What is the difference between a regular and adaptive low pass filter?

Question

I've noticed in Apple's accelerometer sample code they use both regular and adaptive low pass filters, what is the difference?

Answer 1

They are both IIR 1st order low pass filters (simple, and laggy in responsiveness when compared with other DSP techniques). The adaptive filter switches to a higher frequency roll-off (and thus becomes even less smoothing but more responsive) for larger accelerations.

There are other higher quality (and more complicated) DSP filtering techniques for motion sensing often used by portable game developers.