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//
// cvsd_example.c
//
// Continuously-variable slope delta example, sinusoidal input.
// This example demonstrates the CVSD audio encoder interface, and
// its response to a sinusoidal input. The output distortion
// ratio is computed, and the time-domain results are written to
// a file.
//
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "cvsd_example.m"
// print usage/help message
void usage()
{
printf("cvsd_example [options]\n");
printf(" u/h : print usage\n");
printf(" n : number of samples, default: 512\n");
printf(" f : input signal frequency, default: 0.02\n");
printf(" b : cvsd param: num-bits, default: 3\n");
printf(" z : cvsd param: zeta, default: 1.5\n");
printf(" a : cvsd param: alpha, default: 0.95\n");
}
int main(int argc, char*argv[])
{
// options
unsigned int n=512; // number of samples
float fc = 0.02; // input signal frequency
unsigned int nbits=3; // number of adjacent bits to observe
float zeta=1.5f; // slope adjustment multiplier
float alpha = 0.95; // pre-/post-filter coefficient
int dopt;
while ((dopt = getopt(argc,argv,"uhn:f:b:z:a:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'n': n = atoi(optarg); break;
case 'f': fc = atof(optarg); break;
case 'b': nbits = atoi(optarg); break;
case 'z': zeta = atof(optarg); break;
case 'a': alpha = atof(optarg); break;
default:
exit(1);
}
}
// validate input
unsigned int i;
// data arrays
float x[n]; // input time series
unsigned char b[n]; // encoded bit pattern
float y[n]; // reconstructed time series
// create cvsd codecs
cvsd cvsd_encoder = cvsd_create(nbits, zeta, alpha);
cvsd cvsd_decoder = cvsd_create(nbits, zeta, alpha);
cvsd_print(cvsd_encoder);
// generate input time series
for (i=0; i<n; i++)
x[i] = sinf(2.0f*M_PI*fc*i) * liquid_hamming(i,n);
// encode time series
for (i=0; i<n; i++)
b[i] = cvsd_encode(cvsd_encoder, x[i]);
// compute reconstructed time series, RMS error
float rmse=0.0f;
for (i=0; i<n; i++) {
y[i] = cvsd_decode(cvsd_decoder, b[i]);
printf("%1u ", b[i]);
if ( ((i+1)%32) == 0 )
printf("\n");
float e = x[i]-y[i];
rmse += e*e;
}
rmse = sqrtf(rmse/n);
printf("\n");
printf("signal/distortion: %8.2f dB\n", -20*log10f(rmse));
// destroy cvsd objects
cvsd_destroy(cvsd_encoder);
cvsd_destroy(cvsd_decoder);
//
// export results to file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all\n");
fprintf(fid,"close all\n");
fprintf(fid,"n=%u;\n", n);
fprintf(fid,"x=zeros(1,n);\n");
fprintf(fid,"y=zeros(1,n);\n");
for (i=0; i<n; i++) {
fprintf(fid,"x(%3u) = %12.4e;\n", i+1, x[i]);
fprintf(fid,"y(%3u) = %12.4e;\n", i+1, y[i]);
}
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(1:n,x,1:n,y);\n");
fprintf(fid,"xlabel('time [sample index]');\n");
fprintf(fid,"ylabel('signal');\n");
fprintf(fid,"legend('audio input','cvsd output',1);\n");
// close debug file
fclose(fid);
printf("results wrtten to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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