ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with sound
Left Channel Right Channel
Left Channel Right Channel
Values returned by the SoundMixer.computeSpectrum() method
A. fftMode=true B. fftMode=false
The computeSpectrum() method can also return data that has been resampled at a lower bit rate. Generally, this
results in smoother waveform data or frequency data at the expense of detail. The stretchFactor parameter controls
the rate at which the computeSpectrum() method data is sampled. When the stretchFactor parameter is set to 0,
the default, the sound data is sampled at a rate of 44.1 kHz. The rate is halved at each successive value of the
stretchFactor parameter, so a value of 1 specifies a rate of 22.05 kHz, a value of 2 specifies a rate of 11.025 kHz, and so
on. The computeSpectrum() method still returns 256 bytes per stereo channel when a higher stretchFactor value
is used.
The SoundMixer.computeSpectrum() method has some limitations:
Because sound data from a microphone or from RTMP streams do not pass through the global SoundMixer object,
the SoundMixer.computeSpectrum() method will not return data from those sources.
If one or more of the sounds being played come from sources outside the current content sandbox, security
restrictions will cause the SoundMixer.computeSpectrum() method to throw an error. For more detail about the
security limitations of the SoundMixer.computeSpectrum() method please see “Security considerations when
loading and playing sounds” on page 454and “Accessing loaded media as data” on page 1054.
However, in an AIR application, content in the application security sandbox (content installed with the AIR
application) are not restricted by these security limitations.
Building a simple sound visualizer
Flash Player 9 and later, Adobe AIR 1.0 and later
The following example uses the SoundMixer.computeSpectrum() method to show a chart of the sound waveform
that animates with each frame:
Last updated 6/6/2012
A
B
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