SegmentBase and MP4 direct play CENC streaming

[choyakawa]

It seems that only MPD Representation profiles in SegmentTemplate format was implemented.

SegmentBase is somehow not good for a HLS conversion, so MP4 direct streaming with CENC decryption - range header handled - init segment cached separately - would make things easier, or can be played in so-called single (MP4) file HLS playlist - dash.js and some advanced players may work with it.

Or at least, we can still take advantage of decrypted MPD manifest & playlists with direct streaming.