Segments metadata track is shown when changing source

[johnbyers]

Description

If you had captions on, and then change the video source, you get some weird text on the screen. The guys on videojs slack thought it was the segments metadata track.

Steps to reproduce

1. Visit the VHS test page at https://videojs.github.io/http-streaming/
2. Play the video, choosing the very bottom closed caption track, "cc1". (Not sure what language it is for, but the captions show English)
3. Reset the player's source by clicking the "Load" button again.
4. Play the video, and see the weird text/json

Results

Expected

No captions after changing source.

Actual

Even though closed captions are set to "off" after switching the source, this appears as a caption over the video:
{"bandwidth":915905,"resolution":{"width":960,"height":540},"codecs":"mpra.40.2,avc1.4d401f","byteLength":1046972,"uri":"https://d2zihajmogu5jn.cloudfront.net/bipbop-advanced/gear3/main.ts","timeline":0,"playlist":"gear3/prog_index.m3u8","start":9.976644444444446,"end":19.91992222222223}

Error output

Additional Information

versions

videojs

I've seen it in 7.2.2 and 7.2.4

browsers

Chrome, Firefox, and IE11.
Edge doesn't even show captions.
Mobile Safari doesn't show that bottom "CC" caption option, so it doesn't seem to have the problem.

OSes

Microsoft Windows 10

plugins

None

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[gkatsev]

Ooh, thanks for the reproducible test case!

[ldayananda]

From taking the quickest of looks at this, I think it's because userPref.language and track.language(for the metadata-track) are both '' here:

video.js/src/js/tracks/text-track-display.js

Line 154 in 6bff3ce

userPref.language === track.language) {

We should probably ensure that text-track-display completely ignores non-visible track types

[ldayananda]

It might also make sense to clear the TextTrackList queue on source changes too?

https://github.com/videojs/video.js/blame/8c92cbfb3e98259999224d5dd7778f35dfe1cab7/src/js/tracks/text-track-list.js#L31

[gkatsev]

clearing the event queue makes sense.
We should update the preselectTrack method to ignore when language is the empty string and also ignore tracks that are chapters or metadata

[johnbyers]

What is special about that "cc1" caption? All the others have a language, but that one just says "cc1". Is there something different about it?

[gkatsev]

cc1 is the first caption track for 608 captions which live inside the video data. Not sure if that has language data but we should consider setting one for it as well.

[johnbyers]

That is interesting, I thought we were using WebVTT captions in our project, I guess they have turned into 608 captions

[gkatsev]

It looks like any caption without a language would trigger this issue.

[gkatsev]

I have a fix for this in #5556