44 lines
1.3 KiB
Python
44 lines
1.3 KiB
Python
|
import numpy as np
|
||
|
|
|
||
|
|
# fast cepstrum and inverted fast cepstrum
|
||
|
|
fcs = lambda s: np.fft.ifft(np.log(np.fft.fft(s)))
|
||
|
|
ifcs = lambda s: np.fft.fft(np.exp(np.fft.ifft(s)))
|
||
|
|
|
||
|
|
# magnitude
|
||
|
|
mcs = lambda s: (np.abs(np.fft.ifft(np.log(np.abs(np.fft.fft(s))**2)))**2)[:len(s)//2]
|
||
|
|
|
||
|
|
def clipdb(s, cutoff=-100):
|
||
|
|
as_ = np.abs(s)
|
||
|
|
mas = np.max(as_)
|
||
|
|
if mas == 0 or cutoff >= 0:
|
||
|
|
return s
|
||
|
|
thresh = mas*10**(cutoff/20)
|
||
|
|
return np.where(as_ < thresh, thresh, s)
|
||
|
|
|
||
|
|
def fold(r):
|
||
|
|
# via https://ccrma.stanford.edu/~jos/fp/Matlab_listing_fold_m.html
|
||
|
|
# Fold left wing of vector in "FFT buffer format" onto right wing
|
||
|
|
# J.O. Smith, 1982-2002
|
||
|
|
n = len(r)
|
||
|
|
if n < 3:
|
||
|
|
rw = r
|
||
|
|
elif n % 2 == 1:
|
||
|
|
nt = (n + 1)//2
|
||
|
|
rf = r[1:nt] + conj(r[-1:nt-1:-1])
|
||
|
|
rw = np.hstack((r[0], rf, np.zeros(n-nt)))
|
||
|
|
else:
|
||
|
|
nt = n//2
|
||
|
|
rf = np.hstack((r[1:nt], 0)) + np.conj(r[-1:nt-1:-1])
|
||
|
|
rw = np.hstack((r[0], rf, np.zeros(n-nt-1)))
|
||
|
|
return rw
|
||
|
|
|
||
|
|
def minphase(s, os=True):
|
||
|
|
# via https://ccrma.stanford.edu/~jos/fp/Matlab_listing_mps_m.html
|
||
|
|
if os:
|
||
|
|
s = np.hstack((s, np.zeros(len(s))))
|
||
|
|
cepstrum = np.fft.ifft(np.log(clipdb(np.fft.fft(s), -100)))
|
||
|
|
signal = np.real(np.fft.ifft(np.exp(np.fft.fft(fold(cepstrum)))))
|
||
|
|
if os:
|
||
|
|
signal = signal[:len(signal)//2]
|
||
|
|
return signal
|