|
5
|
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 ------------------------------------------------------------*/
|
