AudioContext.createMediaStreamDestination()
The createMediaStreamDestination()
method of the AudioContext
Interface is used to create a new MediaStreamAudioDestinationNode
object associated with a WebRTC MediaStream
representing an audio stream, which may be stored in a local file or sent to another computer.
The MediaStream
is created when the node is created and is accessible via the MediaStreamAudioDestinationNode
's stream
attribute. This stream can be used in a similar way as a MediaStream
obtained via navigator.getUserMedia
— it can, for example, be sent to a remote peer using the RTCPeerConnection
addStream()
method.
For more details about media stream destination nodes, check out the MediaStreamAudioDestinationNode
reference page.
Syntax
var audioCtx = new AudioContext();
var destination = audioCtx.createMediaStreamDestination();
Returns
Examples
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 and MediaRecorder
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 |
---|
Web Audio API # dom-audiocontext-createmediastreamdestination |
Browser compatibility
BCD tables only load in the browser