I got this crazy idea for a half rack 12-16 points for all my ins and outs of spdif.
Is this as simple as a half rack box and some female RCA jacks? Of course I wll be using 75 ohm video rca for patching but is there more to it than that?
I've just done a simple panel with four outs and four ins. It works fine. It's just eight bulkhead mounting 75 ohm BNC socket-socket connectors on a panel.
Digital signals are quite robust, but they have the disadvantage of working perfectly right up to the point where they stop working altogether. That is, a cable with n dodgy joints will work fine, but with n+1 joints it won't. Therefore, it's sensible to minimise the number of joints, and maximise their quality. The BNC bulkhead connectors that I chose mean no internal wiring in the patchbay, and BNC helps to maintain constant impedance better than RCA so it should do a better job of preserving the signal integrity.
You need to select your cables carefully. For the fixed wiring just about any 75 ohm coax will do. For the patch leads it needs to be robust and flexible. Many 75 ohm coaxes seem to be solid core, which I think would break quickly in use. I found some stranded video coax from Van-Damme which seems to work OK. Take care when twisting a tight RCA in or out, as this will put strain on the cable. BNC is better, with its bayonet lock.
And also, Can I put a splitter on a SPDIF connection without degrading quality?
Not something I've ever tried. I wouldn't make a habit of it. But, provided the total signal degradation is below the invisible threshold, it'll probably work. The "correct" way to split SPDIF would be with a video distribution amp or similar.