"Cannot read property 'startTime' of null" on seeking

[sandersaares]

Have you read the FAQ and checked for duplicate issues: yes

What version of Shaka Player are you using: 2.1.4-debug

Can you reproduce the issue with our latest release version: unknown

Can you reproduce the issue with the latest code from master: unknown

Are you using the demo app or your own custom app: shaka-player-demo.appspot.com

If custom app, can you reproduce the issue using our demo app: N/A

What browser and OS are you using: Chrome 58 on Windows 10

What are the manifest and license server URIs: https://media.axprod.net/TestVectors/v8-MultiContent/Clear/Manifest.mpd

What did you do?

• Entered URL and hit Load.
• Change audio language to x-popmusic
• Set video quality to 360p level
• Seek around within the first period (12 minutes or approximately the first third of the content)
• Or just wait - sometimes it appears without any seeking

Issue is erratic. The above steps seem to reproduce it semi-reliably on my PC but they seem very arbitrary to me.

What did you expect to happen?

Normal playback without any funny business or errors.

What actually happened?

Invalid cue times: Infinity - Infinity
shaka.media.TextEngine.makeCue @ text_engine.js:109
shaka.media.Mp4VttParser.assembleCue_ @ mp4_vtt_parser.js:314
shaka.media.Mp4VttParser.parseVTTC_ @ mp4_vtt_parser.js:287
shaka.media.Mp4VttParser.parseMedia @ mp4_vtt_parser.js:182
(anonymous) @ text_engine.js:173
streaming_engine.js:1281 Assertion failed: Should only receive a Shaka error
(anonymous) @ streaming_engine.js:1281
streaming_engine.js:1295 (text:33) failed fetch and append: code=undefined
(anonymous) @ streaming_engine.js:1295
player.js:2470 Assertion failed: Wrong error type!
shaka.Player.onError_ @ player.js:2470
(anonymous) @ streaming_engine.js:1304
main.js:488 Player error TypeError: Cannot read property 'startTime' of null
    at shaka.media.TextEngine.<anonymous> (text_engine.js:176)
    at <anonymous>
shakaDemo.onError_ @ main.js:488
shakaDemo.onErrorEvent_ @ main.js:479
shaka.util.FakeEventTarget.dispatchEvent @ fake_event_target.js:117
shaka.cast.CastProxy.playerProxyLocalEvent_ @ cast_proxy.js:529
shaka.util.FakeEventTarget.dispatchEvent @ fake_event_target.js:117
shaka.Player.onError_ @ player.js:2473
(anonymous) @ streaming_engine.js:1304

Exploration of the code indicates that the error appears to be due to this.timescale_ being null in mp4_vtt_parser.js:184, which leads to an infinity being generated for start/end timestamps. The timescale in mdhd is 1000, so it is not clear to me why a null value exists in this variable.

[joeyparrish]

The fix for this has been cherry-picked and will be released in v2.1.5.