ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with sound
Know exactly when a sound finishes playing
Track the playback progress of a sound
Change volume or panning while a sound plays
To perform these operations during playback, use the SoundChannel, SoundMixer, and SoundTransform classes.
The SoundChannel class controls the playback of a single sound. The SoundChannel.position property can be
thought of as a playhead, indicating the current point in the sound data that’s being played.
When an application calls the Sound.play() method, a new instance of the SoundChannel class is created to control
the playback.
Your application can play a sound from a specific starting position by passing that position, in terms of milliseconds,
as the startTime parameter of the Sound.play() method. It can also specify a fixed number of times to repeat the
sound in rapid succession by passing a numeric value in the loops parameter of the Sound.play() method.
When the Sound.play() method is called with both a startTime parameter and a loops parameter, the sound is
played back repeatedly from the same starting point each time, as shown in the following code:
var snd:Sound = new Sound(new URLRequest("repeatingSound.mp3"));
snd.play(1000, 3);
In this example, the sound is played from a point one second after the start of the sound, three times in succession.
Pausing and resuming a sound
Flash Player 9 and later, Adobe AIR 1.0 and later
If your application plays long sounds, like songs or podcasts, you probably want to let users pause and resume the
playback of those sounds. A sound cannot literally be paused during playback in ActionScript; it can only be stopped.
However, a sound can be played starting from any point. You can record the position of the sound at the time it was
stopped, and then replay the sound starting at that position later.
For example, let’s say your code loads and plays a sound file like this:
var snd:Sound = new Sound(new URLRequest("bigSound.mp3"));
var channel:SoundChannel = snd.play();
While the sound plays, the SoundChannel.position property indicates the point in the sound file that is currently
being played. Your application can store the position value before stopping the sound from playing, as follows:
var pausePosition:int = channel.position;
channel.stop();
To resume playing the sound, pass the previously stored position value to restart the sound from the same point it
stopped at before.
channel = snd.play(pausePosition);
Monitoring playback
Flash Player 9 and later, Adobe AIR 1.0 and later
Your application might want to know when a sound stops playing so it can start playing another sound, or clean up
some resources used during the previous playback. The SoundChannel class dispatches an Event.SOUND_COMPLETE
event when its sound finishes playing. Your application can listen for this event and take appropriate action, as shown
below:
Last updated 6/6/2012
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