Mercurial > hg > audiostuff
comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/oki_adpcm.h @ 5:f762bf195c4b
import spandsp-0.0.3
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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| date | Fri, 25 Jun 2010 16:00:21 +0200 |
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| 4:26cd8f1ef0b1 | 5:f762bf195c4b |
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| 1 /* | |
| 2 * SpanDSP - a series of DSP components for telephony | |
| 3 * | |
| 4 * oki_adpcm.h - Conversion routines between linear 16 bit PCM data and | |
| 5 * OKI (Dialogic) ADPCM format. | |
| 6 * | |
| 7 * Written by Steve Underwood <steveu@coppice.org> | |
| 8 * | |
| 9 * Copyright (C) 2001 Steve Underwood | |
| 10 * | |
| 11 * Based on a bit from here, a bit from there, eye of toad, | |
| 12 * ear of bat, etc - plus, of course, my own 2 cents. | |
| 13 * | |
| 14 * All rights reserved. | |
| 15 * | |
| 16 * This program is free software; you can redistribute it and/or modify | |
| 17 * it under the terms of the GNU General Public License version 2, as | |
| 18 * published by the Free Software Foundation. | |
| 19 * | |
| 20 * This program is distributed in the hope that it will be useful, | |
| 21 * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 23 * GNU General Public License for more details. | |
| 24 * | |
| 25 * You should have received a copy of the GNU General Public License | |
| 26 * along with this program; if not, write to the Free Software | |
| 27 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
| 28 * | |
| 29 * $Id: oki_adpcm.h,v 1.13 2006/10/24 13:45:28 steveu Exp $ | |
| 30 */ | |
| 31 | |
| 32 /*! \file */ | |
| 33 | |
| 34 #if !defined(_OKI_ADPCM_H_) | |
| 35 #define _OKI_ADPCM_H_ | |
| 36 | |
| 37 /*! \page okiadpcm_page OKI (Dialogic) ADPCM encoding and decoding | |
| 38 \section okiadpcm_page_sec_1 What does it do? | |
| 39 OKI ADPCM is widely used in the CTI industry because it is the principal format | |
| 40 supported by Dialogic. As the market leader, they tend to define "common | |
| 41 practice". It offers a good balance of simplicity and quality at rates of | |
| 42 24kbps or 32kbps. 32kbps is obtained by ADPCM compressing 8k samples/second linear | |
| 43 PCM. 24kbps is obtained by resampling to 6k samples/second and using the same ADPCM | |
| 44 compression algorithm on the slower samples. | |
| 45 | |
| 46 The algorithms for this ADPCM codec can be found in "PC Telephony - The complete guide | |
| 47 to designing, building and programming systems using Dialogic and Related Hardware" | |
| 48 by Bob Edgar. pg 272-276. */ | |
| 49 | |
| 50 /*! | |
| 51 Oki (Dialogic) ADPCM conversion state descriptor. This defines the state of | |
| 52 a single working instance of the Oki ADPCM converter. This is used for | |
| 53 either linear to ADPCM or ADPCM to linear conversion. | |
| 54 */ | |
| 55 typedef struct | |
| 56 { | |
| 57 int bit_rate; | |
| 58 int16_t last; | |
| 59 int16_t step_index; | |
| 60 uint8_t oki_byte; | |
| 61 int16_t history[32]; | |
| 62 int ptr; | |
| 63 int mark; | |
| 64 int phase; | |
| 65 } oki_adpcm_state_t; | |
| 66 | |
| 67 #ifdef __cplusplus | |
| 68 extern "C" { | |
| 69 #endif | |
| 70 | |
| 71 /*! Initialise an Oki ADPCM encode or decode context. | |
| 72 \param s The Oki ADPCM context. | |
| 73 \param bit_rate The required bit rate for the ADPCM data. | |
| 74 The valid rates are 24000 and 32000. | |
| 75 \return A pointer to the Oki ADPCM context, or NULL for error. */ | |
| 76 oki_adpcm_state_t *oki_adpcm_init(oki_adpcm_state_t *s, int bit_rate); | |
| 77 | |
| 78 /*! Free an Oki ADPCM encode or decode context. | |
| 79 \param s The Oki ADPCM context. | |
| 80 \return 0 for OK. */ | |
| 81 int oki_adpcm_release(oki_adpcm_state_t *s); | |
| 82 | |
| 83 /*! Decode a buffer of Oki ADPCM data to linear PCM. | |
| 84 \param s The Oki ADPCM context. | |
| 85 \param amp The audio sample buffer. | |
| 86 \param oki_data | |
| 87 \param oki_bytes | |
| 88 \return The number of samples returned. */ | |
| 89 int oki_adpcm_decode(oki_adpcm_state_t *s, | |
| 90 int16_t amp[], | |
| 91 const uint8_t oki_data[], | |
| 92 int oki_bytes); | |
| 93 | |
| 94 /*! Encode a buffer of linear PCM data to Oki ADPCM. | |
| 95 \param s The Oki ADPCM context. | |
| 96 \param oki_data The Oki ADPCM data produced | |
| 97 \param amp The audio sample buffer. | |
| 98 \param len The number of samples in the buffer. | |
| 99 \return The number of bytes of Oki ADPCM data produced. */ | |
| 100 int oki_adpcm_encode(oki_adpcm_state_t *s, | |
| 101 uint8_t oki_data[], | |
| 102 const int16_t amp[], | |
| 103 int len); | |
| 104 | |
| 105 #ifdef __cplusplus | |
| 106 } | |
| 107 #endif | |
| 108 | |
| 109 #endif | |
| 110 /*- End of file ------------------------------------------------------------*/ |