【发布时间】：2014-03-28 09:00:48
【问题描述】：
我正在尝试设置一些网络音频以同时加载/播放多个声源。 现在正在加载声音，并通过按钮输入触发播放。
我的问题是，我希望所有声音都通过一个 BiquadFilter（在本例中为 type:0; // LOWPASS filter）。 我相信我已经创建了正确的过滤器（在两个不同的地方，不确定查看附加代码的哪个地方），但我无法获得范围输入来控制频率，有些东西沟通不畅，我完全迷路了。
另外，围绕同一主题，我希望每个单独的声音都通过自己独立的增益节点（音量控制），这将再次通过范围输入进行更改。 基本上会有 6 个音频文件，通过它们自己的 gainNodes 运行，然后在目的地（即扬声器）之前聚集在一起通过 LOWPASS 过滤器。
我希望能通过单个 pannerNodes，但目前面临着一起放弃该项目的机会。
下面是我的代码（就像我之前说的，按钮触发了所有的声音，但是过滤器是个大问题）：
HTML：
<body>
<div id="startbtn">
<p><input type="button" onClick="tracks.toggle();">PLAY!</p>
</div> <!-- startbtn div -->
<div id="frequency">
<p><input type="range" id="freq1" min="0" max="1" step="0.01" value="1" onchange="sound.changeFrequency(this);" style="width:180px; background-color:#FFF;"> Frequency</p>
</p>
</div>
<script>
var tracks = new SongTracks();
var sound = new playSound();
</script>
</body>
JAVASCRIPT：
var context = new webkitAudioContext();
var myAudioAnalyser;
function init() {
if('webkitAudioContext' in window) {
myAudioContext = new webkitAudioContext();
// an analyser is used for the spectrum
myAudioAnalyser = myAudioContext.createAnalyser();
myAudioAnalyser.smoothingTimeConstant = 0.85;
myAudioAnalyser.connect(myAudioContext.destination);
fetchSounds();
};
};
// shim layer with setTimeout fallback
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
function playSound(buffer, time) {
var source = context.createBufferSource();
source.buffer = buffer;
var filter = context.createBiquadFilter(); ///////////////// HERE
filter.type = filter.LOWPASS;
filter.frequency.value = 5000;
source.connect(filter);
filter.connect(context.destination);
source.start(time);
this.filter = filter;
};
function loadSounds(obj, soundMap, callback) {
var names = []
var paths = []
for (var name in soundMap) {
var path = soundMap[name];
names.push(name);
paths.push(path);
}
bufferLoader = new BufferLoader(context, paths, function(bufferList) {
for (var i = 0; i < bufferList.length; i++) {
var buffer = bufferList[i];
var name = names[i];
obj[name] = buffer;
}
if (callback) {
callback();
}
});
bufferLoader.load();
};
function BufferLoader(context, urlList, callback) {
this.context = context;
this.urlList = urlList;
this.onload = callback;
this.bufferList = new Array();
this.loadCount = 0;
}
BufferLoader.prototype.loadBuffer = function(url, index) {
// Load buffer asynchronously
var request = new XMLHttpRequest();
request.open("GET", url, true);
request.responseType = "arraybuffer";
var loader = this;
request.onload = function() {
// Asynchronously decode the audio file data in request.response
loader.context.decodeAudioData(
request.response,
function(buffer) {
if (!buffer) {
alert('error decoding file data: ' + url);
return;
}
loader.bufferList[index] = buffer;
if (++loader.loadCount == loader.urlList.length)
loader.onload(loader.bufferList);
},
function(error) {
console.error('decodeAudioData error', error);
}
);
}
request.onerror = function() {
alert('BufferLoader: XHR error');
}
request.send();
};
BufferLoader.prototype.load = function() {
for (var i = 0; i < this.urlList.length; ++i)
this.loadBuffer(this.urlList[i], i);
};
var SongTracks = function() {
loadSounds(this, {
vocals: 'tracks/vocals.mp3',
guitar: 'tracks/guitar.mp3',
piano: 'tracks/piano.mp3'
});
};
var filter;
SongTracks.prototype.play = function() {
playSound(this.vocals, 0);
playSound(this.guitar, 0);
playSound(this.piano, 0);
///////////////////////////////////////////////////////////// OR HERE
var source1 = context.createBufferSource();
source1.buffer = this.buffer
source1 = bufferList[0];
var filter = context.createBiquadFilter();
filter.type = filter.LOWPASS;
filter.frequency.value = 5000;
source1.connect(filter);
filter.connect(context.destination);
this.filter = filter;
///////////////////////////////////////////////////////////////////// TO HERE?
};
SongTracks.prototype.stop = function() {
this.source.stop(0);
};
SongTracks.prototype.toggle = function() {
this.isPlaying ? this.stop() : this.play();
this.isPlaying = !this.isPlaying;
};
/* SongTracks.prototype.changeFrequency = function(element) {
var minValue = 40;
var maxValue = context.sampleRate / 2;
var numberOfOctaves = Math.log(maxValue / minValue) / Math.LN2;
var multiplier = Math.pow(2, numberOfOctaves * (element.value - 1.0));
this.filter.frequency.value = maxValue * multiplier;
}; */
playSound.prototype.changeFrequency = function(element) {
var minValue = 40;
var maxValue = context.sampleRate / 2;
var numberOfOctaves = Math.log(maxValue / minValue) / Math.LN2;
var multiplier = Math.pow(2, numberOfOctaves * (element.value - 1.0));
this.filter.frequency.value = maxValue * multiplier;
};
</script>
正如你所看到的，通过我的笔记等，我很困惑，有点碰壁。 我见过区分音频文件的代码，例如；
var source1 = context.createBufferSource();
var source2 = context.createBufferSource();
var source3 = context.createBufferSource();
var source4 = context.createBufferSource();
source1.buffer = bufferList[0];
source2.buffer = bufferList[1];
source3.buffer = bufferList[2];
source4.buffer = bufferList[3];
但我不知道，祝你好运。
【问题讨论】：
标签： javascript audio servlet-filters volume web-audio-api