AudioContext.createMediaElementSource()

AudioContext 接口的 createMediaElementSource() 方法用于创建一个新的 MediaElementAudioSourceNode 对象,输入某个存在的 HTML <audio> or <video> 元素, 对应的音频即可被播放或者修改.

为寻求更多关于媒体元素音频源节点的具体信息,请查阅 MediaElementAudioSourceNode 参考页.

语法

var audioCtx = new AudioContext();
var source = audioCtx.createMediaElementSource(myMediaElement);

参数

myMediaElement
某个被期待被录入音频处理图修改的 HTMLMediaElement 对象.

返回值

一个 MediaElementAudioSourceNode 对象.

示例

该示例由 <audio> 元素,通过使用 createMediaElementSource() 方法,创建了一个音源,将其通过 GainNode 节点,输出到AudioDestinationNode 节点以播放.当鼠标指针移动时, updatePage() 函数被调用,该函数计算当前鼠标Y坐标与页面高度的比值, 改变 GainNode 节点的值以调整音量.您就可以通过鼠标上下移动而改变音乐的音量了.

Note: 您也可以 浏览该示例的在线演示, 或者 浏览源代码.

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var myAudio = document.querySelector('audio');
var pre = document.querySelector('pre');
var myScript = document.querySelector('script');

pre.innerHTML = myScript.innerHTML;

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
var source = audioCtx.createMediaElementSource(myAudio);

// Create a gain node
var gainNode = audioCtx.createGain();

// Create variables to store mouse pointer Y coordinate
// and HEIGHT of screen
var CurY;
var HEIGHT = window.innerHeight;

// Get new mouse pointer coordinates when mouse is moved
// then set new gain value

document.onmousemove = updatePage;

function updatePage(e) {
    CurY = (window.Event) ? e.pageY : event.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);

    gainNode.gain.value = CurY/HEIGHT;
}


// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination, so we can play the
// music and adjust the volume using the mouse cursor
source.connect(gainNode);
gainNode.connect(audioCtx.destination);

Note: 作为调用 createMediaElementSource() 的结果,HTMLMediaElement 的播放将会由AudioContext的音频处理图接管.所以对媒体进行播放/暂停等操作仍可通过media API与播放器面板来进行.

规范

Specification Status Comment
Web Audio API
createMediaElementSource()
Working Draft  

浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help! (en-US)
Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit (en-US) (Yes) 25.0 (25.0)  未实现 15.0webkit (en-US)
22

6.0webkit (en-US)

- buggy! not working -

Feature Android Edge Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? (Yes) 26.0 1.2 ? ?

?

- buggy! not working -

33.0

相关链接