Nope there is no command line option, you will have to use epsxecutor or regedit.
but if you arent using epsxecutor, you aren´t able to see the key for the mdec timing or mdec activation so the solution is, use the epsxecutorOriginally posted by gerbilcannon
Nope there is no command line option, you will have to use epsxecutor or regedit.