public final class DynamicsCompressorNode

Lowers the volume of loud passages so the mix stays clear of clipping: the Web Audio DynamicsCompressorNode.

Every parameter is k-rate. The detector follows the loudest channel, the gain curve has a soft knee getKnee() decibels wide centred on getThreshold(), and gain changes are smoothed by getAttack() and getRelease(). As in browsers the signal is delayed by a 6 ms look-ahead and a make-up gain raises the result so that a full-scale signal comes out near full scale. The specification leaves the exact curve to the implementation, so values match browsers in shape, not to the sample.

OfflineAudioContext audio = new OfflineAudioContext(2, 44100, 44100);
GainNode mix = audio.createGain();
DynamicsCompressorNode comp = audio.createDynamicsCompressor();
comp.getThreshold().setValue(-18);
comp.getRatio().setValue(4);
mix.connect(comp).connect(audio.getDestination());