The number of FFTs is calculated with the following formula:

  guint nfft = 2 * bands - 2;

nfft is passed to gst_fft_f32_new() as the len argument and is of type
unsigned integer. This method required that len is at leas 1, then
maximum G_MAXINT, as other values would be negative. If we extrapolate
from the formula above it means we need "bands" to be between 2 and
((guint)G_MAXINT + 2) / 2).

https://bugzilla.gnome.org/show_bug.cgi?id=744213