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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * imaadpcm.c - Conversion routines between linear 16 bit PCM data and
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5 * IMA/DVI/Intel ADPCM format.
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6 *
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7 * Written by Steve Underwood <steveu@coppice.org>
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8 *
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9 * Copyright (C) 2004 Steve Underwood
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10 *
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11 * Based on a bit from here, a bit from there, eye of toad,
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12 * ear of bat, etc - plus, of course, my own 2 cents.
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13 *
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14 * All rights reserved.
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15 *
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16 * This program is free software; you can redistribute it and/or modify
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17 * it under the terms of the GNU General Public License version 2, as
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18 * published by the Free Software Foundation.
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19 *
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20 * This program is distributed in the hope that it will be useful,
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21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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23 * GNU General Public License for more details.
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24 *
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25 * You should have received a copy of the GNU General Public License
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26 * along with this program; if not, write to the Free Software
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27 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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28 *
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29 * $Id: ima_adpcm.h,v 1.12 2006/10/24 13:45:28 steveu Exp $
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30 */
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31
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32 /*! \file */
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33
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34 #if !defined(_IMA_ADPCM_H_)
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35 #define _IMA_ADPCM_H_
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36
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37 /*! \page ima_adpcm_page IMA/DVI/Intel ADPCM encoding and decoding
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38 \section ima_adpcm_page_sec_1 What does it do?
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39 IMA ADPCM offers a good balance of simplicity and quality at a rate of
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40 32kbps.
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41
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42 \section ima_adpcm_page_sec_2 How does it work?
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43
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44 \section ima_adpcm_page_sec_3 How do I use it?
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45 */
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46
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47 enum
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48 {
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49 IMA_ADPCM_DVI4 = 0,
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50 IMA_ADPCM_VDVI = 1
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51 };
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52
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53 /*!
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54 IMA (DVI/Intel) ADPCM conversion state descriptor. This defines the state of
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55 a single working instance of the IMA ADPCM converter. This is used for
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56 either linear to ADPCM or ADPCM to linear conversion.
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57 */
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58 typedef struct
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59 {
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60 int variant;
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61 int last;
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62 int step_index;
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63 uint16_t ima_byte;
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64 int bits;
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65 } ima_adpcm_state_t;
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66
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67 #ifdef __cplusplus
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68 extern "C" {
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69 #endif
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70
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71 /*! Initialise an IMA ADPCM encode or decode context.
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72 \param s The IMA ADPCM context
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73 \param variant ???
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74 \return A pointer to the IMA ADPCM context, or NULL for error. */
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75 ima_adpcm_state_t *ima_adpcm_init(ima_adpcm_state_t *s, int variant);
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76
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77 /*! Free an IMA ADPCM encode or decode context.
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78 \param s The IMA ADPCM context.
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79 \return 0 for OK. */
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80 int ima_adpcm_release(ima_adpcm_state_t *s);
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81
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82 /*! Encode a buffer of linear PCM data to IMA ADPCM.
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83 \param s The IMA ADPCM context.
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84 \param ima_data The IMA ADPCM data produced.
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85 \param amp The audio sample buffer.
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86 \param len The number of samples in the buffer.
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87 \return The number of bytes of IMA ADPCM data produced. */
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88 int ima_adpcm_encode(ima_adpcm_state_t *s,
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89 uint8_t ima_data[],
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90 const int16_t amp[],
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91 int len);
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92
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93 /*! Decode a buffer of IMA ADPCM data to linear PCM.
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94 \param s The IMA ADPCM context.
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95 \param amp The audio sample buffer.
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96 \param ima_data
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97 \param ima_bytes
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98 \return The number of samples returned. */
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99 int ima_adpcm_decode(ima_adpcm_state_t *s,
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100 int16_t amp[],
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101 const uint8_t ima_data[],
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102 int ima_bytes);
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103
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104 #ifdef __cplusplus
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105 }
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106 #endif
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107
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108 #endif
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109 /*- End of file ------------------------------------------------------------*/
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