Add support for multiple EXT-X-MAP tags (updated)

[elv-peter]

This PR will...

Support multiple EXT-X-MAP tags. I modified #3312 work on the current master (tag v1.0.2)

Why is this Pull Request needed?

Fix #1990 (Broken playback with multiple EXT-X-MAP in fmp4 HLS). That is, this allows splicing multiple videos together with discontinuities.

Verified with https://storage.googleapis.com/gaetan/hls.js/master-fmp4-bug.m3u8 (that it cuts to the commercial and back)

Are there any points in the code the reviewer needs to double check?

Instead of having one global init segment in LevelDetails, I gave each segment/fragment a pointer to its init segment (EXT-X-MAP declares the init segment for all subsequent media segments until the next EXT-X-MAP)

Resolves issues:

#1990

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

[robwalch]

Hi @elv-peter,

I just pushed a change that resolves conflicts in stream-controller changes in v1.0.3.

I ran the functional tests locally (npm run test:func) and am seeing issues with the Apple LL-HLS fmp4 stream:
https://deploy-preview-3859--hls-js-dev.netlify.app/demo/?src=https%3A%2F%2Fll-hls-test.apple.com%2Fcmaf%2Fmaster.m3u8&demoConfig=eyJlbmFibGVTdHJlYW1pbmciOnRydWUsImF1dG9SZWNvdmVyRXJyb3IiOnRydWUsInN0b3BPblN0YWxsIjpmYWxzZSwiZHVtcGZNUDQiOmZhbHNlLCJsZXZlbENhcHBpbmciOi0xLCJsaW1pdE1ldHJpY3MiOi0xfQ==
This warning indicates that there is an issue with these changes:

[passthrough-remuxer.ts]: initSegment does not contain moov or trak boxes.

It looks like the init segment isn't being assigned properly in this case. Can you take a look?

[elv-peter]

I've been working on a fix for LL-HLS delta playlists - they may not have init segments so we have to get them from previous state - which shows improvement, but the passthrough-remuxer.ts still warns sometimes

[elv-peter]

OK, I think I fixed it. Please take a look