Allow missing hours in SubRip (.srt) subtitle timecodes

Add a test for this case, and extend the existing tests to ensure the
hour is parsed when it's present.

issue:#7122
PiperOrigin-RevId: 302472213

RELEASENOTES.md

@@ -2,9 +2,12 @@
 
 ### 2.11.4 (not yet released) ###
 
-* Text: Catch-and-log all fatal exceptions in `TextRenderer` instead of
-  re-throwing, allowing playback to continue even if subtitles fail
-  ([#6885](https://github.com/google/ExoPlayer/issues/6885)).
+* Text:
+  *  Catch-and-log all fatal exceptions in `TextRenderer` instead of
+    re-throwing, allowing playback to continue even if subtitles fail
+    ([#6885](https://github.com/google/ExoPlayer/issues/6885)).
+  * Allow missing hours in SubRip (.srt) timecodes
+    ([#7122](https://github.com/google/ExoPlayer/issues/7122)).
 * UI: Add an option to set whether to use the orientation sensor for rotation
   in spherical playbacks
   ([#6761](https://github.com/google/ExoPlayer/issues/6761)).

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

@@ -41,10 +41,12 @@ 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+)";
   private static final Pattern SUBRIP_TIMING_LINE =
       Pattern.compile("\\s*(" + SUBRIP_TIMECODE + ")\\s*-->\\s*(" + SUBRIP_TIMECODE + ")\\s*");
 
+  // NOTE: Android Studio's suggestion to simplify '\\}' is incorrect [internal: b/144480183].
   private static final Pattern SUBRIP_TAG_PATTERN = Pattern.compile("\\{\\\\.*?\\}");
   private static final String SUBRIP_ALIGNMENT_TAG = "\\{\\\\an[1-9]\\}";
 
@@ -229,7 +231,8 @@ public final class SubripDecoder extends SimpleSubtitleDecoder {
   }
 
   private static long parseTimecode(Matcher matcher, int groupOffset) {
-    long timestampMs = Long.parseLong(matcher.group(groupOffset + 1)) * 60 * 60 * 1000;
+    @Nullable String hours = matcher.group(groupOffset + 1);
+    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));

library/core/src/test/assets/subrip/typical

@@ -8,5 +8,5 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.

library/core/src/test/assets/subrip/typical_extra_blank_line

@@ -9,5 +9,5 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.

library/core/src/test/assets/subrip/typical_missing_sequence

@@ -7,5 +7,5 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.

library/core/src/test/assets/subrip/typical_missing_timecode

@@ -7,13 +7,13 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.
 
 4
-             --> 00:00:10,901
+             --> 02:00:10,901
 This is the fourth subtitle.
 
 5
-00:00:12,901 -->
+02:00:12,901 -->
 This is the fifth subtitle.

library/core/src/test/assets/subrip/typical_negative_timestamps

@@ -8,5 +8,5 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.

library/core/src/test/assets/subrip/typical_no_hours

@@ -0,0 +1,12 @@
+1
+00:00,000 --> 00:01,234
+This is the first subtitle.
+
+2
+00:02,345 --> 00:03,456
+This is the second subtitle.
+Second subtitle with second line.
+
+3
+02:00:04,567 --> 02:00:08,901
+This is the third subtitle.

library/core/src/test/assets/subrip/typical_with_byte_order_mark

@@ -8,5 +8,5 @@ This is the second subtitle.
 Second subtitle with second line.
 
 3
-00:00:04,567 --> 00:00:08,901
+02:00:04,567 --> 02:00:08,901
 This is the third subtitle.

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

@@ -39,6 +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";
 
   @Test
   public void testDecodeEmpty() throws IOException {
@@ -151,9 +152,14 @@ public final class SubripDecoderTest {
         TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_WITH_TAGS);
     Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
 
-    assertTypicalCue1(subtitle, 0);
-    assertTypicalCue2(subtitle, 2);
-    assertTypicalCue3(subtitle, 4);
+    assertThat(subtitle.getCues(subtitle.getEventTime(0)).get(0).text.toString())
+        .isEqualTo("This is the first subtitle.");
+
+    assertThat(subtitle.getCues(subtitle.getEventTime(2)).get(0).text.toString())
+        .isEqualTo("This is the second subtitle.\nSecond subtitle with second line.");
+
+    assertThat(subtitle.getCues(subtitle.getEventTime(4)).get(0).text.toString())
+        .isEqualTo("This is the third subtitle.");
 
     assertThat(subtitle.getCues(subtitle.getEventTime(6)).get(0).text.toString())
         .isEqualTo("This { \\an2} is not a valid tag due to the space after the opening bracket.");
@@ -172,6 +178,19 @@ public final class SubripDecoderTest {
     assertAlignmentCue(subtitle, 26, Cue.ANCHOR_TYPE_START, Cue.ANCHOR_TYPE_END); // {/an9}
   }
 
+  @Test
+  public void decodeTypicalNoHours() throws IOException {
+    SubripDecoder decoder = new SubripDecoder();
+    byte[] bytes =
+        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_NO_HOURS);
+    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
+
+    assertThat(subtitle.getEventTimeCount()).isEqualTo(6);
+    assertTypicalCue1(subtitle, 0);
+    assertTypicalCue2(subtitle, 2);
+    assertTypicalCue3(subtitle, 4);
+  }
+
   private static void assertTypicalCue1(Subtitle subtitle, int eventIndex) {
     assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(0);
     assertThat(subtitle.getCues(subtitle.getEventTime(eventIndex)).get(0).text.toString())
@@ -187,10 +206,12 @@ public final class SubripDecoderTest {
   }
 
   private static void assertTypicalCue3(Subtitle subtitle, int eventIndex) {
-    assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(4567000);
+    long expectedStartTimeUs = (((2L * 60L * 60L) + 4L) * 1000L + 567L) * 1000L;
+    assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(expectedStartTimeUs);
     assertThat(subtitle.getCues(subtitle.getEventTime(eventIndex)).get(0).text.toString())
         .isEqualTo("This is the third subtitle.");
-    assertThat(subtitle.getEventTime(eventIndex + 1)).isEqualTo(8901000);
+    long expectedEndTimeUs = (((2L * 60L * 60L) + 8L) * 1000L + 901L) * 1000L;
+    assertThat(subtitle.getEventTime(eventIndex + 1)).isEqualTo(expectedEndTimeUs);
   }
 
   private static void assertAlignmentCue(