fix: forward parse708captions and captionServices to the mp4 caption parser

Both options reached the transmuxer worker's init config but were dropped
at the fMP4 CaptionParser call site, which was constructed with no options.
As a result parse708captions and captionServices only ever applied to
MPEG-TS streams, never to fMP4/CMAF.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Essk

src/transmuxer-worker.js

@@ -191,7 +191,10 @@ class MessageHandlers {
   pushMp4Captions(data) {
     if (!this.captionParser) {
       this.captionParser = new CaptionParser();
-      this.captionParser.init();
+      this.captionParser.init({
+        parse708captions: this.options.parse708captions,
+        captionServices: this.options.captionServices
+      });
     }
     const segment = new Uint8Array(data.data, data.byteOffset, data.byteLength);
     const parsed = this.captionParser.parse(

test/transmuxer-worker.test.js

@@ -10,11 +10,11 @@ import {
 // needed for plugin registration
 import '../src/videojs-http-streaming';
 
-const createTransmuxer = () => {
-  return createTransmuxer_({
+const createTransmuxer = (options) => {
+  return createTransmuxer_(Object.assign({
     remux: false,
     keepOriginalTimestamps: true
-  });
+  }, options));
 };
 
 // The final done message from the Transmux worker
@@ -354,6 +354,39 @@ QUnit.test('can parse mp4 captions', function(assert) {
   });
 });
 
+QUnit.test('parses mp4 captions when initialized with caption parsing options', function(assert) {
+  const done = assert.async();
+  const data = mp4CaptionsSegment();
+
+  this.transmuxer = createTransmuxer({
+    parse708captions: false,
+    captionServices: {SERVICE1: {language: 'en'}}
+  });
+  this.transmuxer.onmessage = (e) => {
+    const message = e.data;
+
+    assert.equal(message.action, 'mp4Captions', 'returned mp4Captions event');
+    assert.equal(message.captions.length, 2, 'two 608 captions');
+    assert.deepEqual(
+      message.captions.map((caption) => caption.stream),
+      ['CC1', 'CC1'],
+      'only 608 caption streams are present'
+    );
+    assert.deepEqual(message.logs.length, 0, 'no logs returned');
+
+    done();
+  };
+
+  this.transmuxer.postMessage({
+    action: 'pushMp4Captions',
+    data,
+    timescales: 30000,
+    trackIds: [1],
+    byteLength: data.byteLength,
+    byteOffset: 0
+  });
+});
+
 QUnit.test('returns empty array without mp4 captions', function(assert) {
   const done = assert.async();
   const data = muxedSegment();