[Pierre-Marie Baty]

It's the Shannon theorem...

Any information digitally encoded that is to be used without loss has to be sampled at TWICE the sampling rate of the system using it.

This is to prevent signal loss due to filtering.

That's why our digital audio is sampled at 44kHz, even if the human ear rarely goes beyond 20kHz. That's also why the PAL TV standard goes at 30 fps while the eye samples at 15...

On some LCD monitors the LC latency induces a form of filtering between two frames ; that's why I have been able to play CS at 15 fps without noticing much frame skipping. On CRT monitors though, it is different and I would probably have needed 30 fps to play correctly. Anyhow, above this value is luxe only...