int
AudioLevel::dB_to_fader(float dB, int maxLevel, FaderType type)
{
if (dB == DB_FLOOR) return 0;
if (type == IEC268Meter || type == IEC268LongMeter) {
// The IEC scale gives a "percentage travel" for a given dB
// level, but it reaches 100% at 0dB. So we want to treat the
// result not as a percentage, but as a scale between 0 and
// whatever the "percentage" for our (possibly >0dB) max dB is.
float maxPercent = iec_dB_to_fader(faderTypes[type].maxDb);
float percent = iec_dB_to_fader(dB);
int faderLevel = int((maxLevel * percent) / maxPercent + 0.01f);
if (faderLevel < 0) faderLevel = 0;
if (faderLevel > maxLevel) faderLevel = maxLevel;
return faderLevel;
} else {
int zeroLevel = int(maxLevel * faderTypes[type].zeroPoint);
if (dB >= 0.f) {
if (faderTypes[type].maxDb <= 0.f) {
return maxLevel;
} else {
float value = sqrtf(dB);
float scale = (maxLevel - zeroLevel) / sqrtf(faderTypes[type].maxDb);
value *= scale;
int level = int(value + 0.01f) + zeroLevel;
if (level > maxLevel) level = maxLevel;
return level;
}
} else {
dB = 0.f - dB;
float value = sqrtf(dB);
float scale = zeroLevel / sqrtf(0.f - faderTypes[type].minDb);
value *= scale;
int level = zeroLevel - int(value + 0.01f);
if (level < 0) level = 0;
return level;
}
}
}
float
AudioLevel::fader_to_dB(int level, int maxLevel, FaderType type)
{
if (level == 0) return DB_FLOOR;
if (type == IEC268Meter || type == IEC268LongMeter) {
float maxPercent = iec_dB_to_fader(faderTypes[type].maxDb);
float percent = float(level) * maxPercent / float(maxLevel);
float dB = iec_fader_to_dB(percent);
return dB;
} else { // scale proportional to sqrt(fabs(dB))
int zeroLevel = int(maxLevel * faderTypes[type].zeroPoint);
if (level >= zeroLevel) {
float value = level - zeroLevel;
float scale = float(maxLevel - zeroLevel) /
sqrtf(faderTypes[type].maxDb);
value /= scale;
float dB = powf(value, 2.0);
return dB;
} else {
float value = zeroLevel - level;
float scale = zeroLevel / sqrtf(0.0 - faderTypes[type].minDb);
value /= scale;
float dB = powf(value, 2.0);
return 0.0 - dB;
}
}
}