/*
  Copyright (C) 2003-2009 Paul Brossier <piem@aubio.org>

  This file is part of aubio.

  aubio 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 3 of the License, or
  (at your option) any later version.

  aubio 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 aubio.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef _CDESIGN_H
#define _CDESIGN_H

/** \file

  Create a C-weighting filter
  
  This file creates a C-weighting digital filter, which reduces low and high
  frequencies and enhance the middle ones to reflect the ability of the human
  hearing.
  
  The implementation is based on the following standard:

    - IEC/CD 1672: Electroacoustics-Sound Level Meters, IEC, Geneva, Nov.  1996,
  for A- and C-weighting filters.
  
  See also:
  
    - <a href="http://en.wikipedia.org/wiki/A-weighting">A-Weighting on
  Wikipedia</a>
    - <a href="http://en.wikipedia.org/wiki/Weighting_filter">Weighting filter on
  Wikipedia</a>
    - <a href="http://www.mathworks.com/matlabcentral/fileexchange/69">Christophe
  Couvreur's 'octave' toolbox</a>
  
  The coefficients in this file have been computed using Christophe Couvreur's
  scripts in octave 3.0 (debian package 1:3.0.5-6+b2 with octave-signal
  1.0.9-1+b1 on i386), with <pre> [b, a] = cdsign(1/Fs) </pre> for various
  sampling frequencies.

*/

#ifdef __cplusplus
extern "C" {
#endif

/** create new C-design filter

  \param samplerate sampling frequency of the signal to filter. Should be one of 
  8000, 16000, 22050, 44100, 96000, 192000.
  \param channels number of channels to allocate

  \return a new filter object

*/
aubio_filter_t * new_aubio_filter_c_weighting (uint_t samplerate, uint_t channels);

/** set feedback and feedforward coefficients of a C-weighting filter

  \param f filter object to get coefficients from

*/
void aubio_filter_set_c_weighting (aubio_filter_t *f);

#ifdef __cplusplus
}
#endif

#endif /* _CDESIGN_H */