tomwalters@397: /*!
tomwalters@397:  * \file
tomwalters@397:  * \brief Log frequency scale for generating filter banks and their frequencies. Based on the scaling of the ERB scale
tomwalters@397:  *
tomwalters@397:  * \author Tom Walters <tcw24@cam.ac.uk>
tomwalters@397:  * \date created 2006/09/26
tomwalters@397:  * \version \$Id: ScaleLogScaled.h 459 2007-11-08 11:50:04Z tom $
tomwalters@397:  */
tomwalters@397: /* (c) 2006, University of Cambridge, Medical Research Council
tomwalters@397:  * http://www.pdn.cam.ac.uk/groups/cnbh/aimmanual
tomwalters@397:  */
tomwalters@397: #ifndef __MODULE_SCALE_LOGSCALED_H__
tomwalters@397: #define __MODULE_SCALE_LOGSCALED_H__
tomwalters@397: 
tomwalters@397: #include <math.h>
tomwalters@397: 
tom@400: #include "Modules/Output/Graphics/Scale/Scale.h"
tom@400: 
tom@400: namespace aimc {
tomwalters@397: 
tomwalters@397: /*!
tomwalters@397:  * \class ScaleERB "Modules/Scale/ScaleERB.h"
tomwalters@397:  * \brief ERB frequency scale for generating filter banks and their frequencies
tomwalters@397:  *
tomwalters@397:  * It is very advisable to use Scale::Create() to an instance of this scale.
tomwalters@397:  *
tomwalters@397:  * References:
tomwalters@397:  *   - J. Smith and J. Abel (1999), "Bark and ERB bilinear transforms"
tomwalters@397:  *     http://www-ccrma.stanford.edu/~jos/bbt/
tomwalters@397:  */
tomwalters@397: class ScaleLogScaled : public Scale {
tomwalters@397: public:
tomwalters@398:   ScaleLogScaled(unsigned int min, unsigned int max, float density)
tomwalters@398:     : Scale(min, max, density) { m_iType = SCALE_ERB; m_sName = "logscaled"; };
tomwalters@397: 
tomwalters@398:   float FromLinear(float fFreq) {
tomwalters@398:     return 21.4f*log10(0.00437f*fFreq);
tomwalters@398:   };
tomwalters@397: 
tomwalters@398:   float ToLinear(float fFreq) {
tomwalters@398:     return (pow(10, fFreq/21.4f))/0.00437f;
tomwalters@398:   };
tomwalters@397: };
tom@400: }  // namespace aimc
tomwalters@397: #endif /* __MODULE_SCALE_ERB_H__ */