diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 96d1fb1ff3..51264dcfe0 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -39,6 +39,10 @@
 * Remove `player` and `isTopLevelSource` parameters from `MediaSource.prepare`.
 * Change signature of `PlayerNotificationManager.NotificationListener` to better
   fit service requirements. Remove ability to set a custom stop action.
+* Add `startPositionUs` to `MediaSource.createPeriod`. This fixes an issue where
+  using lazy preparation in `ConcatenatingMediaSource` with an
+  `ExtractorMediaSource` overrides initial seek positions
+  ([#5350](https://github.com/google/ExoPlayer/issues/5350)).
 
 ### 2.9.4 ###
 
diff --git a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java
index 574bac5d35..bcccd6cec7 100644
--- a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java
+++ b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java
@@ -93,8 +93,8 @@ public final class ImaAdsMediaSource extends BaseMediaSource implements SourceIn
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
-    return adsMediaSource.createPeriod(id, allocator);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
+    return adsMediaSource.createPeriod(id, allocator, startPositionUs);
   }
 
   @Override
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodHolder.java b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodHolder.java
index 7becac7b55..19622c6801 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodHolder.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodHolder.java
@@ -89,7 +89,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
     this.info = info;
     sampleStreams = new SampleStream[rendererCapabilities.length];
     mayRetainStreamFlags = new boolean[rendererCapabilities.length];
-    mediaPeriod = createMediaPeriod(info.id, mediaSource, allocator);
+    mediaPeriod = createMediaPeriod(info.id, mediaSource, allocator, info.startPositionUs);
   }
 
   /**
@@ -399,8 +399,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
 
   /** Returns a media period corresponding to the given {@code id}. */
   private static MediaPeriod createMediaPeriod(
-      MediaPeriodId id, MediaSource mediaSource, Allocator allocator) {
-    MediaPeriod mediaPeriod = mediaSource.createPeriod(id, allocator);
+      MediaPeriodId id, MediaSource mediaSource, Allocator allocator, long startPositionUs) {
+    MediaPeriod mediaPeriod = mediaSource.createPeriod(id, allocator, startPositionUs);
     if (id.endPositionUs != C.TIME_UNSET && id.endPositionUs != C.TIME_END_OF_SOURCE) {
       mediaPeriod =
           new ClippingMediaPeriod(
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 0ab6eeae18..d3b8226822 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
@@ -206,10 +206,10 @@ public final class ClippingMediaSource extends CompositeMediaSource<Void> {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     ClippingMediaPeriod mediaPeriod =
         new ClippingMediaPeriod(
-            mediaSource.createPeriod(id, allocator),
+            mediaSource.createPeriod(id, allocator, startPositionUs),
             enableInitialDiscontinuity,
             periodStartUs,
             periodEndUs);
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 e6d409c659..6dc7a0a327 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
@@ -438,7 +438,8 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
   }
 
   @Override
-  public final MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public final MediaPeriod createPeriod(
+      MediaPeriodId id, Allocator allocator, long startPositionUs) {
     Object mediaSourceHolderUid = getMediaSourceHolderUid(id.periodUid);
     MediaSourceHolder holder = mediaSourceByUid.get(mediaSourceHolderUid);
     if (holder == null) {
@@ -446,7 +447,8 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
       holder = new MediaSourceHolder(new DummyMediaSource());
       holder.hasStartedPreparing = true;
     }
-    DeferredMediaPeriod mediaPeriod = new DeferredMediaPeriod(holder.mediaSource, id, allocator);
+    DeferredMediaPeriod mediaPeriod =
+        new DeferredMediaPeriod(holder.mediaSource, id, allocator, startPositionUs);
     mediaSourceByMediaPeriod.put(mediaPeriod, holder);
     holder.activeMediaPeriods.add(mediaPeriod);
     if (!holder.hasStartedPreparing) {
@@ -1144,7 +1146,7 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
     }
 
     @Override
-    public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
       throw new UnsupportedOperationException();
     }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/DeferredMediaPeriod.java b/library/core/src/main/java/com/google/android/exoplayer2/source/DeferredMediaPeriod.java
index 26c25a749e..858769180d 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/DeferredMediaPeriod.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/DeferredMediaPeriod.java
@@ -25,7 +25,7 @@ import java.io.IOException;
 
 /**
  * Media period that wraps a media source and defers calling its {@link
- * MediaSource#createPeriod(MediaPeriodId, Allocator)} method until {@link
+ * MediaSource#createPeriod(MediaPeriodId, Allocator, long)} method until {@link
  * #createPeriod(MediaPeriodId)} has been called. This is useful if you need to return a media
  * period immediately but the media source that should create it is not yet prepared.
  */
@@ -60,11 +60,14 @@ public final class DeferredMediaPeriod implements MediaPeriod, MediaPeriod.Callb
    * @param mediaSource The media source to wrap.
    * @param id The identifier used to create the deferred media period.
    * @param allocator The allocator used to create the media period.
+   * @param preparePositionUs The expected start position, in microseconds.
    */
-  public DeferredMediaPeriod(MediaSource mediaSource, MediaPeriodId id, Allocator allocator) {
+  public DeferredMediaPeriod(
+      MediaSource mediaSource, MediaPeriodId id, Allocator allocator, long preparePositionUs) {
     this.id = id;
     this.allocator = allocator;
     this.mediaSource = mediaSource;
+    this.preparePositionUs = preparePositionUs;
     preparePositionOverrideUs = C.TIME_UNSET;
   }
 
@@ -86,28 +89,25 @@ public final class DeferredMediaPeriod implements MediaPeriod, MediaPeriod.Callb
 
   /**
    * Overrides the default prepare position at which to prepare the media period. This value is only
-   * used if the call to {@link MediaPeriod#prepare(Callback, long)} is being deferred.
+   * used if called before {@link #createPeriod(MediaPeriodId)}.
    *
-   * @param defaultPreparePositionUs The default prepare position to use, in microseconds.
+   * @param preparePositionUs The default prepare position to use, in microseconds.
    */
-  public void overridePreparePositionUs(long defaultPreparePositionUs) {
-    preparePositionOverrideUs = defaultPreparePositionUs;
+  public void overridePreparePositionUs(long preparePositionUs) {
+    preparePositionOverrideUs = preparePositionUs;
   }
 
   /**
-   * Calls {@link MediaSource#createPeriod(MediaPeriodId, Allocator)} on the wrapped source then
-   * prepares it if {@link #prepare(Callback, long)} has been called. Call {@link #releasePeriod()}
-   * to release the period.
+   * Calls {@link MediaSource#createPeriod(MediaPeriodId, Allocator, long)} on the wrapped source
+   * then prepares it if {@link #prepare(Callback, long)} has been called. Call {@link
+   * #releasePeriod()} to release the period.
    *
    * @param id The identifier that should be used to create the media period from the media source.
    */
   public void createPeriod(MediaPeriodId id) {
-    mediaPeriod = mediaSource.createPeriod(id, allocator);
+    long preparePositionUs = getPreparePositionWithOverride(this.preparePositionUs);
+    mediaPeriod = mediaSource.createPeriod(id, allocator, preparePositionUs);
     if (callback != null) {
-      long preparePositionUs =
-          preparePositionOverrideUs != C.TIME_UNSET
-              ? preparePositionOverrideUs
-              : this.preparePositionUs;
       mediaPeriod.prepare(this, preparePositionUs);
     }
   }
@@ -124,9 +124,8 @@ public final class DeferredMediaPeriod implements MediaPeriod, MediaPeriod.Callb
   @Override
   public void prepare(Callback callback, long preparePositionUs) {
     this.callback = callback;
-    this.preparePositionUs = preparePositionUs;
     if (mediaPeriod != null) {
-      mediaPeriod.prepare(this, preparePositionUs);
+      mediaPeriod.prepare(this, getPreparePositionWithOverride(this.preparePositionUs));
     }
   }
 
@@ -217,4 +216,9 @@ public final class DeferredMediaPeriod implements MediaPeriod, MediaPeriod.Callb
     callback.onPrepared(this);
   }
 
+  private long getPreparePositionWithOverride(long preparePositionUs) {
+    return preparePositionOverrideUs != C.TIME_UNSET
+        ? preparePositionOverrideUs
+        : preparePositionUs;
+  }
 }
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 91273626c9..5403f9f33b 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
@@ -375,7 +375,7 @@ public final class ExtractorMediaSource extends BaseMediaSource
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     DataSource dataSource = dataSourceFactory.createDataSource();
     if (transferListener != null) {
       dataSource.addTransferListener(transferListener);
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 3cd4ea1dab..0cd87561e7 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
@@ -77,14 +77,15 @@ public final class LoopingMediaSource extends CompositeMediaSource<Void> {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     if (loopCount == Integer.MAX_VALUE) {
-      return childSource.createPeriod(id, allocator);
+      return childSource.createPeriod(id, allocator, startPositionUs);
     }
     Object childPeriodUid = LoopingTimeline.getChildPeriodUidFromConcatenatedUid(id.periodUid);
     MediaPeriodId childMediaPeriodId = id.copyWithPeriodUid(childPeriodUid);
     childMediaPeriodIdToMediaPeriodId.put(childMediaPeriodId, id);
-    MediaPeriod mediaPeriod = childSource.createPeriod(childMediaPeriodId, allocator);
+    MediaPeriod mediaPeriod =
+        childSource.createPeriod(childMediaPeriodId, allocator, startPositionUs);
     mediaPeriodToChildMediaPeriodId.put(mediaPeriod, childMediaPeriodId);
     return mediaPeriod;
   }
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 2d80fb7f13..1419f9a98f 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
@@ -34,8 +34,8 @@ import java.io.IOException;
  *       on the {@link SourceInfoRefreshListener}s passed to {@link
  *       #prepareSource(SourceInfoRefreshListener, TransferListener)}.
  *   <li>To provide {@link MediaPeriod} instances for the periods in its timeline. MediaPeriods are
- *       obtained by calling {@link #createPeriod(MediaPeriodId, Allocator)}, and provide a way for
- *       the player to load and read the media.
+ *       obtained by calling {@link #createPeriod(MediaPeriodId, Allocator, long)}, and provide a
+ *       way for the player to load and read the media.
  * </ul>
  *
  * All methods are called on the player's internal playback thread, as described in the {@link
@@ -261,9 +261,10 @@ public interface MediaSource {
    *
    * @param id The identifier of the period.
    * @param allocator An {@link Allocator} from which to obtain media buffer allocations.
+   * @param startPositionUs The expected start position, in microseconds.
    * @return A new {@link MediaPeriod}.
    */
-  MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator);
+  MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs);
 
   /**
    * Releases the period.
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 fdeb2b6184..1ea3404e81 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
@@ -120,13 +120,13 @@ public final class MergingMediaSource extends CompositeMediaSource<Integer> {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     MediaPeriod[] periods = new MediaPeriod[mediaSources.length];
     int periodIndex = timelines[0].getIndexOfPeriod(id.periodUid);
     for (int i = 0; i < periods.length; i++) {
       MediaPeriodId childMediaPeriodId =
           id.copyWithPeriodUid(timelines[i].getUidOfPeriod(periodIndex));
-      periods[i] = mediaSources[i].createPeriod(childMediaPeriodId, allocator);
+      periods[i] = mediaSources[i].createPeriod(childMediaPeriodId, allocator, startPositionUs);
     }
     return new MergingMediaPeriod(compositeSequenceableLoaderFactory, periods);
   }
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 358875eb1e..d13fa06434 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
@@ -313,7 +313,7 @@ public final class SingleSampleMediaSource extends BaseMediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     return new SingleSampleMediaPeriod(
         dataSpec,
         dataSourceFactory,
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 663f9c64fc..4754466235 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
@@ -334,7 +334,7 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     if (adPlaybackState.adGroupCount > 0 && id.isAd()) {
       int adGroupIndex = id.adGroupIndex;
       int adIndexInAdGroup = id.adIndexInAdGroup;
@@ -353,7 +353,8 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
         prepareChildSource(id, adMediaSource);
       }
       MediaSource mediaSource = adGroupMediaSources[adGroupIndex][adIndexInAdGroup];
-      DeferredMediaPeriod deferredMediaPeriod = new DeferredMediaPeriod(mediaSource, id, allocator);
+      DeferredMediaPeriod deferredMediaPeriod =
+          new DeferredMediaPeriod(mediaSource, id, allocator, startPositionUs);
       deferredMediaPeriod.setPrepareErrorListener(
           new AdPrepareErrorListener(adUri, adGroupIndex, adIndexInAdGroup));
       List<DeferredMediaPeriod> mediaPeriods = deferredMediaPeriodByAdMediaSource.get(mediaSource);
@@ -369,7 +370,8 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
       }
       return deferredMediaPeriod;
     } else {
-      DeferredMediaPeriod mediaPeriod = new DeferredMediaPeriod(contentMediaSource, id, allocator);
+      DeferredMediaPeriod mediaPeriod =
+          new DeferredMediaPeriod(contentMediaSource, id, allocator, startPositionUs);
       mediaPeriod.createPeriod(id);
       return mediaPeriod;
     }
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 b31b770b03..cfdbdac1ea 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
@@ -654,7 +654,8 @@ public final class DashMediaSource extends BaseMediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId periodId, Allocator allocator) {
+  public MediaPeriod createPeriod(
+      MediaPeriodId periodId, Allocator allocator, long startPositionUs) {
     int periodIndex = (Integer) periodId.periodUid - firstPeriodId;
     EventDispatcher periodEventDispatcher =
         createEventDispatcher(periodId, manifest.getPeriod(periodIndex).startMs);
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 8058460b9f..f2b76dddc4 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
@@ -428,7 +428,7 @@ public final class HlsMediaSource extends BaseMediaSource
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     EventDispatcher eventDispatcher = createEventDispatcher(id);
     return new HlsMediaPeriod(
         extractorFactory,
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 39f707b09c..0f5544a993 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
@@ -552,7 +552,7 @@ public final class SsMediaSource extends BaseMediaSource
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     EventDispatcher eventDispatcher = createEventDispatcher(id);
     SsMediaPeriod period =
         new SsMediaPeriod(
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 8165eebaea..de4be82b38 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
@@ -112,7 +112,7 @@ public class FakeMediaSource extends BaseMediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator, long startPositionUs) {
     assertThat(preparedSource).isTrue();
     assertThat(releasedSource).isFalse();
     int periodIndex = timeline.getIndexOfPeriod(id.periodUid);
diff --git a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/MediaSourceTestRunner.java b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/MediaSourceTestRunner.java
index 5de1ab87b6..9514768416 100644
--- a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/MediaSourceTestRunner.java
+++ b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/MediaSourceTestRunner.java
@@ -132,15 +132,28 @@ public class MediaSourceTestRunner {
   }
 
   /**
-   * Calls {@link MediaSource#createPeriod(MediaSource.MediaPeriodId, Allocator)} on the playback
-   * thread, asserting that a non-null {@link MediaPeriod} is returned.
+   * Calls {@link MediaSource#createPeriod(MediaSource.MediaPeriodId, Allocator, long)} with a zero
+   * start position on the playback thread, asserting that a non-null {@link MediaPeriod} is
+   * returned.
    *
    * @param periodId The id of the period to create.
    * @return The created {@link MediaPeriod}.
    */
   public MediaPeriod createPeriod(final MediaPeriodId periodId) {
+    return createPeriod(periodId, /* startPositionUs= */ 0);
+  }
+
+  /**
+   * Calls {@link MediaSource#createPeriod(MediaSource.MediaPeriodId, Allocator, long)} on the
+   * playback thread, asserting that a non-null {@link MediaPeriod} is returned.
+   *
+   * @param periodId The id of the period to create.
+   * @return The created {@link MediaPeriod}.
+   */
+  public MediaPeriod createPeriod(final MediaPeriodId periodId, long startPositionUs) {
     final MediaPeriod[] holder = new MediaPeriod[1];
-    runOnPlaybackThread(() -> holder[0] = mediaSource.createPeriod(periodId, allocator));
+    runOnPlaybackThread(
+        () -> holder[0] = mediaSource.createPeriod(periodId, allocator, startPositionUs));
     assertThat(holder[0]).isNotNull();
     return holder[0];
   }