- AVLD -
Another Video Loopback Device

AVLD is a V4L dummy video device built to simulate an input video device like a webcam or a video capture card. You just have to send the video stream on it (using, for instance, mplayer or ffmpeg), that's all. Then, you can use this device by watching the video on it with your favorite video player. But, one of the most useful interest, is obviously to use it with a VideoConferencing software or Adobe Flash application to show a video over internet. According to the software you are using, you could also be able to capture your screen in realtime. A third interest, and maybe not the last one, could be to use it with an image processing(or other) software which has been designed to use a video device as input.

Download :

You can download AVLD here : avld_0.1.4

Changelog is available here : Changelog

Install :

First of all, you need to install headers of your running kernel to compile AVLD.

Log in as root and type

Run :

• LOAD the AVLD module as root :

  modprobe avld
  
  !!! Be careful that the default video size is 340x240 !!!

  You can specify the video size and the framerate of the input video like that :

  modprobe avld width=640 height=480 fps=25
  

  FPS values:

  • fps = 0 : no framerate. Input video stream is read by device as fast as it is written to the device
  • fps > 0 : the framerate is set to the given value
  • fps < 0 : framerate is synchonized on the reader application
  
  

• WRITE on the device :

  mencoder my_movie.*** -nosound -ovc raw -vf format=bgr24 -of rawvideo -o /dev/video0
  ( or /dev/video1 if you have loaded another video device before AVLD... )
  Note : be careful to send to the dummy video device a video with the exact same size than this used when you loaded the module. You can also scale the video size with mencoder.
  
  
  

• USE the Videoconferencing software of your choice (amsn, gnomemeeting, Skype ...) or mplayer if you want to check that it works on your computer :

  mplayer tv:// -tv "driver=v4l:device=/dev/video0:noaudio:outfmt=rgb24"
  
  
  

• Once you have loaded the module, if you want to CHANGE the video paremeters (width/height/framerate), it is now possible by sending the entire following line to the device :

  "width=[new_video_width] height=[new_video_height"] fps=[new_video_fps]"

  Example :

  echo "width=800 height=600 fps=25" > /dev/video0