ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with sound
Your application can override the global SoundMixer.bufferTime value for an individual sound by explicitly
specifying a new bufferTime value when loading the sound. To override the default buffer time, first create a new
instance of the SoundLoaderContext class, set its bufferTime property, and then pass it as a parameter to the
Sound.load() method, as shown below:
import flash.media.Sound;
import flash.media.SoundLoaderContext;
import flash.net.URLRequest;
var s:Sound = new Sound();
var req:URLRequest = new URLRequest("bigSound.mp3");
var context:SoundLoaderContext = new SoundLoaderContext(8000, true);
s.load(req, context);
s.play();
As playback continues, Flash Player and AIR try to keep the sound buffer at the same size or greater. If the sound data
loads faster than the playback speed, playback will continue without interruption. However, if the data loading rate
slows down because of network limitations, the playhead could reach the end of the sound buffer. If this happens,
playback is suspended, though it automatically resumes once more sound data has been loaded.
To find out if playback is suspended because Flash Player or AIR is waiting for data to load, use the
Sound.isBuffering property.
Working with dynamically generated audio
Flash Player 10 and later, Adobe AIR 1.5 and later
Note: The ability to dynamically generate audio is available starting with Flash Player 10 and Adobe AIR 1.5.
Instead of loading or streaming an existing sound, you can generate audio data dynamically. You can generate audio
data when you assign an event listener for the sampleData event of a Sound object. (The sampleData event is defined
in the SampleDataEvent class in the flash.events package.) In this environment, the Sound object doesn’t load sound
data from a file. Instead, it acts as a socket for sound data that is being streamed to it through the use of the function
you assign to this event.
When you add a sampleData event listener to a Sound object, the object periodically requests data to add to the sound
buffer. This buffer contains data for the Sound object to play. When you call the play() method of the Sound object,
it dispatches the sampleData event when requesting new sound data. (This is true only when the Sound object has not
loaded mp3 data from a file.)
The SampleDataEvent object includes a data property. In your event listener, you write ByteArray objects to this data
object. The byte arrays you write to this object add to buffered sound data that the Sound object plays. The byte array
in the buffer is a stream of floating-point values from -1 to 1. Each floating-point value represents the amplitude of one
channel (left or right) of a sound sample. Sound is sampled at 44,100 samples per second. Each sample contains a left
and right channel, interleaved as floating-point data in the byte array.
In your handler function, you use the ByteArray.writeFloat() method to write to the data property of the
sampleData event. For example, the following code generates a sine wave:
Last updated 6/6/2012
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