LXR linux/drivers/isdn/mISDN/dsp

   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
  15struct 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
  26static 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
  39static 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