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/*
Copyright ( C ) 2003 Arnold Krille <[email protected]>
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., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, 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
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