(function() {
var onDOMContentLoaded = function() {
window.AudioContext = window.AudioContext || window.webkitAudioContext;
try {
// Create the instance of AudioContext
var context = new AudioContext();
} catch (error) {
window.alert(error.message + ' : Please use Chrome or Safari.');
return;
}
// Fundamental Frequency (= A)
var F0 = 440;
// Create the instance of OscillatorNode
var oscillator = context.createOscillator();
// Parameters for the instance of OscillatorNode
var type = oscillator.type;
// for legacy browsers
context.createGain = context.createGain || context.createGainNode;
// Create the instance of GainNode
var gain = context.createGain();
// Flag for starting or stopping sound
var isStop = true;
// for drawing sound wave (spectrum)
// Create the instance of AnalyserNode
var analyser = context.createAnalyser();
analyser.minDecibels = -150; // Default -100 dB
analyser.maxDecibels = 0; // Default -30 dB
var canvas = document.querySelector('canvas');
var canvasContext = canvas.getContext('2d');
var timerid = null;
var drawWave = function() {
var width = canvas.width;
var height = canvas.height;
var paddingTop = 20;
var paddingBottom = 20;
var paddingLeft = 30;
var paddingRight = 30;
var innerWidth = width - paddingLeft - paddingRight;
var innerHeight = height - paddingTop - paddingBottom;
var range = analyser.maxDecibels - analyser.minDecibels; // 70 dB
// Frequency resolution
var fsDivN = context.sampleRate / analyser.fftSize;
// This value is the number of samples during 440 Hz
var n440Hz = Math.floor(oscillator.frequency.value / fsDivN);
// Get data for drawing spectrum (dB)
var spectrums = new Float32Array(analyser.frequencyBinCount / 4);
analyser.getFloatFrequencyData(spectrums);
// Clear previous data
canvasContext.clearRect(0, 0, canvas.width, canvas.height);
// Draw spectrum (dB)
canvasContext.beginPath();
for (var i = 0, len = spectrums.length; i < len; i++) {
var x = Math.floor((i / len) * innerWidth) + paddingLeft;
var y = Math.floor(-1 * ((spectrums[i] - analyser.maxDecibels) / range) * innerHeight) + paddingTop;
if (i === 0) {
canvasContext.moveTo(x, y);
} else {
canvasContext.lineTo(x, y);
}
if (i % n440Hz === 0) {
var text = (oscillator.frequency.value * (i / n440Hz)) + ' Hz'; // index -> frequency
// Draw grid (X)
canvasContext.fillStyle = 'rgba(255, 0, 0, 1.0)';
canvasContext.fillRect(x, paddingTop, 1, innerHeight);
// Draw text (X)
canvasContext.fillStyle = 'rgba(255, 255, 255, 1.0)';
canvasContext.font = '12px "Times New Roman"';
canvasContext.fillText(text, (x - (canvasContext.measureText(text).width / 2)), (height - 3));
}
}
canvasContext.strokeStyle = 'rgba(0, 0, 255, 1.0)';
canvasContext.lineWidth = 2;
canvasContext.lineCap = 'round';
canvasContext.lineJoin = 'miter';
canvasContext.stroke();
// Draw grid and text (Y)
for (var i = analyser.minDecibels; i <= analyser.maxDecibels; i += 10) {
var gy = Math.floor(-1 * ((i - analyser.maxDecibels) / range) * innerHeight) + paddingTop;
// Draw grid (Y)
canvasContext.fillStyle = 'rgba(255, 0, 0, 1.0)';
canvasContext.fillRect(paddingLeft, gy, innerWidth, 1);
// Draw text (Y)
canvasContext.fillStyle = 'rgba(255, 255, 255, 1.0)';
canvasContext.font = '12px "Times New Roman"';
canvasContext.fillText((i + ' dB'), 3, gy);
}
timerid = window.setTimeout(drawWave, 20);
};
/*
* Event Listener
*/
// Start or Stop sound
document.querySelector('button').addEventListener(EventWrapper.CLICK, function() {
if (isStop) {
// Create the instance of OscillatorNode
oscillator = context.createOscillator();
// for legacy browsers
oscillator.start = oscillator.start || oscillator.noteOn;
oscillator.stop = oscillator.stop || oscillator.noteOff;
// OscillatorNode (Input) -> GainNode (Volume) -> AnalyserNode (Visualization) -> AudioDestinationNode (Output)
oscillator.connect(gain)
gain.connect(analyser);
analyser.connect(context.destination);
// Set parameters
oscillator.type = type;
oscillator.frequency.value = F0;
oscillator.detune.value = 0;
// Start sound
oscillator.start(0);
// Start drawing sound wave (spectrum)
drawWave();
isStop = false;
this.innerHTML = '<span class="icon-pause"></span>';
} else {
// Stop sound
oscillator.stop(0);
// Stop drawing sound wave (spectrum)
window.clearTimeout(timerid);
isStop = true;
this.innerHTML = '<span class="icon-start"></span>';
}
}, false);
// Control Volume
document.getElementById('range-volume').addEventListener('input', function() {
var min = gain.gain.minValue || 0;
var max = gain.gain.maxValue || 1;
if ((this.valueAsNumber >= min) && (this.valueAsNumber <= max)) {
gain.gain.value = this.valueAsNumber;
document.getElementById('output-volume').textContent = this.value;
}
}, false);
// Select type
document.getElementById('form-wave-type').addEventListener('change', function() {
for (var i = 0, len = this.elements['radio-wave-type'].length; i < len; i++) {
if (this.elements['radio-wave-type'][i].checked) {
oscillator.type = type = (typeof oscillator.type === 'string') ? this.elements['radio-wave-type'][i].value : i;
break;
}
}
}, false);
};
if ((document.readyState === 'interactive') || (document.readyState === 'complete')) {
onDOMContentLoaded();
} else {
document.addEventListener('DOMContentLoaded', onDOMContentLoaded, true);
}
})();
function EventWrapper(){
}
(function(){
var click = '';
var start = '';
var move = '';
var end = '';
// Touch Panel ?
if (/iPhone|iPad|iPod|Android/.test(navigator.userAgent)) {
click = 'click';
start = 'touchstart';
move = 'touchmove';
end = 'touchend';
} else {
click = 'click';
start = 'mousedown';
move = 'mousemove';
end = 'mouseup';
}
EventWrapper.CLICK = click;
EventWrapper.START = start;
EventWrapper.MOVE = move;
EventWrapper.END = end;
})();