MediaStreamAudioSourceNode

A MediaElementSourceNode has no inputs and exactly one output, and is created using the AudioContext.createMediaStreamSource method. The amount of channels in the output equals the number of channels in AudioMediaStreamTrack. If there is no valid media stream, then the number of output channels will be one silent channel.

Properties

Inherits properties from its parent, AudioNode.

Methods

Inherits methods from its parent, AudioNode.

Example

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!

// fork getUserMedia for multiple browser versions, for those
// that need prefixes

navigator.getUserMedia = (navigator.getUserMedia ||
                          navigator.webkitGetUserMedia ||
                          navigator.mozGetUserMedia ||
                          navigator.msGetUserMedia);

// define other variables

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var myAudio = document.querySelector('audio');
var pre = document.querySelector('pre');
var video = document.querySelector('video');
var myScript = document.querySelector('script');
var range = document.querySelector('input');

// Create variables to store mouse pointer Y coordinate
// and HEIGHT of screen
var CurY;
var HEIGHT = window.innerHeight;

// getUserMedia block - grab stream
// put it into a MediaStreamAudioSourceNode
// also output the visuals into a video element

if (navigator.getUserMedia) {
   console.log('getUserMedia supported.');
   navigator.getUserMedia (
      // constraints: audio and video for this app
      {
         audio: true,
         video: true
      },

      // Success callback
      function(stream) {
         video.src = (window.URL && window.URL.createObjectURL(stream)) || stream;
         video.onloadedmetadata = function(e) {
            video.play();
            video.muted = 'true';
         };

         // Create a MediaStreamAudioSourceNode
         // Feed the HTMLMediaElement into it
         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;
          }

      },

      // Error callback
      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;

Specification

Browser compatibility

See also

• Using the Web Audio API