Make milliseconds optional in SubRip (SRT) subtitles

issue:#7122
PiperOrigin-RevId: 303154493

RELEASENOTES.md

@@ -86,7 +86,7 @@
         ([#6885](https://github.com/google/ExoPlayer/issues/6885)).
     *   Parse `tts:ruby` and `tts:rubyPosition` properties in TTML subtitles
         (rendering is coming later).
-    *   Allow missing hours in SubRip (.srt) timecodes
+    *   Allow missing hours & milliseconds in SubRip (.srt) timecodes
         ([#7122](https://github.com/google/ExoPlayer/issues/7122)).
 *   DRM:
     *   Add support for attaching DRM sessions to clear content in the demo app.

library/core/src/main/java/com/google/android/exoplayer2/text/subrip/SubripDecoder.java

@@ -41,8 +41,8 @@ public final class SubripDecoder extends SimpleSubtitleDecoder {
 
   private static final String TAG = "SubripDecoder";
 
-  // Some SRT files don't include hours in the timecode, so we use an optional group.
-  private static final String SUBRIP_TIMECODE = "(?:(\\d+):)?(\\d+):(\\d+),(\\d+)";
+  // Some SRT files don't include hours or milliseconds in the timecode, so we use optional groups.
+  private static final String SUBRIP_TIMECODE = "(?:(\\d+):)?(\\d+):(\\d+)(?:,(\\d+))?";
   private static final Pattern SUBRIP_TIMING_LINE =
       Pattern.compile("\\s*(" + SUBRIP_TIMECODE + ")\\s*-->\\s*(" + SUBRIP_TIMECODE + ")\\s*");
 
@@ -235,7 +235,10 @@ public final class SubripDecoder extends SimpleSubtitleDecoder {
     long timestampMs = hours != null ? Long.parseLong(hours) * 60 * 60 * 1000 : 0;
     timestampMs += Long.parseLong(matcher.group(groupOffset + 2)) * 60 * 1000;
     timestampMs += Long.parseLong(matcher.group(groupOffset + 3)) * 1000;
-    timestampMs += Long.parseLong(matcher.group(groupOffset + 4));
+    @Nullable String millis = matcher.group(groupOffset + 4);
+    if (millis != null) {
+      timestampMs += Long.parseLong(millis);
+    }
     return timestampMs * 1000;
   }
 

library/core/src/test/java/com/google/android/exoplayer2/text/subrip/SubripDecoderTest.java

@@ -39,7 +39,7 @@ public final class SubripDecoderTest {
   private static final String TYPICAL_NEGATIVE_TIMESTAMPS = "subrip/typical_negative_timestamps";
   private static final String TYPICAL_UNEXPECTED_END = "subrip/typical_unexpected_end";
   private static final String TYPICAL_WITH_TAGS = "subrip/typical_with_tags";
-  private static final String TYPICAL_NO_HOURS = "subrip/typical_no_hours";
+  private static final String TYPICAL_NO_HOURS_AND_MILLIS = "subrip/typical_no_hours_and_millis";
 
   @Test
   public void decodeEmpty() throws IOException {
@@ -179,15 +179,17 @@ public final class SubripDecoderTest {
   }
 
   @Test
-  public void decodeTypicalNoHours() throws IOException {
+  public void decodeTypicalNoHoursAndMillis() throws IOException {
     SubripDecoder decoder = new SubripDecoder();
     byte[] bytes =
-        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_NO_HOURS);
+        TestUtil.getByteArray(
+            ApplicationProvider.getApplicationContext(), TYPICAL_NO_HOURS_AND_MILLIS);
     Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
 
     assertThat(subtitle.getEventTimeCount()).isEqualTo(6);
     assertTypicalCue1(subtitle, 0);
-    assertTypicalCue2(subtitle, 2);
+    assertThat(subtitle.getEventTime(2)).isEqualTo(2_000_000);
+    assertThat(subtitle.getEventTime(3)).isEqualTo(3_000_000);
     assertTypicalCue3(subtitle, 4);
   }
 

testdata/src/test/assets/subrip/typical_no_hours → testdata/src/test/assets/subrip/typical_no_hours_and_millis

@@ -3,7 +3,7 @@
 This is the first subtitle.
 
 2
-00:02,345 --> 00:03,456
+00:00:02 --> 00:00:03
 This is the second subtitle.
 Second subtitle with second line.