It can RecorderJs processing a record of a file without emit any sound in speakers meanwhile? - web-audio-api

Question

While reading some about RecorderJs I ask myself if is possible record a sound without emit any sound in the speakers, all in a background, somebody knows if that is possible? because I don't see something similar in the Recorderjs Repository.

Answer 1

If you really want to use recorder.js, I guess there is a way to feed it directly with a MediaStream, that you'll get from the streamNode.stream.
Reading quickly the source code of this lib, it seems it only accepts AudioContext Source Nodes, not directly streams, and anyway, you just have to comment the line 38 of recorder.js file.
this.node.connect(this.context.destination); //this should not be necessary
comment from the author
And indeed it is.
Otherwise, you can also achieve it vanilla style (except that it will save as ogg instead of wav), by using the official MediaRecorder API, available in latests browsers.
The main key is the MediaStreamDestination which doesn't need to be connected to the AudioContext's destination.
var audio = new Audio();
audio.crossOrigin = 'anonymous';
audio.src = 'https://dl.dropboxusercontent.com/s/agepbh2agnduknz/camera.mp3';
audio.onloadedmetadata = startRecording;
var aCtx = new AudioContext();
var sourceNode = aCtx.createMediaElementSource(audio);
var streamNode = aCtx.createMediaStreamDestination();
sourceNode.connect(streamNode);
function startRecording() {
var recorder = new MediaRecorder(streamNode.stream),
chunks = [];
recorder.ondataavailable = function(e) {
chunks.push(e.data);
}
recorder.onstop = function() {
var blob = new Blob(chunks);
var url = URL.createObjectURL(blob);
var a = new Audio(url);
a.controls = true;
document.body.appendChild(a);
}
audio.onended = function() {
recorder.stop();
};
audio.play();
recorder.start();
}