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+#include "fftease.h" /* S is a spectrum in rfft format, i.e., it contains N real values arranged as real followed by imaginary values, except for first two values, which are real parts of 0 and Nyquist frequencies; convert first changes these into N/2+1 PAIRS of magnitude and phase values to be stored in output array C; the phases are then unwrapped and successive phase differences are used to compute estimates of the instantaneous frequencies for each phase vocoder analysis channel; decimation rate D and sampling rate R are used to render these frequency values directly in Hz. */ void convert(float *S, float *C, int N2, float *lastphase, float fundamental, float factor ) { float phase, phasediff; int real, imag, amp, freq; float a, b; int i; /* float myTWOPI, myPI; */ /* double sin(), cos(), atan(), hypot();*/ /* myTWOPI = 8.*atan(1.); myPI = 4.*atan(1.); */ for ( i = 0; i <= N2; i++ ) { imag = freq = ( real = amp = i<<1 ) + 1; a = ( i == N2 ? S[1] : S[real] ); b = ( i == 0 || i == N2 ? 0. : S[imag] ); C[amp] = hypot( a, b ); if ( C[amp] == 0. ) phasediff = 0.; else { phasediff = ( phase = -atan2( b, a ) ) - lastphase[i]; lastphase[i] = phase; while ( phasediff > PI ) phasediff -= TWOPI; while ( phasediff < -PI ) phasediff += TWOPI; } C[freq] = phasediff*factor + i*fundamental; } } \ No newline at end of file