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convolution.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0"/>
<meta name="format-detection" content="telephone=no"/>
<title>环境音效</title>
</head>
<body>
<h1>环境音效（Convolution）</h1>
<p>
<input type="button" id="play" disabled value="加载中..."/>
</p>
<fieldset id="echo_list">
<legend>环境</legend>
<div><input type="radio" name="echo" id="no_sound" checked /><label for="no_sound">关</label></div>
</fieldset>
<p>环境音效不是 Web Audio API 内置的，而是使用了 Web Audio API 的<strong>卷积运算(Convolution)</strong>功能。</p>
<p>声学中，<strong>回声</strong>可以用源声音与一个反映各种反射效应的波形的<strong>卷积</strong>表示。
<br/>这些反映反射效应的波形可以反映房间回声、教堂回声、电话声等等，并且可以用WAV格式存储。</p>
<p>（参考：<a href="http://zh.wikipedia.org/wiki/%E5%8D%B7%E7%A7%AF">维基百科——卷积</a>）</p>
<p>我已经找到了这样的WAV文件。</p>
<p>WAV来源：<a href="https://googlechrome.github.io/web-audio-samples/samples/audio/convolution-effects.html">https://googlechrome.github.io/web-audio-samples/samples/audio/convolution-effects.html</a></p>
<script type="text/javascript">
var Ctx = window.webkitAudioContext ? window.webkitAudioContext : window.AudioContext;
ctx = new Ctx();
var convolutionInfo = [
{
name: '电话',
mainGain: 0.0,
sendGain: 3.0,
url: 'filter-telephone.wav'
},
{
name: '室内',
mainGain: 1.0,
sendGain: 2.5,
url: 'spreader50-65ms.wav'
},
{
name: '山洞',
mainGain: 0.0,
sendGain: 2.4,
url: 'feedback-spring.wav'
},
{
name: '教堂',
mainGain: 1.8,
sendGain: 0.9,
url: 'bin_dfeq/s2_r4_bd.wav'
},
{
name: '厨房',
mainGain: 0.6,
sendGain: 3.0,
url: 'house-impulses/kitchen-true-stereo.wav'
},
{
name: '洗手间',
mainGain: 0.6,
sendGain: 2.1,
url: 'house-impulses/living-bedroom-leveled.wav'
}
];
(function () {
var sourceNode, sourceGainNode, gainNodes = [], convolutionNodes = [];
var loadedCount = 0, loadNum = convolutionInfo.length + 1;
var i, temp1, temp2;
var IMPULSE_URL_PREFIX = 'impulse/';
var RADIO_TPL = '<div><input type="radio" name="echo" id="{%id%}" /><label for="{%id%}">{%name%}</label></div>';
function loadRes(url, node, callback) {
var request = new XMLHttpRequest();
request.open('GET', url, true);
request.responseType = 'arraybuffer';
request.onload = function () {
ctx.decodeAudioData(request.response, function (buffer) {
node.buffer = buffer;
if (callback && typeof callback === 'function') {
callback(buffer);
}
}, function() {
//decode fail
alert('source not support');
});
};
request.send();
}
function loadMark() {
loadedCount ++;
document.getElementById('play').value = '加载中...(' + loadedCount + '/' + loadNum + ')';
if (loadedCount >= loadNum) {
document.getElementById('play').removeAttribute('disabled');
document.getElementById('play').value = '播放';
}
}
// 初始化 source
sourceNode = ctx.createBufferSource();
sourceGainNode = ctx.createGain();
sourceNode.connect(sourceGainNode);
sourceGainNode.connect(ctx.destination);
loadRes('res/mario.mp3', sourceNode, function(){
loadMark();
sourceNode.loop = true;
sourceNode.loopStart = 2.40;
sourceNode.loopEnd = 88.8;
});
// 初始化各种 Convolution;
for (i = 0; i < convolutionInfo.length; i ++) {
convolutionNodes[i] = ctx.createConvolver();
loadRes(IMPULSE_URL_PREFIX + convolutionInfo[i].url, convolutionNodes[i], loadMark);
gainNodes[i] = ctx.createGain();
gainNodes[i].gain.value = 0.0;
sourceNode.connect(convolutionNodes[i]);
convolutionNodes[i].connect(gainNodes[i]);
gainNodes[i].connect(ctx.destination);
}
function setConvolution(index) {
sourceGainNode.gain.value = 1.7;
for (i = 0; i < gainNodes.length; i ++) {
gainNodes[i].gain.value = 0.0;
}
if (index >= 0) {
gainNodes[index].gain.value = convolutionInfo[index].sendGain;
sourceGainNode.gain.value = convolutionInfo[index].mainGain;
}
}
temp2 = '';
for (i = 0; i < convolutionInfo.length; i ++) {
temp1 = RADIO_TPL.replace(/\{%id%\}/g, 'echo' + i).replace(/\{%name%\}/g, convolutionInfo[i].name);
temp2 += temp1;
}
document.getElementById('echo_list').innerHTML += temp2;
for (i = 0; i < convolutionInfo.length; i ++) {
document.getElementById('echo' + i).onclick = (function(x){
return function () {
setConvolution(x);
}
})(i);
}
document.getElementById('no_sound').onclick = function () {
setConvolution(-1);
};
document.getElementById('play').onclick = function () {
sourceNode.start(0);
document.getElementById('play').setAttribute('disabled', 'disabled');
};
setConvolution(-1);
})();
</script>
</body>
</html>