-Modified recovery to not set if progress position is 0 or less.

-Modified queue item synchronization to no longer trigger update when the sync is run on the identical item.

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

@@ -26,6 +26,7 @@ import android.content.IntentFilter;
 import android.graphics.Bitmap;
 import android.media.AudioManager;
 import android.net.Uri;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.text.TextUtils;
 import android.util.Log;
@@ -76,7 +77,6 @@ import java.util.concurrent.TimeUnit;
 
 import io.reactivex.Observable;
 import io.reactivex.android.schedulers.AndroidSchedulers;
-import io.reactivex.annotations.NonNull;
 import io.reactivex.disposables.Disposable;
 import io.reactivex.functions.Consumer;
 import io.reactivex.functions.Predicate;
@@ -193,7 +193,7 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
                 .observeOn(AndroidSchedulers.mainThread())
                 .filter(new Predicate<Long>() {
                     @Override
-                    public boolean test(@NonNull Long aLong) throws Exception {
+                    public boolean test(Long aLong) throws Exception {
                         return isProgressLoopRunning();
                     }
                 })
@@ -235,7 +235,7 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         initPlayback(queue);
     }
 
-    protected void initPlayback(@NonNull final PlayQueue queue) {
+    protected void initPlayback(final PlayQueue queue) {
         playQueue = queue;
         playQueue.init();
         playbackManager = new MediaSourceManager(this, playQueue);
@@ -514,11 +514,10 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
                 }
                 break;
             case Player.STATE_READY: //3
-                recover();
-
                 if (!isPrepared) {
                     isPrepared = true;
                     onPrepared(playWhenReady);
+                    recover();
                     break;
                 }
                 if (currentState == STATE_PAUSED_SEEK) break;
@@ -631,17 +630,21 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     }
 
     @Override
-    public void sync(@android.support.annotation.NonNull final PlayQueueItem item,
+    public void sync(@NonNull final PlayQueueItem item,
                      @Nullable final StreamInfo info) {
-        if (simpleExoPlayer == null) return;
-        if (DEBUG) Log.d(TAG, "Syncing...");
-
+        if (currentItem == item && currentInfo == info) return;
         currentItem = item;
         currentInfo = info;
 
+        if (DEBUG) Log.d(TAG, "Syncing...");
+        if (simpleExoPlayer == null) return;
+
         // Check if on wrong window
-        final int currentSourceIndex = playQueue.getIndex();
-        if (simpleExoPlayer.getCurrentWindowIndex() != currentSourceIndex) {
+        final int currentSourceIndex = playQueue.indexOf(item);
+        if (currentSourceIndex != playQueue.getIndex()) {
+            throw new IllegalStateException("Play Queue may be desynchronized: item index=[" +
+                    currentSourceIndex + "], queue index=[" + playQueue.getIndex() + "]");
+        } else if (simpleExoPlayer.getCurrentWindowIndex() != currentSourceIndex) {
             final long startPos = info != null ? info.start_position : 0;
             if (DEBUG) Log.d(TAG, "Rewinding to correct window: " + currentSourceIndex + " at: " + getTimeString((int)startPos));
             simpleExoPlayer.seekTo(currentSourceIndex, startPos);
@@ -900,7 +903,9 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         final int queuePos = playQueue.getIndex();
         final long windowPos = simpleExoPlayer.getCurrentPosition();
 
-        setRecovery(queuePos, windowPos);
+        if (windowPos > 0) {
+            setRecovery(queuePos, windowPos);
+        }
     }
 
     public void setRecovery(final int queuePos, final long windowPos) {

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

@@ -52,7 +52,7 @@ public class MediaSourceManager {
 
     public MediaSourceManager(@NonNull final PlaybackListener listener,
                               @NonNull final PlayQueue playQueue) {
-        this(listener, playQueue, 1, 1000L);
+        this(listener, playQueue, 1, 400L);
     }
 
     private MediaSourceManager(@NonNull final PlaybackListener listener,
@@ -162,7 +162,7 @@ public class MediaSourceManager {
             return;
         }
 
-        // why no pattern matching in Java =(
+        // Event specific action
         switch (event.type()) {
             case INIT:
             case REORDER:
@@ -172,31 +172,28 @@ public class MediaSourceManager {
             case APPEND:
                 populateSources();
                 break;
-            case SELECT:
-                sync();
-                break;
             case REMOVE:
                 final RemoveEvent removeEvent = (RemoveEvent) event;
                 remove(removeEvent.getRemoveIndex());
-                // Sync only when the currently playing is removed
-                if (removeEvent.getQueueIndex() == removeEvent.getRemoveIndex()) sync();
                 break;
             case MOVE:
                 final MoveEvent moveEvent = (MoveEvent) event;
                 move(moveEvent.getFromIndex(), moveEvent.getToIndex());
                 break;
+            case SELECT:
             case RECOVERY:
             default:
                 break;
         }
 
+        // Loading and Syncing
         switch (event.type()) {
             case INIT:
             case REORDER:
             case ERROR:
-            case APPEND:
                 loadImmediate(); // low frequency, critical events
                 break;
+            case APPEND:
             case REMOVE:
             case SELECT:
             case MOVE:
@@ -294,7 +291,9 @@ public class MediaSourceManager {
 
         final DeferredMediaSource mediaSource = (DeferredMediaSource) sources.getMediaSource(playQueue.indexOf(item));
         if (mediaSource.state() == DeferredMediaSource.STATE_PREPARED) mediaSource.load();
-        if (tryUnblock()) sync();
+
+        tryUnblock();
+        if (!isBlocked) sync();
     }
 
     private void resetSources() {