midi trigger latency amount

What factors, within the app, determine the latency when triggering video?

I'm aware that the midi-interface itself will have its own latency, probably longer for wifi/bluetooth sent-midi than a hard-wired/connected-device. Also. i expect other applications running in ios may affect the latency time too (so for best performance everything else has been closed) How does the iMix app differ depending on amount of files being used in it, ie switching from one image/video to the midi-triggered video, etc.

I'm running some external hardware that plays the audio and sends a midi-trigger signal and i'm aiming for a consistent latency time with which i can sync the two devices together. I don't expect 100% results but enough to maintain lip-sync to the average audience member.

thanks