MediaStreamAudioDestinationNode - Web APIs 编辑
The MediaStreamAudioDestinationNode interface represents an audio destination consisting of a WebRTC MediaStream with a single AudioMediaStreamTrack, which can be used in a similar way to a MediaStream obtained from Navigator.getUserMedia().
It is an AudioNode that acts as an audio destination, created using the AudioContext.createMediaStreamDestination() method.
| Number of inputs | 1 |
|---|---|
| Number of outputs | 0 |
| Channel count | 2 |
| Channel count mode | "explicit" |
| Channel count interpretation | "speakers" |
Constructor
MediaStreamAudioDestinationNode.MediaStreamAudioDestinationNode()- Creates a new
MediaStreamAudioDestinationNodeobject instance.
Properties
Inherits properties from its parent, AudioNode.
MediaStreamAudioDestinationNode.stream- A
MediaStreamcontaining a singleMediaStreamTrackwhosekindisaudioand with the same number of channels as the node. You can use this property to get a stream out of the audio graph and feed it into another construct, such as a Media Recorder.
Methods
Inherits methods from its parent, AudioNode.
Example
In the following simple example, we create a MediaStreamAudioDestinationNode, an OscillatorNode and a MediaRecorder (the example will therefore only work in Firefox and Chrome at this time.) The MediaRecorder is set up to record information from the MediaStreamDestinationNode.
When the button is clicked, the oscillator starts, and the MediaRecorder is started. When the button is stopped, the oscillator andMediaRecorder both stop. Stopping the MediaRecorder causes the dataavailable event to fire, and the event data is pushed into the chunks array. After that, the stop event fires, a new blob is made of type opus — which contains the data in the chunks array, and a new window (tab) is then opened that points to a URL created from the blob.
From here, you can play and save the opus file.
<!DOCTYPE html>
<html>
<head>
<title>createMediaStreamDestination() demo</title>
</head>
<body>
<h1>createMediaStreamDestination() demo</h1>
<p>Encoding a pure sine wave to an Opus file </p>
<button>Make sine wave</button>
<audio controls></audio>
<script>
var b = document.querySelector("button");
var clicked = false;
var chunks = [];
var ac = new AudioContext();
var osc = ac.createOscillator();
var dest = ac.createMediaStreamDestination();
var mediaRecorder = new MediaRecorder(dest.stream);
osc.connect(dest);
b.addEventListener("click", function(e) {
if (!clicked) {
mediaRecorder.start();
osc.start(0);
e.target.textContent = "Stop recording";
clicked = true;
} else {
mediaRecorder.stop();
osc.stop(0);
e.target.disabled = true;
}
});
mediaRecorder.ondataavailable = function(evt) {
// push each chunk (blobs) in an array
chunks.push(evt.data);
};
mediaRecorder.onstop = function(evt) {
// Make blob out of our blobs, and open it.
var blob = new Blob(chunks, { 'type' : 'audio/ogg; codecs=opus' });
document.querySelector("audio").src = URL.createObjectURL(blob);
};
</script>
</body>
</html>Note: You can view this example live, or study the source code, on Github.
Specifications
| Specification | Status | Comment |
|---|---|---|
| Web Audio API The definition of 'MediaStreamAudioDestinationNode' in that specification. | Working Draft |
Browser compatibility
BCD tables only load in the browser
See also
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