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AudioContext: createMediaStreamTrackSource() method

The createMediaStreamTrackSource() method of the AudioContext interface creates and returns a MediaStreamTrackAudioSourceNode which represents an audio source whose data comes from the specified MediaStreamTrack.

This differs from createMediaStreamSource(), which creates a MediaStreamAudioSourceNode whose audio comes from the audio track in a specified MediaStream whose id is first, lexicographically (alphabetically).

Syntax

js

createMediaStreamTrackSource(track)

Parameters

track

The MediaStreamTrack to use as the source of all audio data for the new node.

Return value

A MediaStreamTrackAudioSourceNode object which acts as a source for audio data found in the specified audio track.

Examples

In this example, getUserMedia() is used to request access to the user's microphone. Once that access is attained, an audio context is established and a MediaStreamTrackAudioSourceNode is created using createMediaStreamTrackSource(), taking its audio from the first audio track in the stream returned by getUserMedia().

Then a BiquadFilterNode is created using createBiquadFilter(), and it's configured as desired to perform a lowshelf filter on the audio coming from the source. The output from the microphone is then routed into the new biquad filter, and the filter's output is in turn routed to the audio context's destination.

js

navigator.mediaDevices
  .getUserMedia({ audio: true, video: false })
  .then((stream) => {
    audio.srcObject = stream;
    audio.onloadedmetadata = (e) => {
      audio.play();
      audio.muted = true;
    };

    const audioCtx = new AudioContext();
    const audioTracks = stream.getAudioTracks();
    const source = audioCtx.createMediaStreamTrackSource(audioTracks[0]);

    const biquadFilter = audioCtx.createBiquadFilter();
    biquadFilter.type = "lowshelf";
    biquadFilter.frequency.value = 3000;
    biquadFilter.gain.value = 20;

    source.connect(biquadFilter);
    biquadFilter.connect(audioCtx.destination);
  })
  .catch((err) => {
    // Handle getUserMedia() error
  });

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
createMediaStreamTrackSource No No
68Firefox 68 implements the updated standard's definition of the "first" audio track; now the first track is the one whose ID comes first lexicographically.
No No No No No
68Firefox 68 implements the updated standard's definition of the "first" audio track; now the first track is the one whose ID comes first lexicographically.
No No No

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/createMediaStreamTrackSource