| 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
|---|---|
| 2 | /* |
| 3 | * SpanDSP - a series of DSP components for telephony |
| 4 | * |
| 5 | * biquad.h - General telephony bi-quad section routines (currently this just |
| 6 | * handles canonic/type 2 form) |
| 7 | * |
| 8 | * Written by Steve Underwood <steveu@coppice.org> |
| 9 | * |
| 10 | * Copyright (C) 2001 Steve Underwood |
| 11 | * |
| 12 | * All rights reserved. |
| 13 | */ |
| 14 | |
| 15 | struct biquad2_state { |
| 16 | int32_t gain; |
| 17 | int32_t a1; |
| 18 | int32_t a2; |
| 19 | int32_t b1; |
| 20 | int32_t b2; |
| 21 | |
| 22 | int32_t z1; |
| 23 | int32_t z2; |
| 24 | }; |
| 25 | |
| 26 | static inline void biquad2_init(struct biquad2_state *bq, |
| 27 | int32_t gain, int32_t a1, int32_t a2, int32_t b1, int32_t b2) |
| 28 | { |
| 29 | bq->gain = gain; |
| 30 | bq->a1 = a1; |
| 31 | bq->a2 = a2; |
| 32 | bq->b1 = b1; |
| 33 | bq->b2 = b2; |
| 34 | |
| 35 | bq->z1 = 0; |
| 36 | bq->z2 = 0; |
| 37 | } |
| 38 | |
| 39 | static inline int16_t biquad2(struct biquad2_state *bq, int16_t sample) |
| 40 | { |
| 41 | int32_t y; |
| 42 | int32_t z0; |
| 43 | |
| 44 | z0 = sample * bq->gain + bq->z1 * bq->a1 + bq->z2 * bq->a2; |
| 45 | y = z0 + bq->z1 * bq->b1 + bq->z2 * bq->b2; |
| 46 | |
| 47 | bq->z2 = bq->z1; |
| 48 | bq->z1 = z0 >> 15; |
| 49 | y >>= 15; |
| 50 | return y; |
| 51 | } |
| 52 |