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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
Sonic Visualiser
An audio file viewer and annotation editor.
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. See the file
COPYING included with this distribution for more information.
*/
#ifndef SV_AUDIO_LEVEL_H
#define SV_AUDIO_LEVEL_H
namespace sv {
/**
* AudioLevel converts audio sample levels between various scales:
*
* - dB values (-inf -> 0dB)
*
* - floating-point values (-1.0 -> 1.0) such as used for nominal
* voltage in floating-point WAV files
*
* - integer values intended to correspond to pixels on a fader
* or level scale.
*/
class AudioLevel
{
public:
static const double DB_FLOOR;
enum class Scale {
Sigmoid, // -80 -> +12 dB (sqrt) - play gain controls
IEC268Meter, // -70 -> 0 dB (piecewise)
IEC268MeterPlus, // -70 -> +10 dB (piecewise)
Preview // -80 -> 0 dB (sqrt) - meter-scale waveforms
};
enum class Quantity {
Power,
RootPower
};
/** Convert a voltage or voltage-like value (a RootPower quantity)
* to a dB value relative to reference +/-1.0.
*
* This is 20 * log10(abs(v)).
*/
static double voltage_to_dB(double v);
/** Convert a dB value relative to reference +1.0V to a voltage.
* This is pow(10, dB / 20).
*/
static double dB_to_voltage(double dB);
/** Convert a power-like value (a Power quantity) relative to full
* scale to a dB value.
* This is 10 * log10(abs(v)).
*/
static double power_to_dB(double power);
/** Convert a dB value relative to reference +1.0V to a power-like
* value.
* This is pow(10, dB / 10).
*/
static double dB_to_power(double dB);
/** Convert a quantity to a dB value relative to reference 1.0.
* If sort is Quantity::RootPower, use voltage_to_dB; if sort is
* Quantity::Power, use power_to_dB.
*/
static double quantity_to_dB(double value, Quantity sort);
/** Convert a dB value to a quantity relative to reference 1.0.
* If sort is Quantity::RootPower, use dB_to_voltage; if sort is
* Quantity::Power, use dB_to_power.
*/
static double dB_to_quantity(double dB, Quantity sort);
/** Convert a fader level on one of the preset scales, in the
* range 0-maxLevel, to a dB value.
*/
static double fader_to_dB(int level, int maxLevel, Scale type);
/** Convert a dB value to a fader level on one of the preset
scales, rounding to the nearest discrete fader level within
the range 0-maxFaderLevel.
*/
static int dB_to_fader(double dB, int maxFaderLevel, Scale type);
/** Convert a fader level on one of the preset scales, in the
* range 0-maxLevel, to a voltage with reference +1.0.
*/
static double fader_to_voltage(int level, int maxLevel, Scale type);
/** Convert a voltage or voltage-like value to a fader level on
one of the preset scales, with reference +/-1.0V, rounding to
the nearest discrete fader level within the range
0-maxFaderLevel.
*/
static int voltage_to_fader(double dB, int maxFaderLevel, Scale type);
};
} // end namespace sv
#endif
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