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AudioContext: createMediaStreamSource() method

The createMediaStreamSource() method of the AudioContext Interface is used to create a new MediaStreamAudioSourceNode object, given a media stream (say, from a MediaDevices.getUserMedia instance), the audio from which can then be played and manipulated.

For more details about media stream audio source nodes, check out the MediaStreamAudioSourceNode reference page.

Syntax

createMediaStreamSource(stream)

Parameters

stream: A MediaStream to serve as an audio source to be fed into an audio processing graph for use and manipulation.

Return value

A new MediaStreamAudioSourceNode object representing the audio node whose media is obtained from the specified source stream.

Examples

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!

Note: You can see this example running live, or view the source.

const pre = document.querySelector("pre");
const video = document.querySelector("video");
const myScript = document.querySelector("script");
const 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((stream) => {
      video.srcObject = stream;
      video.onloadedmetadata = (e) => {
        video.play();
        video.muted = true;
      };

      // Create a MediaStreamAudioSourceNode
      // Feed the HTMLMediaElement into it
      const audioCtx = new AudioContext();
      const source = audioCtx.createMediaStreamSource(stream);

      // Create a biquadfilter
      const 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 = () => {
        biquadFilter.gain.value = range.value;
      };
    })
    .catch((err) => {
      console.log(`The following gUM error occurred: ${err}`);
    });
} else {
  console.log("getUserMedia not supported on your browser!");
}

// dump script to pre element

pre.innerHTML = myScript.innerHTML;

Note: 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.

Specifications

Specification
Web Audio API # dom-audiocontext-createmediastreamsource

Browser compatibility