OfflineAudioContext.startRendering()

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startRendering() 方法在 OfflineAudioContext Interface starts rendering the audio graph, taking into account the current connections and the current scheduled changes.

complete event (of type OfflineAudioCompletionEvent ) is raised when the rendering is finished, containing the resulting AudioBuffer 在其 renderedBuffer 特性。

Browsers currently support two versions of the startRendering() method — an older event-based version and a newer promise-based version. The former will eventually be removed, but currently both mechanisms are provided for legacy reasons.

句法

Event-based version:

offlineAudioCtx.startRendering();
offlineAudioCtx.oncomplete = function(e) {
  // e.renderedBuffer contains the output buffer
}

Promise-based version:

offlineAudioCtx.startRendering().then(function(buffer) {
  // buffer contains the output buffer
});

参数

None.

Void.

范例

In this simple example, we declare both an AudioContext 和 OfflineAudioContext object. We use the AudioContext to load an audio track via XHR ( AudioContext.decodeAudioData ), then the OfflineAudioContext to render the audio into an AudioBufferSourceNode and play the track through. After the offline audio graph is set up, you need to render it to an AudioBuffer 使用 OfflineAudioContext.startRendering .

当 startRendering() promise resolves, rendering has completed and the output AudioBuffer is returned out of the promise.

At this point we create another audio context, create an AudioBufferSourceNode inside it, and set its buffer to be equal to the promise AudioBuffer . This is then played as part of a simple standard audio graph.

注意 : For a working example, see our offline-audio-context-promise Github repo (see the 源代码 too.)

// define online and offline audio context
var audioCtx = new AudioContext();
var offlineCtx = new OfflineAudioContext(2,44100*40,44100);
source = offlineCtx.createBufferSource();
// use XHR to load an audio track, and
// decodeAudioData to decode it and OfflineAudioContext to render it
function getData() {
  request = new XMLHttpRequest();
  request.open('GET', 'viper.ogg', true);
  request.responseType = 'arraybuffer';
  request.onload = function() {
    var audioData = request.response;
    audioCtx.decodeAudioData(audioData, function(buffer) {
      myBuffer = buffer;
      source.buffer = myBuffer;
      source.connect(offlineCtx.destination);
      source.start();
      //source.loop = true;
      offlineCtx.startRendering().then(function(renderedBuffer) {
        console.log('Rendering completed successfully');
        var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
        var song = audioCtx.createBufferSource();
        song.buffer = renderedBuffer;
        song.connect(audioCtx.destination);
        play.onclick = function() {
          song.start();
        }
      }).catch(function(err) {
          console.log('Rendering failed: ' + err);
          // Note: The promise should reject when startRendering is called a second time on an OfflineAudioContext
      });
    });
  }
  request.send();
}
// Run getData to start the process off
getData();

规范

规范	状态	注释
Web 音频 API The definition of 'startRendering()' in that specification.	工作草案

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`startRendering`	Chrome 14	Edge 12	Firefox 25	IE 不支持 No	Opera 15	Safari 6	WebView Android Yes	Chrome Android 18	Firefox Android 26	Opera Android 14	Safari iOS ?	Samsung Internet Android 1.0
Promise-based `startRendering()`	Chrome 42	Edge ≤18	Firefox 37	IE 不支持 No	Opera 29	Safari 不支持 No	WebView Android 42	Chrome Android 42	Firefox Android 37	Opera Android 29	Safari iOS 不支持 No	Samsung Internet Android 4.0

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完整支持
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使用 Web 音频 API

元数据

最后修改： 2020 年 1 月 22 日

Web 音频 API
OfflineAudioContext
构造函数
1. OfflineAudioContext()
特性
1. length
2. oncomplete
方法
1. resume()
2. startRendering()
3. suspend()
事件
1. complete
继承：
1. AudioContext
2. EventTarget
Related pages for Web Audio API

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