/*
	 Copyright (C) 2003 Paul Brossier

	 This program is free software; you can redistribute it and/or modify
	 it under the terms of the GNU General Public License as published by
	 the Free Software Foundation; either version 2 of the License, or
	 (at your option) any later version.

	 This program 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 General Public License for more details.

	 You should have received a copy of the GNU General Public License
	 along with this program; if not, write to the Free Software
	 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifndef BIQUAD_H
#define BIQUAD_H

/** \file 

  Second order Infinite Impulse Response filter

  This file implements a normalised biquad filter (second order IIR):
 
  \f$ y[n] = b_0 x[n] + b_1 x[n-1] + b_2 x[n-2] - a_1 y[n-1] - a_2 y[n-2] \f$

  The filtfilt version runs the filter twice, forward and backward, to
  compensate the phase shifting of the forward operation.

  See also <a href="http://en.wikipedia.org/wiki/Digital_biquad_filter">Digital
  biquad filter</a> on wikipedia.

*/

#ifdef __cplusplus
extern "C" {
#endif

/** set coefficients of a biquad filter

  \param f filter object as returned by new_aubio_filter()
  \param b0 forward filter coefficient
  \param b1 forward filter coefficient
  \param b2 forward filter coefficient
  \param a1 feedback filter coefficient
  \param a2 feedback filter coefficient

*/
uint_t
aubio_filter_set_biquad (aubio_filter_t * f, lsmp_t b0, lsmp_t b1, lsmp_t b2,
    lsmp_t a1, lsmp_t a2);

/** create new biquad filter

  \param b0 forward filter coefficient
  \param b1 forward filter coefficient
  \param b2 forward filter coefficient
  \param a1 feedback filter coefficient
  \param a2 feedback filter coefficient
  \param channels number of channels to allocate

*/
aubio_filter_t *
new_aubio_filter_biquad (lsmp_t b0, lsmp_t b1, lsmp_t b2, lsmp_t a1, lsmp_t a2,
    uint_t channels);

#ifdef __cplusplus
}
#endif

#endif /*BIQUAD_H*/