ref: e9e2a870df3deec70e7eaedd97bfc24412fba595
dir: /src/temporal/filter.h/
/*
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 FILTER_H
#define FILTER_H
/** \file
Digital filter
This object stores a digital filter of order \f$n\f$.
It contains the following data:
- \f$ n*1 b_i \f$ feedforward coefficients
- \f$ n*1 a_i \f$ feedback coefficients
- \f$ n*c x_i \f$ input signal
- \f$ n*c y_i \f$ output signal
For convenience, the samplerate of the input signal is also stored in the
object.
Feedforward and feedback parameters can be modified using
aubio_filter_get_feedback() and aubio_filter_get_feedforward().
The function aubio_filter_do_outplace() computes the following output signal
\f$ y[n] \f$ from the input signal \f$ x[n] \f$:
\f{eqnarray*}{
y[n] = b_0 x[n] & + & b_1 x[n-1] + b_2 x[n-2] + ... + b_P x[n-P] \\
& - & a_1 y[n-1] - a_2 y[n-2] - ... - a_P y[n-P] \\
\f}
The function aubio_filter_do() executes the same computation but modifies
directly the input signal (in-place).
The function aubio_filter_do_filtfilt() version runs the filter twice, first
forward then backward, to compensate with the phase shifting of the forward
operation.
Some convenience functions are provided:
- new_aubio_filter_a_weighting() and aubio_filter_set_a_weighting(),
- new_aubio_filter_c_weighting() and aubio_filter_set_c_weighting().
- new_aubio_filter_biquad() and aubio_filter_set_biquad().
\example temporal/test-filter.c
*/
#ifdef __cplusplus
extern "C" {
#endif
/** Digital filter
*/
typedef struct _aubio_filter_t aubio_filter_t;
/** filter input vector (in-place)
\param f filter object as returned by new_aubio_filter()
\param in input vector to filter
*/
void aubio_filter_do (aubio_filter_t * f, fvec_t * in);
/** filter input vector (out-of-place)
\param f filter object as returned by new_aubio_filter()
\param in input vector to filter
\param out output vector to store filtered input
*/
void aubio_filter_do_outplace (aubio_filter_t * f, fvec_t * in, fvec_t * out);
/** filter input vector forward and backward
\param f ::aubio_filter_t object as returned by new_aubio_filter()
\param in ::fvec_t input vector to filter
\param tmp memory space to use for computation
*/
void aubio_filter_do_filtfilt (aubio_filter_t * f, fvec_t * in, fvec_t * tmp);
/** returns a pointer to feedback coefficients \f$ a_i \f$
\param f filter object to get parameters from
\return a pointer to the \f$ a_0 ... a_i ... a_P \f$ coefficients
*/
lvec_t *aubio_filter_get_feedback (aubio_filter_t * f);
/** returns a pointer to feedforward coefficients \f$ b_i \f$
\param f filter object to get coefficients from
\return a pointer to the \f$ b_0 ... b_i ... b_P \f$ coefficients
*/
lvec_t *aubio_filter_get_feedforward (aubio_filter_t * f);
/** get order of the filter
\param f filter to get order from
\return the order of the filter
*/
uint_t aubio_filter_get_order (aubio_filter_t * f);
/** get sampling rate of the filter
\param f filter to get sampling rate from
\return the sampling rate of the filter, in Hz
*/
uint_t aubio_filter_get_samplerate (aubio_filter_t * f);
/** get sampling rate of the filter
\param f filter to get sampling rate from
\param samplerate sample rate to set the filter to
\return the sampling rate of the filter, in Hz
*/
uint_t aubio_filter_set_samplerate (aubio_filter_t * f, uint_t samplerate);
/** reset filter memory
\param f filter object as returned by new_aubio_filter()
*/
void aubio_filter_do_reset (aubio_filter_t * f);
/** create new filter object
This function creates a new ::aubio_filter_t object, given the order of the
filter.
\param order order of the filter (number of coefficients)
\return the newly created filter object
*/
aubio_filter_t *new_aubio_filter (uint_t order);
/** delete a filter object
\param f filter object to delete
*/
void del_aubio_filter (aubio_filter_t * f);
#ifdef __cplusplus
}
#endif
#endif /*FILTER_H*/