Andreas Eversberg
7 years ago
parent
9de121109d
commit
2a092b8cf7
@ -1,3 +1,3 @@ |
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AUTOMAKE_OPTIONS = foreign
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SUBDIRS = common anetz bnetz nmt
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SUBDIRS = common anetz bnetz nmt test
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@ -1,11 +1,21 @@ |
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typedef struct compander { |
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double step_up; |
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double step_down; |
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double envelop_c; |
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double envelop_e; |
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struct { |
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double unaffected; |
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double step_up; |
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double step_down; |
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double peak; |
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double envelope; |
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} c; |
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struct { |
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double unaffected; |
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double step_up; |
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double step_down; |
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double peak; |
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double envelope; |
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} e; |
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} compander_t; |
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void init_compander(compander_t *state, int samplerate, double attack_ms, double recovery_ms); |
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void init_compander(compander_t *state, int samplerate, double attack_ms, double recovery_ms, int unaffected_level); |
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void compress_audio(compander_t *state, int16_t *samples, int num); |
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void expand_audio(compander_t *state, int16_t *samples, int num); |
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@ -0,0 +1,12 @@ |
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AM_CPPFLAGS = -Wall -g $(all_includes)
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noinst_PROGRAMS = \
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test_compander
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test_compander_SOURCES = test_compander.c
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test_compander_LDADD = \
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$(COMMON_LA) \
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$(top_builddir)/src/common/libcommon.a \
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-lm
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@ -0,0 +1,122 @@ |
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#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/compander.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 ATTACK_MS 15.0 |
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#define RECOVERY_MS 15.0 |
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#define UNAFFECTED 10000.0 |
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static double test_frequency[3] = { 2000.0, 4000.0, 1000.0 }; |
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static int16_t samples_4db[SAMPLERATE]; |
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static int16_t samples_16db[SAMPLERATE]; |
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static int16_t samples_2db[SAMPLERATE]; |
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static int16_t samples_8db[SAMPLERATE]; |
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static int16_t samples_0db[SAMPLERATE]; |
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/* generate 2 samples: one with -4 dB, the other with -16 dB */ |
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static void generate_test_sample(double test_frequency) |
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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 = cos(2.0 * M_PI * test_frequency / (double)SAMPLERATE * i); |
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samples_4db[i] = (int)(UNAFFECTED * value * db2level(-4)); |
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samples_16db[i] = (int)(UNAFFECTED * value * db2level(-16)); |
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samples_2db[i] = (int)(UNAFFECTED * value * db2level(-2)); |
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samples_8db[i] = (int)(UNAFFECTED * value * db2level(-8)); |
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samples_0db[i] = (int)(UNAFFECTED * value); |
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} |
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} |
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static void check_level(int16_t *samples, double duration, const char *desc, double target_db) |
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{ |
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int i; |
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int last = 0, envelop = 0; |
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int up = 0; |
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double factor; |
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int when = (int)((double)SAMPLERATE + (double)SAMPLERATE * duration / 1000.0 + 0.5); |
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for (i = 0; i < when; 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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envelop = last; |
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} |
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up = 0; |
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} |
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#if 0 |
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if (i >= (SAMPLERATE-(SAMPLERATE/100)) && (i % (SAMPLERATE/(SAMPLERATE/10))) == 0) |
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printf("%s: envelop = %.4f (when=%d)\n", desc, level2db((double)envelop / UNAFFECTED), i); |
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#endif |
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last = samples[i]; |
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} |
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factor = (envelop / UNAFFECTED) / db2level(target_db); |
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printf("%s: envelop after the instance of %.1f ms is %.4f db factor =%.4f\n", desc, duration, level2db((double)envelop / UNAFFECTED), factor); |
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} |
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int main(void) |
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{ |
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compander_t cstate; |
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int16_t samples[SAMPLERATE * 2]; |
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int f; |
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init_compander(&cstate, SAMPLERATE, ATTACK_MS, RECOVERY_MS, UNAFFECTED); |
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for (f = 0; f < 3; f++) { |
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/* -16 and -4 dB */ |
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generate_test_sample(test_frequency[f]); |
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/* low to high transition */ |
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memcpy(samples, samples_16db, SAMPLERATE * 2); |
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memcpy(samples + SAMPLERATE, samples_4db, SAMPLERATE * 2); |
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compress_audio(&cstate, samples, SAMPLERATE * 2); |
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check_level(samples, ATTACK_MS, "compressor attack", -2.0); |
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/* high to low transition */ |
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memcpy(samples, samples_4db, SAMPLERATE * 2); |
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memcpy(samples + SAMPLERATE, samples_16db, SAMPLERATE * 2); |
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compress_audio(&cstate, samples, SAMPLERATE * 2); |
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check_level(samples, RECOVERY_MS, "compressor recovery", -8.0); |
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/* low to high transition */ |
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memcpy(samples, samples_8db, SAMPLERATE * 2); |
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memcpy(samples + SAMPLERATE, samples_2db, SAMPLERATE * 2); |
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expand_audio(&cstate, samples, SAMPLERATE * 2); |
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check_level(samples, ATTACK_MS, "expander attack", -4.0); |
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/* high to low transition */ |
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memcpy(samples, samples_2db, SAMPLERATE * 2); |
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memcpy(samples + SAMPLERATE, samples_8db, SAMPLERATE * 2); |
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expand_audio(&cstate, samples, SAMPLERATE * 2); |
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check_level(samples, RECOVERY_MS, "expander recovery", -16.0); |
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/* 0 DB */ |
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memcpy(samples, samples_0db, SAMPLERATE * 2); |
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memcpy(samples + SAMPLERATE, samples_0db, SAMPLERATE * 2); |
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check_level(samples, RECOVERY_MS, "unaffected level", 0.0); |
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puts(""); |
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} |
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return 0; |
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} |
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