This is my first post, so please be gentle!

I have run through dozens of archive entries, but can't find an answer to the following questions:
1. Where in the source code does VLC manage ISO 13818-1 (MPEG-2 TS) PMT descriptors?
2. Is there a (simple) mechanism for implementing preprocessing of an MPEG-2 stream (e.g. from a Kasenna MB server) _before_ it gets demuxed?
Basically, I would like to implement a mechanism for handling of Conditional Access descriptors, ECMs, EMMs, Transport_scrambling_control, etc - but have no idea where to begin looking! `grep -ir descriptor *` in the source tree doesn't find me anything of meaning, so I am a bit stuck!
I believe that VLC uses libdvbpsi to manage the PAT/PMT entries in a stream, but I can't even see any calls into the library made by the VLC code...
If anyone has a clue where I can start on this, it would be greatly appreciated!