fix: handle null return value from CaptionParser.parse (#890)

CaptionParser can return null during parse, we used to handle this case but broke when we switched to the web worker caption parser in #863.

src/transmuxer-worker.js

@@ -306,7 +306,7 @@ class MessageHandlers {
 
  this.self.postMessage({
  action: 'mp4Captions',
- captions: parsed.captions,
+ captions: parsed && parsed.captions || [],
  data: segment.buffer
  }, [segment.buffer]);
  }

test/transmuxer-worker.test.js

@@ -1,6 +1,7 @@
 import QUnit from 'qunit';
 import TransmuxWorker from 'worker!../src/transmuxer-worker.worker.js';
 import {
+ mp4Captions as mp4CaptionsSegment,
  muxed as muxedSegment,
  oneSecond as oneSecondSegment,
  caption as captionSegment
@@ -321,6 +322,64 @@ QUnit.test('caption events are returned', function(assert) {
  });
 });
 
+QUnit.test('can parse mp4 captions', function(assert) {
+ const done = assert.async();
+ const data = mp4CaptionsSegment();
+
+ this.transmuxer = createTransmuxer(false);
+ this.transmuxer.onmessage = (e) => {
+ const message = e.data;
+
+ assert.equal(message.action, 'mp4Captions', 'returned mp4Captions event');
+ assert.deepEqual(message.captions.length, 2, 'two captions');
+ assert.deepEqual(
+ new Uint8Array(message.data),
+ data,
+ 'data returned to main thread'
+ );
+
+ 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();
+
+ this.transmuxer = createTransmuxer(false);
+ this.transmuxer.onmessage = (e) => {
+ const message = e.data;
+
+ assert.equal(message.action, 'mp4Captions', 'returned mp4Captions event');
+ assert.deepEqual(message.captions, [], 'no captions');
+ assert.deepEqual(
+ new Uint8Array(message.data),
+ data,
+ 'data returned to main thread'
+ );
+
+ done();
+ };
+
+ this.transmuxer.postMessage({
+ action: 'pushMp4Captions',
+ data,
+ timescales: 30000,
+ trackIds: [1],
+ byteLength: data.byteLength,
+ byteOffset: 0
+ });
+});
+
 QUnit.module('Transmuxer Worker: Partial Transmuxer', {
  beforeEach(assert) {
  assert.timeout(5000);