Merge pull request #355 from ronaldheft/ios-bug-seek-multi-track

Fixes iOS player seek issues with multi-track books

ios/App/Shared/player/AudioPlayer.swift

@@ -194,35 +194,49 @@ class AudioPlayer: NSObject {
     }
     
     private func setupQueueItemStatusObserver() {
+        NSLog("queueStatusObserver: Setting up")
+
+        // Listen for player item updates
         self.queueItemStatusObserver?.invalidate()
-        self.queueItemStatusObserver = self.audioPlayer.currentItem?.observe(\.status, options: [.new, .old], changeHandler: { (playerItem, change) in
+        self.queueItemStatusObserver = self.audioPlayer.currentItem?.observe(\.status, options: [.new, .old], changeHandler: { playerItem, change in
-            guard let playbackSession = self.getPlaybackSession() else {
+            self.handleQueueItemStatus(playerItem: playerItem)
-                NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
-                return
-            }
-            if (playerItem.status == .readyToPlay) {
-                NSLog("queueStatusObserver: Current Item Ready to play. PlayWhenReady: \(self.playWhenReady)")
-                self.updateNowPlaying()
-                
-                // Seek the player before initializing, so a currentTime of 0 does not appear in MediaProgress / session
-                let firstReady = self.status < 0
-                if firstReady || self.playWhenReady {
-                    self.seek(playbackSession.currentTime, from: "queueItemStatusObserver")
-                }
-                
-                // Mark the player as ready
-                self.status = 0
-                
-                // Start the player, if requested
-                if self.playWhenReady {
-                    self.playWhenReady = false
-                    self.play()
-                }
-            } else if (playerItem.status == .failed) {
-                NSLog("queueStatusObserver: FAILED \(playerItem.error?.localizedDescription ?? "")")
-                NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
-            }
         })
+        
+        // Ensure we didn't miss a player item update during initialization
+        if let playerItem = self.audioPlayer.currentItem {
+            self.handleQueueItemStatus(playerItem: playerItem)
+        }
+    }
+    
+    private func handleQueueItemStatus(playerItem: AVPlayerItem) {
+        NSLog("queueStatusObserver: Current item status changed")
+        guard let playbackSession = self.getPlaybackSession() else {
+            NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
+            return
+        }
+        if (playerItem.status == .readyToPlay) {
+            NSLog("queueStatusObserver: Current Item Ready to play. PlayWhenReady: \(self.playWhenReady)")
+            
+            // Seek the player before initializing, so a currentTime of 0 does not appear in MediaProgress / session
+            let firstReady = self.status < 0
+            if firstReady && !self.playWhenReady {
+                // Seek is async, and if we call this when also pressing play, we will get weird jumps in the scrub bar depending on timing
+                // Seeking to the correct position happens during play()
+                self.seek(playbackSession.currentTime, from: "queueItemStatusObserver")
+            }
+            
+            // Mark the player as ready
+            self.status = 0
+            
+            // Start the player, if requested
+            if self.playWhenReady {
+                self.playWhenReady = false
+                self.play()
+            }
+        } else if (playerItem.status == .failed) {
+            NSLog("queueStatusObserver: FAILED \(playerItem.error?.localizedDescription ?? "")")
+            NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
+        }
     }
     
     private func startPausedTimer() {
@@ -243,59 +257,67 @@ class AudioPlayer: NSObject {
     // MARK: - Methods
     public func play(allowSeekBack: Bool = false) {
         guard self.isInitialized() else { return }
+        guard let session = self.getPlaybackSession() else {
+            NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
+            return
+        }
         
         // Capture remaining sleep time before changing the track position
         let sleepSecondsRemaining = PlayerHandler.remainingSleepTime
         
-        if allowSeekBack, let session = self.getPlaybackSession() {
+        // Stop the paused timer
-            let lastPlayed = (session.updatedAt ?? 0)/1000
-            let difference = Date.timeIntervalSinceReferenceDate - lastPlayed
-            var time: Int?
-            
-            if lastPlayed == 0 {
-                time = 5
-            } else if difference < 6 {
-                time = 2
-            } else if difference < 12 {
-                time = 10
-            } else if difference < 30 {
-                time = 15
-            } else if difference < 180 {
-                time = 20
-            } else if difference < 3600 {
-                time = 25
-            } else {
-                time = 29
-            }
-            
-            if time != nil {
-                guard let currentTime = self.getCurrentTime() else {
-                    NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.failed.rawValue), object: nil)
-                    return
-                }
-                seek(currentTime - Double(time!), from: "play")
-            }
-        }
-        
         self.stopPausedTimer()
         
-        Task {
+        // Determine where we are starting playback
-            if let currentTime = self.getCurrentTime() {
+        let lastPlayed = (session.updatedAt ?? 0)/1000
-                await PlayerProgress.shared.syncFromPlayer(currentTime: currentTime, includesPlayProgress: self.isPlaying(), isStopping: false)
+        let currentTime = allowSeekBack ? calculateSeekBackTimeAtCurrentTime(session.currentTime, lastPlayed: lastPlayed) : session.currentTime
+        
+        // Sync our new playback position
+        Task { await PlayerProgress.shared.syncFromPlayer(currentTime: currentTime, includesPlayProgress: self.isPlaying(), isStopping: false) }
+
+        // Start playback, with a seek, for as smooth a scrub bar start as possible
+        let currentTrackStartOffset = session.audioTracks[self.currentTrackIndex].startOffset ?? 0.0
+        let seekTime = currentTime - currentTrackStartOffset
+        self.audioPlayer.seek(to: CMTime(seconds: seekTime, preferredTimescale: 1000), toleranceBefore: .zero, toleranceAfter: .zero) { [weak self] completed in
+            if completed, let self = self {
+                // Start playback
+                self.audioPlayer.play()
+                self.rate = self.tmpRate
+                self.audioPlayer.rate = self.tmpRate
+                self.status = 1
+                
+                // If we have an active sleep timer, reschedule based on rate
+                self.rescheduleSleepTimerAtTime(time: currentTime, secondsRemaining: sleepSecondsRemaining)
+                
+                // Update the progress
+                self.updateNowPlaying()
             }
         }
+    }
     
-        self.audioPlayer.play()
+    private func calculateSeekBackTimeAtCurrentTime(_ currentTime: Double, lastPlayed: Double) -> Double {
-        self.status = 1
+        let difference = Date.timeIntervalSinceReferenceDate - lastPlayed
-        self.rate = self.tmpRate
+        var time: Double = 0
-        self.audioPlayer.rate = self.tmpRate
         
-        // If we have an active sleep timer, reschedule based on rate
+        // Scale seek back time based on how long since last play
-        if let currentTime = self.getCurrentTime() {
+        if lastPlayed == 0 {
-            self.rescheduleSleepTimerAtTime(time: currentTime, secondsRemaining: sleepSecondsRemaining)
+            time = 5
+        } else if difference < 6 {
+            time = 2
+        } else if difference < 12 {
+            time = 10
+        } else if difference < 30 {
+            time = 15
+        } else if difference < 180 {
+            time = 20
+        } else if difference < 3600 {
+            time = 25
+        } else {
+            time = 29
         }
         
-        updateNowPlaying()
+        // Wind the clock back
+        return currentTime - time
     }
     
     public func pause() {