private/oki_adpcm.h

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00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * private/oki_adpcm.h - Conversion routines between linear 16 bit PCM data
00005  *                               and OKI (Dialogic) ADPCM format.
00006  *
00007  * Written by Steve Underwood <steveu@coppice.org>
00008  *
00009  * Copyright (C) 2001 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 
00027 /*! \file */
00028 
00029 #if !defined(_SPANDSP_PRIVATE_OKI_ADPCM_H_)
00030 #define _SPANDSP_PRIVATE_OKI_ADPCM_H_
00031 
00032 /*!
00033     Oki (Dialogic) ADPCM conversion state descriptor. This defines the state of
00034     a single working instance of the Oki ADPCM converter. This is used for
00035     either linear to ADPCM or ADPCM to linear conversion.
00036 */
00037 struct oki_adpcm_state_s
00038 {
00039     /*! \brief The bit rate - 24000 or 32000. */
00040     int bit_rate;
00041     /*! \brief The last state of the ADPCM algorithm. */
00042     int16_t last;
00043     /*! \brief Current index into the step size table. */
00044     int16_t step_index;
00045     /*! \brief The compressed data byte in progress. */
00046     uint8_t oki_byte;
00047     /*! \brief The signal history for the sample rate converter. */
00048     int16_t history[32];
00049     /*! \brief Pointer into the history buffer. */
00050     int ptr;
00051     /*! \brief Odd/even sample counter. */
00052     int mark;
00053     /*! \brief Phase accumulator for the sample rate converter. */
00054     int phase;
00055 };
00056 
00057 #endif
00058 /*- End of file ------------------------------------------------------------*/

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