fix(id3): cuechange event not being triggered on audio-only HLS streams

[mparisi76]

This is a proposed fix for #130. Instead of adding text-track data only to video segments, we are now adding to all segments.

One change bringing the addTextTrackData invocation outside of the conditional which checks for video buffer.

Sources:

With audio only
http://li720-23.members.linode.com/hls/audio.m3u8
With video and audio
http://li720-23.members.linode.com/hls/video.m3u8

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
• Reviewed by Two Core Contributors

[welcome]

💖 Thanks for opening this pull request! 💖

Things that will help get your PR across the finish line:

• Run npm run lint -- --errors locally to catch formatting errors earlier.
• Include tests when adding/changing behavior.
• Include screenshots and animated GIFs whenever possible.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[ldayananda]

Looks like the build is failing since this should be indented 2 more spaces (and the comment too)

[ldayananda]

One last nice to have would be to add a test!

Here's the test for video-only case: https://github.com/videojs/http-streaming/blob/master/test/mse/html.test.js#L1162

You could add another test that is audio-only be copying that test and modifying

http-streaming/test/mse/html.test.js

Line 1164 in 8f45194

let sourceBuffer = mediaSource.addSourceBuffer('video/mp2t');

to be:

let sourceBuffer = mediaSource.addSourceBuffer('video/mp2t; codecs=\"avc1.4d400d, mp4a.40.2\"');

and modifying

http-streaming/test/mse/html.test.js

Lines 1204 to 1206 in 8f45194

	sourceBuffer.transmuxer_.onmessage(createDataMessage('video', new Uint8Array(1), {
	metadata
	}));

to be:

sourceBuffer.transmuxer_.onmessage(createDataMessage('audio', new Uint8Array(1), {
  metadata
}));

Let me know if you need any help! You can run tests locally by running npm run test

[forbesjo]

Looks good to me. I would also suggest a test.

[ldayananda]

@mparisi76 I've made a PR against your branch with the test! Once that's merged into this branch I think we should be able to merge this PR into master

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉