Fix for pssh box element precedence issue [DRM] - Issue #2249
Created by: siropeich
This PR attempts to fix the pssh box element precedence issue as set by DASH-IF IOP guidelines:
7.7.3. Other Content Protections Constraints In the case where the ‘pssh‘ box element is present in the MPD and in the Initialization Segment, the ‘pssh‘ box element in the MPD SHALL take precedence, because the parameters in the MPD will be processed first, are easier to update, and can be assumed to be up to date at the time the MPD is fetched.
Also, allows reloading of the key system on manifest update, which was disabled.
Fixes #2249 (closed)
NOTE: not a DRM expert myself, feedback will be very welcome.