MediaStreamTrack

The MediaStreamTrack interface represents a single media track within a stream; typically, these are audio or video tracks, but other track types may exist as well.

Properties

In addition to the properties listed below, MediaStreamTrack has constrainable properties which can be set using applyConstraints() and accessed using getConstraints() and getSettings(). See Capabilities, constraints, and settings to learn how to correctly work with constrainable properties. Not doing so correctly will result in your code being unreliable.

MediaStreamTrack.contentHint

A string that may be used by the web application to provide a hint as to what type of content the track contains to guide how it should be treated by API consumers.

MediaStreamTrack.enabled

A Boolean whose value of true if the track is enabled, that is allowed to render the media source stream; or false if it is disabled, that is not rendering the media source stream but silence and blackness. If the track has been disconnected, this value can be changed but has no more effect.

Note: You can implement standard "mute" functionality by setting enabled to false. The muted property refers to a condition in which there's no media because of a technical issue.

MediaStreamTrack.id Read only

Returns a DOMString containing a unique identifier (GUID) for the track; it is generated by the browser.

MediaStreamTrack.isolated Read only

Returns a Boolean value which is true if the track is isolated; that is, the track cannot be accessed by the document that owns the MediaStreamTrack. This happens when the peerIdentity property is set, or if the track comes from a cross-origin source.

MediaStreamTrack.kind Read only

Returns a DOMString set to "audio" if the track is an audio track and to "video", if it is a video track. It doesn't change if the track is deassociated from its source.

MediaStreamTrack.label Read only

Returns a DOMString containing a user agent-assigned label that identifies the track source, as in "internal microphone". The string may be left empty and is empty as long as no source has been connected. When the track is deassociated from its source, the label is not changed.

MediaStreamTrack.muted Read only

Returns a Boolean value indicating whether the track is unable to provide media data due to a technical issue.

Note: You can implement standard "mute" functionality by setting enabled to false, and unmute the media by setting it back to true again.

MediaStreamTrack.readonly Read only

Returns a Boolean value with a value of true if the track is readonly (such a video file source or a camera that settings can't be modified), false otherwise.

MediaStreamTrack.readyState Read only

Returns an enumerated value giving the status of the track. This will be one of the following values:

• "live" which indicates that an input is connected and does its best-effort in providing real-time data. In that case, the output of data can be switched on or off using the enabled attribute.
• "ended" which indicates that the input is not giving any more data and will never provide new data.

MediaStreamTrack.remote  Read only

Returns a Boolean with a value of true if the track is sourced by a RTCPeerConnection, false otherwise.

Methods

MediaStreamTrack.applyConstraints()

Lets the application specify the ideal and/or ranges of acceptable values for any number of the available constrainable properties of the MediaStreamTrack.

MediaStreamTrack.clone()

Returns a duplicate of the MediaStreamTrack.

MediaStreamTrack.getCapabilities()

Returns the a list of constrainable properties available for the MediaStreamTrack.

MediaStreamTrack.getConstraints()

Returns a MediaTrackConstraints object containing the currently set constraints for the track; the returned value matches the constraints last set using applyConstraints().

MediaStreamTrack.getSettings()

Returns a MediaTrackSettings object containing the current values of each of the MediaStreamTrack's constrainable properties.

MediaStreamTrack.stop()

Stops playing the source associated to the track, both the source and the track are deassociated. The track state is set to ended.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface:

ended

Sent when playback of the track ends (when the value readyState changes to ended).
Also available using the onended event handler property.

mute

Sent to the MediaStreamTrack when the value of the muted property is changed to true, indicating that the track is unable to provide data temporarily (such as when the network is experiencing a service malfunction).
Also available using the onmute event handler property.

isolationchange

Sent whenever the value of the isolated property changes due to the document gaining or losing permission to access the track.
Also available through the onisolationchange event handler property.

overconstrained

Send when the constraints specified for the track cause the track to be incompatible and therefore to not be used.
Also available through the onoverconstrained event handler property.

unmute

Sent to the track when data becomes available again, ending the muted state.
Also available through the onunmute event handler property.

Obsolete events

started

Sent when the track exits the new readyState.
Also available through the onstarted event handler property.

Specifications

Browser compatibility

See also

• Media Capture and Streams API
• MediaStream
• AudioStreamTrack and VideoStreamTrack
• Using the MediaStream API