WebAudio API更改其中一个源的音量

Question

我正在阅读这篇文章

我的目标是同时播放两个声音。一个声音的音量不同。有规律的"；音频"；标签不是一个解决方案，因为它在移动设备上运行不好。所以我开始深入研究网络音频API。

我在下面写了代码，它在所有设备上都能很好地工作。唯一的问题是，我不知道如何控制音量。示例中的代码不起作用(

请帮助

function init() {
// Fix up prefixing
window.AudioContext = window.AudioContext || window.webkitAudioContext;
context = new AudioContext();
bufferLoader = new BufferLoader(
context,
[
'mp3/speech.mp3',
'mp3/bg-melody.mp3',
],
finishedLoading
);
bufferLoader.load();
}
function finishedLoading(bufferList) {
document.querySelector('.message').innerHTML = "Ready to play"
// Create two sources and play them both together.
source1 = context.createBufferSource();
source2 = context.createBufferSource();
source1.buffer = bufferList[0];
source2.buffer = bufferList[1];
source1.connect(context.destination);
// This code is not working
var gainNode = context.createGain();
gainNode.gain.value = 0.1;
source2.connect(gainNode);
source2.connect(context.destination);
source2.loop = true;
}

更新：

此更改修复了问题

source2.connect(gainNode).connect(context.destination);

Answer 1

connect()方法返回一个AudioNode，然后必须调用connect()，以便将节点链接在一起：

const gainNode = context.createGain()
source2
.connect(gainNode)
.connect(context.destination)

const $ = document.querySelector.bind(document)
const $$ = document.querySelectorAll.bind(document)
const audioCtx = new (AudioContext || webkitAudioContext)()
const gainNodes = [
audioCtx.createGain(),
audioCtx.createGain(),
]
const url = 'https://opus-bitrates.anthum.com/audio/music-96.opus'
loadAudio(url, gainNodes[0])
loadAudio(url, gainNodes[1],
15.132 / (32 * 2),  // 32 beats in 15.132s
)
$$('input').forEach((el, i) => {
gainNodes[i].gain.value = el.value / 100
el.oninput = () => gainNodes[i].gain.value = el.value / 100
})
$('#play').onclick = play
$('#pause').onclick = pause
async function loadAudio(url, gainNode, delayS = 0) {
const buffer = await (await fetch(url)).arrayBuffer()
const source = audioCtx.createBufferSource()
source.buffer = await audioCtx.decodeAudioData(buffer)
source.loop = true
source
.connect(gainNode)
.connect(audioCtx.destination)
source.start(delayS)
}
function play() { audioCtx.resume() }
function pause() { audioCtx.suspend() }

<button id="play">Play</button><button id="pause">Pause</button><br />
<label><input type="range" value="50" max="100" /> Track 1</label><br />
<label><input type="range" value="50" max="100" /> Track 2</label>