The MediaStreamAudioSourceNode
interface is a type of AudioNode
which operates as an audio source whose media is received from a MediaStream
obtained using the WebRTC or Media Capture and Streams APIs. This media could be from a microphone (through getUserMedia()
) or from a remote peer on a WebRTC call (using the RTCPeerConnection
's audio tracks).
A MediaStreamAudioSourceNode
has no inputs and exactly one output, and is created using the AudioContext.createMediaStreamSource()
method.
The MediaStreamAudioSourceNode
takes the audio from the first MediaStreamTrack
whose kind
attribute's value is audio
. See Track ordering for more information about the order of tracks.
The number of channels output by the node matches the number of tracks found in the selected audio track.
Number of inputs | 0 |
---|---|
Number of outputs | 1 |
Channel count | defined by the first audio MediaStreamTrack passed to the AudioContext.createMediaStreamSource() method that created it. |
Constructor
new MediaStreamAudioSourceNode()
- Creates a new
MediaStreamAudioSourceNode
object instance with the specified options.
Properties
In addition to the following properties, MediaStreamAudioSourceNode
inherits the properties of its parent, AudioNode
.
mediaStream
Read only- The
MediaStream
used when constructing thisMediaStreamAudioSourceNode
.
Methods
Inherits methods from its parent, AudioNode
.
Exceptions
InvalidStateError
- The stream specified by the
mediaStream
parameter does not contain any audio tracks.
Usage notes
Typically, you should probably not use this type of node. It has been replaced with the more predictable MediaStreamTrackAudioSourceNode
, which has better-defined rules for how it chooses the track to output.
If you do chooose to use MediaStreamAudioSourceNode
, you should keep the following in mind.
Track ordering
For the purposes of the MediaStreamTrackAudioSourceNode
interface, the order of the audio tracks on the stream is determined by taking the tracks whose kind
is audio
, then sorting the tracks by their id
property's values, in Unicode code point order (essentially, in alphabetical or lexicographical order, for IDs which are simple alphanumeric strings).
The first track, then, is the track whose id
comes first when the tracks' IDs are all sorted by Unicode code point.
However, it's important to note that the rule establishing this ordering was added long after this interface was first introduced into the Web Audio API. As such, you can't easily rely on the order matching between any two browsers or browser versions. This is why it is typically wiser to use MediaStreamTrackAudioSourceNode
, which provides similar capabilities but was better-defined upon being added to the specification, so it's more reliable.
Example
In this example, we grab a media (audio + video) stream from navigator.getUserMedia
, feed the media into a <video>
element to play then mute the audio, but then also feed the audio into a MediaStreamAudioSourceNode
. Next, we feed this source audio into a low pass BiquadFilterNode
(which effectively serves as a bass booster), then a AudioDestinationNode
.
The range slider below the <video>
element controls the amount of gain given to the lowpass filter — increase the value of the slider to make the audio sound more bass heavy!
Note: You can see this example running live, or view the source.
var pre = document.querySelector('pre'); var video = document.querySelector('video'); var myScript = document.querySelector('script'); var range = document.querySelector('input'); // getUserMedia block - grab stream // put it into a MediaStreamAudioSourceNode // also output the visuals into a video element if (navigator.mediaDevices) { console.log('getUserMedia supported.'); navigator.mediaDevices.getUserMedia ({audio: true, video: true}) .then(function(stream) { video.srcObject = stream; video.onloadedmetadata = function(e) { video.play(); video.muted = true; }; // Create a MediaStreamAudioSourceNode // Feed the HTMLMediaElement into it var audioCtx = new AudioContext(); var source = audioCtx.createMediaStreamSource(stream); // Create a biquadfilter var biquadFilter = audioCtx.createBiquadFilter(); biquadFilter.type = "lowshelf"; biquadFilter.frequency.value = 1000; biquadFilter.gain.value = range.value; // connect the AudioBufferSourceNode to the gainNode // and the gainNode to the destination, so we can play the // music and adjust the volume using the mouse cursor source.connect(biquadFilter); biquadFilter.connect(audioCtx.destination); // Get new mouse pointer coordinates when mouse is moved // then set new gain value range.oninput = function() { biquadFilter.gain.value = range.value; } }) .catch(function(err) { console.log('The following gUM error occured: ' + err); }); } else { console.log('getUserMedia not supported on your browser!'); } // dump script to pre element pre.innerHTML = myScript.innerHTML;
Note: As a consequence of calling createMediaStreamSource()
, audio playback from the media stream will be re-routed into the processing graph of the AudioContext
. So playing/pausing the stream can still be done through the media element API and the player controls.
Specification
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'MediaStreamAudioSourceNode' in that specification. |
Working Draft |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
MediaStreamAudioSourceNode | Chrome Full support 23 | Edge Full support ≤18 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support Yes | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support Yes | Samsung Internet Android Full support Yes |
MediaStreamAudioSourceNode() constructor | Chrome
Full support
55
| Edge Full support ≤79 | Firefox Full support 53 | IE No support No | Opera Full support 42 | Safari ? | WebView Android
Full support
55
| Chrome Android
Full support
55
| Firefox Android Full support 53 | Opera Android Full support 42 | Safari iOS ? | Samsung Internet Android
Full support
6.0
|
mediaStream | Chrome Full support 23 | Edge Full support ≤79 | Firefox Full support 70 | IE No support No | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Firefox Android No support No | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- See implementation notes.
- See implementation notes.