dashdemux: Add support for tree-like SIDX
Submitted by Sebastian Dröge
What happens here is that there is a SIDX in the very beginning (with reftype 1) that points to other SIDX distributed over the whole file. The first one directly following this initial SIDX. Each of these SIDX then points to a moof (with reftype 0).
This can also be more than 2 levels from what I understand. Also each SIDX can only point to things that are following (it can't point backwards).