Vibrato in PCM audio (fixed!)

vibrato.py

#-*- coding: utf8 -*-
import numpy as n, pylab as p, scikits.audiolab as a

fa=44100 # sample rate
Dv=2048 # length of the table
fv=6. # vibrato frequency
nu=.2 # depth in semitones
f=440. # freq of the sound itself


x=n.linspace(0,2*n.pi,Dv,endpoint=False)
tabv=n.sin(x) # sin table

ii=n.arange(fa * 2) # 2 seconds

gv=n.array(ii*fv*float(Dv)/fa, n.int) # indexes of the vibrato pattern
tv=tabv[gv%Dv]*nu # instant semitones deviation for each PCM sample

fi=f*(  2.**(  tv/12.  )   ) # instant freq in Hz of the sound

gi=n.array( ii * fi * (Dv/float(fa)  ) , n.int ) % Dv # indexes of the sound itself in the LUT
ti=tabv[gi]
a.wavwrite(ti,"vibrato.wav",fa)

ff=n.ones(ii.shape[0])*f
gi=n.array(  ii * (Dv/float(fa)) * ff  , n.int ) % Dv
t=tabv[ gi ]
a.wavwrite(t,"original.wav",fa)