Flash CS3 Documentation

Programming ActionScript 3.0 > Working with sound > Security considerations when loading and playing sounds

Security considerations when loading and playing sounds

Your application's ability to access sound data can be limited according to the Flash Player security model. Each sound is subject to the restrictions of two different security sandboxes, the sandbox for the content itself (the "content sandbox"), and the sandbox for the application or object that loads and plays the sound (the "owner sandbox"). For more information about the Flash Player security model in general, and the definition of sandboxes, see Flash Player security.

The content sandbox controls whether detailed sound data can be extracted from the sound using the id3 property or the SoundMixer.computeSpectrum() method. It doesn't restrict the loading or playing of the sound file itself.

The domain of origin of the sound file defines the security limitations of the content sandbox. Generally, if a sound file is located in the same domain or folder as the SWF file of the application or object that loads it, the application or object will have full access to that sound file. If the sound comes from a different domain than the application does, it can still be brought within the content sandbox by using a cross-domain policy file.

Your application can pass a SoundLoaderContext object with a checkPolicyFile property as a parameter to the Sound.load() method. Setting the checkPolicyFile property to true tells Flash Player to look for a cross-domain policy file on the server from which the sound is loaded. If a cross-domain policy file exists, and it grants access to the domain of the loading SWF file, the SWF file can load the sound file, access the id3 property of the Sound object, and call the SoundMixer.computeSpectrum() method for loaded sounds.

The owner sandbox controls local playback of the sounds. The application or object that starts playing a sound defines the owner sandbox.

The SoundMixer.stopAll() method silences the sounds in all SoundChannel objects that are currently playing, as long as they meet the following criteria:

• The sounds were started by objects within the same owner sandbox.
• The sounds are from a source with a cross-domain policy file that grants access to the domain of the application or object that calls the SoundMixer.stopAll() method.

To find out if the SoundMixer.stopAll() method will indeed stop all playing sounds, your application can call the SoundMixer.areSoundsInaccessible() method. If that method returns a value of true, some of the sounds being played are outside the control of the current owner sandbox and will not be stopped by the SoundMixer.stopAll() method.

The SoundMixer.stopAll() method also stops the playhead from continuing for all sounds that were loaded from external files. However, sounds that are embedded in FLA files and attached to frames in the timeline using the Flash Authoring tool might start playing again if the animation moves to a new frame.

Flash CS3