• Support for acceleration
• More solid algorithm for position detection including debouncing and filtering invalid signals
• Feed pin changes from external sources

Encoder counts pulses from quadrature encoded signals, which are commonly available from rotary knobs, motor or shaft sensors and other position sensors.

http://www.pjrc.com/teensy/td_libs_Encoder.html

http://www.youtube.com/watch?v=2puhIong-cs