fix(WebVTT): Remove rollover logic because we always transmux TS (#6397)

Fixes #6320
shaka-project · Apr 4, 2024 · 286126e · 286126e
1 parent d9da783
commit 286126e
Show file tree

Hide file tree

Showing 2 changed files with 1 addition and 69 deletions.
diff --git a/lib/text/vtt_text_parser.js b/lib/text/vtt_text_parser.js
@@ -160,17 +160,9 @@ shaka.text.VttTextParser = class {
           shaka.util.Error.Code.INVALID_TEXT_HEADER);
     }
 
-    let mpegTime = Number(mpegTimeMatch[1]);
+    const mpegTime = Number(mpegTimeMatch[1]);
     const mpegTimescale = shaka.text.VttTextParser.MPEG_TIMESCALE_;
 
-    const rolloverSeconds =
-        shaka.text.VttTextParser.TS_ROLLOVER_ / mpegTimescale;
-    let segmentStart = time.segmentStart - time.periodStart;
-    while (segmentStart >= rolloverSeconds) {
-      segmentStart -= rolloverSeconds;
-      mpegTime += shaka.text.VttTextParser.TS_ROLLOVER_;
-    }
-
     return time.periodStart + mpegTime / mpegTimescale - cueTime;
   }
 
@@ -1015,13 +1007,6 @@ shaka.text.VttTextParser = class {
  */
 shaka.text.VttTextParser.MPEG_TIMESCALE_ = 90000;
 
-/**
- * At this value, timestamps roll over in TS content.
- * @const {number}
- * @private
- */
-shaka.text.VttTextParser.TS_ROLLOVER_ = 0x200000000;
-
 /**
  * @const
  * @private {!RegExp}

diff --git a/test/text/vtt_text_parser_unit.js b/test/text/vtt_text_parser_unit.js
@@ -583,59 +583,6 @@ describe('VttTextParser', () => {
         /* hls= */ true, /* sequenceMode= */ true);
   });
 
-  it('handles timestamp rollover with X-TIMESTAMP-MAP header', () => {
-    verifyHelper(
-        [
-          {startTime: 95443, endTime: 95445, payload: 'Test'},
-        ],
-        // 8589870000/90000 = 95443 sec, so expect every timestamp to be 95443
-        // seconds ahead of what is specified.
-        'WEBVTT\n' +
-        'X-TIMESTAMP-MAP=MPEGTS:8589870000,LOCAL:00:00:00.000\n\n' +
-        '00:00:00.000 --> 00:00:02.000 line:0\n' +
-        'Test',
-        // Non-null segmentStart takes precedence over X-TIMESTAMP-MAP.
-        // This protects us from rollover in the MPEGTS field.
-        {periodStart: 0, segmentStart: 95440, segmentEnd: 95550, vttOffset: 0},
-        /* hls= */ true, /* sequenceMode= */ true);
-
-    verifyHelper(
-        [
-          {startTime: 95552, endTime: 95554, payload: 'Test2'},
-        ],
-        // 95550 is larger than the roll over timestamp, so the timestamp offset
-        // gets rolled over.
-        // (9745408 + 0x200000000) / 90000 = 95552 sec
-        'WEBVTT\n' +
-        'X-TIMESTAMP-MAP=MPEGTS:9745408,LOCAL:00:00:00.000\n\n' +
-        '00:00:00.000 --> 00:00:02.000 line:0\n' +
-        'Test2',
-        {periodStart: 0, segmentStart: 95550, segmentEnd: 95560, vttOffset: 0},
-        /* hls= */ true, /* sequenceMode= */ true);
-  });
-
-  // A mock-up of HLS live subs as seen in b/253104251.
-  it('handles timestamp rollover and negative offset in HLS live', () => {
-    // Similar to values seen in b/253104251, for a realistic regression test.
-    // When using sequence mode on live HLS, we get negative offsets that
-    // represent the timestamp of our first append in sequence mode.
-    verifyHelper(
-        [
-          {startTime: 3600, endTime: 3602, payload: 'Test'},
-        ],
-        'WEBVTT\n' +
-        'X-TIMESTAMP-MAP=MPEGTS:8355814896,LOCAL:00:00:00.000\n\n' +
-        '00:00:00.000 --> 00:00:02.000 line:0\n' +
-        'Test',
-        {
-          periodStart: -1234567,
-          segmentStart: 3600,
-          segmentEnd: 3610,
-          vttOffset: -1234567,
-        },
-        /* hls= */ true, /* sequenceMode= */ true);
-  });
-
   it('supports global style blocks', () => {
     const textShadow = '-1px 0 black, 0 1px black, 1px 0 black, 0 -1px black';
     verifyHelper(