fix: CEA 608 captions not work with H.265 video streams (shaka-projec…

…t#5252)

Fix parsing of CEA 608 captions in H.265 video streams by handling 2
byte nal unit header.

Fixes shaka-project#5251

lib/cea/mp4_cea_parser.js

@@ -277,6 +277,7 @@ shaka.cea.Mp4CeaParser = class {
       const naluHeader = reader.readUint8();
       let naluType = null;
       let isSeiMessage = false;
+      let naluHeaderSize = 1;
 
       goog.asserts.assert(this.bitstreamFormat_ != BitstreamFormat.UNKNOWN,
           'Bitstream format should have been checked before now!');
@@ -287,6 +288,8 @@ shaka.cea.Mp4CeaParser = class {
           break;
 
         case BitstreamFormat.H265:
+          naluHeaderSize = 2;
+          reader.skip(1);
           naluType = (naluHeader >> 1) & 0x3f;
           isSeiMessage =
               naluType == CeaUtils.H265_PREFIX_NALU_TYPE_SEI ||
@@ -306,15 +309,15 @@ shaka.cea.Mp4CeaParser = class {
 
         const pts = (time + timeOffset)/timescale;
         for (const packet of this.seiProcessor_
-            .process(reader.readBytes(naluSize - 1))) {
+            .process(reader.readBytes(naluSize - naluHeaderSize))) {
           captionPackets.push({
             packet,
             pts,
           });
         }
       } else {
         try {
-          reader.skip(naluSize - 1);
+          reader.skip(naluSize - naluHeaderSize);
         } catch (e) {
           // It is necessary to ignore this error because it can break the start
           // of playback even if the user does not want to see the subtitles.

test/cea/mp4_cea_parser_unit.js

@@ -7,20 +7,30 @@
 describe('Mp4CeaParser', () => {
   const ceaInitSegmentUri = '/base/test/test/assets/cea-init.mp4';
   const ceaSegmentUri = '/base/test/test/assets/cea-segment.mp4';
+  const h265ceaInitSegmentUri = '/base/test/test/assets/h265-cea-init.mp4';
+  const h265ceaSegmentUri = '/base/test/test/assets/h265-cea-segment.mp4';
   const Util = shaka.test.Util;
 
   /** @type {!ArrayBuffer} */
   let ceaInitSegment;
   /** @type {!ArrayBuffer} */
   let ceaSegment;
+  /** @type {!ArrayBuffer} */
+  let h265ceaInitSegment;
+  /** @type {!ArrayBuffer} */
+  let h265ceaSegment;
 
   beforeAll(async () => {
     const responses = await Promise.all([
       shaka.test.Util.fetch(ceaInitSegmentUri),
       shaka.test.Util.fetch(ceaSegmentUri),
+      shaka.test.Util.fetch(h265ceaInitSegmentUri),
+      shaka.test.Util.fetch(h265ceaSegmentUri),
     ]);
     ceaInitSegment = responses[0];
     ceaSegment = responses[1];
+    h265ceaInitSegment = responses[2];
+    h265ceaSegment = responses[3];
   });
 
   /**
@@ -70,6 +80,15 @@ describe('Mp4CeaParser', () => {
         .toEqual(expectedCea708Packet);
   });
 
+  it('parses cea data from an h265 mp4 stream', () => {
+    const ceaParser = new shaka.cea.Mp4CeaParser();
+
+    ceaParser.init(h265ceaInitSegment);
+    const ceaPackets = ceaParser.parse(h265ceaSegment);
+    expect(ceaPackets).toBeDefined();
+    expect(ceaPackets.length).toBe(60);
+  });
+
   it('parses an invalid init segment', () => {
     const cea708Parser = new shaka.cea.Mp4CeaParser();