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// Demonstrate fdelay object to add arbitrary fractional delays.
#include <stdio.h>
#include <math.h>
#include <complex.h>
#include "liquid.h"
#define OUTPUT_FILENAME "fdelay_rrrf_example.m"
int main() {
// options
unsigned int nmax = 200; // maximum delay
unsigned int m = 12; // filter semi-length
unsigned int npfb = 10; // fractional delay resolution
unsigned int num_samples= 240; // number of samples to run
float delay =27.8; // requested delay
// create delay object and set delay
fdelay_rrrf q = fdelay_rrrf_create(nmax, m, npfb);
fdelay_rrrf_set_delay(q, delay);
fdelay_rrrf_print(q);
// generate impulse and propagate through object
float x[num_samples];
float y[num_samples];
unsigned int i;
for (i=0; i<num_samples; i++) {
// generate input
x[i] = i==0 ? 1.0f : 0.0f;
// run filter
fdelay_rrrf_push(q, x[i]);
fdelay_rrrf_execute(q, &y[i]);
}
// destroy filter object
fdelay_rrrf_destroy(q);
// estimate delay; assumes input is impulse and uses phase at
// single point of frequency estimate evaluation
float fc = 0.1f / (float)num_samples; // sufficiently small
float complex v = 0.0f;
for (i=0; i<num_samples; i++)
v += y[i] * cexpf(_Complex_I*2*M_PI*fc*i);
float delay_est = cargf(v) / (2*M_PI*fc) - (float)m;
printf("fdelay = %g (%g)\n", delay_est, delay);
// plot results to output file
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all; close all;\n");
fprintf(fid,"delay=%f; m=%u; n=%u;\n",delay,m,num_samples);
fprintf(fid,"x=zeros(1,n);\n");
fprintf(fid,"y=zeros(1,n);\n");
for (i=0; i<num_samples; i++) {
fprintf(fid,"x(%4u) = %12.4e;\n", i+1, x[i]);
fprintf(fid,"y(%4u) = %12.4e;\n", i+1, y[i]);
}
fprintf(fid,"t=0:(n-1);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(t,x,'-x','Color',[0 0.3 0.5],'LineWidth',1);\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('input');\n");
fprintf(fid," xlim([-10 10]);\n");
fprintf(fid," grid on;\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(t-m,y,'-x','Color',[0 0.3 0.5],'LineWidth',1,...\n");
fprintf(fid," [delay delay],[-0.1 1.1],'-r');\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('output');\n");
fprintf(fid," xlim([-3 3]+delay); ylim([-0.2 1.2]);\n");
fprintf(fid," grid on;\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
return 0;
}
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