signals.c

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/*
*   DSP API - a digital signal processing library for astronomy usage
*   Copyright © 2017-2022  Ilia Platone
*
*   This program is free software; you can redistribute it and/or
*   modify it under the terms of the GNU Lesser General Public
*   License as published by the Free Software Foundation; either
*   version 3 of the License, or (at your option) any later version.
*
*   This program is distributed in the hope that it will be useful,
*   but WITHOUT ANY WARRANTY; without even the implied warranty of
*   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*   Lesser General Public License for more details.
*
*   You should have received a copy of the GNU Lesser General Public License
*   along with this program; if not, write to the Free Software Foundation,
*   Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/
 
#include "dsp.h"
 
void dsp_signals_whitenoise(dsp_stream_p stream)
{
    int k;
    for(k = 0; k < stream->len; k++) {
        stream->buf[k] = (rand() % 255) / 255.0;
    }
 
}
 
void dsp_signals_sinewave(dsp_stream_p stream, double samplefreq, double freq)
{
    freq /= samplefreq;
    double rad = 0;
    double x = 0;
    int k;
    for(k = 0; k < stream->len; k++) {
        rad += freq;
        x = rad;
        while (x > 1.0)
            x -= 1.0;
        x *= M_PI * 2;
        stream->buf[k] = sin(x);
    }
 
}
 
void dsp_signals_sawtoothwave(dsp_stream_p stream, double samplefreq, double freq)
{
    freq /= samplefreq;
    double rad = 0;
    double x = 0;
    int k;
    for(k = 0; k < stream->len; k++) {
        rad += freq;
        x = rad;
        while (x > 1.0)
            x -= 1.0;
        stream->buf[k] = (dsp_t)(32768+32767*x);
    }
 
}
 
void dsp_signals_triwave(dsp_stream_p stream, double samplefreq, double freq)
{
    freq /= samplefreq;
    double rad = 0;
    double x = 0;
    int k;
    for(k = 0; k < stream->len; k++) {
        rad += freq;
        x = rad;
        while (x > 2.0)
            x -= 2.0;
        while (x > 1.0)
            x = 2.0 - x;
        stream->buf[k] = (dsp_t)(32768+32767*x);
    }
 
}
 
void dsp_modulation_frequency(dsp_stream_p stream, double samplefreq, double freq, double bandwidth)
{
    dsp_stream_p carrier = dsp_stream_new();
    dsp_signals_sinewave(carrier, samplefreq, freq);
    double mn = dsp_stats_min(stream->buf, stream->len);
    double mx = dsp_stats_max(stream->buf, stream->len);
    double lo = mn * bandwidth * 1.5 / samplefreq;
    double hi = mx * bandwidth * 0.5 / samplefreq;
    dsp_t *deviation = (dsp_t*)malloc(sizeof(dsp_t) * stream->len);
    dsp_buffer_copy(stream->buf, deviation, stream->len);
    dsp_buffer_deviate(carrier, deviation, hi, lo);
    memcpy(stream->buf, carrier->buf, stream->len * sizeof(dsp_t));
    dsp_stream_free(carrier);
 
}
 
void dsp_modulation_amplitude(dsp_stream_p stream, double samplefreq, double freq)
{
    dsp_stream_p carrier = dsp_stream_new();
    dsp_signals_sinewave(carrier, samplefreq, freq);
    dsp_buffer_sum(stream, carrier->buf, stream->len);
    dsp_stream_free_buffer(carrier);
    dsp_stream_free(carrier);
 
}