Loop audio for certain duration on iOS - ios

Question

I am wondering what the best solution to looping audio for a defined duration on iOS is.
I am currently playing around with
AVAudioPlayer (where I can define a repeat count but can't define an end-time)
AVPlayer (where I can define a forwardPlaybackEndTime bot not a loop count)
AVPlayerLooper (that I don't yet fully understand)
So what I need is to define a duration for which a certain sound-file is repeated. F.e. I have a 8 second mp3 and want to play it for f.e one minute.
What would also be suuuuper great, is if I could cross-fade when it starts over again.

Answer 1

You were on the right track with AVPlayerLooper.
This is how you setup AVPlayerLooper
var playerLooper: AVPlayerLooper!
var player: AVQueuePlayer!
func play(_ url: URL) {
let asset = AVAsset(url: url)
let playerItem = AVPlayerItem(asset: asset)
player = AVQueuePlayer(playerItem: playerItem)
playerLooper = AVPlayerLooper(player: player, templateItem: playerItem)
player.play()
}
To stop the loop after a set amount of time you can use addBoundaryTimeObserver(forTimes:queue:using:)
For example:
let assetDuration = CMTimeGetSeconds(asset.duration)
let maxDuration = 60.0 // Define max duration
let maxLoops = floor(maxDuration / assetDuration)
let lastLoopDuration = maxDuration - (assetDuration * maxLoops)
let boundaryTime = CMTimeMakeWithSeconds(lastLoopDuration, preferredTimescale: 1)
let boundaryTimeValue = NSValue(time: boundaryTime)
player.addBoundaryTimeObserver(forTimes: [boundaryTimeValue], queue: DispatchQueue.main) { [weak self] in
if self?.playerLooper.loopCount == Int(maxLoops) {
self?.player.pause()
}
}
For fading in/out you have to set the audioMix property to your AVPlayerItem instance before using it.
let introRange = CMTimeRangeMake(start: CMTimeMakeWithSeconds(0, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
let endingSecond = CMTimeRangeMake(start: CMTimeMakeWithSeconds(assetDuration - 1, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
let inputParams = AVMutableAudioMixInputParameters(track: asset.tracks.first! as AVAssetTrack)
inputParams.setVolumeRamp(fromStartVolume: 0, toEndVolume: 1, timeRange: introRange)
inputParams.setVolumeRamp(fromStartVolume: 1, toEndVolume: 0, timeRange: endingSecond)
let audioMix = AVMutableAudioMix()
audioMix.inputParameters = [inputParams]
playerItem.audioMix = audioMix
Complete function:
func play(_ url: URL) {
let asset = AVAsset(url: url)
let playerItem = AVPlayerItem(asset: asset)
let assetDuration = CMTimeGetSeconds(asset.duration)
let introRange = CMTimeRangeMake(start: CMTimeMakeWithSeconds(0, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
let endingSecond = CMTimeRangeMake(start: CMTimeMakeWithSeconds(assetDuration - 1, preferredTimescale: 1), duration: CMTimeMakeWithSeconds(1, preferredTimescale: 1))
let inputParams = AVMutableAudioMixInputParameters(track: asset.tracks.first! as AVAssetTrack)
inputParams.setVolumeRamp(fromStartVolume: 0, toEndVolume: 1, timeRange: introRange)
inputParams.setVolumeRamp(fromStartVolume: 1, toEndVolume: 0, timeRange: endingSecond)
let audioMix = AVMutableAudioMix()
audioMix.inputParameters = [inputParams]
playerItem.audioMix = audioMix
player = AVQueuePlayer(playerItem: playerItem)
playerLooper = AVPlayerLooper(player: player, templateItem: playerItem)
player.play()
let maxDuration = 60.0 // Define max duration
let maxLoops = floor(maxDuration / assetDuration)
let lastLoopDuration = maxDuration - (assetDuration * maxLoops)
let boundaryTime = CMTimeMakeWithSeconds(lastLoopDuration, preferredTimescale: 1)
let boundaryTimeValue = NSValue(time: boundaryTime)
player.addBoundaryTimeObserver(forTimes: [boundaryTimeValue], queue: DispatchQueue.main) { [weak self] in
if self?.playerLooper.loopCount == Int(maxLoops) {
self?.player.pause()
}
}
}