1. Phase is now changed proportional to the time of the bit change, if
it happens somewhere between samples. The amount of phase change per
bit is now the same for all bits, no matter how many samples
currently lay inside this bit.
2. IIR filter is removed, because it causes distortions. A cosine shape
is now used to transit between phase change of F0 to F1 and vice
versa. This limits the spectrum. This filter is optional.
