ref: 1cdc830867f1a0edcca70884abef27c2661f1d56
dir: /src/btrworth.h/
/*
Butterworth effect file for SoX
Copyright (C) 1999 Jan Paul Schmidt <jps@fundament.org>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Code based on the butterworth implementation in
Sound Processing Kit - A C++ Class Library for Audio Signal Processing
Copyright (C) 1995-1998 Kai Lassfolk
as described in
Computer music: synthesis, composition, and performance
Charles Dodge, Thomas A. Jerse
[2nd ed.]
Page 214
*/
int st_butterworth_start (eff_t effp);
void st_butterworth_plot (eff_t effp);
int st_butterworth_flow (eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp);
typedef struct butterworth {
double x [2];
double y [2];
double a [3];
double b [2];
/*
* Cut off frequency for low-pass and high-pass,
* center frequency for band-pass
*/
double frequency;
double bandwidth;
} *butterworth_t;