HTML5 record audio to file
What I ultimately want to do is record from the user's microphone, and upload the file to the server when they're done. So far, I've managed to make a stream to an element with the following code:
var audio = document.getElementById("audio_preview");
navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
navigator.getUserMedia({video: false, audio: true}, function(stream) {
audio.src = window.URL.createObjectURL(stream);
}, onRecordFail);
var onRecordFail = function (e) {
console.log(e);
}
How do I go from that, to recording to a file?
There is a fairly complete recording demo available at: http://webaudiodemos.appspot.com/AudioRecorder/index.html
It allows you to record audio in the browser, then gives you the option to export and download what you've recorded.
You can view the source of that page to find links to the javascript, but to summarize, there's a Recorder object that contains an exportWAV method, and a forceDownload method.
The code shown below is copyrighted to Matt Diamond and available for use under MIT license. The original files are here:
- http://webaudiodemos.appspot.com/AudioRecorder/index.html
- http://webaudiodemos.appspot.com/AudioRecorder/js/recorderjs/recorderWorker.js
Save this files and use
(function(window){
var WORKER_PATH = 'recorderWorker.js';
var Recorder = function(source, cfg){
var config = cfg || {};
var bufferLen = config.bufferLen || 4096;
this.context = source.context;
this.node = this.context.createScriptProcessor(bufferLen, 2, 2);
var worker = new Worker(config.workerPath || WORKER_PATH);
worker.postMessage({
command: 'init',
config: {
sampleRate: this.context.sampleRate
}
});
var recording = false,
currCallback;
this.node.onaudioprocess = function(e){
if (!recording) return;
worker.postMessage({
command: 'record',
buffer: [
e.inputBuffer.getChannelData(0),
e.inputBuffer.getChannelData(1)
]
});
}
this.configure = function(cfg){
for (var prop in cfg){
if (cfg.hasOwnProperty(prop)){
config[prop] = cfg[prop];
}
}
}
this.record = function(){
recording = true;
}
this.stop = function(){
recording = false;
}
this.clear = function(){
worker.postMessage({ command: 'clear' });
}
this.getBuffer = function(cb) {
currCallback = cb || config.callback;
worker.postMessage({ command: 'getBuffer' })
}
this.exportWAV = function(cb, type){
currCallback = cb || config.callback;
type = type || config.type || 'audio/wav';
if (!currCallback) throw new Error('Callback not set');
worker.postMessage({
command: 'exportWAV',
type: type
});
}
worker.onmessage = function(e){
var blob = e.data;
currCallback(blob);
}
source.connect(this.node);
this.node.connect(this.context.destination); //this should not be necessary
};
Recorder.forceDownload = function(blob, filename){
var url = (window.URL || window.webkitURL).createObjectURL(blob);
var link = window.document.createElement('a');
link.href = url;
link.download = filename || 'output.wav';
var click = document.createEvent("Event");
click.initEvent("click", true, true);
link.dispatchEvent(click);
}
window.Recorder = Recorder;
})(window);
//ADDITIONAL JS recorderWorker.js
var recLength = 0,
recBuffersL = [],
recBuffersR = [],
sampleRate;
this.onmessage = function(e){
switch(e.data.command){
case 'init':
init(e.data.config);
break;
case 'record':
record(e.data.buffer);
break;
case 'exportWAV':
exportWAV(e.data.type);
break;
case 'getBuffer':
getBuffer();
break;
case 'clear':
clear();
break;
}
};
function init(config){
sampleRate = config.sampleRate;
}
function record(inputBuffer){
recBuffersL.push(inputBuffer[0]);
recBuffersR.push(inputBuffer[1]);
recLength += inputBuffer[0].length;
}
function exportWAV(type){
var bufferL = mergeBuffers(recBuffersL, recLength);
var bufferR = mergeBuffers(recBuffersR, recLength);
var interleaved = interleave(bufferL, bufferR);
var dataview = encodeWAV(interleaved);
var audioBlob = new Blob([dataview], { type: type });
this.postMessage(audioBlob);
}
function getBuffer() {
var buffers = [];
buffers.push( mergeBuffers(recBuffersL, recLength) );
buffers.push( mergeBuffers(recBuffersR, recLength) );
this.postMessage(buffers);
}
function clear(){
recLength = 0;
recBuffersL = [];
recBuffersR = [];
}
function mergeBuffers(recBuffers, recLength){
var result = new Float32Array(recLength);
var offset = 0;
for (var i = 0; i < recBuffers.length; i++){
result.set(recBuffers[i], offset);
offset += recBuffers[i].length;
}
return result;
}
function interleave(inputL, inputR){
var length = inputL.length + inputR.length;
var result = new Float32Array(length);
var index = 0,
inputIndex = 0;
while (index < length){
result[index++] = inputL[inputIndex];
result[index++] = inputR[inputIndex];
inputIndex++;
}
return result;
}
function floatTo16BitPCM(output, offset, input){
for (var i = 0; i < input.length; i++, offset+=2){
var s = Math.max(-1, Math.min(1, input[i]));
output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
}
}
function writeString(view, offset, string){
for (var i = 0; i < string.length; i++){
view.setUint8(offset + i, string.charCodeAt(i));
}
}
function encodeWAV(samples){
var buffer = new ArrayBuffer(44 + samples.length * 2);
var view = new DataView(buffer);
/* RIFF identifier */
writeString(view, 0, 'RIFF');
/* file length */
view.setUint32(4, 32 + samples.length * 2, true);
/* RIFF type */
writeString(view, 8, 'WAVE');
/* format chunk identifier */
writeString(view, 12, 'fmt ');
/* format chunk length */
view.setUint32(16, 16, true);
/* sample format (raw) */
view.setUint16(20, 1, true);
/* channel count */
view.setUint16(22, 2, true);
/* sample rate */
view.setUint32(24, sampleRate, true);
/* byte rate (sample rate * block align) */
view.setUint32(28, sampleRate * 4, true);
/* block align (channel count * bytes per sample) */
view.setUint16(32, 4, true);
/* bits per sample */
view.setUint16(34, 16, true);
/* data chunk identifier */
writeString(view, 36, 'data');
/* data chunk length */
view.setUint32(40, samples.length * 2, true);
floatTo16BitPCM(view, 44, samples);
return view;
}<html>
<body>
<audio controls autoplay></audio>
<script type="text/javascript" src="recorder.js"> </script>
<fieldset><legend>RECORD AUDIO</legend>
<input onclick="startRecording()" type="button" value="start recording" />
<input onclick="stopRecording()" type="button" value="stop recording and play" />
</fieldset>
<script>
var onFail = function(e) {
console.log('Rejected!', e);
};
var onSuccess = function(s) {
var context = new webkitAudioContext();
var mediaStreamSource = context.createMediaStreamSource(s);
recorder = new Recorder(mediaStreamSource);
recorder.record();
// audio loopback
// mediaStreamSource.connect(context.destination);
}
window.URL = window.URL || window.webkitURL;
navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
var recorder;
var audio = document.querySelector('audio');
function startRecording() {
if (navigator.getUserMedia) {
navigator.getUserMedia({audio: true}, onSuccess, onFail);
} else {
console.log('navigator.getUserMedia not present');
}
}
function stopRecording() {
recorder.stop();
recorder.exportWAV(function(s) {
audio.src = window.URL.createObjectURL(s);
});
}
</script>
</body>
</html>