Using Component Audio (Chunks) and SyncTracks to Create Compelling Soundtracks with Small File Sizes - Page 4
Forcing Flash's Frame Rate
Flash allows you to select a frame rate for your movie between 1 frame per second and 30 frames per second. The two most common rates are 12fps and 15fps, but any rate is acceptable to a tenth of a frame per second resolution. The tricky part is that no matter what frame rate you pick, actual playback is dependent on the user's processor and the complexity of the movie. So even though you may choose 12fps, your audience may only experience 10fps, or 6fps. This poses a problem when trying to synchronize audio and graphic elements in your Flash movie.
It's fairly easy to synchronize the beginning of a sound clip with an event by simply triggering the audio at the same keyframe as your event. But what if you want to synchronize something with the end of a sound clip, like another sound clip, as in our Lego example? How do you know on which keyframe to trigger your second clip? We need to know what frame the timeline is on when one chunk finishes, so we can then trigger the next chunk to build our arrangement.
In order for all of this to work, we have to force Flash to keep a precise, consistent frame rate. We could set the sound SYNC METHOD to STREAMING for all of our sounds, but this would increase our file size by a factor of 10 or more.
The answer is what DoReMedia calls a Sync Track. Every Sound Family comes with a corresponding, tempo-matched Sync track. The purpose of the Sync Track is two-fold. It forces Flash's frame rate to be constant, and it provides a very useful visual reference which can be used to avoid trial and error in placing and synchronizing sound clips.
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