How to buffer audio using AVPlayer in iOS?

Question

I want to play stream audio from the Internet. I wrote code that plays stream but it don't have any buffer so if signal is weak application stop playing audio. This is my code:

import UIKit
import AVFoundation
import MediaPlayer
import AudioToolbox

class ViewController: UIViewController {

var playerItem:AVPlayerItem?
var player:AVPlayer?

@IBOutlet weak var PlayButton: UIButton!

override func viewDidLoad() {
    super.viewDidLoad()

    var buffer = AVAudioBuffer ()
    let url = NSURL (string: "http://radio.afera.com.pl/afera64.aac")
    playerItem = AVPlayerItem(URL: url!)
    player = AVPlayer(playerItem: playerItem!)

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

@IBAction func PlayButtonTapped(sender: AnyObject)
{
    if ((player!.rate != 0) && (player!.error == nil))
    {
        player!.pause()
        PlayButton.setImage(UIImage(named:"Play"), forState: UIControlState.Normal)
    }
    else
    {
        player!.play()
        PlayButton.setImage(UIImage(named:"Stop"), forState:UIControlState.Normal)
    }
}
}

I have no idea how to buffer this stream. I searched apple documentation but can't find anything in Swift.

I find something like AVAudioBuffer but I don't know how to use it, and if its correct to resolve this problem.

P.S. C# have documentation on MSDN, is something similar on Apple in case of Swift?

Answer 1

The answer is in creating an error delegate that launched a selector every time the player stopped (The error changes when the network connection is interrupted or the stream didn't load properly):

Here are delegates, just outside and above my RadioPlayer class:

protocol errorMessageDelegate {
func errorMessageChanged(newVal: String)
}

class:

import Foundation
import AVFoundation
import UIKit

class RadioPlayer : NSObject {

static let sharedInstance = RadioPlayer()
var instanceDelegate:sharedInstanceDelegate? = nil
var sharedInstanceBool = false {
    didSet {
        if let delegate = self.instanceDelegate {
            delegate.sharedInstanceChanged(self.sharedInstanceBool)
        }
    }
}
private var player = AVPlayer(URL: NSURL(string: Globals.radioURL)!)
private var playerItem = AVPlayerItem?()
private var isPlaying = false

var errorDelegate:errorMessageDelegate? = nil
var errorMessage = "" {
    didSet {
        if let delegate = self.errorDelegate {
            delegate.errorMessageChanged(self.errorMessage)
        }
    }
}

override init() {
    super.init()

    errorMessage = ""

    let asset: AVURLAsset = AVURLAsset(URL: NSURL(string: Globals.radioURL)!, options: nil)

    let statusKey = "tracks"

    asset.loadValuesAsynchronouslyForKeys([statusKey], completionHandler: {
        var error: NSError? = nil

        dispatch_async(dispatch_get_main_queue(), {
            let status: AVKeyValueStatus = asset.statusOfValueForKey(statusKey, error: &error)

            if status == AVKeyValueStatus.Loaded{

                let playerItem = AVPlayerItem(asset: asset)

                self.player = AVPlayer(playerItem: playerItem)
                self.sharedInstanceBool = true

            } else {
                self.errorMessage = error!.localizedDescription
                print(error!)
            }

        })


    })

    NSNotificationCenter.defaultCenter().addObserverForName(
        AVPlayerItemFailedToPlayToEndTimeNotification,
        object: nil,
        queue: nil,
        usingBlock: { notification in
            print("Status: Failed to continue")
            self.errorMessage = "Stream was interrupted"
    })

    print("Initializing new player")

}

func resetPlayer() {
    errorMessage = ""

    let asset: AVURLAsset = AVURLAsset(URL: NSURL(string: Globals.radioURL)!, options: nil)

    let statusKey = "tracks"

    asset.loadValuesAsynchronouslyForKeys([statusKey], completionHandler: {
        var error: NSError? = nil

        dispatch_async(dispatch_get_main_queue(), {
            let status: AVKeyValueStatus = asset.statusOfValueForKey(statusKey, error: &error)

            if status == AVKeyValueStatus.Loaded{

                let playerItem = AVPlayerItem(asset: asset)
                //playerItem.addObserver(self, forKeyPath: "status", options: NSKeyValueObservingOptions.New, context: &ItemStatusContext)

                self.player = AVPlayer(playerItem: playerItem)
                self.sharedInstanceBool = true

            } else {
                self.errorMessage = error!.localizedDescription
                print(error!)
            }

        })
    })
}

func bufferFull() -> Bool {
    return bufferAvailableSeconds() > 45.0
}

func bufferAvailableSeconds() -> NSTimeInterval {
    // Check if there is a player instance
    if ((player.currentItem) != nil) {

        // Get current AVPlayerItem
        let item: AVPlayerItem = player.currentItem!
        if (item.status == AVPlayerItemStatus.ReadyToPlay) {

            let timeRangeArray: NSArray = item.loadedTimeRanges
            if timeRangeArray.count < 1 { return(CMTimeGetSeconds(kCMTimeInvalid)) }
            let aTimeRange: CMTimeRange = timeRangeArray.objectAtIndex(0).CMTimeRangeValue
            //let startTime = CMTimeGetSeconds(aTimeRange.end)
            let loadedDuration = CMTimeGetSeconds(aTimeRange.duration)

            return (NSTimeInterval)(loadedDuration);
        }
        else {
            return(CMTimeGetSeconds(kCMTimeInvalid))
        }
    } 
    else {
        return(CMTimeGetSeconds(kCMTimeInvalid))
    }
}

func play() {
    player.play()
    isPlaying = true
    print("Radio is \(isPlaying ? "" : "not ")playing")
}

func pause() {
    player.pause()
    isPlaying = false
    print("Radio is \(isPlaying ? "" : "not ")playing")
}

func currentlyPlaying() -> Bool {
    return isPlaying
}

}
protocol sharedInstanceDelegate {
func sharedInstanceChanged(newVal: Bool)
}

RadioViewController:

import UIKit
import AVFoundation

class RadioViewController: UIViewController, errorMessageDelegate, sharedInstanceDelegate {

// MARK: Properties

var firstErrorSkip = true
var firstInstanceSkip = true

@IBOutlet weak var listenLabel: UILabel!
@IBOutlet weak var radioSwitch: UIImageView!

@IBAction func back(sender: AnyObject) {
    print("Dismissing radio view")
    if let navigationController = self.navigationController
    {
        navigationController.popViewControllerAnimated(true)
    }
}

@IBAction func switched(sender: AnyObject) {
    toggle()
}

override func viewDidLoad() {
    super.viewDidLoad()

    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
        print("AVAudioSession Category Playback OK")
        do {
            try AVAudioSession.sharedInstance().setActive(true)
            print("AVAudioSession is Active")

        } catch let error as NSError {
            print(error.localizedDescription)
        }
    } catch let error as NSError {
        print(error.localizedDescription)
    }

    RadioPlayer.sharedInstance.errorDelegate = self
    RadioPlayer.sharedInstance.instanceDelegate = self

    if RadioPlayer.sharedInstance.currentlyPlaying() {
        radioSwitch.image = UIImage(named: "Radio_Switch_Active")
        listenLabel.text = "Click to Pause Radio Stream:"
    }

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func toggle() {
    if RadioPlayer.sharedInstance.currentlyPlaying() {
        pauseRadio()
    } else {
        playRadio()
    }
}

func playRadio() {
    firstErrorSkip = false
    firstInstanceSkip = false

    if RadioPlayer.sharedInstance.errorMessage != "" || RadioPlayer.sharedInstance.bufferFull() {
        resetStream()
    } else {
        radioSwitch.image = UIImage(named: "Radio_Switch_Active")
        listenLabel.text = "Click to Pause Radio Stream:"
        RadioPlayer.sharedInstance.play()
    }
}

func pauseRadio() {
    RadioPlayer.sharedInstance.pause()
    radioSwitch.image = UIImage(named: "Radio_Switch_Inactive")
    listenLabel.text = "Click to Play Radio Stream:"
}

func resetStream() {
    print("Reloading interrupted stream");
    RadioPlayer.sharedInstance.resetPlayer()
    //RadioPlayer.sharedInstance = RadioPlayer();
    RadioPlayer.sharedInstance.errorDelegate = self
    RadioPlayer.sharedInstance.instanceDelegate = self
    if RadioPlayer.sharedInstance.bufferFull() {
        radioSwitch.image = UIImage(named: "Radio_Switch_Active")
        listenLabel.text = "Click to Pause Radio Stream:"
        RadioPlayer.sharedInstance.play()
    } else {
        playRadio()
    }
}

func errorMessageChanged(newVal: String) {
    if !firstErrorSkip {
        print("Error changed to '\(newVal)'")
        if RadioPlayer.sharedInstance.errorMessage != "" {
            print("Showing Error Message")
            let alertController = UIAlertController(title: "Stream Failure", message: RadioPlayer.sharedInstance.errorMessage, preferredStyle: UIAlertControllerStyle.Alert)
            alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))

            self.presentViewController(alertController, animated: true, completion: nil)

            pauseRadio()

        }
    } else {
        print("Skipping first init")
        firstErrorSkip = false
    }
}

func sharedInstanceChanged(newVal: Bool) {
    if !firstInstanceSkip {
    print("Detected New Instance")
        if newVal {
            RadioPlayer.sharedInstance.play()
        }
    } else {
        firstInstanceSkip = false
    }
}

}

Hope this will help :)