diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
index d4ede3e59e..14ccbead92 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
@@ -18,6 +18,7 @@ package com.google.android.exoplayer2.source;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.MediaItem;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.upstream.Allocator;
 import com.google.android.exoplayer2.upstream.TransferListener;
@@ -184,12 +185,22 @@ public final class ClippingMediaSource extends CompositeMediaSource<Void> {
     window = new Timeline.Window();
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return mediaSource.getTag();
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return mediaSource.getMediaItem();
+  }
+
   @Override
   protected void prepareSourceInternal(@Nullable TransferListener mediaTransferListener) {
     super.prepareSourceInternal(mediaTransferListener);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
index 8268798ee3..d664219bf3 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
@@ -442,7 +442,7 @@ public final class ConcatenatingMediaSource extends CompositeMediaSource<MediaSo
 
   // CompositeMediaSource implementation.
 
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     // This method is actually never called because getInitialTimeline is implemented and hence the
     // MaskingMediaSource does not need to create a dummy timeline for this media source.
@@ -996,7 +996,7 @@ public final class ConcatenatingMediaSource extends CompositeMediaSource<MediaSo
       // Do nothing.
     }
 
-    // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+    @Override
     public MediaItem getMediaItem() {
       return DUMMY_MEDIA_ITEM;
     }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
index 5b55b4f8f8..c55b424520 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java
@@ -333,12 +333,22 @@ public final class ExtractorMediaSource extends CompositeMediaSource<Void> {
             continueLoadingCheckIntervalBytes);
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return progressiveMediaSource.getTag();
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return progressiveMediaSource.getMediaItem();
+  }
+
   @Override
   protected void prepareSourceInternal(@Nullable TransferListener mediaTransferListener) {
     super.prepareSourceInternal(mediaTransferListener);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java
index 13f9758a73..6d08147a63 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java
@@ -19,6 +19,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.AbstractConcatenatedTimeline;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlayer;
+import com.google.android.exoplayer2.MediaItem;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.ShuffleOrder.UnshuffledShuffleOrder;
@@ -65,12 +66,22 @@ public final class LoopingMediaSource extends CompositeMediaSource<Void> {
     mediaPeriodToChildMediaPeriodId = new HashMap<>();
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return maskingMediaSource.getTag();
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return maskingMediaSource.getMediaItem();
+  }
+
   @Override
   @Nullable
   public Timeline getInitialTimeline() {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
index db8d7e85bf..ee88725193 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
@@ -15,7 +15,6 @@
  */
 package com.google.android.exoplayer2.source;
 
-import android.net.Uri;
 import android.util.Pair;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
@@ -68,10 +67,7 @@ public final class MaskingMediaSource extends CompositeMediaSource<Void> {
               initialTimeline, /* firstWindowUid= */ null, /* firstPeriodUid= */ null);
       hasRealTimeline = true;
     } else {
-      // TODO(bachinger) Use mediasSource.getMediaItem() to provide the media item.
-      timeline =
-          MaskingTimeline.createWithDummyTimeline(
-              new MediaItem.Builder().setUri(Uri.EMPTY).setTag(mediaSource.getTag()).build());
+      timeline = MaskingTimeline.createWithDummyTimeline(mediaSource.getMediaItem());
     }
   }
 
@@ -89,12 +85,22 @@ public final class MaskingMediaSource extends CompositeMediaSource<Void> {
     }
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return mediaSource.getTag();
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return mediaSource.getMediaItem();
+  }
+
   @Override
   @SuppressWarnings("MissingSuperCall")
   public void maybeThrowSourceInfoRefreshError() {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
index 479db2adc2..8e860f6ed1 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java
@@ -18,6 +18,7 @@ package com.google.android.exoplayer2.source;
 import android.os.Handler;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.MediaItem;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.drm.DrmSessionEventListener;
 import com.google.android.exoplayer2.upstream.Allocator;
@@ -273,12 +274,18 @@ public interface MediaSource {
     return true;
   }
 
-  /** Returns the tag set on the media source, or null if none was set. */
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @Deprecated
   @Nullable
   default Object getTag() {
     return null;
   }
 
+  /** Returns the {@link MediaItem} whose media is provided by the source. */
+  MediaItem getMediaItem();
+
   /**
    * Registers a {@link MediaSourceCaller}. Starts source preparation if needed and enables the
    * source for the creation of {@link MediaPeriod MediaPerods}.
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
index d69c037a5a..446f7132b0 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java
@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.source;
 
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.MediaItem;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.upstream.Allocator;
 import com.google.android.exoplayer2.upstream.TransferListener;
@@ -65,6 +66,8 @@ public final class MergingMediaSource extends CompositeMediaSource<Integer> {
   }
 
   private static final int PERIOD_COUNT_UNSET = -1;
+  private static final MediaItem DUMMY_MEDIA_ITEM =
+      new MediaItem.Builder().setMediaId("MergingMediaSource").build();
 
   private final boolean adjustPeriodTimeOffsets;
   private final MediaSource[] mediaSources;
@@ -121,12 +124,22 @@ public final class MergingMediaSource extends CompositeMediaSource<Integer> {
     periodTimeOffsetsUs = new long[0][];
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return mediaSources.length > 0 ? mediaSources[0].getTag() : null;
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return mediaSources.length > 0 ? mediaSources[0].getMediaItem() : DUMMY_MEDIA_ITEM;
+  }
+
   @Override
   protected void prepareSourceInternal(@Nullable TransferListener mediaTransferListener) {
     super.prepareSourceInternal(mediaTransferListener);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ProgressiveMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ProgressiveMediaSource.java
index bfec295568..ffa8ede140 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ProgressiveMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ProgressiveMediaSource.java
@@ -244,14 +244,19 @@ public final class ProgressiveMediaSource extends BaseMediaSource
     this.timelineDurationUs = C.TIME_UNSET;
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return playbackProperties.tag;
   }
 
-  @Nullable
-  public Object getMediaItem() {
+  @Override
+  public MediaItem getMediaItem() {
     return mediaItem;
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/SilenceMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/SilenceMediaSource.java
index a7669ae345..b3653bbc29 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/SilenceMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/SilenceMediaSource.java
@@ -77,7 +77,7 @@ public final class SilenceMediaSource extends BaseMediaSource {
   }
 
   /** The media id used by any media item of silence media sources. */
-  public static final String MEDIA_ID = "com.google.android.exoplayer2.source.SilenceMediaSource";
+  public static final String MEDIA_ID = "SilenceMediaSource";
 
   private static final int SAMPLE_RATE_HZ = 44100;
   @C.PcmEncoding private static final int PCM_ENCODING = C.ENCODING_PCM_16BIT;
@@ -145,18 +145,22 @@ public final class SilenceMediaSource extends BaseMediaSource {
   @Override
   public void releasePeriod(MediaPeriod mediaPeriod) {}
 
-  /** Returns the {@link MediaItem} of this media source. */
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
-  public MediaItem getMediaItem() {
-    return mediaItem;
-  }
-
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Nullable
   @Override
   public Object getTag() {
     return Assertions.checkNotNull(mediaItem.playbackProperties).tag;
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return mediaItem;
+  }
+
   @Override
   protected void releaseSourceInternal() {}
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
index 2edb1a2baa..815e4d95b1 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java
@@ -294,13 +294,18 @@ public final class SingleSampleMediaSource extends BaseMediaSource {
 
   // MediaSource implementation.
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return castNonNull(mediaItem.playbackProperties).tag;
   }
 
-  // TODO(bachinger) Add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     return mediaItem;
   }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
index 07a46f06a9..27df9a66f3 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java
@@ -22,6 +22,7 @@ import android.os.SystemClock;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.MediaItem;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.CompositeMediaSource;
 import com.google.android.exoplayer2.source.LoadEventInfo;
@@ -181,12 +182,22 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
     adsLoader.setSupportedContentTypes(adMediaSourceFactory.getSupportedTypes());
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return contentMediaSource.getTag();
   }
 
+  @Override
+  public MediaItem getMediaItem() {
+    return contentMediaSource.getMediaItem();
+  }
+
   @Override
   protected void prepareSourceInternal(@Nullable TransferListener mediaTransferListener) {
     super.prepareSourceInternal(mediaTransferListener);
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java b/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
index c4325762d8..506d56a89c 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
@@ -140,7 +140,7 @@ public final class ExoPlayerTest {
   public void playEmptyTimeline() throws Exception {
     Timeline timeline = Timeline.EMPTY;
     Timeline expectedMaskingTimeline =
-        new MaskingMediaSource.DummyTimeline(FakeTimeline.FAKE_MEDIA_ITEM);
+        new MaskingMediaSource.DummyTimeline(FakeMediaSource.FAKE_MEDIA_ITEM);
     FakeRenderer renderer = new FakeRenderer(C.TRACK_TYPE_UNKNOWN);
     ExoPlayerTestRunner testRunner =
         new ExoPlayerTestRunner.Builder(context)
@@ -3445,6 +3445,11 @@ public final class ExoPlayerTest {
             return false;
           }
 
+          @Override
+          public MediaItem getMediaItem() {
+            return underlyingSource.getMediaItem();
+          }
+
           @Override
           @Nullable
           public Timeline getInitialTimeline() {
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/MediaSourceListTest.java b/library/core/src/test/java/com/google/android/exoplayer2/MediaSourceListTest.java
index 7ece4f3259..bcea053115 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/MediaSourceListTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/MediaSourceListTest.java
@@ -23,6 +23,7 @@ import static org.mockito.ArgumentMatchers.isNull;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.android.exoplayer2.source.MediaSource;
@@ -42,6 +43,8 @@ import org.junit.runner.RunWith;
 public class MediaSourceListTest {
 
   private static final int MEDIA_SOURCE_LIST_SIZE = 4;
+  private static final MediaItem MINIMAL_MEDIA_ITEM =
+      new MediaItem.Builder().setMediaId("").build();
 
   private MediaSourceList mediaSourceList;
 
@@ -76,7 +79,9 @@ public class MediaSourceListTest {
   @Test
   public void prepareAndReprepareAfterRelease_expectSourcePreparationAfterMediaSourceListPrepare() {
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     mediaSourceList.setMediaSources(
         createFakeHoldersWithSources(
             /* useLazyPreparation= */ false, mockMediaSource1, mockMediaSource2),
@@ -115,7 +120,9 @@ public class MediaSourceListTest {
     ShuffleOrder.DefaultShuffleOrder shuffleOrder =
         new ShuffleOrder.DefaultShuffleOrder(/* length= */ 2);
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> mediaSources =
         createFakeHoldersWithSources(
             /* useLazyPreparation= */ false, mockMediaSource1, mockMediaSource2);
@@ -132,8 +139,10 @@ public class MediaSourceListTest {
     }
 
     // Set media items again. The second holder is re-used.
+    MediaSource mockMediaSource3 = mock(MediaSource.class);
+    when(mockMediaSource3.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> moreMediaSources =
-        createFakeHoldersWithSources(/* useLazyPreparation= */ false, mock(MediaSource.class));
+        createFakeHoldersWithSources(/* useLazyPreparation= */ false, mockMediaSource3);
     moreMediaSources.add(mediaSources.get(1));
     timeline = mediaSourceList.setMediaSources(moreMediaSources, shuffleOrder);
 
@@ -157,7 +166,9 @@ public class MediaSourceListTest {
     ShuffleOrder.DefaultShuffleOrder shuffleOrder =
         new ShuffleOrder.DefaultShuffleOrder(/* length= */ 2);
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> mediaSources =
         createFakeHoldersWithSources(
             /* useLazyPreparation= */ false, mockMediaSource1, mockMediaSource2);
@@ -174,8 +185,10 @@ public class MediaSourceListTest {
             any(MediaSource.MediaSourceCaller.class), /* mediaTransferListener= */ isNull());
 
     // Set media items again. The second holder is re-used.
+    MediaSource mockMediaSource3 = mock(MediaSource.class);
+    when(mockMediaSource3.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> moreMediaSources =
-        createFakeHoldersWithSources(/* useLazyPreparation= */ false, mock(MediaSource.class));
+        createFakeHoldersWithSources(/* useLazyPreparation= */ false, mockMediaSource3);
     moreMediaSources.add(mediaSources.get(1));
     mediaSourceList.setMediaSources(moreMediaSources, shuffleOrder);
 
@@ -193,7 +206,9 @@ public class MediaSourceListTest {
   @Test
   public void addMediaSources_mediaSourceListUnprepared_notUsingLazyPreparation_expectUnprepared() {
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> mediaSources =
         createFakeHoldersWithSources(
             /* useLazyPreparation= */ false, mockMediaSource1, mockMediaSource2);
@@ -228,7 +243,9 @@ public class MediaSourceListTest {
   @Test
   public void addMediaSources_mediaSourceListPrepared_notUsingLazyPreparation_expectPrepared() {
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     mediaSourceList.prepare(/* mediaTransferListener= */ null);
     mediaSourceList.addMediaSources(
         /* index= */ 0,
@@ -287,9 +304,13 @@ public class MediaSourceListTest {
   @Test
   public void removeMediaSources_whenUnprepared_expectNoRelease() {
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource3 = mock(MediaSource.class);
+    when(mockMediaSource3.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource4 = mock(MediaSource.class);
+    when(mockMediaSource4.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     ShuffleOrder.DefaultShuffleOrder shuffleOrder =
         new ShuffleOrder.DefaultShuffleOrder(/* length= */ 4);
 
@@ -319,9 +340,13 @@ public class MediaSourceListTest {
   @Test
   public void removeMediaSources_whenPrepared_expectRelease() {
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource3 = mock(MediaSource.class);
+    when(mockMediaSource3.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource4 = mock(MediaSource.class);
+    when(mockMediaSource4.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     ShuffleOrder.DefaultShuffleOrder shuffleOrder =
         new ShuffleOrder.DefaultShuffleOrder(/* length= */ 4);
 
@@ -350,6 +375,7 @@ public class MediaSourceListTest {
   @Test
   public void release_mediaSourceListUnprepared_expectSourcesNotReleased() {
     MediaSource mockMediaSource = mock(MediaSource.class);
+    when(mockMediaSource.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSourceList.MediaSourceHolder mediaSourceHolder =
         new MediaSourceList.MediaSourceHolder(mockMediaSource, /* useLazyPreparation= */ false);
 
@@ -367,6 +393,7 @@ public class MediaSourceListTest {
   @Test
   public void release_mediaSourceListPrepared_expectSourcesReleasedNotRemoved() {
     MediaSource mockMediaSource = mock(MediaSource.class);
+    when(mockMediaSource.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSourceList.MediaSourceHolder mediaSourceHolder =
         new MediaSourceList.MediaSourceHolder(mockMediaSource, /* useLazyPreparation= */ false);
 
@@ -387,7 +414,9 @@ public class MediaSourceListTest {
     ShuffleOrder.DefaultShuffleOrder shuffleOrder =
         new ShuffleOrder.DefaultShuffleOrder(/* length= */ 4);
     MediaSource mockMediaSource1 = mock(MediaSource.class);
+    when(mockMediaSource1.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     MediaSource mockMediaSource2 = mock(MediaSource.class);
+    when(mockMediaSource2.getMediaItem()).thenReturn(MINIMAL_MEDIA_ITEM);
     List<MediaSourceList.MediaSourceHolder> holders =
         createFakeHoldersWithSources(
             /* useLazyPreparation= */ false, mockMediaSource1, mockMediaSource2);
diff --git a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
index f60e1c15a2..747a24ca63 100644
--- a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
+++ b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
@@ -655,13 +655,18 @@ public final class DashMediaSource extends BaseMediaSource {
 
   // MediaSource implementation.
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return playbackProperties.tag;
   }
 
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     return mediaItem;
   }
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
index fcf4386492..e2d7e47665 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java
@@ -425,13 +425,18 @@ public final class HlsMediaSource extends BaseMediaSource
     this.useSessionKeys = useSessionKeys;
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return playbackProperties.tag;
   }
 
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     return mediaItem;
   }
diff --git a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java
index f75be283e2..6b9a00b486 100644
--- a/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java
+++ b/library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java
@@ -593,13 +593,18 @@ public final class SsMediaSource extends BaseMediaSource
 
   // MediaSource implementation.
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
     return playbackProperties.tag;
   }
 
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     return mediaItem;
   }
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSource.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSource.java
index 1027d7d620..2c5a471c58 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSource.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSource.java
@@ -71,7 +71,7 @@ public class FakeMediaSource extends BaseMediaSource {
 
   /** The media item used by the fake media source. */
   public static final MediaItem FAKE_MEDIA_ITEM =
-      new MediaItem.Builder().setUri("http://manifest.uri").build();
+      new MediaItem.Builder().setMediaId("FakeMediaSource").setUri("http://manifest.uri").build();
 
   private static final DataSpec FAKE_DATA_SPEC =
       new DataSpec(castNonNull(FAKE_MEDIA_ITEM.playbackProperties).uri);
@@ -134,6 +134,11 @@ public class FakeMediaSource extends BaseMediaSource {
     return timeline;
   }
 
+  /**
+   * @deprecated Use {@link #getMediaItem()} and {@link MediaItem.PlaybackProperties#tag} instead.
+   */
+  @SuppressWarnings("deprecation")
+  @Deprecated
   @Override
   @Nullable
   public Object getTag() {
@@ -143,7 +148,7 @@ public class FakeMediaSource extends BaseMediaSource {
     return timeline.getWindow(0, new Timeline.Window()).tag;
   }
 
-  // TODO(bachinger): add @Override annotation once the method is defined by MediaSource.
+  @Override
   public MediaItem getMediaItem() {
     if (timeline == null || timeline.isEmpty()) {
       return FAKE_MEDIA_ITEM;
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
index 81d8844372..3fc9143fa7 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
@@ -184,7 +184,8 @@ public final class FakeTimeline extends Timeline {
   }
 
   /** The fake media item used by the fake timeline. */
-  public static final MediaItem FAKE_MEDIA_ITEM = new MediaItem.Builder().setUri(Uri.EMPTY).build();
+  public static final MediaItem FAKE_MEDIA_ITEM =
+      new MediaItem.Builder().setMediaId("FakeTimeline").setUri(Uri.EMPTY).build();
 
   private static final long AD_DURATION_US = 10 * C.MICROS_PER_SECOND;