realtime audio on ze web @ hhjs

realtime audio on ze web

APIs, Demos, Anwendungen
Jan Krutisch <jan.krutisch@mindmatters.de>
für #hhjs, 21.Februar 2011

Montag, 21. Februar 2011

Moi.


Realtime audio?


In/Out


Status Quo.


nada.


ﬂash.


horizont.


Audio Data API


10 beta


Web Audio API


AudioContext


Das wars.


Ja, sorry, ey.


Code, or it didn‘t happen


<!DOCTYPE html>
<html>
<head>
<title>JavaScript Audio Write Example</title>
</head>
<body>
<input type="text" size="4" id="freq" value="440"><label for="hz">Hz</label>
<button onclick="start()">play</button>
<button onclick="stop()">stop</button>

<script type="text/javascript">
function AudioDataDestination(sampleRate, readFn) {
// Initialize the audio output.
var audio = new Audio();
audio.mozSetup(1, sampleRate);

var currentWritePosition = 0;
var prebufferSize = sampleRate / 2; // buffer 500ms
var tail = null;

// The function called with regular interval to populate
// the audio output buffer.
setInterval(function() {
var written;
// Check if some data was not written in previous attempts.
if(tail) {
written = audio.mozWriteAudio(tail);
currentWritePosition += written;
if(written < tail.length) {
// Not all the data was written, saving the tail...
tail = tail.slice(written);
return; // ... and exit the function.
}
tail = null;
}

// Check if we need add some data to the audio output.
var currentPosition = audio.mozCurrentSampleOffset();
var available = currentPosition + prebufferSize - currentWritePosition;
if(available > 0) {
// Request some sound data from the callback function.
var soundData = new Float32Array(available);
readFn(soundData);

// Writting the data.
written = audio.mozWriteAudio(soundData);
if(written < soundData.length) {
// Not all the data was written, saving the tail.
tail = soundData.slice(written);
}
currentWritePosition += written;
}
}, 100);
}

// Control and generate the sound.

var frequency = 0, currentSoundSample;
var sampleRate = 44100;

function requestSoundData(soundData) {
if (!frequency) {
return; // no sound selected
}

var k = 2* Math.PI * frequency / sampleRate;
for (var i=0, size=soundData.length; i<size; i++) {
soundData[i] = Math.sin(k * currentSoundSample++);
}
}

var audioDestination = new AudioDataDestination(sampleRate, requestSoundData);

function start() {
currentSoundSample = 0;
frequency = parseFloat(document.getElementById("freq").value);
}

function stop() {
frequency = 0;
}
</script>


[...]

var audio = new Audio();
audio.mozSetup(1, sampleRate);

[...]

written = audio.mozWriteAudio(tail);

[...]


https://wiki.mozilla.org/Audio_Data_API#Writing_Audio


context = new webkitAudioContext();

var jsNode = context.createJavaScriptNode(8192, 0, 2);

jsNode.connect(context.destination);

jsNode.onaudioprocess = requestSoundData;


Anwendungen


Musik


Spiele


(
Build and they will come
)


Meine kleine Ecke


http://webloop.pixelpoke.de


http://github.com/halfbyte/soundbridge.js


soundbridge = SoundBridge(2, 44100, '..');

[...]
soundbridge.setCallback(calc);
soundbridge.play();
}, 1000);


realtime audio on ze web @ hhjs

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