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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?

 

7 Answers

up vote103down voteaccepted

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.

 

  • 3
    @Fibericon not anymore (: Stable Chrome does too now (Version 28.0.1500.71 Mac). – JSmythJul 16 ’13 at 6:42
  • 6
    Doesn’t seem to work properly on windows 8, the audio playback is silent. Any ideas? – Mark Murphy Aug 14 ’13 at 22:34
  • 2
    It is fine when testing online. But if I save all the html files (js, png,…), it does not work locally. – Randy Tang Nov 19 ’14 at 7:18
  • 2
    I’ve tested the demo, it works fine in Chrome and Opera but there is issues with firefox (The microphone is recognized but not the sound).. And for Safari and IE, they doesn’t know how to handle that code  
(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>

 

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