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comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/ima_adpcm.h @ 5:f762bf195c4b

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import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
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4:26cd8f1ef0b1 5:f762bf195c4b
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * imaadpcm.c - Conversion routines between linear 16 bit PCM data and
5 * IMA/DVI/Intel ADPCM format.
6 *
7 * Written by Steve Underwood <steveu@coppice.org>
8 *
9 * Copyright (C) 2004 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: ima_adpcm.h,v 1.12 2006/10/24 13:45:28 steveu Exp $
30 */
31
32 /*! \file */
33
34 #if !defined(_IMA_ADPCM_H_)
35 #define _IMA_ADPCM_H_
36
37 /*! \page ima_adpcm_page IMA/DVI/Intel ADPCM encoding and decoding
38 \section ima_adpcm_page_sec_1 What does it do?
39 IMA ADPCM offers a good balance of simplicity and quality at a rate of
40 32kbps.
41
42 \section ima_adpcm_page_sec_2 How does it work?
43
44 \section ima_adpcm_page_sec_3 How do I use it?
45 */
46
47 enum
48 {
49 IMA_ADPCM_DVI4 = 0,
50 IMA_ADPCM_VDVI = 1
51 };
52
53 /*!
54 IMA (DVI/Intel) ADPCM conversion state descriptor. This defines the state of
55 a single working instance of the IMA ADPCM converter. This is used for
56 either linear to ADPCM or ADPCM to linear conversion.
57 */
58 typedef struct
59 {
60 int variant;
61 int last;
62 int step_index;
63 uint16_t ima_byte;
64 int bits;
65 } ima_adpcm_state_t;
66
67 #ifdef __cplusplus
68 extern "C" {
69 #endif
70
71 /*! Initialise an IMA ADPCM encode or decode context.
72 \param s The IMA ADPCM context
73 \param variant ???
74 \return A pointer to the IMA ADPCM context, or NULL for error. */
75 ima_adpcm_state_t *ima_adpcm_init(ima_adpcm_state_t *s, int variant);
76
77 /*! Free an IMA ADPCM encode or decode context.
78 \param s The IMA ADPCM context.
79 \return 0 for OK. */
80 int ima_adpcm_release(ima_adpcm_state_t *s);
81
82 /*! Encode a buffer of linear PCM data to IMA ADPCM.
83 \param s The IMA ADPCM context.
84 \param ima_data The IMA ADPCM data produced.
85 \param amp The audio sample buffer.
86 \param len The number of samples in the buffer.
87 \return The number of bytes of IMA ADPCM data produced. */
88 int ima_adpcm_encode(ima_adpcm_state_t *s,
89 uint8_t ima_data[],
90 const int16_t amp[],
91 int len);
92
93 /*! Decode a buffer of IMA ADPCM data to linear PCM.
94 \param s The IMA ADPCM context.
95 \param amp The audio sample buffer.
96 \param ima_data
97 \param ima_bytes
98 \return The number of samples returned. */
99 int ima_adpcm_decode(ima_adpcm_state_t *s,
100 int16_t amp[],
101 const uint8_t ima_data[],
102 int ima_bytes);
103
104 #ifdef __cplusplus
105 }
106 #endif
107
108 #endif
109 /*- End of file ------------------------------------------------------------*/

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