CSI-2 is defined by the MIPI Alliance (Mobile Industry Processor Interface). The only public information about it is from http://mipi.org/specifications/camera-interface
as the full spec is supposedly only available to their members.
As with so many things these days, there are leaked versions of it online. I am not going to publish links to it, but Google finds a draft copy of 1.01.00 from April 2009.
There is a user on the Camera Board forum (ThomasDK - viewtopic.php?f=43&t=109137&p=752709#p752709
) that has used the standard Pi camera with a Lattice FPGA CSI receive bridge. Google again produces hits for MIPI CSI-2 Transmit Bridge - Lattice Semiconductor
and MIPI CSI-2 Receive Bridge - Lattice Semiconductor
. Their website is down at the moment, but looks like it may provide everything you need for the output side. Up to you to find something to receive and decode the SDI data.
You still haven't said what you want to do with this data once you get it on the Pi. Most things are going to struggle at that sort of data rate, and you may need some data munging before being able to pass it to the video encoder.
(For other readers, this is a follow on question from this thread
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.