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82 lines
2.2 KiB
82 lines
2.2 KiB
/*
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Copyright ( C ) 2003 Arnold Krille <arnold@arnoldarts.de>
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation;
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version 2 of the License.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with this library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#ifndef ARTS_DB2VOL_CALC_H
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#define ARTS_DB2VOL_CALC_H
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#include <math.h>
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class dB2VolCalc {
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private:
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float _base;
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public:
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dB2VolCalc( float _dbmin, float _dbmax )
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: _base( 6/log10( double(2) ) ) // Depends on what you measure: intensity(10), pressure(20), old artscontrol(6/lg2 (near 20))
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, dbmax( _dbmax )
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, dbmin( _dbmin )
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{}
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float dbmax, dbmin;
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/**
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Logarithmic/decimal valuation:
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p = ampfactor ( linear )
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db = dezibel ( logarithmic )
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p = 10^( d/10 )
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db = 10*lg( p )
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artscontrol was using
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db = 6/ln( 2 ) * ln( p )
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which would be
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db = 6/lg( 2 ) * lg( p )
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*/
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float amptodb( float p ) {
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float db = _base*log10( p );
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if ( db < dbmin ) db = dbmin;
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if ( db > dbmax ) db = dbmax;
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return db;
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}
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float dbtoamp( float db ) {
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float amp = pow( 10, db/_base );
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if ( amp <= pow( 10, dbmin/_base ) ) amp = 0;
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return amp;
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}
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/// With ndb = normalized dB (between 0 and 1)
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float amptondb( float p ) {
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return dbtondb( amptodb( p ) ); //- dbmin ) / ( dbmax - dbmin );
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}
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float ndbtoamp( float ndb ) {
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return dbtoamp( ndb * ( dbmax - dbmin ) + dbmin );
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}
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/// Normalizes a dezibel value.
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float dbtondb( float db ) {
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return ( db - dbmin )/( dbmax - dbmin );
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}
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/// Normalizes a volume to a logarithmic value between 0 and 1.
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float dbtovol( float db ) {
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return ( db -dbmin )/( 0-dbmin );
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}
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/// Unnormalizes a dezibel value.
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float ndbtodb( float ndb ) {
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return ( ndb * ( dbmax-dbmin ) +dbmin );
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}
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};
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#endif
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