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// ASCII spectrogram example for complex inputs. This example demonstrates
// the functionality of the ASCII spectrogram. A sweeping complex sinusoid
// is generated and the resulting spectral periodogram is printed to the
// screen.
#include <unistd.h> // usleep
#include <string.h>
#include <stdio.h>
#include <math.h>
#include "liquid.h"
int main() {
// options
unsigned int nfft = 64; // transform size
unsigned int num_frames = 200; // total number of frames
unsigned int msdelay = 25; // delay between transforms [ms]
float noise_floor = -40.0f; // noise floor
// initialize objects
asgramcf q = asgramcf_create(nfft);
asgramcf_set_scale(q, noise_floor+15.0f, 5.0f);
unsigned int i;
unsigned int n;
float theta = 0.0f; // current instantaneous phase
float dtheta = 0.0f; // current instantaneous frequency
float phi = 0.0f; // phase of sinusoidal frequency drift
float dphi = 0.003f; // frequency of sinusoidal frequency drift
float complex x[nfft];
float nstd = powf(10.0f,noise_floor/20.0f); // noise standard deviation
for (n=0; n<num_frames; n++) {
// generate a frame of data samples
for (i=0; i<nfft; i++) {
// complex exponential
x[i] = cexpf(_Complex_I*theta);
// add noise to signal
x[i] += nstd * (randnf() + _Complex_I*randnf()) * M_SQRT1_2;
// adjust frequency and phase
theta += dtheta;
dtheta = 0.9f*M_PI*sinf(phi) * liquid_hamming(n, num_frames);
phi += dphi;
}
// write block of samples to the spectrogram object
asgramcf_write(q, x, nfft);
// print result to screen
asgramcf_print(q);
// sleep for some time before generating the next frame
usleep(msdelay*1000);
}
asgramcf_destroy(q);
printf("done.\n");
return 0;
}
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