Cannot play album with AVAudioPlayer

Question

I'm working on a very simple OSX application that will allow me to play either a song or a folder of songs. I can choose a song and play it and everything is fine. I can choose a folder and create an array of songs and... play the last one.

 var currentSong: NSURL?
 var album: [NSURL] = [] 
 var audioPlayer = AVAudioPlayer()

My playing function is

func playCurrent(){
    do {
        try audioPlayer = AVAudioPlayer(contentsOfURL: currentSong!)
    } catch {
        print("Ignoring errors for now")
    }
    audioPlayer.play()
 }

This works fine whenever I set currentSong to a NSURL. I choose one song, it plays it.

My album function is as follows:

@IBAction func chooseAlbumAndPlay(sender: AnyObject) {
    album = albumFromFile()
    for song in album {
        currentSong = song
        playCurrent()
    }
}

and here I have the problem. albumFromFile opens an NSOpenPanel, lets me choose a folder, and dumps paths to playable items into an array of NSURLs. This part works, I've verified it, so I really have an array with 12 or 20 or whatever correct, playable URLs. If I just run it as is, only the last song in any album gets played. If I set a breakpoint in the playCurrent() function, I can hear that it will actually play a tiny snippet - less than a note in most cases - of all songs but the last. According to the documentation, play() returns a boolean - and it will happily report that it has finished playing every song in this loop.

My - human - opinion is that a song has only finished playing when I have heard all of it.

If I query the duration of the current AVAudioPlayer, they all report perfectly reasonable-sounding values.

I'm completely stumped here. PlayCurrent seems to completely fail to assert itself as a running function. The expected behaviour is that it will not exit until play() has finished playing; observed behaviour is that it will touch every song for the briefest time, go 'been there' and return to the enclosing loop.

How can I force AVAudioPlayer to play the whole of a file before exiting my playCurrent() function? And where would I have found that information? (The class documentation is unhelpful, the mentioned audio guides do not exist - right now, the Developer Library does not mention any basic audio guides for OSX.

Check iOS sample code and get idea how to do it properly. Sorry, no Swift code developer.apple.com/library/ios/samplecode/avTouch/Listings/… developer.apple.com/library/ios/samplecode/AddMusic/Listings/… — Marek H
Hi Marek,the first link only shows how to play a single sound (I can do that); the second link is manually memory-managed iOS code that does not compile under OSX10.11/Xcode 7.2b; given that it's six years old, I have my doubts about its general viability. It also uses the MediaPlayer frameworks' setQueueWithItemCollection method; this isn't available on OSX. — green_knight
What about the delegate that notifies you once the song ended. And also google a bit "AVxxx site:github.com". It might help. — Marek H

green_knight green_knight · Accepted Answer · 2015-10-09T17:35:03

The answer is, once you get around to it, very obvious indeed. Unfortunately, the documentation really is no help at all. I could, in theory, have found the solution by looking at the entry for AVAudioPlayer in the AVFoundationFramework reference, but I didn't. (I found it by wildly casting about and a chance mention).

There appear to be no working OSX examples; Apple's iOS example uses the MediaPlayer framework that is not available on OSX.

The solution is as follows: An AVAudioPlayer plays a single sound. If you want to play more than one sound, you need an AVQueuePlayer which can also play a single sound from a URL or a queue of AVPlayerItems (this class has an init(URL:) method). If anyone has an idea why AVAudioPlayer behaves as it does, I'm still interested to hear it.

Cannot play album with AVAudioPlayer

1 Answers