Fade out volume of AVAudioPlayerNode programmatically

Question

I've got an AVAudioEngine setup with a AVAudioPlayerNode that is playing some background music.

I'm trying to find a best approach to create a volume fadeout on the node over a 2 second timeframe. I'm considering using CADisplayLink in order to do this. I was wondering if somebody had experience with this scenario and could advise me on their approach?

score 5 · Answer 1 · answered Jul 01 '16 at 13:53

My approach is below. Note that I assign the timer to a member var so I can invalidate it at other points (viewWillDisappear, delloc, etc.). I was worried that it wouldn't sound smooth, but I tried it and it works fine, didn't need to use CADisplayLink.

- (void)fadeOutAudioWithDuration:(double)duration {
    double timerInterval = 0.1;
    NSNumber *volumeInterval = [NSNumber numberWithDouble:(timerInterval / duration)];
    self.fadeOutTimer = [NSTimer scheduledTimerWithTimeInterval:timerInterval target:self selector:@selector(fadeOutTimerDidFire:) userInfo:volumeInterval repeats:YES];
}

- (void)fadeOutTimerDidFire:(NSTimer *)timer {
    float volumeInterval = ((NSNumber *)timer.userInfo).floatValue;
    float currentVolume = self.audioEngine.mainMixerNode.outputVolume;
    float newValue = MAX(currentVolume - volumeInterval, 0.0f);
    self.audioEngine.mainMixerNode.outputVolume = newValue;
    if (newValue == 0.0f) {
        [timer invalidate];
    }
}

score 2 · Answer 2 · answered Jan 13 '16 at 10:58

2

You can use global gain in EQ.

for example

AVAudioUnitEQ *Volume;
Volume = [[AVAudioUnitEQ alloc] init];
[engine attachNode:Volume];
[engine connect:Volume to:engine.outputNode format:nil];

And then

Volume.globalGain = /*here your floatValue*/

answered Jan 13 '16 at 10:58

Ray

51
5

score 0 · Answer 3 · answered Mar 17 '21 at 11:10

In case anyone like me still looking for an answer:

As from docs, AVAudioPlayerNode doesn't support volume property, only AVAudioMixerNode node does. So ensure you envelope your AVAudioPlayerNode into AVAudioMixerNode.

Here's a code used to fade in, fade out and generally fade (Swift 5)

 typealias Completion = (() -> Void)

 let mixer = AVAudioMixerNode()

 func fade(from: Float, to: Float, duration: TimeInterval, completion: Completion?) {
     let stepTime = 0.01
     let times = duration / stepTime
     let step = (to - from) / Float(times)
     for i in 0...Int(times) {
         DispatchQueue.main.asyncAfter(deadline: .now() + Double(i) * stepTime) {
             mixer.volume = from + Float(i) * step

             if i == Int(times) {
                 completion?()
             }
         }
     }
 }

 func fadeIn(duration: TimeInterval = 1.3, completion: Completion? = nil) {
     fade(from: 0, to: 1, duration: duration, completion: completion)
 }

 func fadeOut(duration: TimeInterval = 1.3, completion: Completion? = nil) {
     fade(from: 1, to: 0, duration: duration, completion: completion)
 }

Fade out volume of AVAudioPlayerNode programmatically

3 Answers3