Web/API/ChannelMergerNode

The ChannelMergerNode interface, often used in conjunction with its opposite, ChannelSplitterNode, reunites different mono inputs into a single output. Each input is used to fill a channel of the output. This is useful for accessing each channels separately, e.g. for performing channel mixing where gain must be separately controlled on each channel.

[[File:../../../../../media.prod.mdn.mozit.cloud/attachments/2014/12/07/9709/5bc1705dc2e18d97af5131dee01dfb58/WebAudioMerger.png]]

If ChannelMergerNode has one single output, but as many inputs as there are channels to merge; the number of inputs is defined as a parameter of its constructor and the call to AudioContext.createChannelMerger. In the case that no value is given, it will default to 6.

Using a ChannelMergerNode, it is possible to create outputs with more channels than the rendering hardware is able to process. In that case, when the signal is sent to the AudioContext.listener object, supernumerary channels will be ignored.

Number of inputs	variable; default to `6`.
Number of outputs	`1`
Channel count mode	`"max"`
Channel count	`2` (not used in the default count mode)
Channel interpretation	`"speakers"`

Constructor

ChannelMergerNode(): Creates a new ChannelMergerNode object instance.

Properties

No specific property; inherits properties from its parent, AudioNode.

Methods

No specific method; inherits methods from its parent, AudioNode.

Example

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.

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

 // Reduce the volume of the left channel only
 var 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);

 var 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

Specification	Status	Comment
Web Audio APIThe definition of 'ChannelMergerNode' in that specification.	Working Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`ChannelMergerNode`	Chrome Full support 14	Edge Full support ≤18	Firefox Full support 25	IE No support No	Opera Full support 15	Safari Full support 6	WebView Android Full support Yes	Chrome Android Full support 18	Firefox Android Full support 26	Opera Android Full support 14	Safari iOS Full support Yes	Samsung Internet Android Full support 1.0
`ChannelMergerNode()` constructor	Chrome Full support 55	Edge Full support 79	Firefox Full support 53	IE No support No	Opera Full support 42	Safari No support No	WebView Android Full support 55	Chrome Android Full support 55	Firefox Android Full support 53	Opera Android Full support 42	Safari iOS No support No	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
No support: No support