DisplayMediaStreamConstraints.audio - Web APIs 编辑

The DisplayMediaStreamConstraints dictionary's audio property is used to specify whether or not to request that the MediaStream containing screen display contents also include an audio track. This value may be a Boolean, where true indicates that an audio track should be included an false (the default) indicates that no audio should be included in the stream.

More precise control over the audio data may be exercised by instead providing a MediaTrackConstraints object, which is used to process the audio prior to adding it to the stream.

Note: The specification for the Screen Capture API does not define what the contents of the audio track should be. This is left up to the user agent to decide. Likely sources are the computer's system audio output and the user's microphone, but there is no way to specify which source to use.

Syntax

displayMediaStreamConstraints.audio = allowAudioFlag;
displayMediaStreamConstraints.audio = mediaTrackConstraints;

displayMediaStreamConstraints = {
  audio: allowAudioFlag|mediaTrackConstraints;
}

Value

The value may be either a Boolean or a MediaTrackConstraints object.

If a Boolean is specified, a value of true indicates that an audio track should be included in the stream returned by getDisplayMedia(), if an appropriate audio source exists and the user agent supports audio on display media. A value of false—the default—indicates that no audio track is to be included in the stream.

If a MediaTrackConstraints object is given, and an audio source is available, an audio track matching the settings given in the constraints object is included in the MediaStream returned by getDisplayMedia().

If no audio source is available, or the user agent doesn't support audio tracks with getDisplayMedia(), the returned MediaStream has no audio track, but no error occurs. The audio track is always considered optional.

Example

Specifications

See also

• Screen Capture API
• Using the Screen Capture API
• Capabilities, constraints, and settings