much ado about nothing when it comes to gain control

git-svn-id: svn://localhost/ardour2/branches/3.0@9748 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 58 insertions, 1 deletions

diff --git a/libs/ardour/ardour/utils.h b/libs/ardour/ardour/utils.h
index dac4086cba..17fa9070ff 100644
--- a/libs/ardour/ardour/utils.h
+++ b/libs/ardour/ardour/utils.h
@@ -36,6 +36,7 @@ bool string_is_affirmative (const std::string&);
 
 #include "ardour/ardour.h"
 #include "ardour/data_type.h"
+#include "ardour/dB.h"
 
 class XMLNode;
 
@@ -70,22 +71,78 @@ ARDOUR::SyncSource string_to_sync_source (std::string str);
 const char* edit_mode_to_string (ARDOUR::EditMode);
 ARDOUR::EditMode string_to_edit_mode (std::string);
 
+#undef  OLD_GAIN_MATH
+#define OLD_GAIN_MATH
 
 static inline double
 gain_to_slider_position (ARDOUR::gain_t g)
 {
 	if (g == 0) return 0;
-	return pow((6.0*log(g)/log(2.0)+192.0)/198.0, 8.0);
 
+#ifndef OLD_GAIN_MATH
+	/* Power Law With Exponential Cutoff 2D, fit to data from TC Spectra
+	   console (image of fader gradations
+
+	   y = C * x(-T) * exp(-x/K)
+
+	   C =  8.2857630370864188E-01
+	   T = -5.1526743785019269E-01
+	   K =  7.8990885960495589E+00
+
+	 */
+	
+	return 8.2857630370864188E-01 * pow(g,5.1526743785019269E-01) * exp (-g/7.8990885960495589E+00);
+#else
+	return pow((6.0*log(g)/log(2.0)+192.0)/198.0, 8.0);
+#endif
 }
 
 static inline ARDOUR::gain_t
 slider_position_to_gain (double pos)
 {
+	if (pos == 0.0) {
+		return 0.0;
+	}
+
+#ifndef OLD_GAIN_MATH
+	/* 5th order polynomial function fit to data from a TC Spectra console
+	   fader (image of fader gradations).
+	 
+	   y = a + bx1 + cx2 + dx3 + fx4 + gx5
+	   
+	   a = -1.1945480381045521E-02
+	   b =  1.5809476525537265E+00
+	   c = -1.5850710838966151E+01
+	   d =  6.1643128605961991E+01
+	   f = -8.5525246160607693E+01
+	   g =  4.1312725896188283E+01
+
+	*/
+
+	double p = pos;
+	double g = -1.1945480381045521E-02;
+
+	g +=  1.5809476525537265E+00 * pos;
+	pos *= p;
+	g += -1.5850710838966151E+01 * pos;
+	pos *= p;
+	g += 6.1643128605961991E+01 * pos;
+	pos *= p;
+	g += -8.5525246160607693E+01 * pos;
+	pos *= p;
+	g += 4.1312725896188283E+01 * pos;
+
+	return g;
+#else
 	/* XXX Marcus writes: this doesn't seem right to me. but i don't have a better answer ... */
 	if (pos == 0.0) return 0;
 	return pow (2.0,(sqrt(sqrt(sqrt(pos)))*198.0-192.0)/6.0);
+#endif
 }
+#undef OLD_GAIN_MATH
+
+double gain_to_slider_position_with_max (double g, double max_gain = 2.0);
+double slider_position_to_gain_with_max (double g, double max_gain = 2.0);
 
 /* I don't really like hard-coding these falloff rates here
  * Probably should use a map of some kind that could be configured