MediaStream - Web APIs 编辑

The MediaStream interface represents a stream of media content. A stream consists of several tracks such as video or audio tracks. Each track is specified as an instance of MediaStreamTrack.You can obtain a MediaStream object either by using the constructor or by calling MediaDevices.getUserMedia().

Some user agents subclass this interface to provide more precise information or functionality, like in CanvasCaptureMediaStream.

Constructor

MediaStream()

Creates and returns a new MediaStream object. You can create an empty stream, a stream which is based upon an existing stream, or a stream that contains a specified list of tracks (specified as an array of MediaStreamTrack objects).

Properties

This interface inherits properties from its parent, EventTarget.

MediaStream.active Read only

A Boolean value that returns true if the MediaStream is active, or false otherwise.

MediaStream.ended Read only

A Boolean value set to true if the end of the stream has been reached. This has been removed from the specification; you should instead check the value of MediaStreamTrack.readyState to see if its value is ended for the track or tracks you want to ensure have finished playing.

MediaStream.id Read only

A DOMString containing 36 characters denoting a universally unique identifier (UUID) for the object.

Event handlers

MediaStream.onaddtrack

An EventHandler containing the action to perform when an addtrack event is fired when a new MediaStreamTrack object is added.

MediaStream.onremovetrack

An EventHandler containing the action to perform when a removetrack event is fired when a MediaStreamTrack object is removed from it.

Methods

This interface inherits methods from its parent, EventTarget.

MediaStream.addTrack()

Stores a copy of the MediaStreamTrack given as argument. If the track has already been added to the MediaStream object, nothing happens.

MediaStream.clone()

Returns a clone of the MediaStream object. The clone will, however, have a unique value for id.

MediaStream.getAudioTracks()

Returns a list of the MediaStreamTrack objects stored in the MediaStream object that have their kind attribute set to audio. The order is not defined, and may not only vary from one browser to another, but also from one call to another.

MediaStream.getTrackById()

Returns the track whose ID corresponds to the one given in parameters, trackid. If no parameter is given, or if no track with that ID does exist, it returns null. If several tracks have the same ID, it returns the first one.

MediaStream.getTracks()

Returns a list of all MediaStreamTrack objects stored in the MediaStream object, regardless of the value of the kind attribute. The order is not defined, and may not only vary from one browser to another, but also from one call to another.

MediaStream.getVideoTracks()

Returns a list of the MediaStreamTrack objects stored in the MediaStream object that have their kind attribute set to "video". The order is not defined, and may not only vary from one browser to another, but also from one call to another.

MediaStream.removeTrack()

Removes the MediaStreamTrack given as argument. If the track is not part of the MediaStream object, nothing happens.

Events

addtrack

Fired when a new MediaStreamTrack object is added.
Also available via the onaddtrack property.

removetrack

Fired when a MediaStreamTrack object has been removed.
Also available via the onremovetrack property.

active

Fired when the MediaStream is activated.

inactive

Fired when the MediaStream is inactivated.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using the MediaStream API
• WebRTC API
• Web Audio API
• MediaStreamTrack