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#include "engine/enginexfader.h"
#include "util/math.h"
//static
const char* EngineXfader::kXfaderConfigKey = "[Mixer Profile]";
const double EngineXfader::kTransformDefault = 1.0;
const double EngineXfader::kTransformMax = 1000.0;
const double EngineXfader::kTransformMin = 0.6;
double EngineXfader::getPowerCalibration(double transform) {
// get the transform_root of -3db (.5)
return pow(0.5, 1.0 / transform);
}
void EngineXfader::getXfadeGains(double xfadePosition,
double transform,
double powerCalibration,
double curve,
bool reverse,
CSAMPLE_GAIN* gain1,
CSAMPLE_GAIN* gain2) {
if (gain1 == nullptr || gain2 == nullptr) {
return;
}
// Slow-fade/fast-cut
double xfadePositionLeft = xfadePosition;
double xfadePositionRight = xfadePosition;
if (curve == MIXXX_XFADER_CONSTPWR) {
// Apply Calibration
xfadePosition *= powerCalibration;
xfadePositionLeft = xfadePosition - powerCalibration;
xfadePositionRight = xfadePosition + powerCalibration;
}
if (xfadePositionLeft < 0) { // on left side
xfadePositionLeft *= -1;
*gain2 = static_cast<CSAMPLE_GAIN>(1.0 - (1.0 * pow(xfadePositionLeft, transform)));
} else {
*gain2 = 1.0f;
}
if(xfadePositionRight > 0) { // right side
*gain1 = static_cast<CSAMPLE_GAIN>(1.0 - (1.0 * pow(xfadePositionRight, transform)));
} else {
*gain1 = 1.0f;
}
//prevent phase reversal
if (*gain1 < 0.0) {
*gain1 = 0.0f;
}
if (*gain2 < 0.0) {
*gain2 = 0.0f;
}
if (curve == MIXXX_XFADER_CONSTPWR) {
if (*gain1 > *gain2) {
*gain2 = 1 - *gain1;
} else {
*gain1 = 1 - *gain2;
}
// The resulting power at the crossover point depends on the correlation of the input signals
// In theory the gain ratio varies from 0.5 for two equal signals to sqrt(0.5) = 0.707 for totally
// uncorrelated signals.
// Since the underlying requirement for this curve is constant loudness, we did a test with 30 s
// snippets of various genres and ReplayGain 2.0 analysis. Almost all results where near 0.707
// with one exception of mixing two parts of the same track, which resulted in 0.66.
// Based on the testing, we normalize the gain as if the signals were uncorrelated. The
// correction on the following lines ensures that gain1^2 + gain2^2 == 1.
CSAMPLE_GAIN gain = static_cast<CSAMPLE_GAIN>(sqrt(*gain1 * *gain1 + *gain2 * *gain2));
*gain1 = *gain1 / gain;
*gain2 = *gain2 / gain;
}
if (reverse) {
CSAMPLE_GAIN gain_temp = *gain1;
*gain1 = *gain2;
*gain2 = gain_temp;
}
}
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