Reload HLS media playlist when merging delta update fails

Issue: #5011
PiperOrigin-RevId: 350550204

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java

@@ -603,11 +603,16 @@ public final class DefaultHlsPlaylistTracker
               loadDurationMs,
               loadable.bytesLoaded());
       boolean isBlockingRequest = loadable.getUri().getQueryParameter(BLOCK_MSN_PARAM) != null;
-      if (isBlockingRequest && error instanceof HttpDataSource.InvalidResponseCodeException) {
+      boolean deltaUpdateFailed = error instanceof HlsPlaylistParser.DeltaUpdateException;
-        int responseCode = ((HttpDataSource.InvalidResponseCodeException) error).responseCode;
+      if (isBlockingRequest || deltaUpdateFailed) {
-        if (responseCode == 400 || responseCode == 503) {
+        int responseCode = Integer.MAX_VALUE;
-          // Intercept bad request and service unavailable to force a full, non-blocking request
+        if (error instanceof HttpDataSource.InvalidResponseCodeException) {
-          // (see RFC 8216, section 6.2.5.2).
+          responseCode = ((HttpDataSource.InvalidResponseCodeException) error).responseCode;
+        }
+        if (deltaUpdateFailed || responseCode == 400 || responseCode == 503) {
+          // Intercept failed delta updates and blocking requests producing a Bad Request (400) and
+          // Service Unavailable (503). In such cases, force a full, non-blocking request (see RFC
+          // 8216, section 6.2.5.2 and 6.3.7).
           earliestNextLoadTimeMs = SystemClock.elapsedRealtime();
           loadPlaylist();
           castNonNull(eventDispatcher)

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistParser.java

@@ -69,6 +69,9 @@ import org.checkerframework.checker.nullness.qual.PolyNull;
  */
 public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlaylist> {
 
+  /** Exception thrown when merging a delta update fails. */
+  public static final class DeltaUpdateException extends IOException {}
+
   private static final String LOG_TAG = "HlsPlaylistParser";
 
   private static final String PLAYLIST_HEADER = "#EXTM3U";
@@ -744,8 +747,10 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
         checkState(previousMediaPlaylist != null && segments.isEmpty());
         int startIndex = (int) (mediaSequence - castNonNull(previousMediaPlaylist).mediaSequence);
         int endIndex = startIndex + skippedSegmentCount;
-        if (startIndex >= 0 && endIndex <= previousMediaPlaylist.segments.size()) {
+        if (startIndex < 0 || endIndex > previousMediaPlaylist.segments.size()) {
-          // Merge only if all skipped segments are available in the previous playlist.
+          // Throw to force a reload if not all segments are available in the previous playlist.
+          throw new DeltaUpdateException();
+        }
         for (int i = startIndex; i < endIndex; i++) {
           Segment segment = previousMediaPlaylist.segments.get(i);
           if (mediaSequence != previousMediaPlaylist.mediaSequence) {
@@ -774,7 +779,6 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
           }
           segmentMediaSequence++;
         }
-        }
       } else if (line.startsWith(TAG_KEY)) {
         String method = parseStringAttr(line, REGEX_METHOD, variableDefinitions);
         String keyFormat =

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTrackerTest.java

@@ -37,7 +37,6 @@ import okhttp3.mockwebserver.MockWebServer;
 import okio.Buffer;
 import org.junit.After;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -50,6 +49,8 @@ public class DefaultHlsPlaylistTrackerTest {
       "media/m3u8/live_low_latency_master_media_uri_with_param";
   private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL =
       "media/m3u8/live_low_latency_media_can_skip_until";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL_FULL_RELOAD_AFTER_ERROR =
+      "media/m3u8/live_low_latency_media_can_skip_until_full_reload_after_error";
   private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_DATERANGES =
       "media/m3u8/live_low_latency_media_can_skip_dateranges";
   private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED =
@@ -168,18 +169,21 @@ public class DefaultHlsPlaylistTrackerTest {
     assertThat(mergedPlaylist.segments.get(1).relativeStartTimeUs).isEqualTo(4000000);
   }
 
-  @Ignore // Test disabled because playlist delta updates are temporarily disabled.
   @Test
-  public void start_playlistCanSkip_missingSegments_correctedMediaSequence()
+  public void start_playlistCanSkip_missingSegments_reloadsWithoutSkipping()
       throws IOException, TimeoutException, InterruptedException {
     List<HttpUrl> httpUrls =
         enqueueWebServerResponses(
             new String[] {
-              "/master.m3u8", "/media0/playlist.m3u8", "/media0/playlist.m3u8?_HLS_skip=YES"
+              "/master.m3u8",
+              "/media0/playlist.m3u8",
+              "/media0/playlist.m3u8?_HLS_skip=YES",
+              "/media0/playlist.m3u8"
             },
             getMockResponse(SAMPLE_M3U8_LIVE_MASTER),
             getMockResponse(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL),
-            getMockResponse(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED_MEDIA_SEQUENCE_NO_OVERLAPPING));
+            getMockResponse(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED_MEDIA_SEQUENCE_NO_OVERLAPPING),
+            getMockResponse(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL_FULL_RELOAD_AFTER_ERROR));
 
     List<HlsMediaPlaylist> mediaPlaylists =
         runPlaylistTrackerAndCollectMediaPlaylists(
@@ -192,8 +196,8 @@ public class DefaultHlsPlaylistTrackerTest {
     assertThat(initialPlaylistWithAllSegments.mediaSequence).isEqualTo(10);
     assertThat(initialPlaylistWithAllSegments.segments).hasSize(6);
     HlsMediaPlaylist mergedPlaylist = mediaPlaylists.get(1);
-    assertThat(mergedPlaylist.mediaSequence).isEqualTo(22);
+    assertThat(mergedPlaylist.mediaSequence).isEqualTo(20);
-    assertThat(mergedPlaylist.segments).hasSize(4);
+    assertThat(mergedPlaylist.segments).hasSize(6);
   }
 
   @Test

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_until_and_block_reload_next_skipped

@@ -2,8 +2,8 @@
 #EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24,CAN-BLOCK-RELOAD=YES
 #EXT-X-TARGETDURATION:4
 #EXT-X-VERSION:3
-#EXT-X-SKIP:SKIPPED-SEGMENTS=2
 #EXT-X-MEDIA-SEQUENCE:12
+#EXT-X-SKIP:SKIPPED-SEGMENTS=2
 #EXTINF:4.00000,
 fileSequence14.ts
 #EXTINF:4.00000,

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_until_full_reload_after_error

@@ -0,0 +1,17 @@
+#EXTM3U
+#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:20
+#EXTINF:4.00000,
+fileSequence20.ts
+#EXTINF:4.00000,
+fileSequence21.ts
+#EXTINF:4.00000,
+fileSequence22.ts
+#EXTINF:4.00000,
+fileSequence23.ts
+#EXTINF:4.00000,
+fileSequence24.ts
+#EXTINF:4.00000,
+fileSequence25.ts