Add support for multiple EXT-X-MAP tags

[erkreutzer]

This PR will...

Support multiple EXT-X-MAP tags (a slightly updated version of #2279)

Why is this Pull Request needed?

To fix #1990 and support playlists that have multiple EXT-X-MAP tags.

I've verified with some private streams and also using the demo stream from the original issue (~12 seconds time offset): https://storage.googleapis.com/gaetan/hls.js/master-fmp4-bug.m3u8

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

Per the old PR there was a comment regarding keeping the levelDetails.initSegment property up to date. I've addressed what I believe the feedback to be, but may have missed the intent of the comment.

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

[Sylvain228]

Hello, here is a sliding window m3u8 which contains new EXT-X-MAP (so it includes 2) after every discontinuity (about every 3 to 4 minutes)
https://ireplay.tv/pausing/video.m3u8

[robwalch]

Hello, here is a sliding window m3u8 which contains new EXT-X-MAP (so it includes 2) after every discontinuity (about every 3 to 4 minutes)

Looks OK to me. Is it supposed to be video-only?
https://deploy-preview-3312--hls-js-dev.netlify.app/demo/?src=https%3A%2F%2Fireplay.tv%2Fpausing%2Fvideo.m3u8&demoConfig=eyJlbmFibGVTdHJlYW1pbmciOnRydWUsImF1dG9SZWNvdmVyRXJyb3IiOnRydWUsImR1bXBmTVA0IjpmYWxzZSwibGV2ZWxDYXBwaW5nIjotMSwibGltaXRNZXRyaWNzIjotMX0=

There is no planned release date for v0.15.0. I can merge this but would very much like to see the same/similar changes made and tested against master/latest v1 rc.

[Sylvain228]

Yes, this stream is video-only. Looking forward to having this fix in 1.0 to get fMP4 ad insertion support

[elv-peter]

@robwalch @erkreutzer How to move this along? A new PR against master?

[robwalch]

Yes. This PR surpassed the earlier one against master, but 0.15 is on-hold indefinitely. Merging this and porting the changes to head would be a lot for me, especially while tackling regressions and responding to incoming issues.

A new PR against master@v1.0.1+ with sample streams would go a long way to getting this into an upcoming release sooner.

[elv-peter]

@robwalch Alright I've got something in progress here that seems to work so far here: https://github.com/elv-peter/hls.js/tree/v1.0.1/bugfix/multi-ext-x-map-init. I temporarily commented out some code that loads a SIDX URL. Do you know what SidxRequest stuff is intended to do? It seems like it only gets there if MP4 fragments are found without an init, which seems a little strange.

[elv-peter]

Should be able to close this now