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https://github.com/radio95-rnt/fm95.git
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74 lines
2.6 KiB
C
74 lines
2.6 KiB
C
#include "bs412.h"
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#define BS412_TIME 60
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#define ENABLE_TIME 50
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#define CLAMP(x, lo, hi) (((x) < (lo)) ? (lo) : ((x) > (hi) ? (hi) : (x)))
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inline float dbr_to_deviation(float dbr) {
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return 19000.0f * sqrtf(pow(10.0, dbr / 10.0));
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}
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// #define SQRT19000 180499999.99999997f // (19000 / sqrt(2)) * 19000 / sqrt(2)
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// inline float deviation_to_dbr(float deviation) {
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// if (deviation < 1e-6f) return -100.0f;
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// return 10*log10f((deviation*deviation)/SQRT19000);
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// }
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void init_bs412(BS412Compressor* comp, uint32_t mpx_deviation, float target_power, float attack, float release, float max_gain, uint32_t sample_rate) {
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comp->mpx_deviation = mpx_deviation;
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comp->avg_power = 0.0f;
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comp->alpha = 1.0f / (BS412_TIME * sample_rate);
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comp->sample_rate = sample_rate;
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comp->attack = expf(-1.0f / (attack * sample_rate));
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comp->release = expf(-1.0f / (release * sample_rate));
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comp->target = dbr_to_deviation(target_power) * dbr_to_deviation(target_power);
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comp->gain = 1.0f;
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comp->can_compress = 0;
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comp->second_counter = 0;
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comp->max_gain = max_gain;
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#ifdef BS412_DEBUG
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debug_printf("Initialized MPX power measurement with sample rate: %d\n", sample_rate);
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#endif
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}
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float bs412_compress(BS412Compressor* comp, float audio, float sample_mpx, float* mpx_power) {
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float combined = audio + sample_mpx;
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float output_sample = (audio * comp->gain) + sample_mpx;
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comp->avg_power += comp->alpha * ((output_sample * output_sample * comp->mpx_deviation * comp->mpx_deviation) - comp->avg_power);
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if(comp->sample_counter > comp->sample_rate) {
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comp->sample_counter = 0;
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if(comp->can_compress == 0) comp->second_counter++;
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}
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if(comp->can_compress == 0 && comp->second_counter > ENABLE_TIME) {
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#ifdef BS412_DEBUG
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debug_printf("Can compress.\n");
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#endif
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comp->can_compress = 1;
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comp->second_counter = 0;
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}
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float safe_power = fmaxf(comp->avg_power, 1e-12f);
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float target_gain = sqrtf(comp->target / safe_power);
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if (comp->avg_power > comp->target) comp->gain = comp->attack * comp->gain + (1.0f - comp->attack) * target_gain;
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else comp->gain = comp->release * comp->gain + (1.0f - comp->release) * target_gain;
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comp->gain = CLAMP(comp->gain, 0.0f, comp->max_gain);
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float power_after_gain = comp->avg_power * comp->gain * comp->gain;
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if(power_after_gain > comp->target && comp->avg_power < comp->target) {
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float reduction = sqrtf(comp->target / power_after_gain);
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comp->gain = CLAMP(comp->gain * reduction, 0.01f, comp->max_gain);
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}
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comp->sample_counter++;
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if(mpx_power != NULL) *mpx_power = deviation_to_dbr(avg_power);
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if(comp->can_compress) return output_sample;
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return combined;
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}
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