Monitoring the Webcam

To monitor changes in the video stream captured from the webcam, you need to take regular snapshots of the video object. I use setInterval to call a snapshot function every x milliseconds. Then, to actually determine whether there has been movement, at any moment in time two bitmaps have to be in memory—the bitmap created last time a snapshot was taken (“before”) and a bitmap containing the current state of the video (“now”). Using the BitmapData class you can then compare the two bitmaps:

import flash.geom.Matrix
 import flash.display.BitmapData 

 setInterval(this,"snapshot",100);
 now=new BitmapData(output_vid.width,output_vid.height);
 m=new Matrix();

  function snapshot()
 {
     now.draw(output_vid,m); 
     //…… code that check's difference between 'now' and 'before'
      before=now.clone();
 }