WaveShaperNode outputs incorrect values in Safari

Not sure if the intention of this library is to normalize the functionality as well as the interface of Web Audio across implementations, but there a known issue with the WaveShaperNode in Safari that i’ll point out in case you want to include the fix somehow:

Try running this code:

import {OfflineAudioContext} from 'standardized-audio-context'

const context = new OfflineAudioContext(1, 441, 44100)

const waveshaper = context.createWaveShaper()
waveshaper.curve = Float32Array.from([0, 0.25, 0.5, 0.75, 1])

const signal = context.createConstantSource()
signal.offset.value = 0
signal.start(0)
signal.connect(waveshaper).connect(context.destination)

context.startRendering().then(buffer => {
	console.log(buffer.getChannelData(0)[0])
})

You’ll see in Chrome and Firefox, the output is 0.5, while in Safari the output is 0.625.

I’ve found that a simple fix to this issue is to increase the curve array length in Safari and repeat the first value. Something like this:

function setCurve(curve){
  var array = new Float32Array(curve.length+1);
  array.set(curve, 1);
  array[0] = curve[0];
  _internalNode.curve = array;
}

One issue is that this is a hard thing to test for without using the OfflineAudioContext like i did above, so the only way to know when to add the polyfill is by testing the userAgent which is often not the best practice.

[chrisguttandin]

Version 17.5.6 finally includes the changes.

As always, please let me know if you encounter any bugs or problems.

[chrisguttandin]

Hi @tambien, I’m sorry I initially planned to release a patch version, but now I have a problem with the tests running on Travis. I have to fix this first.