AVLD - Another Video Loopback Device

AVLD is a video loopback device for GNU-Linux, written by Pierre Parent and licensed under GPL.

With AVLD you can use Elphel cameras for image acquisition in v4l compatible applications, video conferencing, etc

Video is playing smoothly on a 2.4Ghz dual core notebook at 25fps in 1440x896,

and CPU usage is 'only' 20-25% per core

I could not test beyond the screen and the specific camera/sensor capabilities :)

avld-0.13 VIDIOCGWIN null framesize patch

Opencv v4l capture initialization method was receiving a framesize of 0x0 when it was run before watching once the stream with mplayer which is using an alternative initialization method.

--- video_device.c.orig 2008-09-14 21:28:41.000000000 +0200
+++ video_device.c      2008-09-14 22:00:35.000000000 +0200
@@ -212,7 +212,10 @@
                        #ifdef DEBUG
                                printk (KERNEL_PREFIX "VIDIOCGWIN\n");
                        #endif
-
+
+                       capture_win.width=width;
+                       capture_win.height=height;
+
                        if(copy_to_user((void*)arg, &capture_win, sizeof(capture_win)))
                                return -EFAULT;
                        return 0;

Accessing Elphel camera streams through a v4l device (eg: /dev/video0)

After loading the AVLD module:

modprobe avld width=1440 height=896 fps=0

You just have to feed the video device:

mencoder rtsp://192.168.0.9 -nosound -ovc raw -vf format=bgr24 -of rawvideo -o /dev/video0

(or /dev/video1 if you had already another video device driver loaded before)

And you can play the stream for testing:

mplayer tv:// -tv driver=v4l:device=/dev/video0:outfmt=rgb24 -cache 8192 -vo xv

You can change the device parameters when module is already loaded with:

echo "width=800 height=600 fps=0" > /dev/video0

AVLD homepage: http://allonlinux.free.fr/Projets/AVLD/