-Modified quality update to no longer invalidate concatenated media sources.

-Improved play queue and timeline update.

app/src/main/java/org/schabi/newpipe/player/BasePlayer.java

@@ -543,23 +543,21 @@ public abstract class BasePlayer implements Player.EventListener,
     }
 
     /*//////////////////////////////////////////////////////////////////////////
-    // ExoPlayer Listener
+    // Timeline
     //////////////////////////////////////////////////////////////////////////*/
 
-    @Override
+    private void refreshTimeline() {
-    public void onTimelineChanged(Timeline timeline, Object manifest) {
-        if (DEBUG) Log.d(TAG, "onTimelineChanged(), timeline size = " + timeline.getWindowCount());
-
         final int currentSourceIndex = playbackManager.getCurrentSourceIndex();
 
-        // Sanity check
+        // Sanity checks
         if (currentSourceIndex < 0) return;
 
         // Check if already playing correct window
         final boolean isCurrentWindowCorrect = simpleExoPlayer.getCurrentWindowIndex() == currentSourceIndex;
         if (isCurrentWindowCorrect && getCurrentState() == STATE_PLAYING) return;
 
-        // Check timeline has window
+        // Check timeline is up-to-date and has window
+        if (playbackManager.size() != simpleExoPlayer.getCurrentTimeline().getWindowCount()) return;
         if (simpleExoPlayer.getCurrentTimeline().getWindowCount() <= currentSourceIndex) return;
 
         // Check if window is ready
@@ -574,7 +572,7 @@ public abstract class BasePlayer implements Player.EventListener,
             simpleExoPlayer.seekTo(currentSourceIndex, startPos);
         }
 
-        // Check if recovering on correct item
+        // Check if recovering
         if (isRecovery && queuePos == playQueue.getIndex() && isCurrentWindowCorrect) {
             if (DEBUG) Log.d(TAG, "Rewinding to recovery window: " + currentSourceIndex + " at: " + getTimeString((int)videoPos));
             simpleExoPlayer.seekTo(videoPos);
@@ -585,6 +583,17 @@ public abstract class BasePlayer implements Player.EventListener,
         simpleExoPlayer.setPlayWhenReady(wasPlaying);
     }
 
+    /*//////////////////////////////////////////////////////////////////////////
+    // ExoPlayer Listener
+    //////////////////////////////////////////////////////////////////////////*/
+
+    @Override
+    public void onTimelineChanged(Timeline timeline, Object manifest) {
+        if (DEBUG) Log.d(TAG, "onTimelineChanged(), timeline size = " + timeline.getWindowCount());
+
+        refreshTimeline();
+    }
+
     @Override
     public void onTracksChanged(TrackGroupArray trackGroups, TrackSelectionArray trackSelections) {
     }
@@ -699,7 +708,7 @@ public abstract class BasePlayer implements Player.EventListener,
         if (DEBUG) Log.d(TAG, "Syncing...");
 
         currentInfo = info;
-        onTimelineChanged(simpleExoPlayer.getCurrentTimeline(), null);
+        refreshTimeline();
 
         initThumbnail(info.thumbnail_url);
     }

app/src/main/java/org/schabi/newpipe/player/playback/PlaybackManager.java

@@ -12,6 +12,7 @@ import org.schabi.newpipe.playlist.PlayQueue;
 import org.schabi.newpipe.playlist.PlayQueueItem;
 import org.schabi.newpipe.playlist.events.PlayQueueMessage;
 import org.schabi.newpipe.playlist.events.RemoveEvent;
+import org.schabi.newpipe.playlist.events.UpdateEvent;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -71,6 +72,9 @@ public class PlaybackManager {
         return sourceToQueueIndex.indexOf(playQueue.getIndex());
     }
 
+    public int size() {
+        return sourceToQueueIndex.size();
+    }
 
     public void dispose() {
         if (playQueueReactor != null) playQueueReactor.cancel();
@@ -116,9 +120,13 @@ public class PlaybackManager {
                     case REMOVE:
                         final RemoveEvent removeEvent = (RemoveEvent) event;
                         if (removeEvent.isCurrent()) tryBlock();
-                        remove(removeEvent.index());
+                        remove(removeEvent.index(), true);
                         break;
                     case UPDATE:
+                        final UpdateEvent updateEvent = (UpdateEvent) event;
+                        tryBlock();
+                        remove(updateEvent.index(), false);
+                        break;
                     case SHUFFLE:
                         tryBlock();
                         resetSources();
@@ -261,7 +269,7 @@ public class PlaybackManager {
         }
     }
 
-    private void remove(final int queueIndex) {
+    private void remove(final int queueIndex, final boolean cascade) {
         if (queueIndex < 0) return;
 
         final int sourceIndex = sourceToQueueIndex.indexOf(queueIndex);
@@ -270,9 +278,11 @@ public class PlaybackManager {
         sourceToQueueIndex.remove(sourceIndex);
         sources.removeMediaSource(sourceIndex);
 
+        if (cascade) {
             // Will be slow on really large arrays, fast enough for typical use case
             for (int i = sourceIndex; i < sourceToQueueIndex.size(); i++) {
                 sourceToQueueIndex.set(i, sourceToQueueIndex.get(i) - 1);
             }
         }
+    }
 }

app/src/main/java/org/schabi/newpipe/playlist/PlayQueue.java

@@ -21,6 +21,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import io.reactivex.BackpressureStrategy;
 import io.reactivex.Flowable;
+import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.subjects.BehaviorSubject;
 
 public abstract class PlayQueue implements Serializable {
@@ -58,7 +59,7 @@ public abstract class PlayQueue implements Serializable {
         broadcastReceiver = Flowable.merge(
                 streamsEventBroadcast.toFlowable(BackpressureStrategy.BUFFER),
                 indexEventBroadcast.toFlowable(BackpressureStrategy.BUFFER)
-        ).startWith(new InitEvent());
+        ).observeOn(AndroidSchedulers.mainThread()).startWith(new InitEvent());
 
         if (DEBUG) broadcastReceiver.subscribe(getSelfReporter());
     }