Jumpy UISlider when scrubbing - Using UISlider with AVPlayer

Question

I am using AvPlayer and am trying to set up a slider to allow scrubbing of audio files. Im having a problem with the slider jumping all over the place when its selected. It then goes back to the origin position for a second before going back to the location it was dragged to.

You cant see my cursor on the Gif, but the smooth elongated drags are me moving the knob, then the quick whips are the slider misbehaving.

Ive spent hours googling and combing through Stack Overflow and cant figure out what I'm doing wrong here, a lot of similar questions are quite old and in ObjC.

This is the section of code i think is responsible for the problem, it does handle the event of the slider being moved: Ive tried it without the if statement also and didn't see a different result.

@IBAction func horizontalSliderActioned(_ sender: Any) {

    horizontalSlider.isContinuous = true

    if self.horizontalSlider.isTouchInside {

        audioPlayer?.pause()
            let seconds : Int64 = Int64(horizontalSlider.value)
                let preferredTimeScale : Int32 = 1
                    let seekTime : CMTime = CMTimeMake(seconds, preferredTimeScale)
                        audioPlayerItem?.seek(to: seekTime)
                            audioPlayer?.play()

    } else {

        let duration : CMTime = (self.audioPlayer?.currentItem!.asset.duration)!
            let seconds : Float64 = CMTimeGetSeconds(duration)
                self.horizontalSlider.value = Float(seconds)
    }
}

I will include my entire class below for reference.

import UIKit
import Parse
import AVFoundation
import AVKit


class PlayerViewController: UIViewController, AVAudioPlayerDelegate {

    @IBOutlet var horizontalSlider: UISlider!

    var selectedAudio: String!

    var audioPlayer: AVPlayer?
    var audioPlayerItem: AVPlayerItem?

    var timer: Timer?


    func getAudio() {

        let query = PFQuery(className: "Part")
                query.whereKey("objectId", equalTo: selectedAudio)
                    query.getFirstObjectInBackground { (object, error) in

                if error != nil || object == nil {
                    print("The getFirstObject request failed.")

                } else {
                    print("There is an object now get the Audio. ")

                        let audioFileURL = (object?.object(forKey: "partAudio") as! PFFile).url
                            self.audioPlayerItem = AVPlayerItem(url: NSURL(string: audioFileURL!) as! URL)
                                self.audioPlayer = AVPlayer(playerItem: self.audioPlayerItem)
                                    let playerLayer = AVPlayerLayer(player: self.audioPlayer)
                                        playerLayer.frame = CGRect(x: 0, y: 0, width: 10, height: 10)
                                            self.view.layer.addSublayer(playerLayer)

                        let duration : CMTime = (self.audioPlayer?.currentItem!.asset.duration)!
                            let seconds : Float64 = CMTimeGetSeconds(duration)
                                let maxTime : Float = Float(seconds)
                                    self.horizontalSlider.maximumValue = maxTime

                        self.audioPlayer?.play()

                        self.timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(PlayerViewController.audioSliderUpdate), userInfo: nil, repeats: true)
                }
            }
    }


    @IBOutlet var playerButton: UIButton!


    func playerButtonTapped() {

        if audioPlayer?.rate == 0 {
            audioPlayer?.play()
                self.playerButton.setImage(UIImage(named: "play"), for: UIControlState.normal)

        } else {
            audioPlayer?.pause()
                self.playerButton.setImage(UIImage(named: "pause"), for: UIControlState.normal)
        }

    }


    override func viewDidLoad() {
        super.viewDidLoad()

        horizontalSlider.minimumValue = 0
            horizontalSlider.value = 0

                self.playerButton.addTarget(self, action: #selector(PlayerViewController.playerButtonTapped), for: UIControlEvents.touchUpInside)

                    getAudio()
    }



    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        NotificationCenter.default.addObserver(self, selector: #selector(PlayerViewController.finishedPlaying), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: self.audioPlayerItem)

    }



    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillAppear(animated)
            // remove the timer
                self.timer?.invalidate()
                    // remove the observer when leaving page
                        NotificationCenter.default.removeObserver(audioPlayer?.currentItem! as Any)
        }



    func finishedPlaying() {

        // need option to play next track

        self.playerButton.setImage(UIImage(named: "play"), for: UIControlState.normal)

            let seconds : Int64 = 0
                let preferredTimeScale : Int32 = 1
                    let seekTime : CMTime = CMTimeMake(seconds, preferredTimeScale)

                        audioPlayerItem!.seek(to: seekTime)
    }

    @IBAction func horizontalSliderActioned(_ sender: Any) {

        horizontalSlider.isContinuous = true

        if self.horizontalSlider.isTouchInside {

            audioPlayer?.pause()
                let seconds : Int64 = Int64(horizontalSlider.value)
                    let preferredTimeScale : Int32 = 1
                        let seekTime : CMTime = CMTimeMake(seconds, preferredTimeScale)
                            audioPlayerItem?.seek(to: seekTime)
                                audioPlayer?.play()

        } else {

            let duration : CMTime = (self.audioPlayer?.currentItem!.asset.duration)!
                let seconds : Float64 = CMTimeGetSeconds(duration)
                    self.horizontalSlider.value = Float(seconds)
        }
    }



    func audioSliderUpdate() {

        let currentTime : CMTime = (self.audioPlayerItem?.currentTime())!
            let seconds : Float64 = CMTimeGetSeconds(currentTime)
                let time : Float = Float(seconds)
                    self.horizontalSlider.value = time
    }

}

Answer 1

Swift 5, Xcode 11

I faced the same issue, it was apparently periodicTimeObserver which was causing to return incorrect time which caused lag or jump in the slider. I solved it by removing periodic time observer when the slider was changing and adding it back when seeking completion handler was called.

@objc func sliderValueChanged(_ playbackSlider: UISlider, event: UIEvent){

    let seconds : Float = Float(playbackSlider.value)
    let targetTime:CMTime = CMTimeMake(value: Int64(seconds), timescale: 1)


    if let touchEvent = event.allTouches?.first {
        switch touchEvent.phase {
        case .began:
            // handle drag began
            //Remove observer when dragging is in progress
            self.removePeriodicTimeObserver()


            break
        case .moved:
            // handle drag moved

            break
        case .ended:
            // handle drag ended

            //Add Observer back when seeking got completed
            player.seek(to: targetTime, toleranceBefore: .zero, toleranceAfter: .zero) { [weak self] (value) in
                self?.addTimeObserver()
            }

            break
        default:
            break
        }
    }
}

Answer 2

you need to remove observers and invalidate timers as soon as user selects the thumb on slider and add them back again when dragging is done

to do add targets like this where you load your player:

    mySlider.addTarget(self, 
action: #selector(PlayerViewController.mySliderBeganTracking(_:)),
forControlEvents:.TouchDown)

    mySlider.addTarget(self,
action: #selector(PlayerViewController.mySliderEndedTracking(_:)),
forControlEvents: .TouchUpInside)

   mySlider.addTarget(self,
action: #selector(PlayerViewController.mySliderEndedTracking(_:)),
forControlEvents: .TouchUpOutside )

and remove observers and invalidate timers in mySliderBeganTracking then add observers in mySliderEndedTracking for better control on what happens in your player write 2 functions : addObservers and removeObservers and call them when needed