Enhancement Suggestion: add timespan(s) option

[keeyor]

This is a great tool, but unfortunately we cannot incorporate it in our project. The video process duration is prohibitive ( FHD video, typically 1 hour long).
Suggestion: since in our videos, faces appear rarely and for a few seconds, it would be great if an option existed where we could mark the time span that the faces appear, so the tool would process just a few seconds and not the entire video. This would significantly speed up the process.

Thanks for your time.