MediaStreamAudioSourceNode

在此页

构造函数
特性
方法
异常
用法注意事项
范例
规范
浏览器兼容性
另请参阅
相关话题

MediaStreamAudioSourceNode interface is a type of AudioNode which operates as an audio source whose media is received from a MediaStream obtained using the WebRTC or Media Capture and Streams APIs. This media could be from a microphone (through getUserMedia() ) or from a remote peer on a WebRTC call (using the RTCPeerConnection 's audio tracks).

A MediaStreamAudioSourceNode has no inputs and exactly one output, and is created using the AudioContext.createMediaStreamSource() 方法。

MediaStreamAudioSourceNode takes the audio from the 第一 MediaStreamTrack whose kind attribute's value is audio 。见 Track ordering for more information about the order of tracks.

The number of channels output by the node matches the number of tracks found in the selected audio track.

输入数	`0`
输出数	`1`
通道计数	defined by the first audio `MediaStreamTrack` passed to the `AudioContext.createMediaStreamSource()` method that created it.

构造函数

new MediaStreamAudioSourceNode(): 创建新的 MediaStreamAudioSourceNode object instance with the specified options.

特性

In addition to the following properties, MediaStreamAudioSourceNode inherits the properties of its parent, AudioNode .

mediaStream 只读: MediaStream used when constructing this MediaStreamAudioSourceNode .

方法

继承方法来自其父级 AudioNode .

异常

InvalidStateError: The stream specified by the mediaStream parameter does not contain any audio tracks.

用法注意事项

Typically, you should probably not use this type of node. It has been replaced with the more predictable MediaStreamTrackAudioSourceNode , which has better-defined rules for how it chooses the track to output.

If you do chooose to use MediaStreamAudioSourceNode , you should keep the following in mind.

Track ordering

For the purposes of the MediaStreamTrackAudioSourceNode interface, the order of the audio tracks on the stream is determined by taking the tracks whose kind is audio , then sorting the tracks by their id property's values, in Unicode code point order (essentially, in alphabetical or lexicographical order, for IDs which are simple alphanumeric strings).

第一 track, then, is the track whose id comes first when the tracks' IDs are all sorted by Unicode code point.

However, it's important to note that the rule establishing this ordering was added long after this interface was first introduced into the Web 音频 API . As such, you can't easily rely on the order matching between any two browsers or browser versions. This is why it is typically wiser to use MediaStreamTrackAudioSourceNode , which provides similar capabilities but was better-defined upon being added to the specification, so it's more reliable.

范例

In this example, we grab a media (audio + video) stream from navigator.getUserMedia , feed the media into a <video> element to play then mute the audio, but then also feed the audio into a MediaStreamAudioSourceNode . Next, we feed this source audio into a low pass BiquadFilterNode (which effectively serves as a bass booster), then a AudioDestinationNode .

The range slider below the <video> element controls the amount of gain given to the lowpass filter — increase the value of the slider to make the audio sound more bass heavy!

注意 : You can see this example running live ，或 view the source .

var pre = document.querySelector('pre');
var video = document.querySelector('video');
var myScript = document.querySelector('script');
var range = document.querySelector('input');
// getUserMedia block - grab stream
// put it into a MediaStreamAudioSourceNode
// also output the visuals into a video element
if (navigator.mediaDevices) {
    console.log('getUserMedia supported.');
    navigator.mediaDevices.getUserMedia ({audio: true, video: true})
    .then(function(stream) {
        video.srcObject = stream;
        video.onloadedmetadata = function(e) {
            video.play();
            video.muted = true;
        };
        // Create a MediaStreamAudioSourceNode
        // Feed the HTMLMediaElement into it
        var audioCtx = new AudioContext();
        var source = audioCtx.createMediaStreamSource(stream);
        // Create a biquadfilter
        var biquadFilter = audioCtx.createBiquadFilter();
        biquadFilter.type = "lowshelf";
        biquadFilter.frequency.value = 1000;
        biquadFilter.gain.value = range.value;
        // 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(biquadFilter);
        biquadFilter.connect(audioCtx.destination);
        // Get new mouse pointer coordinates when mouse is moved
        // then set new gain value
        range.oninput = function() {
            biquadFilter.gain.value = range.value;
        }
    })
    .catch(function(err) {
        console.log('The following gUM error occured: ' + err);
    });
} else {
   console.log('getUserMedia not supported on your browser!');
}
// dump script to pre element
pre.innerHTML = myScript.innerHTML;

注意 : As a consequence of calling createMediaStreamSource() , audio playback from the media stream will be re-routed into the processing graph of the AudioContext . So playing/pausing the stream can still be done through the media element API and the player controls.

规范

规范	状态	注释
Web 音频 API The definition of 'MediaStreamAudioSourceNode' 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
`MediaStreamAudioSourceNode`	Chrome 23	Edge ≤18	Firefox 25	IE 不支持 No	Opera 15	Safari 6	WebView Android Yes	Chrome Android Yes	Firefox Android 26	Opera Android 14	Safari iOS Yes	Samsung Internet Android Yes
`MediaStreamAudioSourceNode()` 构造函数	Chrome 55	Edge ≤79	Firefox 53	IE 不支持 No	Opera 42	Safari ?	WebView Android 55 注意事项 55 注意事项 Before Chrome 59, the default values were not supported.	Chrome Android 55 注意事项 55 注意事项 Before Chrome 59, the default values were not supported.	Firefox Android 53	Opera Android 42	Safari iOS ?	Samsung Internet Android 6.0 注意事项 6.0 注意事项 Before Samsung Internet 7.0, the default values were not supported.
`mediaStream`	Chrome 23	Edge ≤79	Firefox 70	IE 不支持 No	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android 不支持 No	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

在此页

构造函数

特性

方法

异常

用法注意事项

Track ordering

范例

规范

浏览器兼容性

图例

另请参阅

元数据

相关话题