Round input MIDIs to 48 (or 24?) ticks per beat

[mtolly]

Probably the input MIDI tracks should be rounded to 48 ticks per beat, because this is the natural resolution of the Red/Blue engine. A note/rest length is (number of ticks) * (notetype speed) / 48 of a beat. Input MIDIs are usually stored at a resolution of 480, 960, or something similar, so this would allow events in them to be one tick off with no problems.

This should be done with discretize from the event-list library to avoid compounding rounding errors.

[mtolly]

As per #9, 48 ticks per beat may not be safe. A resolution of 24 ensures that all durations can be translated correctly, but at the cost of not allowing some otherwise legal durations. 24 should be fine though; none of the game's built-in songs require a 48 resolution, and 24 still gives you plenty of possible subdivisions (for example, 32nd notes and 32nd note triplets are both fine).