andrew@0: /*
andrew@0: 	 Copyright (C) 2003 Paul Brossier
andrew@0: 
andrew@0: 	 This program is free software; you can redistribute it and/or modify
andrew@0: 	 it under the terms of the GNU General Public License as published by
andrew@0: 	 the Free Software Foundation; either version 2 of the License, or
andrew@0: 	 (at your option) any later version.
andrew@0: 
andrew@0: 	 This program is distributed in the hope that it will be useful,
andrew@0: 	 but WITHOUT ANY WARRANTY; without even the implied warranty of
andrew@0: 	 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
andrew@0: 	 GNU General Public License for more details.
andrew@0: 
andrew@0: 	 You should have received a copy of the GNU General Public License
andrew@0: 	 along with this program; if not, write to the Free Software
andrew@0: 	 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
andrew@0: 
andrew@0: */
andrew@0: 
andrew@0: #ifndef BIQUAD_H
andrew@0: #define BIQUAD_H
andrew@0: 
andrew@0: /** \file 
andrew@0: 
andrew@0:   Second order Infinite Impulse Response filter
andrew@0: 
andrew@0:   This file implements a normalised biquad filter (second order IIR):
andrew@0:  
andrew@0:   \f$ y[n] = b_1 x[n] + b_2 x[n-1] + b_3 x[n-2] - a_2 y[n-1] - a_3 y[n-2] \f$
andrew@0: 
andrew@0:   The filtfilt version runs the filter twice, forward and backward, to
andrew@0:   compensate the phase shifting of the forward operation.
andrew@0: 
andrew@0: */
andrew@0: 
andrew@0: #ifdef __cplusplus
andrew@0: extern "C" {
andrew@0: #endif
andrew@0: 
andrew@0: /** biquad filter object */
andrew@0: typedef struct _aubio_biquad_t aubio_biquad_t;
andrew@0: 
andrew@0: /** filter input vector
andrew@0: 
andrew@0:   \param b biquad object as returned by new_aubio_biquad
andrew@0:   \param in input vector to filter
andrew@0: 
andrew@0: */
andrew@0: void aubio_biquad_do(aubio_biquad_t * b, fvec_t * in);
andrew@0: /** filter input vector forward and backward
andrew@0: 
andrew@0:   \param b biquad object as returned by new_aubio_biquad
andrew@0:   \param in input vector to filter
andrew@0:   \param tmp memory space to use for computation
andrew@0: 
andrew@0: */
andrew@0: void aubio_biquad_do_filtfilt(aubio_biquad_t * b, fvec_t * in, fvec_t * tmp);
andrew@0: /** create new biquad filter
andrew@0: 
andrew@0:   \param b1 forward filter coefficient
andrew@0:   \param b2 forward filter coefficient
andrew@0:   \param b3 forward filter coefficient
andrew@0:   \param a2 feedback filter coefficient
andrew@0:   \param a3 feedback filter coefficient
andrew@0: 
andrew@0: */
andrew@0: aubio_biquad_t * new_aubio_biquad(lsmp_t b1, lsmp_t b2, lsmp_t b3, lsmp_t a2, lsmp_t a3);
andrew@0: 
andrew@0: /** delete biquad filter 
andrew@0:  
andrew@0:   \param b biquad object to delete 
andrew@0: 
andrew@0: */
andrew@0: void del_aubio_biquad(aubio_biquad_t * b);
andrew@0: 
andrew@0: #ifdef __cplusplus
andrew@0: }
andrew@0: #endif
andrew@0: 
andrew@0: #endif /*BIQUAD_H*/