76 lines
1.6 KiB
C
76 lines
1.6 KiB
C
#include <stdio.h>
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#include <stdint.h>
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#include <math.h>
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#include <string.h>
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#include "../common/emphasis.h"
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#include "../common/debug.h"
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#define level2db(level) (20 * log10(level))
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#define db2level(db) pow(10, (double)db / 20.0)
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#define SAMPLERATE 48000
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#define DEVIATION 8000.0
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static double test_freq[] = { 25, 50, 100, 150, 200, 250, 300, 350, 400, 500, 1000, 2000, 4000, 0 };
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static void check_level(int16_t *samples, double freq, const char *desc)
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{
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int i;
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int last = 0, envelope = 0;
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int up = 0;
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for (i = 0; i < SAMPLERATE; i++) {
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if (last < samples[i]) {
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up = 1;
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} else if (last > samples[i]) {
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if (up) {
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if (last > envelope)
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envelope = last;
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}
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up = 0;
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}
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last = samples[i];
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}
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printf("%s: f = %.0f envelop = %.4f\n", desc, freq, level2db((double)envelope / DEVIATION));
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}
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static void gen_samples(int16_t *samples, double freq)
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{
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int i;
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double value;
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for (i = 0; i < SAMPLERATE; i++) {
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value = sin(2.0 * M_PI * freq / (double)SAMPLERATE * (double)i);
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samples[i] = value * DEVIATION;
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}
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}
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int main(void)
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{
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emphasis_t estate;
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int16_t samples[SAMPLERATE];
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int i;
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debuglevel = DEBUG_DEBUG;
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printf("1000 Hz shall be close to 0 dB, that is no significant change in volume.\n\n");
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init_emphasis(&estate, SAMPLERATE);
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for (i = 0; test_freq[i]; i++) {
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gen_samples(samples, test_freq[i]);
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pre_emphasis(&estate, samples, SAMPLERATE);
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check_level(samples, test_freq[i], "pre-emphasis");
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}
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/* generate sweep 0..4khz */
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for (i = 0; test_freq[i]; i++) {
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gen_samples(samples, test_freq[i]);
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de_emphasis(&estate, samples, SAMPLERATE);
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check_level(samples, test_freq[i], "de-emphasis");
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}
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return 0;
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}
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