BaseAudioContext.createDynamicsCompressor()

The createDynamicsCompressor() method of the BaseAudioContext Interface is used to create a DynamicsCompressorNode, which can be used to apply compression to an audio signal.

Compression lowers the volume of the loudest parts of the signal and raises the volume of the softest parts. Overall, a louder, richer, and fuller sound can be achieved. It is especially important in games and musical applications where large numbers of individual sounds are played simultaneously, where you want to control the overall signal level and help avoid clipping (distorting) of the audio output.

Note: The DynamicsCompressorNode() constructor is the recommended way to create a DynamicsCompressorNode; see Creating an AudioNode.

Syntax

baseAudioCtx.createDynamicsCompressor();

Returns

A DynamicsCompressorNode.

Example

The code below demonstrates a simple usage of createDynamicsCompressor() to add compression to an audio track. For a more complete example, have a look at our basic Compressor example (view the source code). 

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
var source = audioCtx.createMediaElementSource(myAudio);

// Create a compressor node
var compressor = audioCtx.createDynamicsCompressor();
compressor.threshold.setValueAtTime(-50, audioCtx.currentTime);
compressor.knee.setValueAtTime(40, audioCtx.currentTime);
compressor.ratio.setValueAtTime(12, audioCtx.currentTime);
compressor.attack.setValueAtTime(0, audioCtx.currentTime);
compressor.release.setValueAtTime(0.25, audioCtx.currentTime);

// connect the AudioBufferSourceNode to the destination
source.connect(audioCtx.destination);

button.onclick = function() {
  var active = button.getAttribute('data-active');
  if(active == 'false') {
    button.setAttribute('data-active', 'true');
    button.textContent = 'Remove compression';

    source.disconnect(audioCtx.destination);
    source.connect(compressor);
    compressor.connect(audioCtx.destination);
  } else if(active == 'true') {
    button.setAttribute('data-active', 'false');
    button.textContent = 'Add compression';

    source.disconnect(compressor);
    compressor.disconnect(audioCtx.destination);
    source.connect(audioCtx.destination);
  }
}

Specifications

Specification
Web Audio API
# dom-baseaudiocontext-createdynamicscompressor

Browser compatibility

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See also