MediaStreamTrack.enabled - Web APIs 编辑

The enabled property on the MediaStreamTrack interface is a Boolean value which is true if the track is allowed to render the source stream or false if it is not. This can be used to intentionally mute a track. When enabled, a track's data is output from the source to the destination; otherwise, empty frames are output.

In the case of audio, a disabled track generates frames of silence (that is, frames in which every sample's value is 0). For video tracks, every frame is filled entirely with black pixels.

The value of enabled, in essence, represents what a typical user would consider the muting state for a track, whereas the muted property indicates a state in which the track is temporarily unable to output data, such as a scenario in which frames have been lost in transit.

Note: If the track has been disconnected, the value of this property can be changed, but has no effect.

Syntax

const enabledFlag = track.enabled
track.enabled = [true | false]

Value

When true, enabled indicates that the track is permitted to render its actual media to the output. When enabled is set to false, the track only generates empty frames.

Empty audio frames have every sample's value set to 0. Empty video frames have every pixel set to black.

Note: When implementing a mute/unmute feature, you should use the enabled property.

Usage notes

If the MediaStreamTrack represents the video input from a camera, disabling the track by setting enabled to false also updates device activity indicators to show that the camera is not currently recording or streaming. For example, the green "in use" light next to the camera in iMac and MacBook computers turns off while the track is muted in this way.

Example

This example demonstrates a click event handler for a pause button.

pauseButton.onclick = function(evt) {
  const newState = !myAudioTrack.enabled;

  pauseButton.innerHTML = newState ? "▶️" : "⏸️";
  myAudioTrack.enabled = newState;
}

This creates a variable, newState, which is the opposite of the current value of enabled, then uses that to select either the Emoji character for the "play" icon or the character for the "pause" icon as the new innerHTML of the pause button's element.

Finally, the new value of enabled is saved, making the change take effect.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• MediaStream API
• MediaStream
• MediaStreamTrack
• WebRTC