* don't store fft values scaled by fftsize/2; that's a special requirement for the spectrogram, and other applications will not expect it -- make the spectrogram do that scaling itself * add a higher-resolution memory cache (still polar, though) as an alternative to the 16-bit compact cache * don't use the memory cache if we want rectangular coords (unless the disc cache is totally infeasible) as conversion slows it down anyway * avoid redundant rectangular -> polar -> rectangular conversion when storing values in a rectangular-mode disc cache