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/*
* multiply current input I by window W (both of length Nw);
* using modulus arithmetic, fold and rotate windowed input
* into output array O of (FFT) length N according to current
* input time n
*/
void fold( float *I, float *W, int Nw, float *O, int N, int n )
{
#if 1
int i;
for ( i = 0; i < N; i++ ) O[i] = 0.;
while ( n < 0 ) n += N;
n %= N;
for ( i = 0; i < Nw; i++ ) {
O[n] += I[i]*W[i];
if ( ++n == N ) n = 0;
}
#else
int i;
for ( i = 0; i < N; i++ )
O[i] = 0.;
while ( n < 0 )
n += N;
n %= N;
for ( i = 0; i < Nw; i++ ) {
O[n] += I[i]*W[i];
if ( ++n == N )
n = 0;
}
#endif
}
/*
* input I is a folded spectrum of length N; output O and
* synthesis window W are of length Nw--overlap-add windowed,
* unrotated, unfolded input data into output O
*/
void overlapadd( float *I, int N, float *W, float *O, int Nw, int n )
{
#if 1
int i ;
while ( n < 0 ) n += N ;
n %= N ;
for ( i = 0 ; i < Nw ; i++ ) {
O[i] += I[n]*W[i] ;
if ( ++n == N ) n = 0 ;
}
#else
int i ;
while ( n < 0 )
n += N ;
n %= N ;
for ( i = 0 ; i < Nw ; i++ ) {
O[i] += I[n]*W[i] ;
if ( ++n == N )
n = 0 ;
}
#endif
}
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