MediaStreamAudioSourceNode

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 first 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.

Number of inputs 0
Number of outputs 1
Channel count 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

Inherits methods from its parent, AudioNode .

异常

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

Usage notes

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).

first 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 Comment
Web 音频 API
The definition of 'MediaStreamAudioSourceNode' in that specification.
工作草案

浏览器兼容性

更新 GitHub 上的兼容性数据
Desktop Mobile
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
注意事项
55
注意事项
Before Chrome 59, the default values were not supported.
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

图例

完整支持
完整支持
不支持
不支持
兼容性未知
兼容性未知
见实现注意事项。

另请参阅