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#include "pv.h"
/*
* oscillator bank resynthesizer for phase vocoder analyzer
* uses sum of N+1 cosinusoidal table lookup oscillators to
* compute I (interpolation factor) samples of output O
* from N+1 amplitude and frequency value-pairs in C;
* frequencies are scaled by P
*/
oscbank( C, N, lpcoef, npoles, R, Nw, I, P, O )
float C[], lpcoef[], O[], P ; int N, Nw, npoles, R, I ;
{
static int NP, L = 8192, first = 1 ;
static float Iinv, *lastamp, *lastfreq, *index, *table ;
static float Pinc, ffac ;
int amp, freq, n, chan ;
float a0, lpamp() ;
/*
* FIRST TIME ONLY: allocate memory to hold previous values
* of amplitude and frequency for each channel, the table
* index for each oscillator, and the table itself; also
* compute constants
*/
if ( first ) {
float TWOPIoL = TWOPI/L, tabscale ;
first = 0 ;
fvec( lastamp, N+1 ) ;
fvec( lastfreq, N+1 ) ;
fvec( index, N+1 ) ;
fvec( table, L ) ;
tabscale = npoles ? 2./Nw : ( Nw >= N ? N : 8*N ) ;
for ( n = 0 ; n < L ; n++ )
table[n] = tabscale*cos( TWOPIoL*n ) ;
Iinv = 1./I ;
Pinc = P*L/R ;
ffac = P*PI/N ;
if ( P > 1. )
NP = N/P ;
else
NP = N ;
}
/*
* for each channel, compute I samples using linear
* interpolation on the amplitude and frequency
* control values
*/
for ( chan = npoles ? P : 0 ; chan < NP ; chan++ ) {
register float a, ainc, f, finc, address ;
freq = ( amp = ( chan << 1 ) ) + 1 ;
if ( C[amp] < synt ) /* skip the little ones */
continue ;
C[freq] *= Pinc ;
finc = ( C[freq] - ( f = lastfreq[chan] ) )*Iinv ;
/*
* if linear prediction specified, REPLACE phase vocoder amplitude
* measurements with linear prediction estimates
*/
if ( npoles ) {
if ( f == 0. )
C[amp] = 0. ;
else
C[amp] = lpamp( chan*ffac, lpcoef[0], lpcoef, npoles ) ;
}
ainc = ( C[amp] - ( a = lastamp[chan] ) )*Iinv ;
address = index[chan] ;
/*
* accumulate the I samples from each oscillator into
* output array O (initially assumed to be zero);
* f is frequency in Hz scaled by oscillator increment
* factor and pitch (Pinc); a is amplitude;
*/
for ( n = 0 ; n < I ; n++ ) {
O[n] += a*table[ (int) address ] ;
address += f ;
while ( address >= L )
address -= L ;
while ( address < 0 )
address += L ;
a += ainc ;
f += finc ;
}
/*
* save current values for next iteration
*/
lastfreq[chan] = C[freq] ;
lastamp[chan] = C[amp] ;
index[chan] = address ;
}
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.