Alpha channel support lets you encode video in which Flash removes and saves the background as a transparency. This allows you to overlay (or composite) the video on top of other Flash content, while the subject of the video remains in the foreground. For example, you can use alpha channels to record a video clip of a presenter using a blue screen as a backdrop. You can then encode the video with an alpha channel and place the presenter in front of another image as the backdrop to the video. Bitmap filter effects let you use ActionScript to apply filters.
