Receiving Midi Time Code messages slows down my app

I noticed, that when I’m receiving MTC (midi time code) messages from another device, my cpu load in the audio process jumps up to 60-70%. I’m not even doing anything with the data yet. What’s going on in the midi callbacks that simple MTC messages bring the app to it’s knees?

I think your profiler will be able to give you a better answer than anyone here…

I guess my initial question is, if other people have observed this as well.