fix(ttml): use endTimeSegment as fallback for last cue end time

PascalThuet · PascalThuet · commit ea4ed1aec145 · 2026-03-15T12:33:31.000+01:00
When a TTML cue has no explicit end attribute, mediaTimeEvents[i+1] is undefined on the last iteration. undefined + offsetTime = NaN, and startTime < NaN is always false, so the cue is silently dropped. Use endTimeSegment (already declared, documented in JSDoc, and passed by TextSourceBuffer) as the fallback end time for the last cue. Fixes Dash-Industry-Forum#4985
diff --git a/src/streaming/utils/TTMLParser.js b/src/streaming/utils/TTMLParser.js
@@ -144,7 +144,9 @@ function TTMLParser() {
             if (isd.contents.some(topLevelContents => topLevelContents.contents.length)) {
                 //be sure that mediaTimeEvents values are in the mp4 segment time ranges.
                 startTime = mediaTimeEvents[i] + offsetTime;
-                endTime = mediaTimeEvents[i + 1] + offsetTime;
+                endTime = (i + 1 < mediaTimeEvents.length)
+                    ? mediaTimeEvents[i + 1] + offsetTime
+                    : endTimeSegment;
 
                 if (startTime < endTime) {
                     captionArray.push({
diff --git a/test/unit/data/subtitles/ttmlLastCue.ttml b/test/unit/data/subtitles/ttmlLastCue.ttml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<tt xmlns="http://www.w3.org/ns/ttml"
+    xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
+    xmlns:tts="http://www.w3.org/ns/ttml#styling"
+    xml:lang="en" xml:space="default"
+    ttp:timeBase="media" ttp:cellResolution="40 24">
+
+    <head>
+        <styling>
+            <style xml:id="S0" tts:wrapOption="wrap" tts:fontFamily="UnitTestFont,Arial,Roboto,proportionalSansSerif, default" tts:textAlign="center" tts:fontSize="80%" />
+        </styling>
+        <layout>
+            <region xml:id="R1" tts:origin="12.5% 75%" tts:extent="75% 20%" tts:overflow="hidden" tts:displayAlign="before"/>
+        </layout>
+    </head>
+    <body style="S0">
+        <div region="R1">
+            <p xml:id="p1" begin="00:00:00">
+                Last cue without explicit end
+            </p>
+        </div>
+    </body>
+</tt>
diff --git a/test/unit/test/streaming/streaming.utils.TTMLParser.js b/test/unit/test/streaming/streaming.utils.TTMLParser.js
@@ -5,13 +5,15 @@ import {expect} from 'chai';
 const context = {};
 const ttmlParser = TTMLParser(context).getInstance();
 let ttml_file;
+let ttml_last_cue_file;
 
 describe('TTMLParser', function () {
 
     describe('parse', async () => {
 
         before(async function () {
             ttml_file = await FileLoader.loadTextFile('/data/subtitles/ttmlSample.ttml');
+            ttml_last_cue_file = await FileLoader.loadTextFile('/data/subtitles/ttmlLastCue.ttml');
         });
 
         it('should return an empty array when parse is called and parameters are undefined', () => {
@@ -25,5 +27,13 @@ describe('TTMLParser', function () {
             expect(captionsArray[0].start).to.equal(0);
             expect(captionsArray[0].end).to.equal(5);
         });
+
+        it('should use endTimeSegment as fallback for the last cue end time', () => {
+            const endTimeSegment = 10;
+            const captionsArray = ttmlParser.parse(ttml_last_cue_file, 0, 0, endTimeSegment, []);
+            expect(captionsArray).to.have.lengthOf(1);
+            expect(captionsArray[0].start).to.equal(0);
+            expect(captionsArray[0].end).to.equal(endTimeSegment);
+        });
     });
 });
