strict matching of segment boundary

RELEASENOTES.md

@@ -303,6 +303,8 @@
     *   Fix bug where the start time of the playlist was dropped when the
         EXT-X-PROGRAM-START-DATE tag defining the start time was removed from a
         playlist ([#2760](https://github.com/androidx/media/issues/2760)).
+    *   Use binary search to find the segment index of a given position in the
+        playlist ([#2826](https://github.com/androidx/media/pull/2826).
 *   DASH extension:
     *   Fix `UnsupportedOperationException` when playing DASH streams with a
         non-hierarchical `data:` URI manifest

libraries/exoplayer_hls/src/main/java/androidx/media3/exoplayer/hls/HlsInterstitialsAdsLoader.java

@@ -38,13 +38,13 @@
 import static com.google.common.base.Preconditions.checkState;
 import static java.lang.Math.abs;
 import static java.lang.Math.max;
-import static java.lang.Math.min;
 
 import android.content.Context;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Looper;
 import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
 import androidx.media3.common.AdPlaybackState;
 import androidx.media3.common.AdPlaybackState.AdGroup;
 import androidx.media3.common.AdPlaybackState.SkipInfo;
@@ -1514,18 +1514,41 @@ private static long resolveInterstitialStartTimeUs(
     }
   }
 
-  private static long getClosestSegmentBoundaryUs(long unixTimeUs, HlsMediaPlaylist mediaPlaylist) {
+  @VisibleForTesting
+  /* package */ static long getClosestSegmentBoundaryUs(
+      long unixTimeUs, HlsMediaPlaylist mediaPlaylist) {
     long positionInPlaylistUs = unixTimeUs - mediaPlaylist.startTimeUs;
     if (positionInPlaylistUs <= 0 || mediaPlaylist.segments.isEmpty()) {
       return mediaPlaylist.startTimeUs;
     } else if (positionInPlaylistUs >= mediaPlaylist.durationUs) {
       return mediaPlaylist.startTimeUs + mediaPlaylist.durationUs;
     }
-    long segmentIndex =
-        min(
-            positionInPlaylistUs / mediaPlaylist.targetDurationUs,
-            mediaPlaylist.segments.size() - 1);
-    HlsMediaPlaylist.Segment segment = mediaPlaylist.segments.get((int) segmentIndex);
+
+    // Binary search to find the segment containing or closest to the position
+    int left = 0;
+    int right = mediaPlaylist.segments.size() - 1;
+    int closestIndex = 0;
+
+    while (left <= right) {
+      int mid = left + (right - left) / 2;
+      HlsMediaPlaylist.Segment midSegment = mediaPlaylist.segments.get(mid);
+      long segmentStart = midSegment.relativeStartTimeUs;
+      long segmentEnd = segmentStart + midSegment.durationUs;
+
+      if (positionInPlaylistUs >= segmentStart && positionInPlaylistUs <= segmentEnd) {
+        // Position is within this segment
+        closestIndex = mid;
+        break;
+      } else if (positionInPlaylistUs < segmentStart) {
+        closestIndex = mid;
+        right = mid - 1;
+      } else {
+        closestIndex = mid;
+        left = mid + 1;
+      }
+    }
+
+    HlsMediaPlaylist.Segment segment = mediaPlaylist.segments.get(closestIndex);
     return positionInPlaylistUs - segment.relativeStartTimeUs
             < abs(positionInPlaylistUs - (segment.relativeStartTimeUs + segment.durationUs))
         ? mediaPlaylist.startTimeUs + segment.relativeStartTimeUs

libraries/exoplayer_hls/src/test/java/androidx/media3/exoplayer/hls/HlsInterstitialsAdsLoaderTest.java

@@ -17,6 +17,8 @@
 
 import static androidx.media3.common.Player.DISCONTINUITY_REASON_AUTO_TRANSITION;
 import static androidx.media3.common.Player.TIMELINE_CHANGE_REASON_PLAYLIST_CHANGED;
+import static androidx.media3.common.util.Util.msToUs;
+import static androidx.media3.exoplayer.hls.HlsInterstitialsAdsLoader.getClosestSegmentBoundaryUs;
 import static androidx.media3.test.utils.robolectric.RobolectricUtil.runMainLooperUntil;
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.truth.Truth.assertThat;
@@ -5741,6 +5743,80 @@ public void state_constructorWithAdsIdsThatDoNotMatch_throwsIllegalArgumentExcep
         IllegalArgumentException.class, () -> new AdsResumptionState("5678", adPlaybackState));
   }
 
+  @Test
+  public void getClosestSegmentBoundaryUs_vastlyVariedSegmentSize() throws IOException {
+    String interstitialStartDate = "2025-10-07T01:00:14.000Z";
+    long interstitialStartDateUs = msToUs(Util.parseXsDateTime(interstitialStartDate));
+    String playlistString =
+        "#EXTM3U\n"
+            + "#EXT-X-TARGETDURATION:10\n"
+            + "#EXT-X-PROGRAM-DATE-TIME:2025-10-07T01:00:00.000Z\n"
+            + "#EXTINF:2,\n"
+            + "1.aac\n"
+            + "#EXTINF:2,\n"
+            + "2.aac\n"
+            + "#EXTINF:10,\n"
+            + "3.aac\n"
+            + "#EXT-X-DATERANGE:ID=\"1\","
+            + "CLASS=\"com.apple.hls.interstitial\","
+            + "START-DATE=\""
+            + interstitialStartDate
+            + "\","
+            + "X-ASSET-LIST=\"http://example.com/assetlist-0-0.json\","
+            + "X-SNAP=\"OUT,IN\"\n"
+            + "#EXTINF:10,\n"
+            + "4.aac";
+
+    InputStream inputStream = new ByteArrayInputStream(Util.getUtf8Bytes(playlistString));
+    HlsMediaPlaylist contentMediaPlaylist =
+        (HlsMediaPlaylist) new HlsPlaylistParser().parse(Uri.EMPTY, inputStream);
+
+    long closestSegmentBoundaryUs =
+        getClosestSegmentBoundaryUs(interstitialStartDateUs, contentMediaPlaylist);
+
+    assertThat(closestSegmentBoundaryUs)
+        .isEqualTo(contentMediaPlaylist.startTimeUs + 2_000_000 + 2_000_000 + 10_000_000);
+  }
+
+  @Test
+  public void getClosestSegmentBoundaryUs_positionBeforeAndAfterPlaylist_getsSanitizedValues()
+      throws IOException {
+    String timestampBeforePlaylist = "2025-10-07T00:00:00.000Z";
+    long timeBeforePlaylistUs = msToUs(Util.parseXsDateTime(timestampBeforePlaylist));
+    String timestampLastNonPostRollSnap = "2025-10-07T01:00:18.999Z";
+    long timestampLastNonPostRollSnapUs = msToUs(
+        Util.parseXsDateTime(timestampLastNonPostRollSnap));
+    String timestampPostRollSnap = "2025-10-07T01:00:19.000Z";
+    long timestampPostRollSnapUs = msToUs(Util.parseXsDateTime(timestampPostRollSnap));
+    String timestampAfterPlaylist = "2025-10-07T23:59:59.000Z";
+    long timestampAfterPlaylistUs = msToUs(Util.parseXsDateTime(timestampAfterPlaylist));
+    String playlistString =
+        "#EXTM3U\n"
+            + "#EXT-X-TARGETDURATION:10\n"
+            + "#EXT-X-PROGRAM-DATE-TIME:2025-10-07T01:00:00.000Z\n"
+            + "#EXTINF:2,\n"
+            + "1.aac\n"
+            + "#EXTINF:2,\n"
+            + "2.aac\n"
+            + "#EXTINF:10,\n"
+            + "3.aac\n"
+            + "#EXTINF:10,\n"
+            + "4.aac";
+
+    InputStream inputStream = new ByteArrayInputStream(Util.getUtf8Bytes(playlistString));
+    HlsMediaPlaylist contentMediaPlaylist =
+        (HlsMediaPlaylist) new HlsPlaylistParser().parse(Uri.EMPTY, inputStream);
+
+    assertThat(getClosestSegmentBoundaryUs(timeBeforePlaylistUs, contentMediaPlaylist))
+        .isEqualTo(contentMediaPlaylist.startTimeUs);
+    assertThat(getClosestSegmentBoundaryUs(timestampLastNonPostRollSnapUs, contentMediaPlaylist))
+        .isEqualTo(contentMediaPlaylist.startTimeUs + 14_000_000L);
+    assertThat(getClosestSegmentBoundaryUs(timestampPostRollSnapUs, contentMediaPlaylist))
+        .isEqualTo(contentMediaPlaylist.startTimeUs + 24_000_000L);
+    assertThat(getClosestSegmentBoundaryUs(timestampAfterPlaylistUs, contentMediaPlaylist))
+        .isEqualTo(contentMediaPlaylist.startTimeUs + 24_000_000L);
+  }
+
   private List<AdPlaybackState> callHandleContentTimelineChangedForLiveAndCaptureAdPlaybackStates(
       HlsInterstitialsAdsLoader adsLoader,
       boolean startAdsLoader,