meziantou/Index.html

## Index.html
<!DOCTYPE html>

<html>
<head>
    <meta charset="utf-8" />
    <title></title>
</head>
<body>
    <h1>Audio</h1>

    <button id="startRecordingButton">Start recording</button>
    <button id="stopRecordingButton">Stop recording</button>
    <button id="playButton">Play</button>
    <button id="downloadButton">Download</button>

    <script>
        var startRecordingButton = document.getElementById("startRecordingButton");
        var stopRecordingButton = document.getElementById("stopRecordingButton");
        var playButton = document.getElementById("playButton");
        var downloadButton = document.getElementById("downloadButton");


        var leftchannel = [];
        var rightchannel = [];
        var recorder = null;
        var recordingLength = 0;
        var volume = null;
        var mediaStream = null;
        var sampleRate = 44100;
        var context = null;
        var blob = null;

        startRecordingButton.addEventListener("click", function () {
            // Initialize recorder
            navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
            navigator.getUserMedia(
            {
                audio: true
            },
            function (e) {
                console.log("user consent");

                // creates the audio context
                window.AudioContext = window.AudioContext || window.webkitAudioContext;
                context = new AudioContext();

                // creates an audio node from the microphone incoming stream
                mediaStream = context.createMediaStreamSource(e);

                // https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/createScriptProcessor
                // bufferSize: the onaudioprocess event is called when the buffer is full
                var bufferSize = 2048;
                var numberOfInputChannels = 2;
                var numberOfOutputChannels = 2;
                if (context.createScriptProcessor) {
                    recorder = context.createScriptProcessor(bufferSize, numberOfInputChannels, numberOfOutputChannels);
                } else {
                    recorder = context.createJavaScriptNode(bufferSize, numberOfInputChannels, numberOfOutputChannels);
                }

                recorder.onaudioprocess = function (e) {
                    leftchannel.push(new Float32Array(e.inputBuffer.getChannelData(0)));
                    rightchannel.push(new Float32Array(e.inputBuffer.getChannelData(1)));
                    recordingLength += bufferSize;
                }

                // we connect the recorder
                mediaStream.connect(recorder);
                recorder.connect(context.destination);
            },
                        function (e) {
                            console.error(e);
                        });
        });

        stopRecordingButton.addEventListener("click", function () {

            // stop recording
            recorder.disconnect(context.destination);
            mediaStream.disconnect(recorder);

            // we flat the left and right channels down
            // Float32Array[] => Float32Array
            var leftBuffer = flattenArray(leftchannel, recordingLength);
            var rightBuffer = flattenArray(rightchannel, recordingLength);
            // we interleave both channels together
            // [left[0],right[0],left[1],right[1],...]
            var interleaved = interleave(leftBuffer, rightBuffer);

            // we create our wav file
            var buffer = new ArrayBuffer(44 + interleaved.length * 2);
            var view = new DataView(buffer);

            // RIFF chunk descriptor
            writeUTFBytes(view, 0, 'RIFF');
            view.setUint32(4, 44 + interleaved.length * 2, true);
            writeUTFBytes(view, 8, 'WAVE');
            // FMT sub-chunk
            writeUTFBytes(view, 12, 'fmt ');
            view.setUint32(16, 16, true); // chunkSize
            view.setUint16(20, 1, true); // wFormatTag
            view.setUint16(22, 2, true); // wChannels: stereo (2 channels)
            view.setUint32(24, sampleRate, true); // dwSamplesPerSec
            view.setUint32(28, sampleRate * 4, true); // dwAvgBytesPerSec
            view.setUint16(32, 4, true); // wBlockAlign
            view.setUint16(34, 16, true); // wBitsPerSample
            // data sub-chunk
            writeUTFBytes(view, 36, 'data');
            view.setUint32(40, interleaved.length * 2, true);

            // write the PCM samples
            var index = 44;
            var volume = 1;
            for (var i = 0; i < interleaved.length; i++) {
                view.setInt16(index, interleaved[i] * (0x7FFF * volume), true);
                index += 2;
            }

            // our final blob
            blob = new Blob([view], { type: 'audio/wav' });
        });

        playButton.addEventListener("click", function () {
            if (blob == null) {
                return;
            }

            var url = window.URL.createObjectURL(blob);
            var audio = new Audio(url);
            audio.play();
        });

        downloadButton.addEventListener("click", function () {
            if (blob == null) {
                return;
            }

            var url = URL.createObjectURL(blob);

            var a = document.createElement("a");
            document.body.appendChild(a);
            a.style = "display: none";
            a.href = url;
            a.download = "sample.wav";
            a.click();
            window.URL.revokeObjectURL(url);
        });

        function flattenArray(channelBuffer, recordingLength) {
            var result = new Float32Array(recordingLength);
            var offset = 0;
            for (var i = 0; i < channelBuffer.length; i++) {
                var buffer = channelBuffer[i];
                result.set(buffer, offset);
                offset += buffer.length;
            }
            return result;
        }

        function interleave(leftChannel, rightChannel) {
            var length = leftChannel.length + rightChannel.length;
            var result = new Float32Array(length);

            var inputIndex = 0;

            for (var index = 0; index < length;) {
                result[index++] = leftChannel[inputIndex];
                result[index++] = rightChannel[inputIndex];
                inputIndex++;
            }
            return result;
        }

        function writeUTFBytes(view, offset, string) {
            for (var i = 0; i < string.length; i++) {
                view.setUint8(offset + i, string.charCodeAt(i));
            }
        }

    </script>
</body>
</html>
	<!DOCTYPE html>

	<html>
	<head>
	<meta charset="utf-8" />
	<title></title>
	</head>
	<body>
	<h1>Audio</h1>

	<button id="startRecordingButton">Start recording</button>
	<button id="stopRecordingButton">Stop recording</button>
	<button id="playButton">Play</button>
	<button id="downloadButton">Download</button>

	<script>
	var startRecordingButton = document.getElementById("startRecordingButton");
	var stopRecordingButton = document.getElementById("stopRecordingButton");
	var playButton = document.getElementById("playButton");
	var downloadButton = document.getElementById("downloadButton");


	var leftchannel = [];
	var rightchannel = [];
	var recorder = null;
	var recordingLength = 0;
	var volume = null;
	var mediaStream = null;
	var sampleRate = 44100;
	var context = null;
	var blob = null;

	startRecordingButton.addEventListener("click", function () {
	// Initialize recorder
	navigator.getUserMedia = navigator.getUserMedia \|\| navigator.webkitGetUserMedia \|\| navigator.mozGetUserMedia \|\| navigator.msGetUserMedia;
	navigator.getUserMedia(
	{
	audio: true
	},
	function (e) {
	console.log("user consent");

	// creates the audio context
	window.AudioContext = window.AudioContext \|\| window.webkitAudioContext;
	context = new AudioContext();

	// creates an audio node from the microphone incoming stream
	mediaStream = context.createMediaStreamSource(e);

	// https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/createScriptProcessor
	// bufferSize: the onaudioprocess event is called when the buffer is full
	var bufferSize = 2048;
	var numberOfInputChannels = 2;
	var numberOfOutputChannels = 2;
	if (context.createScriptProcessor) {
	recorder = context.createScriptProcessor(bufferSize, numberOfInputChannels, numberOfOutputChannels);
	} else {
	recorder = context.createJavaScriptNode(bufferSize, numberOfInputChannels, numberOfOutputChannels);
	}

	recorder.onaudioprocess = function (e) {
	leftchannel.push(new Float32Array(e.inputBuffer.getChannelData(0)));
	rightchannel.push(new Float32Array(e.inputBuffer.getChannelData(1)));
	recordingLength += bufferSize;
	}

	// we connect the recorder
	mediaStream.connect(recorder);
	recorder.connect(context.destination);
	},
	function (e) {
	console.error(e);
	});
	});

	stopRecordingButton.addEventListener("click", function () {

	// stop recording
	recorder.disconnect(context.destination);
	mediaStream.disconnect(recorder);

	// we flat the left and right channels down
	// Float32Array[] => Float32Array
	var leftBuffer = flattenArray(leftchannel, recordingLength);
	var rightBuffer = flattenArray(rightchannel, recordingLength);
	// we interleave both channels together
	// [left[0],right[0],left[1],right[1],...]
	var interleaved = interleave(leftBuffer, rightBuffer);

	// we create our wav file
	var buffer = new ArrayBuffer(44 + interleaved.length * 2);
	var view = new DataView(buffer);

	// RIFF chunk descriptor
	writeUTFBytes(view, 0, 'RIFF');
	view.setUint32(4, 44 + interleaved.length * 2, true);
	writeUTFBytes(view, 8, 'WAVE');
	// FMT sub-chunk
	writeUTFBytes(view, 12, 'fmt ');
	view.setUint32(16, 16, true); // chunkSize
	view.setUint16(20, 1, true); // wFormatTag
	view.setUint16(22, 2, true); // wChannels: stereo (2 channels)
	view.setUint32(24, sampleRate, true); // dwSamplesPerSec
	view.setUint32(28, sampleRate * 4, true); // dwAvgBytesPerSec
	view.setUint16(32, 4, true); // wBlockAlign
	view.setUint16(34, 16, true); // wBitsPerSample
	// data sub-chunk
	writeUTFBytes(view, 36, 'data');
	view.setUint32(40, interleaved.length * 2, true);

	// write the PCM samples
	var index = 44;
	var volume = 1;
	for (var i = 0; i < interleaved.length; i++) {
	view.setInt16(index, interleaved[i] * (0x7FFF * volume), true);
	index += 2;
	}

	// our final blob
	blob = new Blob([view], { type: 'audio/wav' });
	});

	playButton.addEventListener("click", function () {
	if (blob == null) {
	return;
	}

	var url = window.URL.createObjectURL(blob);
	var audio = new Audio(url);
	audio.play();
	});

	downloadButton.addEventListener("click", function () {
	if (blob == null) {
	return;
	}

	var url = URL.createObjectURL(blob);

	var a = document.createElement("a");
	document.body.appendChild(a);
	a.style = "display: none";
	a.href = url;
	a.download = "sample.wav";
	a.click();
	window.URL.revokeObjectURL(url);
	});

	function flattenArray(channelBuffer, recordingLength) {
	var result = new Float32Array(recordingLength);
	var offset = 0;
	for (var i = 0; i < channelBuffer.length; i++) {
	var buffer = channelBuffer[i];
	result.set(buffer, offset);
	offset += buffer.length;
	}
	return result;
	}

	function interleave(leftChannel, rightChannel) {
	var length = leftChannel.length + rightChannel.length;
	var result = new Float32Array(length);

	var inputIndex = 0;

	for (var index = 0; index < length;) {
	result[index++] = leftChannel[inputIndex];
	result[index++] = rightChannel[inputIndex];
	inputIndex++;
	}
	return result;
	}

	function writeUTFBytes(view, offset, string) {
	for (var i = 0; i < string.length; i++) {
	view.setUint8(offset + i, string.charCodeAt(i));
	}
	}

	</script>
	</body>
	</html>