webrtc学习——mediaStream和MediaStreamTrack
This is an experimental technology
Because this technology‘s specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.
The MediaStream
interface represents a stream of media content. A stream consists of several tracks, like video or audio tracks.
Attributes
MediaStream.ended
Read only- Is a Boolean value with a value of
true
if theended
event has been fired on the object, meaning that the stream has been completely read, orfalse
if the end of hte stream has not been reached.
MediaStream.id
Read only- Is a
DOMString
containing 36 characters denoting a unique identifier (GUID) for the object.
Event handlers
MediaStream.onaddtrack
- Is a
EventHandler
containing the action to perform when anaddtrack
event is fired on the object, that is when a newMediaStreamTrack
object is added. MediaStream.onended
- Is a
EventHandler
containing the action to perform when anended
event is fired on the object, that is when the streaming is terminating. MediaStream.onremovetrack
- Is a
EventHandler
containing the action to perform when anremovetrack
event is fired on the object, that is when aMediaStreamTrack
object is removed from it.
Methods
MediaStream.addTrack()
- Stores a copy of the
MediaStreamTrack
given as argument. If the track has already been added to theMediaStream
object, nothing happens; if the track is in thefinished
state, that is has already reached its end, the exceptionINVALID_STATE_RAISE
is raised.
MediaStream.clone()
- Return a clone of the
MediaStream
objet. The clone will have a new id value. - 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 exists, it returnsnull
. If several tracks have the same id, it returns the first one.
MediaStream.getAudioTracks()
- Returns a list of the
MediaStreamTrack
stored in theMediaStream
object that have theirkind
attribute set to"audio"
. The order is not defined, and may vary from one browser to an other, but also from one call to the method 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 exists, it returnsnull
. If several tracks have the same id, it returns the first one.
MediaStream.getVideoTracks()
- Returns a list of the
MediaStreamTrack
stored in theMediaStream
object that have theirkind
attribute set to"video"
. The order is not defined, and may vary from one browser to an other, but also from one call to the method to another.
MediaStream.removeTrack()
- Removes the
MediaStreamTrack
given as argument. If the track is not part of theMediaStream
object, nothing happens; if the track is in thefinished
state, that is has already reached its end, the exceptionINVALID_STATE_RAISE
is raised.
MediaStreamTrack
Summary
The MediaStream
interface represents a stream of media content. A stream consists of several tracks, like video or audio tracks.
Properties
MediaStreamTrack.enabled
- Is a Boolean value with a value of
true
if the track is enabled, that is allowed to render the media source stream; orfalse
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. MediaStreamTrack.id
Read only- Returns a
DOMString
containing a unique identifier (GUID) for the track; it is generated by the browser. 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 with a value of
true
if the track is muted,false
otherwise. 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.It takes 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 theMediaStreamTrack.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 value with a value of
true
if the track is sourced by aRTCPeerConnection
,false
otherwise.
Event handlers
MediaStreamTrack.onstarted
- Is a
EventHandler
containing the action to perform when anstarted
event is fired on the object, that is when a newMediaStreamTrack
object is added. MediaStreamTrack.onmute
- Is a
EventHandler
containing the action to perform when anmute
event is fired on the object, that is when the streaming is terminating. MediaStreamTrack.onunmute
- Is a
EventHandler
containing the action to perform when anunmute
event is fired on the object, that is when aMediaStreamTrack
object is removed from it. MediaStreamTrack.onoverconstrained
- Is a
EventHandler
containing the action to perform when anoverconstrained
event is fired on the object, that is when aMediaStreamTrack
object is removed from it. MediaStreamTrack.oneended
- Is a
EventHandler
containing the action to perform when anended
event is fired on the object, that is when aMediaStreamTrack
object is removed from it.
Methods
MediaStreamTrack.getConstraints()
MediaStreamTrack.applyConstraints()
MediaStreamTrack.getSettings()
MediaStreamTrack.getCapabilities()
MediaStreamTrack.clone()
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
.
Specifications
Specification | Status | Comment |
---|---|---|
Media Capture and Streams The definition of ‘MediaStreamTrack‘ in that specification. |
Candidate Recommendation | Initial definition |
https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamTrack
https://developer.mozilla.org/en-US/docs/Web/API/MediaStream
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