20 Introduction
Alpha channel support Alpha channels let you encode video such that the background is
removed and saved as a transparency. This lets you overlay (or composite) the video on top of
other Flash content, while the subject of the video remains in the foreground. For example, a
common use of alpha channels is to record a video clip of a presenter using a blue screen as a
backdrop. The video can then be encoded with an alpha channel, and the presenter can be
placed in front of another image as the backdrop to the video. For more information, see
“Specifying advanced encoding settings (Flash Professional only)” on page 294.
Embedded cue points The Flash Video Encoder lets you embed cue points directly into
your Flash Video (FLV) files. Cue points cause the video playback to trigger other actions
within the presentation, letting you synchronize the video with animation, text, graphics, and
other interactive content. Used in conjunction with the new Flash Video component
FLVPlayback, you can coordinate the playback of a video clip with accompanying interactive
content when individual cue points are reached. For example, you can create a Flash
presentation that has video playing in one area of the screen while descriptive text and
graphics appear in another area. Cue points cause the video playback to trigger these other
actions in the presentation, letting you create richer interactive content. “Using the
FLVPlayback component (Flash Professional only)” on page 304.
Enhancements to ActionScript 2.0
The ActionScript language has grown and developed since its introduction several years ago.
With each new release of Flash, additional keywords, objects, methods, and other language
elements have been added to ActionScript. There are also ActionScript-related improvements
to the Flash 8 authoring environments. Flash Basic 8 and Flash Professional 8 introduce
several new language elements for expressive features, such as filters and blending modes, and
application development, such as JavaScript integration (
ExternalInterface) and File I/O
(
FileReference and FileReferenceList).
To learn more about the improvements made to ActionScript 2.0, see “What’s New in Flash 8
ActionScript” in Learning ActionScript 2.0 in Flash.
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