diff --git a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionMediaSource.java b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionMediaSource.java
index 0251ee2621..248b7648ec 100644
--- a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionMediaSource.java
+++ b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionMediaSource.java
@@ -994,7 +994,6 @@ public final class ServerSideAdInsertionMediaSource extends BaseMediaSource
     public ServerSideAdInsertionTimeline(
         Timeline contentTimeline, ImmutableMap<Object, AdPlaybackState> adPlaybackStates) {
       super(contentTimeline);
-      checkState(contentTimeline.getPeriodCount() == 1);
       checkState(contentTimeline.getWindowCount() == 1);
       Period period = new Period();
       for (int i = 0; i < contentTimeline.getPeriodCount(); i++) {
@@ -1008,25 +1007,23 @@ public final class ServerSideAdInsertionMediaSource extends BaseMediaSource
     public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
       super.getWindow(windowIndex, window, defaultPositionProjectionUs);
       Object firstPeriodUid =
-          checkNotNull(getPeriod(/* periodIndex= */ 0, new Period(), /* setIds= */ true).uid);
-      AdPlaybackState adPlaybackState = checkNotNull(adPlaybackStates.get(firstPeriodUid));
+          checkNotNull(getPeriod(window.firstPeriodIndex, new Period(), /* setIds= */ true).uid);
+      AdPlaybackState firstAdPlaybackState = checkNotNull(adPlaybackStates.get(firstPeriodUid));
       long positionInPeriodUs =
           getMediaPeriodPositionUsForContent(
               window.positionInFirstPeriodUs,
               /* nextAdGroupIndex= */ C.INDEX_UNSET,
-              adPlaybackState);
+              firstAdPlaybackState);
       if (window.durationUs == C.TIME_UNSET) {
-        if (adPlaybackState.contentDurationUs != C.TIME_UNSET) {
-          window.durationUs = adPlaybackState.contentDurationUs - positionInPeriodUs;
+        if (firstAdPlaybackState.contentDurationUs != C.TIME_UNSET) {
+          window.durationUs = firstAdPlaybackState.contentDurationUs - positionInPeriodUs;
         }
       } else {
-        long actualWindowEndPositionInPeriodUs = window.positionInFirstPeriodUs + window.durationUs;
-        long windowEndPositionInPeriodUs =
-            getMediaPeriodPositionUsForContent(
-                actualWindowEndPositionInPeriodUs,
-                /* nextAdGroupIndex= */ C.INDEX_UNSET,
-                adPlaybackState);
-        window.durationUs = windowEndPositionInPeriodUs - positionInPeriodUs;
+        Period lastPeriod = getPeriod(/* periodIndex= */ window.lastPeriodIndex, new Period());
+        window.durationUs =
+            lastPeriod.durationUs == C.TIME_UNSET
+                ? C.TIME_UNSET
+                : lastPeriod.positionInWindowUs + lastPeriod.durationUs;
       }
       window.positionInFirstPeriodUs = positionInPeriodUs;
       return window;
@@ -1044,11 +1041,26 @@ public final class ServerSideAdInsertionMediaSource extends BaseMediaSource
             getMediaPeriodPositionUsForContent(
                 durationUs, /* nextAdGroupIndex= */ C.INDEX_UNSET, adPlaybackState);
       }
-      long positionInWindowUs =
-          -getMediaPeriodPositionUsForContent(
-              -period.getPositionInWindowUs(),
-              /* nextAdGroupIndex= */ C.INDEX_UNSET,
-              adPlaybackState);
+      long positionInWindowUs = 0;
+      Period innerPeriod = new Period();
+      for (int i = 0; i < periodIndex + 1; i++) {
+        timeline.getPeriod(/* periodIndex= */ i, innerPeriod, /* setIds= */ true);
+        AdPlaybackState innerAdPlaybackState = checkNotNull(adPlaybackStates.get(innerPeriod.uid));
+        if (i == 0) {
+          positionInWindowUs =
+              -getMediaPeriodPositionUsForContent(
+                  -innerPeriod.getPositionInWindowUs(),
+                  /* nextAdGroupIndex= */ C.INDEX_UNSET,
+                  innerAdPlaybackState);
+        }
+        if (i != periodIndex) {
+          positionInWindowUs +=
+              getMediaPeriodPositionUsForContent(
+                  innerPeriod.durationUs,
+                  /* nextAdGroupIndex= */ C.INDEX_UNSET,
+                  innerAdPlaybackState);
+        }
+      }
       period.set(
           period.id,
           period.uid,
diff --git a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionUtil.java b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionUtil.java
index e1e97f7d93..052181ec33 100644
--- a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionUtil.java
+++ b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/ads/ServerSideAdInsertionUtil.java
@@ -74,29 +74,6 @@ public final class ServerSideAdInsertionUtil {
         adPlaybackState, insertionIndex, adDurationUs, contentResumeOffsetUs);
   }
 
-  /**
-   * Returns the duration of the underlying server-side inserted ads stream for the current {@link
-   * Timeline.Period} in the {@link Player}.
-   *
-   * @param player The {@link Player}.
-   * @param adPlaybackState The {@link AdPlaybackState} defining the ad groups.
-   * @return The duration of the underlying server-side inserted ads stream, in microseconds, or
-   *     {@link C#TIME_UNSET} if it can't be determined.
-   */
-  public static long getStreamDurationUs(Player player, AdPlaybackState adPlaybackState) {
-    Timeline timeline = player.getCurrentTimeline();
-    if (timeline.isEmpty()) {
-      return C.TIME_UNSET;
-    }
-    Timeline.Period period =
-        timeline.getPeriod(player.getCurrentPeriodIndex(), new Timeline.Period());
-    if (period.durationUs == C.TIME_UNSET) {
-      return C.TIME_UNSET;
-    }
-    return getStreamPositionUsForContent(
-        period.durationUs, /* nextAdGroupIndex= */ C.INDEX_UNSET, adPlaybackState);
-  }
-
   /**
    * Returns the position in the underlying server-side inserted ads stream for the current playback
    * position in the {@link Player}.