当我播放音频与AudioBufferSourceNode
,可我没有任何间隙之前(增益或声像或其他可能的节点)添加其他节点或在播放跳跃?这是在规范中提到的地方?有人对这个有经验么?
// Play audio
var source = context.createBufferSource();
source.buffer = someBuffer;
source.connect(context.destination);
source.start();
// Later, when source is still playing, is this safe?
source.disconnect();
source.connect(gain);
gain.connect(context.destination);
// And removing nodes is safe too?
gain.disconnect();
source.disconnect();
source.connect(context.destination);
我知道,因为我希望我能重新安排节点,但我的问题是关于实际播放过程中重新排列。
我没有检查了规范,但是从测试,实现根本的不同呢?
当完全断开Chrome和Safari浏览器将暂停AudioBufferSourceNode的播放,而Firefox将保持运行。
const ctx = new(window.AudioContext || window.webkitAudioContext);
let source;
let connected = true;
btn.onclick = e => {
btn.textContent = 'loading...';
btn.disabled = true;
fetch('https://upload.wikimedia.org/wikipedia/commons/2/23/Turdus_fuscater_-_Great_Thrush_XC243229.mp3')
.then(r => r.arrayBuffer())
.then(buf => ctx.decodeAudioData(buf))
.then(audioBuf => {
source = ctx.createBufferSource();
source.buffer = audioBuf;
source.onended = e => console.log('done');
source.connect(ctx.destination);
btn.onclick = e => {
source.start(0);
btn.onclick = switchConnect;
btn.textContent = 'switch connection';
};
btn.textContent = 'play';
btn.disabled = false;
});
};
function switchConnect() {
if (connected)
source.disconnect();
else
source.connect(ctx.destination);
connected = !connected;
}
<script src="https://cdn.jsdelivr.net/gh/mohayonao/promise-decode-audio-data@eb4b1322113b08614634559bc12e6a8163b9cf0c/build/promise-decode-audio-data.min.js"></script>
<button id="btn">fetch</button>
现在,即使播放不会暂停,你可以遇到一些杂音。这就是为什么即使AudioNode.disconnect()
has been extended to allow for a destination
parameter的原因,这使我们能够从中目的地,我们要断开微调,而不是从任何地方断开。
所以这样做,你可以简单地首先连接您的节点到新的目标,然后从以前的断开。这应该摆脱明显的杂音,而在播放WebKit的停顿。
但是,请注意,所有的浏览器仍然不支持该选项,从我测试的,Chrome和Firefox做,Safari浏览器没有。因为在非支持的浏览器调用disconnect(destination)
实际上将其所有目的地断开连接,我们在我们的代码来处理这两种情况。
let supportFineDisconnect = false;
const ctx = new(window.AudioContext || window.webkitAudioContext);
const osc = ctx.createOscillator();
const gain = ctx.createGain();
// lazy checks support for AudioNode.disconnect(destination)
try {
osc.disconnect(osc);
} catch (e) {
supportFineDisconnect = "maybe";
}
btn1.onclick = begin;
onchange = switchRoute;
function begin(){
osc.connect(gain);
gain.connect(ctx.destination);
gain.gain.value = 1;
osc.start(0);
btn1.textContent = 'stop';
btn1.onclick = e => osc.stop(0);
}
function switchRoute() {
if (!supportFineDisconnect) { // might click
osc.disconnect(); // disconnect from all
}
if (+document.querySelector('input:checked').value) {
connectDirect();
} else {
connectGain();
}
}
function connectDirect() {
// first connect to new dest
osc.connect(ctx.destination);
if (supportFineDisconnect) {
osc.disconnect(gain); // then disconnect only from gain
}
}
function connectGain() {
// first connect to new dest
osc.connect(gain);
if (supportFineDisconnect) {
osc.disconnect(ctx.destination); // then disconnect only from main
}
}
<button id="btn1">start playing a 440hz osc</button>
switch: <input type="radio" checked value="0" name="switch"><label>through gain</label>
<input type="radio" value="1" name="switch"><label>direct</label>
但当然,这仍然不能阻止由其他因素引起的点击或持久性有机污染物(如增益或他人的变化等)。