ref: 1d09da3a87e43eee7a345f970378c37312a71895
dir: /src/btrworth.h/
/*
Butterworth effect file for SoX
Copyright (C) 1999 Jan Paul Schmidt <jps@fundament.org>
This source code 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 source code 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 Library General Public
License along with this library; if not, write to the Free
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
*/
void butterworth_start (P1 (eff_t effp));
void butterworth_flow (P5 (eff_t effp, LONG *ibuf, LONG *obuf,
int *isamp, int *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;