Mercurial > hg > audiostuff
comparison spandsp-0.0.6pre17/src/spandsp/biquad.h @ 4:26cd8f1ef0b1
import spandsp-0.0.6pre17
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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| date | Fri, 25 Jun 2010 15:50:58 +0200 |
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| 3:c6c5a16ce2f2 | 4:26cd8f1ef0b1 |
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| 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 Lesser General Public License version 2.1, | |
| 15 * as published by the Free Software Foundation. | |
| 16 * | |
| 17 * This program is distributed in the hope that it will be useful, | |
| 18 * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 20 * GNU Lesser General Public License for more details. | |
| 21 * | |
| 22 * You should have received a copy of the GNU Lesser General Public | |
| 23 * License along with this program; if not, write to the Free Software | |
| 24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
| 25 * | |
| 26 * $Id: biquad.h,v 1.14 2008/04/17 14:26:59 steveu Exp $ | |
| 27 */ | |
| 28 | |
| 29 /*! \page biquad_page Bi-quadratic filter sections | |
| 30 \section biquad_page_sec_1 What does it do? | |
| 31 ???. | |
| 32 | |
| 33 \section biquad_page_sec_2 How does it work? | |
| 34 ???. | |
| 35 */ | |
| 36 | |
| 37 #if !defined(_SPANDSP_BIQUAD_H_) | |
| 38 #define _SPANDSP_BIQUAD_H_ | |
| 39 | |
| 40 typedef struct | |
| 41 { | |
| 42 int32_t gain; | |
| 43 int32_t a1; | |
| 44 int32_t a2; | |
| 45 int32_t b1; | |
| 46 int32_t b2; | |
| 47 | |
| 48 int32_t z1; | |
| 49 int32_t z2; | |
| 50 | |
| 51 #if FIRST_ORDER_NOISE_SHAPING | |
| 52 int32_t residue; | |
| 53 #elif SECOND_ORDER_NOISE_SHAPING | |
| 54 int32_t residue1; | |
| 55 int32_t residue2; | |
| 56 #endif | |
| 57 } biquad2_state_t; | |
| 58 | |
| 59 #if defined(__cplusplus) | |
| 60 extern "C" | |
| 61 { | |
| 62 #endif | |
| 63 | |
| 64 static __inline__ void biquad2_init(biquad2_state_t *bq, | |
| 65 int32_t gain, | |
| 66 int32_t a1, | |
| 67 int32_t a2, | |
| 68 int32_t b1, | |
| 69 int32_t b2) | |
| 70 { | |
| 71 bq->gain = gain; | |
| 72 bq->a1 = a1; | |
| 73 bq->a2 = a2; | |
| 74 bq->b1 = b1; | |
| 75 bq->b2 = b2; | |
| 76 | |
| 77 bq->z1 = 0; | |
| 78 bq->z2 = 0; | |
| 79 | |
| 80 #if FIRST_ORDER_NOISE_SHAPING | |
| 81 bq->residue = 0; | |
| 82 #elif SECOND_ORDER_NOISE_SHAPING | |
| 83 bq->residue1 = 0; | |
| 84 bq->residue2 = 0; | |
| 85 #endif | |
| 86 } | |
| 87 /*- End of function --------------------------------------------------------*/ | |
| 88 | |
| 89 static __inline__ int16_t biquad2(biquad2_state_t *bq, int16_t sample) | |
| 90 { | |
| 91 int32_t y; | |
| 92 int32_t z0; | |
| 93 | |
| 94 z0 = sample*bq->gain + bq->z1*bq->a1 + bq->z2*bq->a2; | |
| 95 y = z0 + bq->z1*bq->b1 + bq->z2*bq->b2; | |
| 96 | |
| 97 bq->z2 = bq->z1; | |
| 98 bq->z1 = z0 >> 15; | |
| 99 #if FIRST_ORDER_NOISE_SHAPING | |
| 100 y += bq->residue; | |
| 101 bq->residue = y & 0x7FFF; | |
| 102 #elif SECOND_ORDER_NOISE_SHAPING | |
| 103 y += (2*bq->residue1 - bq->residue2); | |
| 104 bq->residue2 = bq->residue1; | |
| 105 bq->residue1 = y & 0x7FFF; | |
| 106 #endif | |
| 107 y >>= 15; | |
| 108 return (int16_t) y; | |
| 109 } | |
| 110 /*- End of function --------------------------------------------------------*/ | |
| 111 | |
| 112 #if defined(__cplusplus) | |
| 113 } | |
| 114 #endif | |
| 115 | |
| 116 #endif | |
| 117 /*- End of file ------------------------------------------------------------*/ |