-Improved player queue stability by using more aggressive synchronization policy.

-Added sync buttons on live streams to allow seeking to live edge.
-Added custom cache key for extractor sources to allow more persistent reuse.
-Refactored player data source factories into own class and separating live and non-live data sources.

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

@@ -46,6 +46,7 @@ import org.schabi.newpipe.extractor.stream.AudioStream;
 import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.player.event.PlayerEventListener;
 import org.schabi.newpipe.player.helper.LockManager;
+import org.schabi.newpipe.player.helper.PlayerHelper;
 import org.schabi.newpipe.playlist.PlayQueueItem;
 import org.schabi.newpipe.util.ListHelper;
 import org.schabi.newpipe.util.NavigationHelper;
@@ -398,7 +399,8 @@ public final class BackgroundPlayer extends Service {
             if (index < 0 || index >= info.audio_streams.size()) return null;
 
             final AudioStream audio = info.audio_streams.get(index);
-            return buildMediaSource(audio.getUrl(), MediaFormat.getSuffixById(audio.getFormatId()));
+            return buildMediaSource(audio.getUrl(), PlayerHelper.cacheKeyOf(info, audio),
+                    MediaFormat.getSuffixById(audio.getFormatId()));
         }
 
         @Override

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

@@ -43,20 +43,11 @@ import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.RenderersFactory;
 import com.google.android.exoplayer2.SimpleExoPlayer;
 import com.google.android.exoplayer2.Timeline;
-import com.google.android.exoplayer2.source.ExtractorMediaSource;
 import com.google.android.exoplayer2.source.MediaSource;
-import com.google.android.exoplayer2.source.SingleSampleMediaSource;
 import com.google.android.exoplayer2.source.TrackGroupArray;
-import com.google.android.exoplayer2.source.dash.DashMediaSource;
-import com.google.android.exoplayer2.source.dash.DefaultDashChunkSource;
-import com.google.android.exoplayer2.source.hls.HlsMediaSource;
-import com.google.android.exoplayer2.source.smoothstreaming.DefaultSsChunkSource;
-import com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource;
 import com.google.android.exoplayer2.trackselection.AdaptiveTrackSelection;
 import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
-import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.DefaultBandwidthMeter;
-import com.google.android.exoplayer2.upstream.DefaultHttpDataSourceFactory;
 import com.google.android.exoplayer2.util.Util;
 import com.nostra13.universalimageloader.core.ImageLoader;
 import com.nostra13.universalimageloader.core.listener.SimpleImageLoadingListener;
@@ -66,8 +57,8 @@ import org.schabi.newpipe.R;
 import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.history.HistoryRecordManager;
 import org.schabi.newpipe.player.helper.AudioReactor;
-import org.schabi.newpipe.player.helper.CacheFactory;
 import org.schabi.newpipe.player.helper.LoadController;
+import org.schabi.newpipe.player.helper.PlayerDataSource;
 import org.schabi.newpipe.player.playback.CustomTrackSelector;
 import org.schabi.newpipe.player.playback.MediaSourceManager;
 import org.schabi.newpipe.player.playback.PlaybackListener;
@@ -149,14 +140,8 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     protected boolean isPrepared = false;
 
     protected CustomTrackSelector trackSelector;
-    protected DataSource.Factory cacheDataSourceFactory;
-    protected DataSource.Factory cachelessDataSourceFactory;
 
-    protected SsMediaSource.Factory ssMediaSourceFactory;
+    protected PlayerDataSource dataSource;
-    protected HlsMediaSource.Factory hlsMediaSourceFactory;
-    protected DashMediaSource.Factory dashMediaSourceFactory;
-    protected ExtractorMediaSource.Factory extractorMediaSourceFactory;
-    protected SingleSampleMediaSource.Factory sampleMediaSourceFactory;
 
     protected Disposable progressUpdateReactor;
     protected CompositeDisposable databaseUpdateReactor;
@@ -193,20 +178,11 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
 
         final String userAgent = Downloader.USER_AGENT;
         final DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
+        dataSource = new PlayerDataSource(context, userAgent, bandwidthMeter);
+
         final AdaptiveTrackSelection.Factory trackSelectionFactory =
                 new AdaptiveTrackSelection.Factory(bandwidthMeter);
-
         trackSelector = new CustomTrackSelector(trackSelectionFactory);
-        cacheDataSourceFactory = new CacheFactory(context, userAgent, bandwidthMeter);
-        cachelessDataSourceFactory = new DefaultHttpDataSourceFactory(userAgent, bandwidthMeter);
-
-        ssMediaSourceFactory = new SsMediaSource.Factory(
-                new DefaultSsChunkSource.Factory(cachelessDataSourceFactory), cachelessDataSourceFactory);
-        hlsMediaSourceFactory = new HlsMediaSource.Factory(cachelessDataSourceFactory);
-        dashMediaSourceFactory = new DashMediaSource.Factory(
-                new DefaultDashChunkSource.Factory(cachelessDataSourceFactory), cachelessDataSourceFactory);
-        extractorMediaSourceFactory = new ExtractorMediaSource.Factory(cacheDataSourceFactory);
-        sampleMediaSourceFactory = new SingleSampleMediaSource.Factory(cacheDataSourceFactory);
 
         final LoadControl loadControl = new LoadController(context);
         final RenderersFactory renderFactory = new DefaultRenderersFactory(context);
@@ -319,26 +295,56 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
         recordManager = null;
     }
 
-    public MediaSource buildMediaSource(String url, String overrideExtension) {
+    /*//////////////////////////////////////////////////////////////////////////
+    // MediaSource Building
+    //////////////////////////////////////////////////////////////////////////*/
+
+    public MediaSource buildLiveMediaSource(@NonNull final String sourceUrl,
+                                            @C.ContentType final int type) {
         if (DEBUG) {
-            Log.d(TAG, "buildMediaSource() called with: url = [" + url +
+            Log.d(TAG, "buildLiveMediaSource() called with: url = [" + sourceUrl +
-                    "], overrideExtension = [" + overrideExtension + "]");
+                    "], content type = [" + type + "]");
         }
-        Uri uri = Uri.parse(url);
+        if (dataSource == null) return null;
-        int type = TextUtils.isEmpty(overrideExtension) ? Util.inferContentType(uri) :
+
-                Util.inferContentType("." + overrideExtension);
+        final Uri uri = Uri.parse(sourceUrl);
         switch (type) {
             case C.TYPE_SS:
-                return ssMediaSourceFactory.createMediaSource(uri);
+                return dataSource.getLiveSsMediaSourceFactory().createMediaSource(uri);
             case C.TYPE_DASH:
-                return dashMediaSourceFactory.createMediaSource(uri);
+                return dataSource.getLiveDashMediaSourceFactory().createMediaSource(uri);
             case C.TYPE_HLS:
-                return hlsMediaSourceFactory.createMediaSource(uri);
+                return dataSource.getLiveHlsMediaSourceFactory().createMediaSource(uri);
-            case C.TYPE_OTHER:
+            default:
-                return extractorMediaSourceFactory.createMediaSource(uri);
+                throw new IllegalStateException("Unsupported type: " + type);
-            default: {
+        }
+    }
+
+    public MediaSource buildMediaSource(@NonNull final String sourceUrl,
+                                        @NonNull final String cacheKey,
+                                        @NonNull final String overrideExtension) {
+        if (DEBUG) {
+            Log.d(TAG, "buildMediaSource() called with: url = [" + sourceUrl +
+                    "], cacheKey = [" + cacheKey + "]" +
+                    "], overrideExtension = [" + overrideExtension + "]");
+        }
+        if (dataSource == null) return null;
+
+        final Uri uri = Uri.parse(sourceUrl);
+        @C.ContentType final int type = TextUtils.isEmpty(overrideExtension) ?
+                Util.inferContentType(uri) : Util.inferContentType("." + overrideExtension);
+
+        switch (type) {
+            case C.TYPE_SS:
+                return dataSource.getLiveSsMediaSourceFactory().createMediaSource(uri);
+            case C.TYPE_DASH:
+                return dataSource.getDashMediaSourceFactory().createMediaSource(uri);
+            case C.TYPE_HLS:
+                return dataSource.getHlsMediaSourceFactory().createMediaSource(uri);
+            case C.TYPE_OTHER:
+                return dataSource.getExtractorMediaSourceFactory(cacheKey).createMediaSource(uri);
+            default:
                 throw new IllegalStateException("Unsupported type: " + type);
-            }
         }
     }
 
@@ -478,7 +484,7 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     // ExoPlayer Listener
     //////////////////////////////////////////////////////////////////////////*/
 
-    private void recover() {
+    private void maybeRecover() {
         final int currentSourceIndex = playQueue.getIndex();
         final PlayQueueItem currentSourceItem = playQueue.getItem();
 
@@ -554,7 +560,7 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
                 }
                 break;
             case Player.STATE_READY: //3
-                recover();
+                maybeRecover();
                 if (!isPrepared) {
                     isPrepared = true;
                     onPrepared(playWhenReady);
@@ -566,7 +572,8 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
             case Player.STATE_ENDED: // 4
                 // Ensure the current window has actually ended
                 // since single windows that are still loading may produce an ended state
-                if (isCurrentWindowValid() && simpleExoPlayer.getCurrentPosition() >= simpleExoPlayer.getDuration()) {
+                if (isCurrentWindowValid() &&
+                        simpleExoPlayer.getCurrentPosition() >= simpleExoPlayer.getDuration()) {
                     changeState(STATE_COMPLETED);
                     isPrepared = false;
                 }
@@ -730,9 +737,9 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
     @Override
     public MediaSource sourceOf(PlayQueueItem item, StreamInfo info) {
         if (!info.getHlsUrl().isEmpty()) {
-            return buildMediaSource(info.getHlsUrl(), "m3u8");
+            return buildLiveMediaSource(info.getHlsUrl(), C.TYPE_HLS);
         } else if (!info.getDashMpdUrl().isEmpty()) {
-            return buildMediaSource(info.getDashMpdUrl(), "mpd");
+            return buildLiveMediaSource(info.getDashMpdUrl(), C.TYPE_DASH);
         }
 
         return null;
@@ -852,8 +859,11 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
 
     public void seekBy(int milliSeconds) {
         if (DEBUG) Log.d(TAG, "seekBy() called with: milliSeconds = [" + milliSeconds + "]");
-        if (simpleExoPlayer == null || (isCompleted() && milliSeconds > 0) || ((milliSeconds < 0 && simpleExoPlayer.getCurrentPosition() == 0)))
+        if (simpleExoPlayer == null || (isCompleted() && milliSeconds > 0) ||
+                ((milliSeconds < 0 && simpleExoPlayer.getCurrentPosition() == 0))) {
             return;
+        }
+
         int progress = (int) (simpleExoPlayer.getCurrentPosition() + milliSeconds);
         if (progress < 0) progress = 0;
         simpleExoPlayer.seekTo(progress);
@@ -864,6 +874,10 @@ public abstract class BasePlayer implements Player.EventListener, PlaybackListen
                 && simpleExoPlayer.getCurrentPosition() >= 0;
     }
 
+    public void seekToDefault() {
+        if (simpleExoPlayer != null) simpleExoPlayer.seekToDefaultPosition();
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
     // Utils
     //////////////////////////////////////////////////////////////////////////*/

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

@@ -76,6 +76,7 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
     private SeekBar progressSeekBar;
     private TextView progressCurrentTime;
     private TextView progressEndTime;
+    private TextView progressLiveSync;
     private TextView seekDisplay;
 
     private ImageButton repeatButton;
@@ -294,9 +295,11 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
         progressCurrentTime = rootView.findViewById(R.id.current_time);
         progressSeekBar = rootView.findViewById(R.id.seek_bar);
         progressEndTime = rootView.findViewById(R.id.end_time);
+        progressLiveSync = rootView.findViewById(R.id.live_sync);
         seekDisplay = rootView.findViewById(R.id.seek_display);
 
         progressSeekBar.setOnSeekBarChangeListener(this);
+        progressLiveSync.setOnClickListener(this);
     }
 
     private void buildControls() {
@@ -513,6 +516,9 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
         } else if (view.getId() == metadata.getId()) {
             scrollToSelected();
 
+        } else if (view.getId() == progressLiveSync.getId()) {
+            player.seekToDefault();
+
         }
     }
 
@@ -574,6 +580,19 @@ public abstract class ServicePlayerActivity extends AppCompatActivity
         if (info != null) {
             metadataTitle.setText(info.getName());
             metadataArtist.setText(info.uploader_name);
+
+            progressEndTime.setVisibility(View.GONE);
+            progressLiveSync.setVisibility(View.GONE);
+            switch (info.getStreamType()) {
+                case LIVE_STREAM:
+                case AUDIO_LIVE_STREAM:
+                    progressLiveSync.setVisibility(View.VISIBLE);
+                    break;
+                default:
+                    progressEndTime.setVisibility(View.VISIBLE);
+                    break;
+            }
+
             scrollToSelected();
         }
     }

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

@@ -50,7 +50,6 @@ import android.widget.TextView;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.Player;
-import com.google.android.exoplayer2.SimpleExoPlayer;
 import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.source.MergingMediaSource;
 import com.google.android.exoplayer2.source.TrackGroup;
@@ -58,6 +57,7 @@ import com.google.android.exoplayer2.source.TrackGroupArray;
 import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
 import com.google.android.exoplayer2.ui.AspectRatioFrameLayout;
 import com.google.android.exoplayer2.ui.SubtitleView;
+import com.google.android.exoplayer2.video.VideoListener;
 
 import org.schabi.newpipe.R;
 import org.schabi.newpipe.extractor.MediaFormat;
@@ -87,7 +87,7 @@ import static org.schabi.newpipe.util.AnimationUtils.animateView;
  */
 @SuppressWarnings({"WeakerAccess", "unused"})
 public abstract class VideoPlayer extends BasePlayer
-        implements SimpleExoPlayer.VideoListener,
+        implements VideoListener,
         SeekBar.OnSeekBarChangeListener,
         View.OnClickListener,
         Player.EventListener,
@@ -131,6 +131,7 @@ public abstract class VideoPlayer extends BasePlayer
     private SeekBar playbackSeekBar;
     private TextView playbackCurrentTime;
     private TextView playbackEndTime;
+    private TextView playbackLiveSync;
     private TextView playbackSpeedTextView;
 
     private View topControlsRoot;
@@ -180,6 +181,7 @@ public abstract class VideoPlayer extends BasePlayer
         this.playbackSeekBar = rootView.findViewById(R.id.playbackSeekBar);
         this.playbackCurrentTime = rootView.findViewById(R.id.playbackCurrentTime);
         this.playbackEndTime = rootView.findViewById(R.id.playbackEndTime);
+        this.playbackLiveSync = rootView.findViewById(R.id.playbackLiveSync);
         this.playbackSpeedTextView = rootView.findViewById(R.id.playbackSpeed);
         this.bottomControlsRoot = rootView.findViewById(R.id.bottomControls);
         this.topControlsRoot = rootView.findViewById(R.id.topControls);
@@ -221,6 +223,7 @@ public abstract class VideoPlayer extends BasePlayer
         qualityTextView.setOnClickListener(this);
         captionTextView.setOnClickListener(this);
         resizeView.setOnClickListener(this);
+        playbackLiveSync.setOnClickListener(this);
     }
 
     @Override
@@ -261,7 +264,8 @@ public abstract class VideoPlayer extends BasePlayer
         qualityPopupMenu.getMenu().removeGroup(qualityPopupMenuGroupId);
         for (int i = 0; i < availableStreams.size(); i++) {
             VideoStream videoStream = availableStreams.get(i);
-            qualityPopupMenu.getMenu().add(qualityPopupMenuGroupId, i, Menu.NONE, MediaFormat.getNameById(videoStream.format) + " " + videoStream.resolution);
+            qualityPopupMenu.getMenu().add(qualityPopupMenuGroupId, i, Menu.NONE,
+                    MediaFormat.getNameById(videoStream.getFormatId()) + " " + videoStream.resolution);
         }
         if (getSelectedVideoStream() != null) {
             qualityTextView.setText(getSelectedVideoStream().resolution);
@@ -327,9 +331,22 @@ public abstract class VideoPlayer extends BasePlayer
         qualityTextView.setVisibility(View.GONE);
         playbackSpeedTextView.setVisibility(View.GONE);
 
+        playbackEndTime.setVisibility(View.GONE);
+        playbackLiveSync.setVisibility(View.GONE);
+
         final StreamType streamType = info == null ? StreamType.NONE : info.getStreamType();
 
         switch (streamType) {
+            case AUDIO_STREAM:
+                surfaceView.setVisibility(View.GONE);
+                break;
+
+            case AUDIO_LIVE_STREAM:
+                surfaceView.setVisibility(View.GONE);
+            case LIVE_STREAM:
+                playbackLiveSync.setVisibility(View.VISIBLE);
+                break;
+
             case VIDEO_STREAM:
                 if (info.video_streams.size() + info.video_only_streams.size() == 0) break;
 
@@ -344,14 +361,10 @@ public abstract class VideoPlayer extends BasePlayer
 
                 buildQualityMenu();
                 qualityTextView.setVisibility(View.VISIBLE);
-                surfaceView.setVisibility(View.VISIBLE);
-                break;
 
-            case AUDIO_STREAM:
+                surfaceView.setVisibility(View.VISIBLE);
-            case AUDIO_LIVE_STREAM:
-                surfaceView.setVisibility(View.GONE);
-                break;
             default:
+                playbackEndTime.setVisibility(View.VISIBLE);
                 break;
         }
 
@@ -381,6 +394,7 @@ public abstract class VideoPlayer extends BasePlayer
         final VideoStream video = index >= 0 && index < videos.size() ? videos.get(index) : null;
         if (video != null) {
             final MediaSource streamSource = buildMediaSource(video.getUrl(),
+                    PlayerHelper.cacheKeyOf(info, video),
                     MediaFormat.getSuffixById(video.getFormatId()));
             mediaSources.add(streamSource);
         }
@@ -393,6 +407,7 @@ public abstract class VideoPlayer extends BasePlayer
         // Merge with audio stream in case if video does not contain audio
         if (audio != null && ((video != null && video.isVideoOnly) || video == null)) {
             final MediaSource audioSource = buildMediaSource(audio.getUrl(),
+                    PlayerHelper.cacheKeyOf(info, audio),
                     MediaFormat.getSuffixById(audio.getFormatId()));
             mediaSources.add(audioSource);
         }
@@ -408,8 +423,8 @@ public abstract class VideoPlayer extends BasePlayer
 
             final Format textFormat = Format.createTextSampleFormat(null, mimeType,
                     SELECTION_FLAG_AUTOSELECT, PlayerHelper.captionLanguageOf(context, subtitle));
-            final MediaSource textSource = sampleMediaSourceFactory.createMediaSource(
+            final MediaSource textSource = dataSource.getSampleMediaSourceFactory()
-                    Uri.parse(subtitle.getURL()), textFormat, TIME_UNSET);
+                    .createMediaSource(Uri.parse(subtitle.getURL()), textFormat, TIME_UNSET);
             mediaSources.add(textSource);
         }
 
@@ -635,6 +650,8 @@ public abstract class VideoPlayer extends BasePlayer
             onResizeClicked();
         } else if (v.getId() == captionTextView.getId()) {
             onCaptionClicked();
+        } else if (v.getId() == playbackLiveSync.getId()) {
+            seekToDefault();
         }
     }
 

app/src/main/java/org/schabi/newpipe/player/helper/CacheFactory.java

@@ -21,7 +21,7 @@ import org.schabi.newpipe.Downloader;
 
 import java.io.File;
 
-public class CacheFactory implements DataSource.Factory {
+/* package-private */ class CacheFactory implements DataSource.Factory {
     private static final String TAG = "CacheFactory";
     private static final String CACHE_FOLDER_NAME = "exoplayer";
     private static final int CACHE_FLAGS = CacheDataSource.FLAG_BLOCK_ON_CACHE | CacheDataSource.FLAG_IGNORE_CACHE_ON_ERROR;

app/src/main/java/org/schabi/newpipe/player/helper/PlayerDataSource.java

@@ -0,0 +1,76 @@
+package org.schabi.newpipe.player.helper;
+
+import android.content.Context;
+import android.support.annotation.NonNull;
+
+import com.google.android.exoplayer2.source.ExtractorMediaSource;
+import com.google.android.exoplayer2.source.SingleSampleMediaSource;
+import com.google.android.exoplayer2.source.dash.DashMediaSource;
+import com.google.android.exoplayer2.source.dash.DefaultDashChunkSource;
+import com.google.android.exoplayer2.source.hls.HlsMediaSource;
+import com.google.android.exoplayer2.source.smoothstreaming.DefaultSsChunkSource;
+import com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource;
+import com.google.android.exoplayer2.upstream.DataSource;
+import com.google.android.exoplayer2.upstream.DefaultDataSourceFactory;
+import com.google.android.exoplayer2.upstream.TransferListener;
+
+public class PlayerDataSource {
+    private static final int MANIFEST_MINIMUM_RETRY = 5;
+    private static final int LIVE_STREAM_EDGE_GAP_MILLIS = 10000;
+
+    private final DataSource.Factory cacheDataSourceFactory;
+    private final DataSource.Factory cachelessDataSourceFactory;
+
+    public PlayerDataSource(@NonNull final Context context,
+                            @NonNull final String userAgent,
+                            @NonNull final TransferListener<? super DataSource> transferListener) {
+        cacheDataSourceFactory = new CacheFactory(context, userAgent, transferListener);
+        cachelessDataSourceFactory = new DefaultDataSourceFactory(context, userAgent, transferListener);
+    }
+
+    public SsMediaSource.Factory getLiveSsMediaSourceFactory() {
+        return new SsMediaSource.Factory(new DefaultSsChunkSource.Factory(
+                cachelessDataSourceFactory), cachelessDataSourceFactory)
+                .setMinLoadableRetryCount(MANIFEST_MINIMUM_RETRY)
+                .setLivePresentationDelayMs(LIVE_STREAM_EDGE_GAP_MILLIS);
+    }
+
+    public HlsMediaSource.Factory getLiveHlsMediaSourceFactory() {
+        return new HlsMediaSource.Factory(cachelessDataSourceFactory)
+                .setAllowChunklessPreparation(true)
+                .setMinLoadableRetryCount(MANIFEST_MINIMUM_RETRY);
+    }
+
+    public DashMediaSource.Factory getLiveDashMediaSourceFactory() {
+        return new DashMediaSource.Factory(new DefaultDashChunkSource.Factory(
+                cachelessDataSourceFactory), cachelessDataSourceFactory)
+                .setMinLoadableRetryCount(MANIFEST_MINIMUM_RETRY)
+                .setLivePresentationDelayMs(LIVE_STREAM_EDGE_GAP_MILLIS);
+    }
+
+    public SsMediaSource.Factory getSsMediaSourceFactory() {
+        return new SsMediaSource.Factory(new DefaultSsChunkSource.Factory(
+                cacheDataSourceFactory), cacheDataSourceFactory);
+    }
+
+    public HlsMediaSource.Factory getHlsMediaSourceFactory() {
+        return new HlsMediaSource.Factory(cacheDataSourceFactory);
+    }
+
+    public DashMediaSource.Factory getDashMediaSourceFactory() {
+        return new DashMediaSource.Factory(new DefaultDashChunkSource.Factory(
+                cacheDataSourceFactory), cacheDataSourceFactory);
+    }
+
+    public ExtractorMediaSource.Factory getExtractorMediaSourceFactory() {
+        return new ExtractorMediaSource.Factory(cacheDataSourceFactory);
+    }
+
+    public ExtractorMediaSource.Factory getExtractorMediaSourceFactory(@NonNull final String key) {
+        return new ExtractorMediaSource.Factory(cacheDataSourceFactory).setCustomCacheKey(key);
+    }
+
+    public SingleSampleMediaSource.Factory getSampleMediaSourceFactory() {
+        return new SingleSampleMediaSource.Factory(cacheDataSourceFactory);
+    }
+}

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHelper.java

@@ -10,7 +10,10 @@ import com.google.android.exoplayer2.util.MimeTypes;
 
 import org.schabi.newpipe.R;
 import org.schabi.newpipe.extractor.Subtitles;
+import org.schabi.newpipe.extractor.stream.AudioStream;
+import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.extractor.stream.SubtitlesFormat;
+import org.schabi.newpipe.extractor.stream.VideoStream;
 
 import java.text.DecimalFormat;
 import java.text.NumberFormat;
@@ -69,8 +72,7 @@ public class PlayerHelper {
     public static String captionLanguageOf(@NonNull final Context context,
                                            @NonNull final Subtitles subtitles) {
         final String displayName = subtitles.getLocale().getDisplayName(subtitles.getLocale());
-        return displayName + (subtitles.isAutoGenerated() ?
+        return displayName + (subtitles.isAutoGenerated() ? " (" + context.getString(R.string.caption_auto_generated)+ ")" : "");
-                " (" + context.getString(R.string.caption_auto_generated)+ ")" : "");
     }
 
     public static String resizeTypeOf(@NonNull final Context context,
@@ -83,6 +85,14 @@ public class PlayerHelper {
         }
     }
 
+    public static String cacheKeyOf(@NonNull final StreamInfo info, @NonNull VideoStream video) {
+        return info.getUrl() + video.getResolution() + video.getFormat().getName();
+    }
+
+    public static String cacheKeyOf(@NonNull final StreamInfo info, @NonNull AudioStream audio) {
+        return info.getUrl() + audio.getAverageBitrate() + audio.getFormat().getName();
+    }
+
     public static boolean isResumeAfterAudioFocusGain(@NonNull final Context context) {
         return isResumeAfterAudioFocusGain(context, false);
     }

app/src/main/java/org/schabi/newpipe/player/mediasource/FailedMediaSource.java

@@ -1,6 +1,7 @@
 package org.schabi.newpipe.player.mediasource;
 
 import android.support.annotation.NonNull;
+import android.util.Log;
 
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.source.MediaPeriod;
@@ -11,6 +12,7 @@ import org.schabi.newpipe.playlist.PlayQueueItem;
 import java.io.IOException;
 
 public class FailedMediaSource implements ManagedMediaSource {
+    private final String TAG = "ManagedMediaSource@" + Integer.toHexString(hashCode());
 
     private final PlayQueueItem playQueueItem;
     private final Throwable error;
@@ -36,7 +38,7 @@ public class FailedMediaSource implements ManagedMediaSource {
         this.retryTimestamp = Long.MAX_VALUE;
     }
 
-    public PlayQueueItem getPlayQueueItem() {
+    public PlayQueueItem getStream() {
         return playQueueItem;
     }
 
@@ -44,12 +46,14 @@ public class FailedMediaSource implements ManagedMediaSource {
         return error;
     }
 
-    public boolean canRetry() {
+    private boolean canRetry() {
         return System.currentTimeMillis() >= retryTimestamp;
     }
 
     @Override
-    public void prepareSource(ExoPlayer player, boolean isTopLevelSource, Listener listener) {}
+    public void prepareSource(ExoPlayer player, boolean isTopLevelSource, Listener listener) {
+        Log.e(TAG, "Loading failed source: ", error);
+    }
 
     @Override
     public void maybeThrowSourceInfoRefreshError() throws IOException {
@@ -68,7 +72,7 @@ public class FailedMediaSource implements ManagedMediaSource {
     public void releaseSource() {}
 
     @Override
-    public boolean canReplace() {
+    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
-        return canRetry();
+        return newIdentity != playQueueItem || canRetry();
     }
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/LoadedMediaSource.java

@@ -7,7 +7,6 @@ import com.google.android.exoplayer2.source.MediaPeriod;
 import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.upstream.Allocator;
 
-import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.playlist.PlayQueueItem;
 
 import java.io.IOException;
@@ -15,15 +14,25 @@ import java.io.IOException;
 public class LoadedMediaSource implements ManagedMediaSource {
 
     private final MediaSource source;
-
+    private final PlayQueueItem stream;
     private final long expireTimestamp;
 
-    public LoadedMediaSource(@NonNull final MediaSource source, final long expireTimestamp) {
+    public LoadedMediaSource(@NonNull final MediaSource source,
+                             @NonNull final PlayQueueItem stream,
+                             final long expireTimestamp) {
         this.source = source;
-
+        this.stream = stream;
         this.expireTimestamp = expireTimestamp;
     }
 
+    public PlayQueueItem getStream() {
+        return stream;
+    }
+
+    private boolean isExpired() {
+        return System.currentTimeMillis() >= expireTimestamp;
+    }
+
     @Override
     public void prepareSource(ExoPlayer player, boolean isTopLevelSource, Listener listener) {
         source.prepareSource(player, isTopLevelSource, listener);
@@ -50,7 +59,7 @@ public class LoadedMediaSource implements ManagedMediaSource {
     }
 
     @Override
-    public boolean canReplace() {
+    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
-        return System.currentTimeMillis() >= expireTimestamp;
+        return newIdentity != stream || isExpired();
     }
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/ManagedMediaSource.java

@@ -1,7 +1,11 @@
 package org.schabi.newpipe.player.mediasource;
 
+import android.support.annotation.NonNull;
+
 import com.google.android.exoplayer2.source.MediaSource;
 
+import org.schabi.newpipe.playlist.PlayQueueItem;
+
 public interface ManagedMediaSource extends MediaSource {
-    boolean canReplace();
+    boolean canReplace(@NonNull final PlayQueueItem newIdentity);
 }

app/src/main/java/org/schabi/newpipe/player/mediasource/PlaceholderMediaSource.java

@@ -1,10 +1,13 @@
 package org.schabi.newpipe.player.mediasource;
 
+import android.support.annotation.NonNull;
+
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.source.MediaPeriod;
-import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.upstream.Allocator;
 
+import org.schabi.newpipe.playlist.PlayQueueItem;
+
 import java.io.IOException;
 
 public class PlaceholderMediaSource implements ManagedMediaSource {
@@ -16,7 +19,7 @@ public class PlaceholderMediaSource implements ManagedMediaSource {
     @Override public void releaseSource() {}
 
     @Override
-    public boolean canReplace() {
+    public boolean canReplace(@NonNull final PlayQueueItem newIdentity) {
         return true;
     }
 }

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

@@ -1,6 +1,7 @@
 package org.schabi.newpipe.player.playback;
 
 import android.support.annotation.Nullable;
+import android.util.Log;
 
 import com.google.android.exoplayer2.source.DynamicConcatenatingMediaSource;
 import com.google.android.exoplayer2.source.MediaSource;
@@ -34,7 +35,11 @@ import io.reactivex.disposables.SerialDisposable;
 import io.reactivex.functions.Consumer;
 import io.reactivex.subjects.PublishSubject;
 
+import static org.schabi.newpipe.playlist.PlayQueue.DEBUG;
+
 public class MediaSourceManager {
+    private final String TAG = "MediaSourceManager";
+
     // One-side rolling window size for default loading
     // Effectively loads windowSize * 2 + 1 streams per call to load, must be greater than 0
     private final int windowSize;
@@ -233,10 +238,16 @@ public class MediaSourceManager {
         return playQueue.isComplete() || isWindowLoaded;
     }
 
-    // Checks if the current playback media source is a placeholder, if so, then it is not ready.
     private boolean isPlaybackReady() {
-        return sources != null && playQueue != null && sources.getSize() > playQueue.getIndex() &&
+        if (sources == null || playQueue == null || sources.getSize() != playQueue.size()) {
-                !(sources.getMediaSource(playQueue.getIndex()) instanceof PlaceholderMediaSource);
+            return false;
+        }
+
+        final MediaSource mediaSource = sources.getMediaSource(playQueue.getIndex());
+        if (!(mediaSource instanceof LoadedMediaSource)) return false;
+
+        final PlayQueueItem playQueueItem = playQueue.getItem();
+        return playQueueItem == ((LoadedMediaSource) mediaSource).getStream();
     }
 
     private void tryBlock() {
@@ -280,7 +291,7 @@ public class MediaSourceManager {
         if (playQueue == null || playbackListener == null) return;
         // Ensure the current item is up to date with the play queue
         if (playQueue.getItem() == item && playQueue.getItem() == syncedItem) {
-            playbackListener.sync(syncedItem,info);
+            playbackListener.sync(syncedItem, info);
         }
     }
 
@@ -329,14 +340,19 @@ public class MediaSourceManager {
         if (index > sources.getSize() - 1) return;
 
         final Consumer<ManagedMediaSource> onDone = mediaSource -> {
-            update(playQueue.indexOf(item), mediaSource);
+            if (DEBUG) Log.d(TAG, " Loaded: [" + item.getTitle() +
+                    "] with url: " + item.getUrl());
+
+            if (isCorrectionNeeded(item)) update(playQueue.indexOf(item), mediaSource);
+
             loadingItems.remove(item);
             tryUnblock();
             sync();
         };
 
-        if (!loadingItems.contains(item) &&
+        if (!loadingItems.contains(item) && isCorrectionNeeded(item)) {
-                ((ManagedMediaSource) sources.getMediaSource(index)).canReplace()) {
+            if (DEBUG) Log.d(TAG, "Loading: [" + item.getTitle() +
+                    "] with url: " + item.getUrl());
 
             loadingItems.add(item);
             final Disposable loader = getLoadedMediaSource(item)
@@ -358,16 +374,32 @@ public class MediaSourceManager {
 
             final MediaSource source = playbackListener.sourceOf(stream, streamInfo);
             if (source == null) {
-                return new FailedMediaSource(stream, new IllegalStateException(
+                final Exception exception = new IllegalStateException(
-                        "MediaSource cannot be resolved"));
+                        "Unable to resolve source from stream info." +
+                                " URL: " + stream.getUrl() +
+                                ", audio count: " + streamInfo.audio_streams.size() +
+                                ", video count: " + streamInfo.video_only_streams.size() +
+                                streamInfo.video_streams.size());
+                return new FailedMediaSource(stream, new IllegalStateException(exception));
             }
 
             final long expiration = System.currentTimeMillis() +
                     TimeUnit.MILLISECONDS.convert(expirationTimeMillis, expirationTimeUnit);
-            return new LoadedMediaSource(source, expiration);
+            return new LoadedMediaSource(source, stream, expiration);
         }).onErrorReturn(throwable -> new FailedMediaSource(stream, throwable));
     }
 
+    private boolean isCorrectionNeeded(@NonNull final PlayQueueItem item) {
+        if (playQueue == null || sources == null) return false;
+
+        final int index = playQueue.indexOf(item);
+        if (index == -1 || index >= sources.getSize()) return false;
+
+        final MediaSource mediaSource = sources.getMediaSource(index);
+        return !(mediaSource instanceof ManagedMediaSource) ||
+                ((ManagedMediaSource) mediaSource).canReplace(item);
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
     // MediaSource Playlist Helpers
     //////////////////////////////////////////////////////////////////////////*/

app/src/main/res/layout-land/activity_player_queue_control.xml

@@ -296,5 +296,15 @@
             android:textColor="?attr/colorAccent"
             tools:ignore="HardcodedText"
             tools:text="1:23:49"/>
+
+        <TextView
+            android:id="@+id/live_sync"
+            android:layout_width="wrap_content"
+            android:layout_height="match_parent"
+            android:gravity="center"
+            android:text="@string/live_sync"
+            android:textColor="?attr/colorAccent"
+            android:background="?attr/selectableItemBackground"
+            android:visibility="gone"/>
     </LinearLayout>
 </RelativeLayout>

app/src/main/res/layout/activity_main_player.xml

@@ -397,6 +397,17 @@
                     android:textColor="@android:color/white"
                     tools:ignore="HardcodedText"
                     tools:text="1:23:49"/>
+
+                <TextView
+                    android:id="@+id/playbackLiveSync"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:gravity="center_vertical"
+                    android:text="@string/live_sync"
+                    android:textColor="@android:color/white"
+                    android:visibility="gone"
+                    android:background="?attr/selectableItemBackground"
+                    tools:ignore="HardcodedText,RtlHardcoded,RtlSymmetry" />
             </LinearLayout>
         </RelativeLayout>
 

app/src/main/res/layout/activity_player_queue_control.xml

@@ -146,6 +146,16 @@
             android:textColor="?attr/colorAccent"
             tools:ignore="HardcodedText"
             tools:text="1:23:49"/>
+
+        <TextView
+            android:id="@+id/live_sync"
+            android:layout_width="wrap_content"
+            android:layout_height="match_parent"
+            android:gravity="center"
+            android:text="@string/live_sync"
+            android:textColor="?attr/colorAccent"
+            android:background="?attr/selectableItemBackground"
+            android:visibility="gone"/>
     </LinearLayout>
 
     <RelativeLayout

app/src/main/res/layout/player_popup.xml

@@ -190,6 +190,17 @@
                 android:textColor="@android:color/white"
                 tools:ignore="HardcodedText,RtlHardcoded,RtlSymmetry"
                 tools:text="1:23:49"/>
+
+            <TextView
+                android:id="@+id/playbackLiveSync"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:gravity="center_vertical"
+                android:text="@string/live_sync"
+                android:textColor="@android:color/white"
+                android:visibility="gone"
+                android:background="?attr/selectableItemBackground"
+                tools:ignore="HardcodedText,RtlHardcoded,RtlSymmetry" />
         </LinearLayout>
     </RelativeLayout>
 

app/src/main/res/values/strings.xml

@@ -413,6 +413,8 @@
     <string name="normal_caption_font_size">Normal Font</string>
     <string name="larger_caption_font_size">Larger Font</string>
 
+    <string name="live_sync">SYNC</string>
+
     <!-- Debug Settings -->
     <string name="enable_leak_canary_title">Enable LeakCanary</string>
     <string name="enable_leak_canary_summary">Memory leak monitoring may cause app to become unresponsive when heap dumping</string>