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/* FluidSynth - A Software Synthesizer
*
* Copyright (C) 2003 Peter Hanappe and others.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public License
* as published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA
*/
#ifndef _FLUID_IIR_FILTER_H
#define _FLUID_IIR_FILTER_H
#include "fluidsynth_priv.h"
typedef struct _fluid_iir_filter_t fluid_iir_filter_t;
void fluid_iir_filter_apply(fluid_iir_filter_t* iir_filter,
fluid_real_t *dsp_buf, int dsp_buf_count);
void fluid_iir_filter_reset(fluid_iir_filter_t* iir_filter);
void fluid_iir_filter_set_q_dB(fluid_iir_filter_t* iir_filter,
fluid_real_t q_dB);
void fluid_iir_filter_set_fres(fluid_iir_filter_t* iir_filter,
fluid_real_t fres);
void fluid_iir_filter_calc(fluid_iir_filter_t* iir_filter,
fluid_real_t output_rate,
fluid_real_t fres_mod);
/* We can't do information hiding here, as fluid_voice_t includes the struct
without a pointer. */
struct _fluid_iir_filter_t
{
/* filter coefficients */
/* The coefficients are normalized to a0. */
/* b0 and b2 are identical => b02 */
fluid_real_t b02; /* b0 / a0 */
fluid_real_t b1; /* b1 / a0 */
fluid_real_t a1; /* a0 / a0 */
fluid_real_t a2; /* a1 / a0 */
fluid_real_t b02_incr;
fluid_real_t b1_incr;
fluid_real_t a1_incr;
fluid_real_t a2_incr;
int filter_coeff_incr_count;
int compensate_incr; /* Flag: If set, must compensate history */
fluid_real_t hist1, hist2; /* Sample history for the IIR filter */
int filter_startup; /* Flag: If set, the filter will be set directly.
Else it changes smoothly. */
fluid_real_t fres; /* the resonance frequency, in cents (not absolute cents) */
fluid_real_t last_fres; /* Current resonance frequency of the IIR filter */
/* Serves as a flag: A deviation between fres and last_fres */
/* indicates, that the filter has to be recalculated. */
fluid_real_t q_lin; /* the q-factor on a linear scale */
fluid_real_t filter_gain; /* Gain correction factor, depends on q */
};
#endif
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