fix(WebVTT): Fix times when using HLS without X-TIMESTAMP-MAP (#9313)

Author: avelad

lib/text/vtt_text_parser.js

@@ -87,10 +87,6 @@ shaka.text.VttTextParser = class {
       // Only use 'X-TIMESTAMP-MAP' with HLS.
       if (blocks[0].includes('X-TIMESTAMP-MAP')) {
         offset = this.computeHlsOffset_(blocks[0], time);
-      } else if (time.periodStart && time.vttOffset == time.periodStart) {
-        // In the case where X-TIMESTAMP-MAP is not used and it is HLS, we
-        // should not use offset unless segment-relative times are used.
-        offset = 0;
       }
     }
 
@@ -398,6 +394,10 @@ shaka.text.VttTextParser = class {
     start += timeOffset;
     end += timeOffset;
 
+    if (start < 0) {
+      start = 0;
+    }
+
     // Get the payload.
     const payload = text.slice(1).join('\n').trim();
 

test/hls/hls_parser_integration.js

@@ -136,12 +136,12 @@ describe('HlsParser', () => {
 
     const cues = video.textTracks[0].cues;
     expect(cues.length).toBe(3);
-    expect(cues[0].startTime).toBeCloseTo(0.6, 0);
-    expect(cues[0].endTime).toBeCloseTo(2.88, 0);
-    expect(cues[1].startTime).toBeCloseTo(2.88, 0);
-    expect(cues[1].endTime).toBeCloseTo(6.36, 0);
-    expect(cues[2].startTime).toBeCloseTo(6.36, 0);
-    expect(cues[2].endTime).toBeCloseTo(10.68, 0);
+    expect(cues[0].startTime).toBeCloseTo(0, 0);
+    expect(cues[0].endTime).toBeCloseTo(1.48, 0);
+    expect(cues[1].startTime).toBeCloseTo(1.48, 0);
+    expect(cues[1].endTime).toBeCloseTo(4.96, 0);
+    expect(cues[2].startTime).toBeCloseTo(4.96, 0);
+    expect(cues[2].endTime).toBeCloseTo(9.28, 0);
 
     await player.unload();
   });