51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
#include "loudness.h"
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#include "common.h"
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#include <math.h>
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loudness_processor loudness_r;
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loudness_processor loudness_l;
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void _loudness_set_volume(loudness_processor *p, float volume) {
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float gain = -(volume - config.loudness_reference_volume_db) * 0.5;
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if (gain < 0)
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gain = 0;
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float Fc = 10.0;
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float Q = 0.5;
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// Formula from http://www.earlevel.com/main/2011/01/02/biquad-formulas/
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float Fs = 44100.0;
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float K = tan(M_PI * Fc / Fs);
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float V = pow(10.0, gain / 20.0);
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float norm = 1 / (1 + 1 / Q * K + K * K);
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p->a0 = (1 + V / Q * K + K * K) * norm;
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p->a1 = 2 * (K * K - 1) * norm;
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p->a2 = (1 - V / Q * K + K * K) * norm;
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p->b1 = p->a1;
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p->b2 = (1 - 1 / Q * K + K * K) * norm;
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}
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float loudness_process(loudness_processor *p, float i0) {
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float o0 = p->a0 * i0 + p->a1 * p->i1 + p->a2 * p->i2 - p->b1 * p->o1 - p->b2 * p->o2;
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p->o2 = p->o1;
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p->o1 = o0;
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p->i2 = p->i1;
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p->i1 = i0;
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return o0;
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}
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void loudness_set_volume(float volume) {
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float gain = -(volume - config.loudness_reference_volume_db) * 0.5;
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if (gain < 0)
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gain = 0;
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debug(2, "Volume: %.1f dB - Loudness gain @10Hz: %.1f dB", volume, gain);
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_loudness_set_volume(&loudness_l, volume);
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_loudness_set_volume(&loudness_r, volume);
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}
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