AVAudioPlayer fade volume out

Question

I have an AVAudioPlayer playing some audio (duh!)

The audio is initiated when the user presses a button. When they release it I want the audio to fade out.

I

Answer 1

Swift solution:

The top rated answer here is great but it gives a stuttering effect as the volume step of 0.1 is too much. Using 0.01 gives a smoother fade effect to hear.

Using this code you can specify how long you want the fade transition to last.

let fadeVolumeStep: Float = 0.01

let fadeTime = 0.5 // Fade time in seconds

var fadeVolumeStepTime: Double {
     return fadeTime / Double(1.0 / fadeVolumeStep)
}

func fadeOut() {
    guard let player = self.player else {
        return
    }

    if !player.playing { return }

    func fadeOutPlayer() {
        if player.volume > fadeVolumeStep {
            player.volume -= fadeVolumeStep
            delay(time: fadeVolumeStepTime, closure: {
                fadeOutPlayer()
            })
        } else {
            player.stop()
            player.currentTime = 0
            player.prepareToPlay()
        }
    }

    fadeOutPlayer()
}

func fadeIn() {
    guard let player = self.player else {
        return
    }

    if player.playing { return }
    player.volume = 0
    player.play()

    func fadeInPlayer() {
        if player.volume <= 1 - fadeVolumeStep {
            player.volume += fadeVolumeStep
            delay(time: fadeVolumeStepTime, closure: {
                fadeInPlayer()
            })
        } else {
            player.volume = 1
        }
    }

    fadeInPlayer()
}

func delay(time delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

you can adjust the time using fadeTime constant.