| Karsten Keil | 960366c | 2008-07-27 01:56:38 +0200 | [diff] [blame^] | 1 | /* |
| 2 | * SpanDSP - a series of DSP components for telephony |
| 3 | * |
| 4 | * biquad.h - General telephony bi-quad section routines (currently this just |
| 5 | * handles canonic/type 2 form) |
| 6 | * |
| 7 | * Written by Steve Underwood <steveu@coppice.org> |
| 8 | * |
| 9 | * Copyright (C) 2001 Steve Underwood |
| 10 | * |
| 11 | * All rights reserved. |
| 12 | * |
| 13 | * This program is free software; you can redistribute it and/or modify |
| 14 | * it under the terms of the GNU General Public License as published by |
| 15 | * the Free Software Foundation; either version 2 of the License, or |
| 16 | * (at your option) any later version. |
| 17 | * |
| 18 | * This program is distributed in the hope that it will be useful, |
| 19 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 20 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 21 | * GNU General Public License for more details. |
| 22 | * |
| 23 | * You should have received a copy of the GNU General Public License |
| 24 | * along with this program; if not, write to the Free Software |
| 25 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| 26 | * |
| 27 | */ |
| 28 | |
| 29 | struct biquad2_state { |
| 30 | int32_t gain; |
| 31 | int32_t a1; |
| 32 | int32_t a2; |
| 33 | int32_t b1; |
| 34 | int32_t b2; |
| 35 | |
| 36 | int32_t z1; |
| 37 | int32_t z2; |
| 38 | }; |
| 39 | |
| 40 | static inline void biquad2_init(struct biquad2_state *bq, |
| 41 | int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2) |
| 42 | { |
| 43 | bq->gain = gain; |
| 44 | bq->a1 = a1; |
| 45 | bq->a2 = a2; |
| 46 | bq->b1 = b1; |
| 47 | bq->b2 = b2; |
| 48 | |
| 49 | bq->z1 = 0; |
| 50 | bq->z2 = 0; |
| 51 | } |
| 52 | |
| 53 | static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample) |
| 54 | { |
| 55 | int32_t y; |
| 56 | int32_t z0; |
| 57 | |
| 58 | z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2; |
| 59 | y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2; |
| 60 | |
| 61 | bq->z2 = bq->z1; |
| 62 | bq->z1 = z0 >> 15; |
| 63 | y >>= 15; |
| 64 | return y; |
| 65 | } |