BaseAudioContext: createChannelMerger() method

The createChannelMerger() method of the BaseAudioContext interface creates a ChannelMergerNode, which combines channels from multiple audio streams into a single audio stream.

[!NOTE] The ChannelMergerNode() constructor is the recommended way to create a ChannelMergerNode; see Creating an AudioNode.

Syntax

createChannelMerger(numberOfInputs)

Parameters

• numberOfInputs
  • : The number of channels in the input audio streams, which the output stream will contain; the default is 6 if this parameter is not specified.

Return value

A ChannelMergerNode.

Examples

The following example shows how you could separate a stereo track (say, a piece of music), and process the left and right channel differently. To use them, you need to use the second and third parameters of the AudioNode.connect(AudioNode) method, which allow you to specify both the index of the channel to connect from and the index of the channel to connect to.

const ac = new AudioContext();
ac.decodeAudioData(someStereoBuffer, (data) => {
  const source = ac.createBufferSource();
  source.buffer = data;
  const splitter = ac.createChannelSplitter(2);
  source.connect(splitter);
  const merger = ac.createChannelMerger(2);

  // Reduce the volume of the left channel only
  const gainNode = ac.createGain();
  gainNode.gain.setValueAtTime(0.5, ac.currentTime);
  splitter.connect(gainNode, 0);

  // Connect the splitter back to the second input of the merger: we
  // effectively swap the channels, here, reversing the stereo image.
  gainNode.connect(merger, 0, 1);
  splitter.connect(merger, 1, 0);

  const dest = ac.createMediaStreamDestination();

  // Because we have used a ChannelMergerNode, we now have a stereo
  // MediaStream we can use to pipe the Web Audio graph to WebRTC,
  // MediaRecorder, etc.
  merger.connect(dest);
});

Specifications

Browser compatibility

See also

• Using the Web Audio API