logmeter.h

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/*
 * Copyright (C) 2016 Paul Davis <paul@linuxaudiosystems.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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.
 */
 
#pragma once
 
#include "ardour/dB.h"
 
#if 1
static inline float
_log_meter (float power, double lower_db, double upper_db, double non_linearity)
{
        return (power < lower_db ? 0.0 : pow((power-lower_db)/(upper_db-lower_db), non_linearity));
}
 
static inline float
alt_log_meter (float power)
{
        return _log_meter (power, -192.0, 0.0, 8.0);
}
#endif
 
/* prototypes - avoid compiler warning */
static inline float log_meter (float db);
static inline float meter_deflect_ppm (float);
static inline float meter_deflect_din (float);
static inline float meter_deflect_nordic (float);
static inline float meter_deflect_vu (float);
static inline float meter_deflect_k (float, float);
 
 
 
static inline float
log_meter (float db)
{
         float def = 0.0f; /* Meter deflection %age */
 
         if (db < -70.0f) {
                 def = 0.0f;
         } else if (db < -60.0f) {
                 def = (db + 70.0f) * 0.25f;
         } else if (db < -50.0f) {
                 def = (db + 60.0f) * 0.5f + 2.5f;
         } else if (db < -40.0f) {
                 def = (db + 50.0f) * 0.75f + 7.5f;
         } else if (db < -30.0f) {
                 def = (db + 40.0f) * 1.5f + 15.0f;
         } else if (db < -20.0f) {
                 def = (db + 30.0f) * 2.0f + 30.0f;
         } else if (db < 6.0f) {
                 def = (db + 20.0f) * 2.5f + 50.0f;
         } else {
                 def = 115.0f;
         }
 
         /* 115 is the deflection %age that would be
            when db=6.0. this is an arbitrary
            endpoint for our scaling.
         */
 
         return def/115.0f;
}
 
static inline float
log_meter0dB (float db)
{
        float def = 0.0f; /* Meter deflection %age */
 
         if (db < -70.0f) {
                 def = 0.0f;
         } else if (db < -60.0f) {
                 def = (db + 70.0f) * 0.25f;
         } else if (db < -50.0f) {
                 def = (db + 60.0f) * 0.5f + 2.5f;
         } else if (db < -40.0f) {
                 def = (db + 50.0f) * 0.75f + 7.5f;
         } else if (db < -30.0f) {
                 def = (db + 40.0f) * 1.5f + 15.0f;
         } else if (db < -20.0f) {
                 def = (db + 30.0f) * 2.0f + 30.0f;
         } else if (db < 0.0f) {
                 def = (db + 20.0f) * 2.5f + 50.0f;
         } else {
                 def = 100.0f;
         }
        return def/100.0f;
}
 
static inline float
meter_deflect_ppm (float db)
{
        if (db < -30) {
                // 2.258 == ((-30 + 32.0)/ 28.0) / 10^(-30 / 20);
                return (dB_to_coefficient(db) * 2.258769757f);
        } else {
                const float rv = (db + 32.0f) / 28.0f;
                if (rv < 1.0) {
                        return rv;
                } else {
                        return 1.0;
                }
        }
}
 
static inline float
meter_deflect_din (float db)
{
        float rv = dB_to_coefficient(db);
        rv = sqrtf (sqrtf (2.3676f * rv)) - 0.1803f;
        if (rv >= 1.0) {
                return 1.0;
        } else {
                return (rv > 0 ? rv : 0.0);
        }
}
 
static inline float
meter_deflect_nordic (float db)
{
        if (db < -60) {
                return 0.0;
        } else {
                const float rv = (db + 60.0f) / 54.0f;
                if (rv < 1.0) {
                        return rv;
                } else {
                        return 1.0;
                }
        }
}
 
static inline float
meter_deflect_vu (float db)
{
        const float rv = 6.77165f * dB_to_coefficient(db);
        if (rv > 1.0) return 1.0;
        return rv;
}
 
static inline float
meter_deflect_k (float db, float krange)
{
        db+=krange;
        if (db < -40.0f) {
                return (dB_to_coefficient(db) * 500.0f / (krange + 45.0f));
        } else {
                const float rv = (db + 45.0f) / (krange + 45.0f);
                if (rv < 1.0) {
                        return rv;
                } else {
                        return 1.0;
                }
        }
}