.

http://code.google.com/p/v4lsink/ & http://code.google.com/p/v4l2loopback/

Design your OpenCV code as GStreamer plugin

http://github.com/Elleo/gst-opencv

Tutorials

Tennis balls recognizing

OpenCV Tennis balls recognizing tutorial

Go game record (kifu) generator

Kifu:_Go_game_record_(kifu)_generator