ima_adpcm.h

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00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * ima_adpcm.c - Conversion routines between linear 16 bit PCM data and
00005  *                       IMA/DVI/Intel ADPCM format.
00006  *
00007  * Written by Steve Underwood <steveu@coppice.org>
00008  *
00009  * Copyright (C) 2004 Steve Underwood
00010  *
00011  * All rights reserved.
00012  *
00013  * This program is free software; you can redistribute it and/or modify
00014  * it under the terms of the GNU Lesser General Public License version 2.1,
00015  * as published by the Free Software Foundation.
00016  *
00017  * This program is distributed in the hope that it will be useful,
00018  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00019  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00020  * GNU Lesser General Public License for more details.
00021  *
00022  * You should have received a copy of the GNU Lesser General Public
00023  * License along with this program; if not, write to the Free Software
00024  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00025  *
00026  * Based on a bit from here, a bit from there, eye of toad,
00027  * ear of bat, etc - plus, of course, my own 2 cents.
00028  *
00029  * $Id: ima_adpcm.h,v 1.25 2009/04/11 18:11:19 steveu Exp $
00030  */
00031 
00032 /*! \file */
00033 
00034 #if !defined(_SPANDSP_IMA_ADPCM_H_)
00035 #define _SPANDSP_IMA_ADPCM_H_
00036 
00037 /*! \page ima_adpcm_page IMA/DVI/Intel ADPCM encoding and decoding
00038 \section ima_adpcm_page_sec_1 What does it do?
00039 IMA ADPCM offers a good balance of simplicity and quality at a rate of
00040 32kbps.
00041 
00042 \section ima_adpcm_page_sec_2 How does it work?
00043 
00044 \section ima_adpcm_page_sec_3 How do I use it?
00045 */
00046 
00047 enum
00048 {
00049     /*! IMA4 is the original IMA ADPCM variant */
00050     IMA_ADPCM_IMA4 = 0,
00051     /*! DVI4 is the IMA ADPCM variant defined in RFC3551 */
00052     IMA_ADPCM_DVI4 = 1,
00053     /*! VDVI is the variable bit rate IMA ADPCM variant defined in RFC3551 */
00054     IMA_ADPCM_VDVI = 2
00055 };
00056 
00057 /*!
00058     IMA (DVI/Intel) ADPCM conversion state descriptor. This defines the state of
00059     a single working instance of the IMA ADPCM converter. This is used for
00060     either linear to ADPCM or ADPCM to linear conversion.
00061 */
00062 typedef struct ima_adpcm_state_s ima_adpcm_state_t;
00063 
00064 #if defined(__cplusplus)
00065 extern "C"
00066 {
00067 #endif
00068 
00069 /*! Initialise an IMA ADPCM encode or decode context.
00070     \param s The IMA ADPCM context.
00071     \param variant IMA_ADPCM_IMA4, IMA_ADPCM_DVI4, or IMA_ADPCM_VDVI.
00072     \param chunk_size The size of a chunk, in samples. A chunk size of
00073            zero sample samples means treat each encode or decode operation
00074            as a chunk.
00075     \return A pointer to the IMA ADPCM context, or NULL for error. */
00076 SPAN_DECLARE(ima_adpcm_state_t *) ima_adpcm_init(ima_adpcm_state_t *s,
00077                                                  int variant,
00078                                                  int chunk_size);
00079 
00080 /*! Release an IMA ADPCM encode or decode context.
00081     \param s The IMA ADPCM context.
00082     \return 0 for OK. */
00083 SPAN_DECLARE(int) ima_adpcm_release(ima_adpcm_state_t *s);
00084 
00085 /*! Free an IMA ADPCM encode or decode context.
00086     \param s The IMA ADPCM context.
00087     \return 0 for OK. */
00088 SPAN_DECLARE(int) ima_adpcm_free(ima_adpcm_state_t *s);
00089 
00090 /*! Encode a buffer of linear PCM data to IMA ADPCM.
00091     \param s The IMA ADPCM context.
00092     \param ima_data The IMA ADPCM data produced.
00093     \param amp The audio sample buffer.
00094     \param len The number of samples in the buffer.
00095     \return The number of bytes of IMA ADPCM data produced. */
00096 SPAN_DECLARE(int) ima_adpcm_encode(ima_adpcm_state_t *s,
00097                                    uint8_t ima_data[],
00098                                    const int16_t amp[],
00099                                    int len);
00100 
00101 /*! Decode a buffer of IMA ADPCM data to linear PCM.
00102     \param s The IMA ADPCM context.
00103     \param amp The audio sample buffer.
00104     \param ima_data The IMA ADPCM data
00105     \param ima_bytes The number of bytes of IMA ADPCM data
00106     \return The number of samples returned. */
00107 SPAN_DECLARE(int) ima_adpcm_decode(ima_adpcm_state_t *s,
00108                                    int16_t amp[],
00109                                    const uint8_t ima_data[],
00110                                    int ima_bytes);
00111 
00112 #if defined(__cplusplus)
00113 }
00114 #endif
00115 
00116 #endif
00117 /*- End of file ------------------------------------------------------------*/

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