Using getUserMedia to get audio from the microphone as it is being recorded? - audio

Question

I'm trying to write a Meteor.JS app that uses peer to peer "radio" communication. When a user presses a button it broadcasts their microphone output to people.
I have some code that gets permission to record audio, and it successfully gets a MediaStream object, but I can't figure out how to get the data from the MediaStream object as it is being recorded.
I see there is an method defined somewhere for getting all of the tracks of the recorded audio. I'm sure I could find a way to write some kind of loop that notifies me when audio has been added, but it seems like there should be a native, event-driven way to retrieve the audio from getUserMedia. Am I missing something? Thanks

Answer 1

What you will want to do is to access the stream through the AudioAPI(for the recording part). This is after assigning a var to your stream that was grabbed through getUserMedia (I call it localStream). So, you can create as many MediaStreamsource nodes as you want from one stream, so you can record it WHILE sending it to numerous people through different rtcpeerconnections.
var audioContext = new webkitAudioContext() || AudioContext();
var source = audioContext.createMediastreamSource(localStream);
var AudioRecorder = function (source) {
var recording = false;
var worker = new Worker(WORKER_PATH);
var config = {};
var bufferLen = 4096;
this.context = source.context;
this.node = (this.context.createScriptProcessor ||
this.context.createJavaScriptNode).call(this.context,
bufferLen, 2, 2);
this.node.onaudioprocess = function (e) {
var sample = e.inputBuffer.getChannelData(0);
//do what you want with the audio Sample, push to a blob or send over a WebSocket
}
source.connect(this.node);
this.node.connect(this.context.destination);
};
Here is a version I wrote/modified to send audio over websockets for recording on a server.
For sending the audio only when it is available, you COULD use websockets or a webrtc peerconnection.
You will grab the stream through getUserMedia success object(you should have a global variable that will be the stream for all your connection). And when it becomes available, you can use a signalling server to forward the requesting SDPs to the audio supplier. You can set it the requesting SDPs to receive only and your connection.
PeerConnection example 1
PeerConnection example 2

Answer 2

Try with code like this:
navigator.webkitGetUserMedia({audio: true, video: false},
function(stream) { // Success Callback
var audioElement = document.createElement("audio");
document.body.appendChild(audioElement);
audioElement.src = URL.createObjectURL(stream);
audioElement.play();
}, function () { // Error callback
console.log("error")
});
You may use the stream from success callback to create a object URL and pass it into an HTML5 audio element.
Fiddle around in http://jsfiddle.net/veritas/2B9Pq/