TypeError: cue.scaleCue is not a function

[l1bbcsg]

Environment

• Dash.js version: 4.1.0

Steps to reproduce

Any vtt text track that starts at 0 timestamp (or probably close to it) causes Dash.js to throw an uncaught exception. Playback is not affected, however.

Example of such track:

WEBVTT
Language: en

00:00:00.000 --> 00:00:05.000
Oh

It could be embedded into any manifest as follows:

    <AdaptationSet contentType="text" lang="en" mimeType="text/vtt">
      <Representation id="subtitles">
        <BaseURL>subtitles.vtt</BaseURL>
      </Representation>
    </AdaptationSet>

It seems scaleCue is monkey patched only for TTML tracks, but is invoked for VTT tracks as well at start.
If a text track happens to have activeCues by the time loadedmetada event is fired the error happens.

Observed behavior

Video plays normally

Console output

Uncaught TypeError: cue.scaleCue is not a function
    at Object.checkVideoSize (TextTracks.js:283)
    at Object.onMetadataLoaded (TextTracks.js:164)
    at EventBus.js:124
    at Array.forEach (<anonymous>)
    at Object.trigger (EventBus.js:124)
    at HTMLVideoElement._onPlaybackMetaDataLoaded (PlaybackController.js:550)

Expected behavior

No uncaught exceptions

[bbert]

@l1bbcsg do you have a test stream to reproduce the issue?

[bbert]

@l1bbcsg I managed to reproduce.
Indeed the patch was applied not only for TTML tracks on loadedmetadata event handler
Did fix in PR #3791

[dsilhavy]

@l1bbcsg Can you please confirm that #3791 did fix your issue

[l1bbcsg]

Yep, no errors with http://reference.dashif.org/dash.js/nightly/dist/dash.all.debug.js

Thanks!