spandsp  0.0.6
private/oki_adpcm.h
Go to the documentation of this file.
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * private/oki_adpcm.h - Conversion routines between linear 16 bit PCM data
5  * and OKI (Dialogic) ADPCM format.
6  *
7  * Written by Steve Underwood <steveu@coppice.org>
8  *
9  * Copyright (C) 2001 Steve Underwood
10  *
11  * All rights reserved.
12  *
13  * This program is free software; you can redistribute it and/or modify
14  * it under the terms of the GNU Lesser General Public License version 2.1,
15  * as published by the Free Software Foundation.
16  *
17  * This program is distributed in the hope that it will be useful,
18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20  * GNU Lesser General Public License for more details.
21  *
22  * You should have received a copy of the GNU Lesser General Public
23  * License along with this program; if not, write to the Free Software
24  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
25  */
26 
27 /*! \file */
28 
29 #if !defined(_SPANDSP_PRIVATE_OKI_ADPCM_H_)
30 #define _SPANDSP_PRIVATE_OKI_ADPCM_H_
31 
32 /*!
33  Oki (Dialogic) ADPCM conversion state descriptor. This defines the state of
34  a single working instance of the Oki ADPCM converter. This is used for
35  either linear to ADPCM or ADPCM to linear conversion.
36 */
37 struct oki_adpcm_state_s
38 {
39  /*! \brief The bit rate - 24000 or 32000. */
40  int bit_rate;
41  /*! \brief The last state of the ADPCM algorithm. */
42  int16_t last;
43  /*! \brief Current index into the step size table. */
44  int16_t step_index;
45  /*! \brief The compressed data byte in progress. */
46  uint8_t oki_byte;
47  /*! \brief The signal history for the sample rate converter. */
48  int16_t history[32];
49  /*! \brief Pointer into the history buffer. */
50  int ptr;
51  /*! \brief Odd/even sample counter. */
52  int mark;
53  /*! \brief Phase accumulator for the sample rate converter. */
54  int phase;
55 };
56 
57 #endif
58 /*- End of file ------------------------------------------------------------*/