Thanks, I don't understand too.
I realised that I can see the latence between midi In and midi Out in Ableton (the two square on the top right, between "key" button and "midi" button. When I launch a simple note, the yellow square (midi In) and the blue square (midi out) get colored in the same time. But when I send midi information about a potentiometer or a fader, the blue square light up after the yellow one. So I think the latency is there.
The odd thing is that when I move the fader with my mouse and not with my midi controller, there is no latency ! I tried with 3 different Midi controller and two computers, I have the same issue
So, it's clearly not a Resolume problem, so it's off topic here, sorry !!
(but if everyone got an idea, let me know )