1 files changed, 82 insertions, 0 deletions
diff --git a/arts/gui/kde/dbvolcalc.h b/arts/gui/kde/dbvolcalc.h
new file mode 100644
index 00000000..8d99bf59
--- /dev/null
+++ b/arts/gui/kde/dbvolcalc.h
@@ -0,0 +1,82 @@
+/*
+    Copyright (  C ) 2003 Arnold Krille <arnold@arnoldarts.de>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation;
+    version 2 of the License.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+    Boston, MA 02111-1307, USA.
+
+*/
+
+#ifndef ARTS_DB2VOL_CALC_H
+#define ARTS_DB2VOL_CALC_H
+
+#include <math.h>
+
+class dB2VolCalc {
+private:
+	float _base;
+public:
+	dB2VolCalc( float _dbmin, float _dbmax )
+	  : _base( 6/log10( double(2) ) ) // Depends on what you measure: intensity(10), pressure(20), old artscontrol(6/lg2 (near 20))
+	  , dbmax( _dbmax )
+	  , dbmin( _dbmin )
+	{}
+
+	float dbmax, dbmin;
+	/**
+		Logarithmic/decimal valuation:
+		p = ampfactor ( linear )
+		db = dezibel ( logarithmic )
+		p = 10^( d/10 )
+		db = 10*lg( p )
+
+		artscontrol was using
+			db = 6/ln( 2 ) * ln( p )
+		which would be
+			db = 6/lg( 2 ) * lg( p )
+	*/
+	float amptodb( float p ) {
+		float db = _base*log10( p );
+		if ( db < dbmin ) db = dbmin;
+		if ( db > dbmax ) db = dbmax;
+		return db;
+	}
+	float dbtoamp( float db ) {
+		float amp = pow( 10, db/_base );
+		if ( amp <= pow( 10, dbmin/_base ) ) amp = 0;
+		return amp;
+	}
+	/// With ndb = normalized dB (between 0 and 1)
+	float amptondb( float p ) {
+		return  dbtondb( amptodb( p ) ); //- dbmin ) / ( dbmax - dbmin );
+	}
+	float ndbtoamp( float ndb ) {
+		return dbtoamp( ndb * ( dbmax - dbmin ) + dbmin );
+	}
+	/// Normalizes a dezibel value.
+	float dbtondb( float db ) {
+		return ( db - dbmin )/( dbmax - dbmin );
+	}
+	/// Normalizes a volume to a logarithmic value between 0 and 1.
+	float dbtovol( float db ) {
+		return ( db -dbmin )/( 0-dbmin );
+	}
+	/// Unnormalizes a dezibel value.
+	float ndbtodb( float ndb ) {
+		return ( ndb * ( dbmax-dbmin ) +dbmin );
+	}
+};
+
+#endif
+// vim: sw=4 ts=4