ref: 012443916146c670f7f9a521c89a45d8b7ab0c7a
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); 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;