Dataton WATCHOUT User's Guide

Using Transparency
Computer generated movie with
transparent background and semitransparent
drop shadow playing
over a background image.
Some applications support inclusion of transparency information in the generated
QuickTime movie file. Such transparency can either come from the source
material (eg, a computer generated animation), or be added afterwards (for
example, a feathered, round mask applied to a video clip).
Being able to create arbitrarily shaped movies, or movies with holes in them,
means you can combine moving and still images in many creative ways.
In order to include transparency information in the movie file, you must choose
a codec that’s capable of handling “Millions+” of colors. The “+” at the end
stands for the transparency information. This is sometimes also called
“Millions+Alpha”. You must also use an application that’s capable of reproducing
and/or generating transparency information, such as After Effects).
See “Making a Round Movie” on page 73 for more details.
When masking video material in this way, crop the resulting movie to minimize
the size of the enclosing frame while still retaining all important image information.
For example, if you need only the upper left portion of a video frame,
only save the minimum rectangular area (see illustration). Doing so cuts the
amount of processing required to play back the video as time is not wasted on
de-compressing parts of the image that will never be shown anyway.
Original movie size.
Masked out circle.
Crop rectangle.
72 Chapter 6: Media Files