AudioKit: Fade in from AKOperationGenerator - swift

Question

Is there a way to fade in a sound from an AKOperationGenerator?
E.g. in the code below .start() begins at full amplitude with a click.
let whiteNoiseGenerator = AKOperationGenerator { _ in
let white = AKOperation.whiteNoise()
return white
}
AudioKit.output = whiteNoiseGenerator
whiteNoiseGenerator.start()

Answer 1

There are a lot of ways to skin this cat. I'll give you a couple:
One would be to wrap the noise generator in an AKBooster:
let volumeControl = AKBooster(whiteNoiseGenerator)
volumeControl.gain = 0
volumeControl.rampTime = 1 // number of seconds to fade in/out
AudioKit.output = volumeControl
AudioKit.start() // Don't forget this, I assume you just didn't paste it in
whiteNoiseGenerator.start() // nothing will be heard
Then starting and stopping the sound will just be done by setting
volumeControl.gain = 1 // or 0 for stopping
Alternatively, I know you wanted to know how to do this in the context of an operation, so you can do that by giving your operation parameters of gain and portamento time:
let whiteNoiseGenerator = AKOperationGenerator { parameters in
let white = AKOperation.whiteNoise() * parameters[0].portamento(halfDuration: parameters[1])
return white
}
whiteNoiseGenerator.parameters = [0,0.1] // first number is gain, second is portamento time
AudioKit.output = whiteNoiseGenerator
AudioKit.start()
whiteNoiseGenerator.start()
And then, when you want to turn on the noise do this:
whiteNoiseGenerator.parameters[0] = 1
you will get a smooth variation to full volume over 0.1 seconds.
HTH!