var tvStatic:MovieClip = new MovieClip();
addChild(tvStatic);

var bmpData:BitmapData = new BitmapData(320,240);
var bmp:Bitmap = new Bitmap(bmpData);

tvStatic.addChild(bmp);


addEventListener(Event.ENTER_FRAME,generateStatic, false, 0, true);

private function generateStatic(e:Event){
   bmpData.noise(Math.floor(100000*Math.random()), 0, 255,0, true);
}

Generate snow, like on a TV set.

Generate TV static in AS3

ActionScript 3