54
Client-Side ActionScript Language Reference
Description
Method; sets the minimum input level that should be considered sound and (optionally) the
amount of silent time signifying that silence has actually begun.
■
To prevent the microphone from detecting sound at all, pass a value of 100 for
silenceLevel
;
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.
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. If the audio stream is not silent, the progress bar displays the activity level of
the audio stream.
