User Guide

Microphone 799
■ To prevent the microphone from detecting sound at all, pass a value of 100 for level;
Microphone.onActivity is never invoked.
■ To determine the amount of sound the microphone is currently detecting, use
Microphone.activityLevel.
Activity detection is the ability to detect when audio levels suggest that a person is talking.
When someone is not talking, bandwidth can be saved because there is no need to send the
associated audio stream. This information can also be used for visual feedback so that users
know they (or others) are silent.
Silence values correspond directly to activity values. Complete silence is an activity value of 0.
Constant loud noise (as loud as can be registered based on the current gain setting) is an
activity value of 100. After gain is appropriately adjusted, your activity value is less than your
silence value when you're not talking; when you are talking, the activity value exceeds your
silence value.
This method is similar in purpose to
Camera.setMotionLevel(); both methods are used to
specify when the
onActivity event handler should be invoked. However, these methods have
a significantly different impact on publishing streams:
■ Camera.setMotionLevel() is designed to detect motion and does not affect bandwidth
usage. Even if a video stream does not detect motion, video is still sent.
■ Microphone.setSilenceLevel() is designed to optimize bandwidth. When an audio
stream is considered silent, no audio data is sent. Instead, a single message is sent,
indicating that silence has started.
Availability: ActionScript 1.0; Flash Player 6
Parameters
silenceLevel:Number - An integer that specifies the amount of sound required to activate
the microphone and invoke
Microphone.onActivity(true). Acceptable values range from
0 to 100. The default value is 10.
timeOut:Number [optional] - An integer that specifies how many milliseconds must elapse
without activity before Flash considers sound to have stopped and invokes
Microphone.onActivity(false). The default value is 2000 (2 seconds).
Example
The following example changes the silence level based on the user's input in a
NumericStepper instance called
silenceLevel_nstep. The ProgressBar instance called
silenceLevel_pb modifies its appearance depending on whether the audio stream is
considered silent. Otherwise, it displays the activity level of the audio stream.
var silenceLevel_pb:mx.controls.ProgressBar;