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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.
What is a
Sync Track?
A Sync Track is a one measure sound clip that is recorded
at the same tempo as the Sound Family. It is a multiple in length
of every component (layers and chunks) in a Sound Family. It also
has an audio spike at the beginning of the clip, which provides
the visual reference on your Flash timeline that corresponds to
every musical measure. By inserting this low-resolution clip throughout
the length of your movie soundtrack with a SYNC SETTING of STREAMING,
we can force Flash's frame rate to be constant and determine when
to trigger the next chunk.
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