diff --git a/library/common/src/main/java/com/google/android/exoplayer2/source/MediaPeriodId.java b/library/common/src/main/java/com/google/android/exoplayer2/source/MediaPeriodId.java
new file mode 100644
index 0000000000..ad0e289ba9
--- /dev/null
+++ b/library/common/src/main/java/com/google/android/exoplayer2/source/MediaPeriodId.java
@@ -0,0 +1,187 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source;
+
+import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Timeline;
+
+/**
+ * Identifies a specific playback of a {@link Timeline.Period}.
+ *
+ * <p>A {@link Timeline.Period} can be played multiple times, for example if it is repeated. Each
+ * instances of this class identifies a specific playback of a {@link Timeline.Period}.
+ *
+ * <p>In ExoPlayer's implementation, {@link MediaPeriodId} identifies a {@code MediaPeriod}.
+ */
+// TODO(b/172315872) Should be final, but subclassed in MediaSource for backward-compatibility.
+public class MediaPeriodId {
+
+  /** The unique id of the timeline period. */
+  public final Object periodUid;
+
+  /**
+   * If the media period is in an ad group, the index of the ad group in the period. {@link
+   * C#INDEX_UNSET} otherwise.
+   */
+  public final int adGroupIndex;
+
+  /**
+   * If the media period is in an ad group, the index of the ad in its ad group in the period.
+   * {@link C#INDEX_UNSET} otherwise.
+   */
+  public final int adIndexInAdGroup;
+
+  /**
+   * The sequence number of the window in the buffered sequence of windows this media period is part
+   * of. {@link C#INDEX_UNSET} if the media period id is not part of a buffered sequence of windows.
+   */
+  public final long windowSequenceNumber;
+
+  /**
+   * The index of the next ad group to which the media period's content is clipped, or {@link
+   * C#INDEX_UNSET} if there is no following ad group or if this media period is an ad.
+   */
+  public final int nextAdGroupIndex;
+
+  /**
+   * Creates a media period identifier for a period which is not part of a buffered sequence of
+   * windows.
+   *
+   * @param periodUid The unique id of the timeline period.
+   */
+  public MediaPeriodId(Object periodUid) {
+    this(periodUid, /* windowSequenceNumber= */ C.INDEX_UNSET);
+  }
+
+  /**
+   * Creates a media period identifier for the specified period in the timeline.
+   *
+   * @param periodUid The unique id of the timeline period.
+   * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
+   *     windows this media period is part of.
+   */
+  public MediaPeriodId(Object periodUid, long windowSequenceNumber) {
+    this(
+        periodUid,
+        /* adGroupIndex= */ C.INDEX_UNSET,
+        /* adIndexInAdGroup= */ C.INDEX_UNSET,
+        windowSequenceNumber,
+        /* nextAdGroupIndex= */ C.INDEX_UNSET);
+  }
+
+  /**
+   * Creates a media period identifier for the specified clipped period in the timeline.
+   *
+   * @param periodUid The unique id of the timeline period.
+   * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
+   *     windows this media period is part of.
+   * @param nextAdGroupIndex The index of the next ad group to which the media period's content is
+   *     clipped.
+   */
+  public MediaPeriodId(Object periodUid, long windowSequenceNumber, int nextAdGroupIndex) {
+    this(
+        periodUid,
+        /* adGroupIndex= */ C.INDEX_UNSET,
+        /* adIndexInAdGroup= */ C.INDEX_UNSET,
+        windowSequenceNumber,
+        nextAdGroupIndex);
+  }
+
+  /**
+   * Creates a media period identifier that identifies an ad within an ad group at the specified
+   * timeline period.
+   *
+   * @param periodUid The unique id of the timeline period that contains the ad group.
+   * @param adGroupIndex The index of the ad group.
+   * @param adIndexInAdGroup The index of the ad in the ad group.
+   * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
+   *     windows this media period is part of.
+   */
+  public MediaPeriodId(
+      Object periodUid, int adGroupIndex, int adIndexInAdGroup, long windowSequenceNumber) {
+    this(
+        periodUid,
+        adGroupIndex,
+        adIndexInAdGroup,
+        windowSequenceNumber,
+        /* nextAdGroupIndex= */ C.INDEX_UNSET);
+  }
+
+  /** Copy constructor for inheritance. */
+  // TODO(b/172315872) Delete when client have migrated from MediaSource.MediaPeriodId
+  protected MediaPeriodId(MediaPeriodId mediaPeriodId) {
+    this.periodUid = mediaPeriodId.periodUid;
+    this.adGroupIndex = mediaPeriodId.adGroupIndex;
+    this.adIndexInAdGroup = mediaPeriodId.adIndexInAdGroup;
+    this.windowSequenceNumber = mediaPeriodId.windowSequenceNumber;
+    this.nextAdGroupIndex = mediaPeriodId.nextAdGroupIndex;
+  }
+
+  private MediaPeriodId(
+      Object periodUid,
+      int adGroupIndex,
+      int adIndexInAdGroup,
+      long windowSequenceNumber,
+      int nextAdGroupIndex) {
+    this.periodUid = periodUid;
+    this.adGroupIndex = adGroupIndex;
+    this.adIndexInAdGroup = adIndexInAdGroup;
+    this.windowSequenceNumber = windowSequenceNumber;
+    this.nextAdGroupIndex = nextAdGroupIndex;
+  }
+
+  /** Returns a copy of this period identifier but with {@code newPeriodUid} as its period uid. */
+  public MediaPeriodId copyWithPeriodUid(Object newPeriodUid) {
+    return periodUid.equals(newPeriodUid)
+        ? this
+        : new MediaPeriodId(
+            newPeriodUid, adGroupIndex, adIndexInAdGroup, windowSequenceNumber, nextAdGroupIndex);
+  }
+
+  /** Returns whether this period identifier identifies an ad in an ad group in a period. */
+  public boolean isAd() {
+    return adGroupIndex != C.INDEX_UNSET;
+  }
+
+  @Override
+  public boolean equals(@Nullable Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (!(obj instanceof MediaPeriodId)) {
+      return false;
+    }
+
+    MediaPeriodId periodId = (MediaPeriodId) obj;
+    return periodUid.equals(periodId.periodUid)
+        && adGroupIndex == periodId.adGroupIndex
+        && adIndexInAdGroup == periodId.adIndexInAdGroup
+        && windowSequenceNumber == periodId.windowSequenceNumber
+        && nextAdGroupIndex == periodId.nextAdGroupIndex;
+  }
+
+  @Override
+  public int hashCode() {
+    int result = 17;
+    result = 31 * result + periodUid.hashCode();
+    result = 31 * result + adGroupIndex;
+    result = 31 * result + adIndexInAdGroup;
+    result = 31 * result + (int) windowSequenceNumber;
+    result = 31 * result + nextAdGroupIndex;
+    return result;
+  }
+}
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlaybackException.java b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlaybackException.java
index 6653cf572c..7e8f613e73 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlaybackException.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlaybackException.java
@@ -21,6 +21,7 @@ import androidx.annotation.CheckResult;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C.FormatSupport;
+import com.google.android.exoplayer2.source.MediaPeriodId;
 import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.util.Assertions;
 import java.io.IOException;
@@ -133,11 +134,8 @@ public final class ExoPlaybackException extends Exception {
   /** The value of {@link SystemClock#elapsedRealtime()} when this exception was created. */
   public final long timestampMs;
 
-  /**
-   * The {@link MediaSource.MediaPeriodId} of the media associated with this error, or null if
-   * undetermined.
-   */
-  @Nullable public final MediaSource.MediaPeriodId mediaPeriodId;
+  /** The {@link MediaPeriodId} of the media associated with this error, or null if undetermined. */
+  @Nullable public final MediaPeriodId mediaPeriodId;
 
   /**
    * Whether the error may be recoverable.
@@ -334,7 +332,7 @@ public final class ExoPlaybackException extends Exception {
       int rendererIndex,
       @Nullable Format rendererFormat,
       @FormatSupport int rendererFormatSupport,
-      @Nullable MediaSource.MediaPeriodId mediaPeriodId,
+      @Nullable MediaPeriodId mediaPeriodId,
       @TimeoutOperation int timeoutOperation,
       long timestampMs,
       boolean isRecoverable) {
@@ -402,14 +400,13 @@ public final class ExoPlaybackException extends Exception {
   }
 
   /**
-   * Returns a copy of this exception with the provided {@link MediaSource.MediaPeriodId}.
+   * Returns a copy of this exception with the provided {@link MediaPeriodId}.
    *
-   * @param mediaPeriodId The {@link MediaSource.MediaPeriodId}.
+   * @param mediaPeriodId The {@link MediaPeriodId}.
    * @return The copied exception.
    */
   @CheckResult
-  /* package */ ExoPlaybackException copyWithMediaPeriodId(
-      @Nullable MediaSource.MediaPeriodId mediaPeriodId) {
+  /* package */ ExoPlaybackException copyWithMediaPeriodId(@Nullable MediaPeriodId mediaPeriodId) {
     return new ExoPlaybackException(
         getMessage(),
         cause,
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
index e7be6c342c..e8ab433d55 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
@@ -646,7 +646,7 @@ public class AnalyticsCollector
   public final void onPlayerError(ExoPlaybackException error) {
     EventTime eventTime =
         error.mediaPeriodId != null
-            ? generateEventTime(error.mediaPeriodId)
+            ? generateEventTime(new MediaPeriodId(error.mediaPeriodId))
             : generateCurrentPlayerMediaPeriodEventTime();
     sendEvent(
         eventTime,
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 94a9f82030..f6f2ab496d 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
@@ -17,7 +17,6 @@ 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;
@@ -61,155 +60,52 @@ public interface MediaSource {
     void onSourceInfoRefreshed(MediaSource source, Timeline timeline);
   }
 
-  /** Identifier for a {@link MediaPeriod}. */
-  final class MediaPeriodId {
+  // TODO(b/172315872) Delete when all clients have been migrated to base class.
+  /**
+   * Identifier for a {@link MediaPeriod}.
+   *
+   * <p>Extends for backward-compatibility {@link
+   * com.google.android.exoplayer2.source.MediaPeriodId}.
+   */
+  final class MediaPeriodId extends com.google.android.exoplayer2.source.MediaPeriodId {
 
-    /** The unique id of the timeline period. */
-    public final Object periodUid;
-
-    /**
-     * If the media period is in an ad group, the index of the ad group in the period.
-     * {@link C#INDEX_UNSET} otherwise.
-     */
-    public final int adGroupIndex;
-
-    /**
-     * If the media period is in an ad group, the index of the ad in its ad group in the period.
-     * {@link C#INDEX_UNSET} otherwise.
-     */
-    public final int adIndexInAdGroup;
-
-    /**
-     * The sequence number of the window in the buffered sequence of windows this media period is
-     * part of. {@link C#INDEX_UNSET} if the media period id is not part of a buffered sequence of
-     * windows.
-     */
-    public final long windowSequenceNumber;
-
-    /**
-     * The index of the next ad group to which the media period's content is clipped, or {@link
-     * C#INDEX_UNSET} if there is no following ad group or if this media period is an ad.
-     */
-    public final int nextAdGroupIndex;
-
-    /**
-     * Creates a media period identifier for a period which is not part of a buffered sequence of
-     * windows.
-     *
-     * @param periodUid The unique id of the timeline period.
-     */
+    /** See {@link com.google.android.exoplayer2.source.MediaPeriodId#MediaPeriodId(Object)}. */
     public MediaPeriodId(Object periodUid) {
-      this(periodUid, /* windowSequenceNumber= */ C.INDEX_UNSET);
+      super(periodUid);
     }
 
     /**
-     * Creates a media period identifier for the specified period in the timeline.
-     *
-     * @param periodUid The unique id of the timeline period.
-     * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
-     *     windows this media period is part of.
+     * See {@link com.google.android.exoplayer2.source.MediaPeriodId#MediaPeriodId(Object, long)}.
      */
     public MediaPeriodId(Object periodUid, long windowSequenceNumber) {
-      this(
-          periodUid,
-          /* adGroupIndex= */ C.INDEX_UNSET,
-          /* adIndexInAdGroup= */ C.INDEX_UNSET,
-          windowSequenceNumber,
-          /* nextAdGroupIndex= */ C.INDEX_UNSET);
+      super(periodUid, windowSequenceNumber);
     }
 
     /**
-     * Creates a media period identifier for the specified clipped period in the timeline.
-     *
-     * @param periodUid The unique id of the timeline period.
-     * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
-     *     windows this media period is part of.
-     * @param nextAdGroupIndex The index of the next ad group to which the media period's content is
-     *     clipped.
+     * See {@link com.google.android.exoplayer2.source.MediaPeriodId#MediaPeriodId(Object, long,
+     * int)}.
      */
     public MediaPeriodId(Object periodUid, long windowSequenceNumber, int nextAdGroupIndex) {
-      this(
-          periodUid,
-          /* adGroupIndex= */ C.INDEX_UNSET,
-          /* adIndexInAdGroup= */ C.INDEX_UNSET,
-          windowSequenceNumber,
-          nextAdGroupIndex);
+      super(periodUid, windowSequenceNumber, nextAdGroupIndex);
     }
 
     /**
-     * Creates a media period identifier that identifies an ad within an ad group at the specified
-     * timeline period.
-     *
-     * @param periodUid The unique id of the timeline period that contains the ad group.
-     * @param adGroupIndex The index of the ad group.
-     * @param adIndexInAdGroup The index of the ad in the ad group.
-     * @param windowSequenceNumber The sequence number of the window in the buffered sequence of
-     *     windows this media period is part of.
+     * See {@link com.google.android.exoplayer2.source.MediaPeriodId#MediaPeriodId(Object, int, int,
+     * long)}.
      */
     public MediaPeriodId(
         Object periodUid, int adGroupIndex, int adIndexInAdGroup, long windowSequenceNumber) {
-      this(
-          periodUid,
-          adGroupIndex,
-          adIndexInAdGroup,
-          windowSequenceNumber,
-          /* nextAdGroupIndex= */ C.INDEX_UNSET);
+      super(periodUid, adGroupIndex, adIndexInAdGroup, windowSequenceNumber);
     }
 
-    private MediaPeriodId(
-        Object periodUid,
-        int adGroupIndex,
-        int adIndexInAdGroup,
-        long windowSequenceNumber,
-        int nextAdGroupIndex) {
-      this.periodUid = periodUid;
-      this.adGroupIndex = adGroupIndex;
-      this.adIndexInAdGroup = adIndexInAdGroup;
-      this.windowSequenceNumber = windowSequenceNumber;
-      this.nextAdGroupIndex = nextAdGroupIndex;
+    /** Wraps an {@link com.google.android.exoplayer2.source.MediaPeriodId} into a MediaPeriodId. */
+    public MediaPeriodId(com.google.android.exoplayer2.source.MediaPeriodId mediaPeriodId) {
+      super(mediaPeriodId);
     }
 
-    /** Returns a copy of this period identifier but with {@code newPeriodUid} as its period uid. */
+    /** See {@link com.google.android.exoplayer2.source.MediaPeriodId#copyWithPeriodUid(Object)}. */
     public MediaPeriodId copyWithPeriodUid(Object newPeriodUid) {
-      return periodUid.equals(newPeriodUid)
-          ? this
-          : new MediaPeriodId(
-              newPeriodUid, adGroupIndex, adIndexInAdGroup, windowSequenceNumber, nextAdGroupIndex);
-    }
-
-    /**
-     * Returns whether this period identifier identifies an ad in an ad group in a period.
-     */
-    public boolean isAd() {
-      return adGroupIndex != C.INDEX_UNSET;
-    }
-
-    @Override
-    public boolean equals(@Nullable Object obj) {
-      if (this == obj) {
-        return true;
-      }
-      if (obj == null || getClass() != obj.getClass()) {
-        return false;
-      }
-
-      MediaPeriodId periodId = (MediaPeriodId) obj;
-      return periodUid.equals(periodId.periodUid)
-          && adGroupIndex == periodId.adGroupIndex
-          && adIndexInAdGroup == periodId.adIndexInAdGroup
-          && windowSequenceNumber == periodId.windowSequenceNumber
-          && nextAdGroupIndex == periodId.nextAdGroupIndex;
-    }
-
-    @Override
-    public int hashCode() {
-      int result = 17;
-      result = 31 * result + periodUid.hashCode();
-      result = 31 * result + adGroupIndex;
-      result = 31 * result + adIndexInAdGroup;
-      result = 31 * result + (int) windowSequenceNumber;
-      result = 31 * result + nextAdGroupIndex;
-      return result;
+      return new MediaPeriodId(super.copyWithPeriodUid(newPeriodUid));
     }
   }