index.md

---

title: AudioContext.createMediaStreamTrackSource()
slug: Web/API/AudioContext/createMediaStreamTrackSource
page-type: web-api-instance-method
browser-compat: api.AudioContext.createMediaStreamTrackSource

---

{{ APIRef("Web Audio API") }}

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

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

Syntax

createMediaStreamTrackSource(track)

Parameters

• track

  • : The {{domxref("MediaStreamTrack")}} to use as the source of all audio data for the new node.

Return value

A {{domxref("MediaStreamTrackAudioSourceNode")}} object which acts as a source for audio data found in the specified audio track.

Examples

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

Then a {{domxref("BiquadFilterNode")}} is created using {{domxref("BaseAudioContext/createBiquadFilter", "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 {{domxref("BaseAudioContext/destination", "destination")}}.

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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Web Audio API

• Using the Web Audio API

• {{domxref("MediaStreamTrackAudioSourceNode")}}