feat: add sidx information to segment base playlists

[ldayananda]

Attempted fix for videojs/http-streaming#162.

Status

This appears to be working on the issue source.

Changes proposed:

• expose sidxMapping option on the parse method to allow modifying a complete master playlist with metadata from a parsed sidx box
• attach a sidx property with byteRange references to manifest objects generated with SegmentBase. This applies to both video and audio playlists
• replace media playlist segments with those generated from sidx.references when the sidxMapping option is given

Sources

{ 
  src: "https://dash.akamaized.net/dash264/TestCases/10a/1/iis_forest_short_poem_multi_lang_480p_single_adapt_aaclc_sidx.mpd",
  type: "application/dash+xml"
}

To do

• additional testing
• add unit tests

[ldayananda]

Requires #43 (merged)

[ldayananda]

This appears to be working to some degree. Will do more testing next week.

[gkatsev]

Another test stream that works: http://download.tsi.telecom-paristech.fr/gpac/DASH_CONFORMANCE/TelecomParisTech/mp4-onDemand/mp4-onDemand-mpd-AV.mpd https://gpac.wp.imt.fr/2012/02/23/dash-sequences/

[gkatsev]

This stream fails: http://yt-dash-mse-test.commondatastorage.googleapis.com/media/car-20120827-manifest.mpd, from http://dash-mse-test.appspot.com/media.html
Something about not being able to set discontinuity on a segment.

[gkatsev]

So, the youtube car stream has something that is potentially against the spec, it has two representations with the same id. Both Shaka and Youtube test player work.

Realized that if I do a null check they work fine.

Also, the two comments above should've been in the VHS repo.

[ldayananda]

I think the null check makes sense since the playlist.segments would be empty on the first time through the parser for a sidx playlist because of this change

https://github.com/videojs/mpd-parser/pull/41/files#diff-09d49417dae2795e5eab7a01f6db04daR56

Though I'm surprised I didn't run into it earlier