script.crossfaderCurve does not work as desired

[Daniel Schürmann]

The code implies that we are able to tweak the xFader independently for each mode.

script.crossfaderCurve = function (value, min, max) {
    if (engine.getValue("[Mixer Profile]", "xFaderMode")==1) {
        // Constant Power
        engine.setValue("[Mixer Profile]", "xFaderCalibration", script.absoluteLin(value, 0.5, 0.962, min, max));
    } else {
        // Additive
        engine.setValue("[Mixer Profile]", "xFaderCurve", script.absoluteLin(value, 1, 2, min, max));
    }
}

Unfortunately the slider in the xFader preferences tweaks xFaderCalibration and xFaderCurve in both modes.
Tweaking the modes independently seams to be desirable. So I consider the CO interface and the preference dialog and the underlying calculation as broken.

[Daniel Schürmann (daschuer)]

If we fix this this, it should be easy to fix Bug #829538 as well, by shifting the maximum towards a steep cut.

IMHO this is a 1.12 bug, and it should be fixes without any interface changes.

Thoughts?

[Daniel Schürmann (daschuer)]

xFaderCalibration is used in both modes.
The range is now 1 ... 1000

[Daniel Schürmann (daschuer)]

Please note: the xFaderCalibration depends on the value of xFaderCurve to achieve a desired curve.

Fading:
xFaderCalibration 0.5 / 0
xFaderCurve = 1 / 0
Scratching:
xFaderCalibration 0.999307 / 0.998614
xFaderCurve = 1000 / 1

See:
https://github.com/mixxxdj/mixxx/blob/d46433b0ae51edf2ca7529b0889691dd54f2bb90/src/engine/enginexfader.cpp#L10

xFaderCalibration = pow(0.5, 1.0 / xFaderCurve);

[Dariusz Janik (kejbil)]

Maybe this comment will be helpful:
https://github.com/mixxxdj/mixxx/blob/479c9e15159299667f2f7d16d65a8565f656a376/src/preferences/dialog/dlgprefcrossfader.cpp#L203

So, the xFaderCurve is in the range of 1 to 1000 while 50 % slider results to about 2, which represents a medium rounded fader curve.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8192