Arduino implementation of Incremental encoder speed calculation using mixed time and frequency measurement Mixed time and frequency approach of velocity calucaiton. The main benefit of this approach is that has very low error for both low and high speed calculation using the incremental encoder

This approach was introduced in the paper:

"An embedded system for position and speed measurement adopting incremental encoders." by Petrella, Roberto, and Marco Tursini. IEEE Transactions on industry applications 44.5 (2008): 1436-1444.