| /* |
| * Copyright (c) 2011 Justin Ruggles |
| * |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg 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 2.1 of the License, or (at your option) any later version. |
| * |
| * FFmpeg 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 FFmpeg; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include "libavutil/common.h" |
| #include "libavutil/mathematics.h" |
| #include "adx.h" |
| |
| void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff) |
| { |
| double a, b, c; |
| |
| a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate); |
| b = M_SQRT2 - 1.0; |
| c = (a - sqrt((a + b) * (a - b))) / b; |
| |
| coeff[0] = lrintf(c * 2.0 * (1 << bits)); |
| coeff[1] = lrintf(-(c * c) * (1 << bits)); |
| } |