Mercurial > hg > audiostuff
comparison spandsp-0.0.6pre17/src/spandsp/oki_adpcm.h @ 4:26cd8f1ef0b1
import spandsp-0.0.6pre17
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
---|---|
date | Fri, 25 Jun 2010 15:50:58 +0200 |
parents | |
children |
comparison
equal
deleted
inserted
replaced
3:c6c5a16ce2f2 | 4:26cd8f1ef0b1 |
---|---|
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 * 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: oki_adpcm.h,v 1.24 2009/02/10 13:06:47 steveu Exp $ | |
27 */ | |
28 | |
29 /*! \file */ | |
30 | |
31 #if !defined(_SPANDSP_OKI_ADPCM_H_) | |
32 #define _SPANDSP_OKI_ADPCM_H_ | |
33 | |
34 /*! \page okiadpcm_page OKI (Dialogic) ADPCM encoding and decoding | |
35 \section okiadpcm_page_sec_1 What does it do? | |
36 OKI ADPCM is widely used in the CTI industry because it is the principal format | |
37 supported by Dialogic. As the market leader, they tend to define "common | |
38 practice". It offers a good balance of simplicity and quality at rates of | |
39 24kbps or 32kbps. 32kbps is obtained by ADPCM compressing 8k samples/second linear | |
40 PCM. 24kbps is obtained by resampling to 6k samples/second and using the same ADPCM | |
41 compression algorithm on the slower samples. | |
42 | |
43 The algorithms for this ADPCM codec can be found in "PC Telephony - The complete guide | |
44 to designing, building and programming systems using Dialogic and Related Hardware" | |
45 by Bob Edgar. pg 272-276. */ | |
46 | |
47 /*! | |
48 Oki (Dialogic) ADPCM conversion state descriptor. This defines the state of | |
49 a single working instance of the Oki ADPCM converter. This is used for | |
50 either linear to ADPCM or ADPCM to linear conversion. | |
51 */ | |
52 typedef struct oki_adpcm_state_s oki_adpcm_state_t; | |
53 | |
54 #if defined(__cplusplus) | |
55 extern "C" | |
56 { | |
57 #endif | |
58 | |
59 /*! Initialise an Oki ADPCM encode or decode context. | |
60 \param s The Oki ADPCM context. | |
61 \param bit_rate The required bit rate for the ADPCM data. | |
62 The valid rates are 24000 and 32000. | |
63 \return A pointer to the Oki ADPCM context, or NULL for error. */ | |
64 SPAN_DECLARE(oki_adpcm_state_t *) oki_adpcm_init(oki_adpcm_state_t *s, | |
65 int bit_rate); | |
66 | |
67 /*! Release an Oki ADPCM encode or decode context. | |
68 \param s The Oki ADPCM context. | |
69 \return 0 for OK. */ | |
70 SPAN_DECLARE(int) oki_adpcm_release(oki_adpcm_state_t *s); | |
71 | |
72 /*! Free an Oki ADPCM encode or decode context. | |
73 \param s The Oki ADPCM context. | |
74 \return 0 for OK. */ | |
75 SPAN_DECLARE(int) oki_adpcm_free(oki_adpcm_state_t *s); | |
76 | |
77 /*! Decode a buffer of Oki ADPCM data to linear PCM. | |
78 \param s The Oki ADPCM context. | |
79 \param amp The audio sample buffer. | |
80 \param oki_data | |
81 \param oki_bytes | |
82 \return The number of samples returned. */ | |
83 SPAN_DECLARE(int) oki_adpcm_decode(oki_adpcm_state_t *s, | |
84 int16_t amp[], | |
85 const uint8_t oki_data[], | |
86 int oki_bytes); | |
87 | |
88 /*! Encode a buffer of linear PCM data to Oki ADPCM. | |
89 \param s The Oki ADPCM context. | |
90 \param oki_data The Oki ADPCM data produced | |
91 \param amp The audio sample buffer. | |
92 \param len The number of samples in the buffer. | |
93 \return The number of bytes of Oki ADPCM data produced. */ | |
94 SPAN_DECLARE(int) oki_adpcm_encode(oki_adpcm_state_t *s, | |
95 uint8_t oki_data[], | |
96 const int16_t amp[], | |
97 int len); | |
98 | |
99 #if defined(__cplusplus) | |
100 } | |
101 #endif | |
102 | |
103 #endif | |
104 /*- End of file ------------------------------------------------------------*/ |