Add HLS support for parsing TTML subs muxed into MP4 during extraction

This removes the flakiness of the HLS playback test as well.

Previously, this flow only worked for standalone WebVTT subtitles (7b762642db)

PiperOrigin-RevId: 582359383

RELEASENOTES.md

@@ -69,6 +69,8 @@
     *   Add experimental support for parsing subtitles during extraction. You
         can enable this using
         `HlsMediaSource.Factory.experimentalParseSubtitlesDuringExtraction()`.
+        This works for standalone WebVTT subtitles and IMSC1 subtitles muxed
+        into MP4.
 *   DASH Extension:
     *   Extend experimental support for parsing subtitles during extraction to
         work with standalone text files (previously it only worked with

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

@@ -201,7 +201,11 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
       case FileTypes.MP3:
         return new Mp3Extractor(/* flags= */ 0, /* forcedFirstSampleTimestampUs= */ 0);
       case FileTypes.MP4:
-        return createFragmentedMp4Extractor(timestampAdjuster, format, muxedCaptionFormats);
+        Extractor mp4Extractor =
+            createFragmentedMp4Extractor(timestampAdjuster, format, muxedCaptionFormats);
+        return subtitleParserFactory != null
+            ? new SubtitleTranscodingExtractor(mp4Extractor, subtitleParserFactory)
+            : mp4Extractor;
       case FileTypes.TS:
         return createTsExtractor(
             payloadReaderFactoryFlags,

libraries/exoplayer_hls/src/test/java/androidx/media3/exoplayer/hls/e2etest/HlsPlaybackTest.java

@@ -32,7 +32,6 @@ import androidx.media3.test.utils.robolectric.ShadowMediaCodecConfig;
 import androidx.media3.test.utils.robolectric.TestPlayerRunHelper;
 import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -72,14 +71,15 @@ public final class HlsPlaybackTest {
   }
 
   @Test
-  @Ignore(
-      "Disabled until subtitles are reliably asserted in robolectric tests [internal b/174661563].")
   public void ttmlInMp4() throws Exception {
     Context applicationContext = ApplicationProvider.getApplicationContext();
     CapturingRenderersFactory capturingRenderersFactory =
         new CapturingRenderersFactory(applicationContext);
     ExoPlayer player =
         new ExoPlayer.Builder(applicationContext, capturingRenderersFactory)
+            .setMediaSourceFactory(
+                new HlsMediaSource.Factory(new DefaultDataSource.Factory(applicationContext))
+                    .experimentalParseSubtitlesDuringExtraction(true))
             .setClock(new FakeClock(/* isAutoAdvancing= */ true))
             .build();
     player.setVideoSurface(new Surface(new SurfaceTexture(/* texName= */ 1)));

libraries/test_data/src/test/assets/playbackdumps/hls/ttml-in-mp4.dump

@@ -222,22 +222,26 @@ TextOutput:
     presentationTimeUs = 0
     Cues = []
   Subtitle[1]:
+    presentationTimeUs = 20000
+    Cue[0]:
+      text = First Subtitle after 20ms of silence
+  Subtitle[2]:
     presentationTimeUs = 250000
     Cue[0]:
       text = First Subtitle after 20ms of silence
              Second Subtitle overlaps with first
-  Subtitle[2]:
+  Subtitle[3]:
     presentationTimeUs = 400000
     Cue[0]:
       text = First Subtitle after 20ms of silence
-  Subtitle[3]:
+  Subtitle[4]:
     presentationTimeUs = 500000
     Cues = []
-  Subtitle[4]:
+  Subtitle[5]:
     presentationTimeUs = 700000
     Cue[0]:
       text = Last subtitle
              And More
-  Subtitle[5]:
+  Subtitle[6]:
     presentationTimeUs = 950000
     Cues = []