diff --git a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
index b3d6fe4ee6..4939e62a2b 100644
--- a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
+++ b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
@@ -107,6 +107,11 @@ import java.util.Map;
     return uid instanceof Integer ? idsToIndex.get((int) uid, C.INDEX_UNSET) : C.INDEX_UNSET;
   }
 
+  @Override
+  public Object getUidOfPeriod(int periodIndex) {
+    return ids[periodIndex];
+  }
+
   // equals and hashCode implementations.
 
   @Override
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
index cc338385cd..ba80407860 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
@@ -904,7 +904,7 @@ import java.util.Collections;
       pendingMessageInfo.setResolvedPosition(
           periodPosition.first,
           periodPosition.second,
-          playbackInfo.timeline.getPeriod(periodPosition.first, period, true).uid);
+          playbackInfo.timeline.getUidOfPeriod(periodPosition.first));
     } else {
       // Position has been resolved for a previous timeline. Try to find the updated period index.
       int index = playbackInfo.timeline.getIndexOfPeriod(pendingMessageInfo.resolvedPeriodUid);
@@ -1203,8 +1203,8 @@ import java.util.Collections;
       return;
     }
     MediaPeriodHolder periodHolder = queue.getFrontPeriod();
-    Object playingPeriodUid = periodHolder == null
-        ? oldTimeline.getPeriod(playingPeriodIndex, period, true).uid : periodHolder.uid;
+    Object playingPeriodUid =
+        periodHolder == null ? oldTimeline.getUidOfPeriod(playingPeriodIndex) : periodHolder.uid;
     int periodIndex = timeline.getIndexOfPeriod(playingPeriodUid);
     if (periodIndex == C.INDEX_UNSET) {
       // We didn't find the current period in the new timeline. Attempt to resolve a subsequent
@@ -1221,11 +1221,10 @@ import java.util.Collections;
       newPeriodIndex = defaultPosition.first;
       contentPositionUs = defaultPosition.second;
       MediaPeriodId periodId = queue.resolveMediaPeriodIdForAds(newPeriodIndex, contentPositionUs);
-      timeline.getPeriod(newPeriodIndex, period, true);
       if (periodHolder != null) {
         // Clear the index of each holder that doesn't contain the default position. If a holder
         // contains the default position then update its index so it can be re-used when seeking.
-        Object newPeriodUid = period.uid;
+        Object newPeriodUid = timeline.getUidOfPeriod(newPeriodIndex);
         periodHolder.info = periodHolder.info.copyWithPeriodIndex(C.INDEX_UNSET);
         while (periodHolder.next != null) {
           periodHolder = periodHolder.next;
@@ -1293,8 +1292,7 @@ import java.util.Collections;
         // We've reached the end of the old timeline.
         break;
       }
-      newPeriodIndex = newTimeline.getIndexOfPeriod(
-          oldTimeline.getPeriod(oldPeriodIndex, period, true).uid);
+      newPeriodIndex = newTimeline.getIndexOfPeriod(oldTimeline.getUidOfPeriod(oldPeriodIndex));
     }
     return newPeriodIndex;
   }
@@ -1338,8 +1336,7 @@ import java.util.Collections;
       return periodPosition;
     }
     // Attempt to find the mapped period in the internal timeline.
-    int periodIndex = timeline.getIndexOfPeriod(
-        seekTimeline.getPeriod(periodPosition.first, period, true).uid);
+    int periodIndex = timeline.getIndexOfPeriod(seekTimeline.getUidOfPeriod(periodPosition.first));
     if (periodIndex != C.INDEX_UNSET) {
       // We successfully located the period in the internal timeline.
       return Pair.create(periodIndex, periodPosition.second);
@@ -1497,7 +1494,7 @@ import java.util.Collections;
       if (info == null) {
         mediaSource.maybeThrowSourceInfoRefreshError();
       } else {
-        Object uid = playbackInfo.timeline.getPeriod(info.id.periodIndex, period, true).uid;
+        Object uid = playbackInfo.timeline.getUidOfPeriod(info.id.periodIndex);
         MediaPeriod mediaPeriod =
             queue.enqueueNextMediaPeriod(
                 rendererCapabilities,
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
index 010de547a2..be618275c4 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
@@ -314,7 +314,7 @@ import com.google.android.exoplayer2.util.Assertions;
       } else {
         // Check this period holder still follows the previous one, based on the new timeline.
         if (periodIndex == C.INDEX_UNSET
-            || !periodHolder.uid.equals(timeline.getPeriod(periodIndex, period, true).uid)) {
+            || !periodHolder.uid.equals(timeline.getUidOfPeriod(periodIndex))) {
           // The holder uid is inconsistent with the new timeline.
           return !removeAfter(previousPeriodHolder);
         }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java b/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
index 600fbc3014..a1a0e9b152 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
@@ -520,6 +520,11 @@ public abstract class Timeline {
         public int getIndexOfPeriod(Object uid) {
           return C.INDEX_UNSET;
         }
+
+        @Override
+        public Object getUidOfPeriod(int periodIndex) {
+          throw new IndexOutOfBoundsException();
+        }
       };
 
   /**
@@ -737,6 +742,17 @@ public abstract class Timeline {
     return Pair.create(periodIndex, periodPositionUs);
   }
 
+  /**
+   * Populates a {@link Period} with data for the period with the specified unique identifier.
+   *
+   * @param periodUid The unique identifier of the period.
+   * @param period The {@link Period} to populate. Must not be null.
+   * @return The populated {@link Period}, for convenience.
+   */
+  public Period getPeriodByUid(Object periodUid, Period period) {
+    return getPeriod(getIndexOfPeriod(periodUid), period, /* setIds= */ true);
+  }
+
   /**
    * Populates a {@link Period} with data for the period at the specified index. Does not populate
    * {@link Period#id} and {@link Period#uid}.
@@ -770,4 +786,11 @@ public abstract class Timeline {
    */
   public abstract int getIndexOfPeriod(Object uid);
 
+  /**
+   * Returns the unique id of the period identified by its index in the timeline.
+   *
+   * @param periodIndex The index of the period.
+   * @return The unique id of the period.
+   */
+  public abstract Object getUidOfPeriod(int periodIndex);
 }
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 1d51e68d4a..3efe0a00cc 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
@@ -784,8 +784,7 @@ public class AnalyticsCollector
       if (newTimeline.isEmpty() || timeline.isEmpty()) {
         return mediaPeriod;
       }
-      Object uid =
-          timeline.getPeriod(mediaPeriod.mediaPeriodId.periodIndex, period, /* setIds= */ true).uid;
+      Object uid = timeline.getUidOfPeriod(mediaPeriod.mediaPeriodId.periodIndex);
       int newPeriodIndex = newTimeline.getIndexOfPeriod(uid);
       if (newPeriodIndex == C.INDEX_UNSET) {
         return mediaPeriod;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
index 8663b4c05c..305a249e4a 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
@@ -168,6 +168,19 @@ import com.google.android.exoplayer2.Timeline;
     return window;
   }
 
+  @Override
+  public final Period getPeriodByUid(Object uid, Period period) {
+    Pair<?, ?> childUidAndPeriodUid = (Pair<?, ?>) uid;
+    Object childUid = childUidAndPeriodUid.first;
+    Object periodUid = childUidAndPeriodUid.second;
+    int childIndex = getChildIndexByChildUid(childUid);
+    int firstWindowIndexInChild = getFirstWindowIndexByChildIndex(childIndex);
+    getTimelineByChildIndex(childIndex).getPeriodByUid(periodUid, period);
+    period.windowIndex += firstWindowIndexInChild;
+    period.uid = uid;
+    return period;
+  }
+
   @Override
   public final Period getPeriod(int periodIndex, Period period, boolean setIds) {
     int childIndex = getChildIndexByPeriodIndex(periodIndex);
@@ -199,6 +212,15 @@ import com.google.android.exoplayer2.Timeline;
         : getFirstPeriodIndexByChildIndex(childIndex) + periodIndexInChild;
   }
 
+  @Override
+  public final Object getUidOfPeriod(int periodIndex) {
+    int childIndex = getChildIndexByPeriodIndex(periodIndex);
+    int firstPeriodIndexInChild = getFirstPeriodIndexByChildIndex(childIndex);
+    Object periodUidInChild =
+        getTimelineByChildIndex(childIndex).getUidOfPeriod(periodIndex - firstPeriodIndexInChild);
+    return Pair.create(getChildUidByChildIndex(childIndex), periodUidInChild);
+  }
+
   /**
    * Returns the index of the child timeline containing the given period index.
    *
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 01a8cd3425..985c43fa55 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
@@ -66,7 +66,6 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
   private final boolean isAtomic;
   private final boolean useLazyPreparation;
   private final Timeline.Window window;
-  private final Timeline.Period period;
 
   private @Nullable ExoPlayer player;
   private @Nullable Handler playerApplicationHandler;
@@ -133,7 +132,6 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
     this.isAtomic = isAtomic;
     this.useLazyPreparation = useLazyPreparation;
     window = new Timeline.Window();
-    period = new Timeline.Period();
     addMediaSources(Arrays.asList(mediaSources));
   }
 
@@ -594,7 +592,7 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
           windowOffsetUpdate,
           periodOffsetUpdate);
     }
-    mediaSourceHolder.timeline = deferredTimeline.cloneWithNewTimeline(timeline, period);
+    mediaSourceHolder.timeline = deferredTimeline.cloneWithNewTimeline(timeline);
     if (!mediaSourceHolder.isPrepared && !timeline.isEmpty()) {
       timeline.getWindow(/* windowIndex= */ 0, window);
       long defaultPeriodPositionUs =
@@ -823,11 +821,11 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
       this.replacedId = replacedId;
     }
 
-    public DeferredTimeline cloneWithNewTimeline(Timeline timeline, Period period) {
+    public DeferredTimeline cloneWithNewTimeline(Timeline timeline) {
       return new DeferredTimeline(
           timeline,
           replacedId == DUMMY_ID && timeline.getPeriodCount() > 0
-              ? timeline.getPeriod(0, period, true).uid
+              ? timeline.getUidOfPeriod(0)
               : replacedId);
     }
 
@@ -848,6 +846,12 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
     public int getIndexOfPeriod(Object uid) {
       return timeline.getIndexOfPeriod(DUMMY_ID.equals(uid) ? replacedId : uid);
     }
+
+    @Override
+    public Object getUidOfPeriod(int periodIndex) {
+      Object uid = timeline.getUidOfPeriod(periodIndex);
+      return Util.areEqual(uid, replacedId) ? DUMMY_ID : uid;
+    }
   }
 
   /** Dummy placeholder timeline with one dynamic window with a period of indeterminate duration. */
@@ -894,6 +898,11 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
     public int getIndexOfPeriod(Object uid) {
       return uid == DeferredTimeline.DUMMY_ID ? 0 : C.INDEX_UNSET;
     }
+
+    @Override
+    public Object getUidOfPeriod(int periodIndex) {
+      return DeferredTimeline.DUMMY_ID;
+    }
   }
 }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
index c7ab7615d8..45997aced4 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
@@ -77,4 +77,8 @@ public abstract class ForwardingTimeline extends Timeline {
     return timeline.getIndexOfPeriod(uid);
   }
 
+  @Override
+  public Object getUidOfPeriod(int periodIndex) {
+    return timeline.getUidOfPeriod(periodIndex);
+  }
 }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
index 0bddd482ac..9e33a2d898 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
@@ -193,4 +193,9 @@ public final class SinglePeriodTimeline extends Timeline {
     return UID.equals(uid) ? 0 : C.INDEX_UNSET;
   }
 
+  @Override
+  public Object getUidOfPeriod(int periodIndex) {
+    Assertions.checkIndex(periodIndex, 0, 1);
+    return UID;
+  }
 }
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/source/ConcatenatingMediaSourceTest.java b/library/core/src/test/java/com/google/android/exoplayer2/source/ConcatenatingMediaSourceTest.java
index f6df4721e1..f9c327ed2b 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/source/ConcatenatingMediaSourceTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/source/ConcatenatingMediaSourceTest.java
@@ -23,7 +23,6 @@ import android.os.ConditionVariable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Timeline;
-import com.google.android.exoplayer2.Timeline.Period;
 import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
 import com.google.android.exoplayer2.source.ShuffleOrder.DefaultShuffleOrder;
 import com.google.android.exoplayer2.testutil.DummyMainThread;
@@ -876,21 +875,20 @@ public final class ConcatenatingMediaSourceTest {
 
   @Test
   public void testReleaseAndReprepareSource() throws IOException {
-    Period period = new Period();
     FakeMediaSource[] fakeMediaSources = createMediaSources(/* count= */ 2);
     mediaSource.addMediaSource(fakeMediaSources[0]); // Child source with 1 period.
     mediaSource.addMediaSource(fakeMediaSources[1]); // Child source with 2 periods.
     Timeline timeline = testRunner.prepareSource();
-    Object periodId0 = timeline.getPeriod(/* periodIndex= */ 0, period, /* setIds= */ true).uid;
-    Object periodId1 = timeline.getPeriod(/* periodIndex= */ 1, period, /* setIds= */ true).uid;
-    Object periodId2 = timeline.getPeriod(/* periodIndex= */ 2, period, /* setIds= */ true).uid;
+    Object periodId0 = timeline.getUidOfPeriod(/* periodIndex= */ 0);
+    Object periodId1 = timeline.getUidOfPeriod(/* periodIndex= */ 1);
+    Object periodId2 = timeline.getUidOfPeriod(/* periodIndex= */ 2);
     testRunner.releaseSource();
 
     mediaSource.moveMediaSource(/* currentIndex= */ 1, /* newIndex= */ 0);
     timeline = testRunner.prepareSource();
-    Object newPeriodId0 = timeline.getPeriod(/* periodIndex= */ 0, period, /* setIds= */ true).uid;
-    Object newPeriodId1 = timeline.getPeriod(/* periodIndex= */ 1, period, /* setIds= */ true).uid;
-    Object newPeriodId2 = timeline.getPeriod(/* periodIndex= */ 2, period, /* setIds= */ true).uid;
+    Object newPeriodId0 = timeline.getUidOfPeriod(/* periodIndex= */ 0);
+    Object newPeriodId1 = timeline.getUidOfPeriod(/* periodIndex= */ 1);
+    Object newPeriodId2 = timeline.getUidOfPeriod(/* periodIndex= */ 2);
     assertThat(newPeriodId0).isEqualTo(periodId1);
     assertThat(newPeriodId1).isEqualTo(periodId2);
     assertThat(newPeriodId2).isEqualTo(periodId0);
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 42b180200a..e61400b5cc 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
@@ -1204,6 +1204,11 @@ public final class DashMediaSource extends BaseMediaSource {
           - defaultStartPositionInPeriodUs;
     }
 
+    @Override
+    public Object getUidOfPeriod(int periodIndex) {
+      Assertions.checkIndex(periodIndex, 0, getPeriodCount());
+      return firstPeriodId + periodIndex;
+    }
   }
 
   private final class DefaultPlayerEmsgCallback implements PlayerEmsgCallback {
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 4e118366d7..56438a51ef 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
@@ -19,6 +19,7 @@ import android.util.Pair;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.ads.AdPlaybackState;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.util.Arrays;
 
@@ -206,15 +207,25 @@ public final class FakeTimeline extends Timeline {
 
   @Override
   public int getIndexOfPeriod(Object uid) {
-    Period period = new Period();
     for (int i = 0; i < getPeriodCount(); i++) {
-      if (getPeriod(i, period, true).uid.equals(uid)) {
+      if (getUidOfPeriod(i).equals(uid)) {
         return i;
       }
     }
     return C.INDEX_UNSET;
   }
 
+  @Override
+  public Object getUidOfPeriod(int periodIndex) {
+    Assertions.checkIndex(periodIndex, 0, getPeriodCount());
+    int windowIndex =
+        Util.binarySearchFloor(
+            periodOffsets, periodIndex, /* inclusive= */ true, /* stayInBounds= */ false);
+    int windowPeriodIndex = periodIndex - periodOffsets[windowIndex];
+    TimelineWindowDefinition windowDefinition = windowDefinitions[windowIndex];
+    return Pair.create(windowDefinition.id, windowPeriodIndex);
+  }
+
   private static TimelineWindowDefinition[] createDefaultWindowDefinitions(int windowCount) {
     TimelineWindowDefinition[] windowDefinitions = new TimelineWindowDefinition[windowCount];
     for (int i = 0; i < windowCount; i++) {
diff --git a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
index a0ca6af8a9..1e3c9c61d9 100644
--- a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
+++ b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
@@ -141,6 +141,7 @@ public final class TimelineAsserts {
       }
       assertThat(period.windowIndex).isEqualTo(expectedWindowIndex);
       assertThat(timeline.getIndexOfPeriod(period.uid)).isEqualTo(i);
+      assertThat(timeline.getUidOfPeriod(i)).isEqualTo(period.uid);
       for (int repeatMode : REPEAT_MODES) {
         if (i < accumulatedPeriodCounts[expectedWindowIndex + 1] - 1) {
           assertThat(timeline.getNextPeriodIndex(i, period, window, repeatMode, false))