private/ima_adpcm.h

00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * private/ima_adpcm.c - Conversion routines between linear 16 bit PCM data
00005  *                               and 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 1.1 2008/11/30 10:17:31 steveu Exp $
00030  */
00031 
00032 #if !defined(_SPANDSP_PRIVATE_IMA_ADPCM_H_)
00033 #define _SPANDSP_PRIVATE_IMA_ADPCM_H_
00034 
00035 /*!
00036     IMA (DVI/Intel) ADPCM conversion state descriptor. This defines the state of
00037     a single working instance of the IMA ADPCM converter. This is used for
00038     either linear to ADPCM or ADPCM to linear conversion.
00039 */
00040 struct ima_adpcm_state_s
00041 {
00042     int variant;
00043     /*! \brief The size of a chunk, in samples. */
00044     int chunk_size;
00045     /*! \brief The last state of the ADPCM algorithm. */
00046     int last;
00047     /*! \brief Current index into the step size table. */
00048     int step_index;
00049     /*! \brief The current IMA code byte in progress. */
00050     uint16_t ima_byte;
00051     int bits;
00052 };
00053 
00054 #endif
00055 /*- End of file ------------------------------------------------------------*/

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