The Arduino shield can be used in both ways ?

I know that the Arduino shield can be used to send commands for a BMD camera (insert commands into SDI). Is it possible to use an Arduino shield with opposite purpose, i.e. to receive commands sent by a BMD ATEM switcher (extract commands from SDI) ?

There are a few users that done it. But it is not documented. You need to be a skilled programmer to do so. Dive deep into the BMD library and you will find a receive command. But the implementation is buggy.

It often skips a message.