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158 lines
4.6 KiB
JavaScript

(function(window){
var RECORDER_WORKER_PATH = '/static/js/recorderWorker.js';
var ENCODER_WORKER_PATH = '/static/js/mp3Worker.js';
var MP3Recorder = function(context, stream, cfg) {
var config = cfg || { statusContainer: null, statusMethod: 'append' }
var bufferLen = 4096;
var recording = false;
this.source = context.createMediaStreamSource(stream);
this.node = (context.createScriptProcessor || context.createJavaScriptNode).call(context, bufferLen, 1, 1);
var recorderWorker = new Worker(RECORDER_WORKER_PATH);
var encoderWorker = new Worker(ENCODER_WORKER_PATH);
var exportCallback;
// initialize the Recorder Worker
recorderWorker.postMessage({ cmd: 'init', sampleRate: context.sampleRate });
// the recording loop
this.node.onaudioprocess = function(e) {
if(!recording) return;
recorderWorker.postMessage({ cmd: 'record', buffer: e.inputBuffer.getChannelData(0) });
}
this.start = function() {
recording = true;
this.logStatus('recording...');
}
this.stop = function() {
recording = false;
this.logStatus('stopping...');
}
this.destroy = function() { recorderWorker.postMessage({ cmd: 'destroy' }); }
this.logStatus = function(status) {
if(config.statusContainer) {
if(config.statusMethod == 'append') {
config.statusContainer.text(config.statusContainer.text + "\n" + status);
} else {
config.statusContainer.text(status);
}
}
}
this.exportBlob = function(cb) {
exportCallback = cb;
if (!exportCallback) throw new Error('Callback not set');
recorderWorker.postMessage({ cmd: 'exportBlob' });
}
this.exportWAV = function(cb) {
// export the blob from the worker
this.exportBlob(function(blob) {
var fileReader = new FileReader();
// read the blob as array buffer and convert it
// to a base64 encoded WAV buffer
fileReader.addEventListener("loadend", function() {
var resultBuffer = new Uint8Array(this.result);
cb(encode64(resultBuffer));
});
fileReader.readAsArrayBuffer(blob);
});
}
this.exportMP3 = function(cb) {
this.logStatus('converting...');
// export the blob from the worker
this.exportBlob(function(blob) {
var fileReader = new FileReader();
fileReader.addEventListener("loadend", function() {
var wavBuffer = new Uint8Array(this.result);
var wavData = parseWav(wavBuffer);
encoderWorker.addEventListener('message', function(e) {
if (e.data.cmd == 'data') {
cb(encode64(e.data.buffer));
}
});
encoderWorker.postMessage({ cmd: 'init', config: { mode: 3, channels: 1, samplerate: wavData.sampleRate, bitrate: wavData.bitsPerSample } });
encoderWorker.postMessage({ cmd: 'encode', buf: Uint8ArrayToFloat32Array(wavData.samples) });
encoderWorker.postMessage({ cmd: 'finish' });
});
fileReader.readAsArrayBuffer(blob);
});
}
// event listener for return values of the recorderWorker
recorderWorker.addEventListener('message', function(e) {
switch(e.data.from) {
case 'exportBlob':
exportCallback(e.data.blob);
break;
};
});
// HELPER FUNCTIONS
function encode64(buffer) {
var binary = '';
var bytes = new Uint8Array(buffer);
var len = bytes.byteLength;
for(var i = 0; i < len; i++) {
binary += String.fromCharCode(bytes[i]);
}
return window.btoa(binary);
}
function parseWav(wav) {
function readInt(i, bytes) {
var ret = 0, shft = 0;
while(bytes) {
ret += wav[i] << shft; shft += 8;
i++; bytes--;
}
return ret;
}
if(readInt(20, 2) != 1) throw 'Invalid compression code, not PCM';
if(readInt(22, 2) != 1) throw 'Invalid number of channels, not 1';
return { sampleRate: readInt(24, 4), bitsPerSample: readInt(34, 2), samples: wav.subarray(44) };
}
function Uint8ArrayToFloat32Array(u8a){
var f32Buffer = new Float32Array(u8a.length);
for (var i = 0; i < u8a.length; i++) {
var value = u8a[i<<1] + (u8a[(i<<1)+1]<<8);
if (value >= 0x8000) value |= ~0x7FFF;
f32Buffer[i] = value / 0x8000;
}
return f32Buffer;
}
this.source.connect(this.node);
this.node.connect(context.destination); // this should not be necessary
}
window.MP3Recorder = MP3Recorder;
})(window);