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/*
* SpanDSP - a series of DSP components for telephony
*
* g726.h - ITU G.726 codec.
*
* Written by Steve Underwood <steveu@coppice.org>
*
* Copyright (C) 2006 Steve Underwood
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Based on G.721/G.723 code which is:
*
* This source code is a product of Sun Microsystems, Inc. and is provided
* for unrestricted use. Users may copy or modify this source code without
* charge.
*
* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
*
* Sun source code is provided with no support and without any obligation on
* the part of Sun Microsystems, Inc. to assist in its use, correction,
* modification or enhancement.
*
* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
* OR ANY PART THEREOF.
*
* In no event will Sun Microsystems, Inc. be liable for any lost revenue
* or profits or other special, indirect and consequential damages, even if
* Sun has been advised of the possibility of such damages.
*
* Sun Microsystems, Inc.
* 2550 Garcia Avenue
* Mountain View, California 94043
*
* $Id: g726.h,v 1.18 2007/12/13 11:31:32 steveu Exp $
*/
/*! \file */
#if !defined(_SPANDSP_G726_H_)
#define _SPANDSP_G726_H_
/*! \page g726_page G.726 encoding and decoding
\section g726_page_sec_1 What does it do?
The G.726 module is a bit exact implementation of the full ITU G.726 specification.
It supports:
- 16 kbps, 24kbps, 32kbps, and 40kbps operation.
- Tandem adjustment, for interworking with A-law and u-law.
- Annex A support, for use in environments not using A-law or u-law.
It passes the ITU tests.
\section g726_page_sec_2 How does it work?
???.
*/
enum
{
G726_ENCODING_LINEAR = 0, /* Interworking with 16 bit signed linear */
G726_ENCODING_ULAW, /* Interworking with u-law */
G726_ENCODING_ALAW /* Interworking with A-law */
};
enum
{
G726_PACKING_NONE = 0,
G726_PACKING_LEFT = 1,
G726_PACKING_RIGHT = 2
};
struct g726_state_s;
typedef int16_t (*g726_decoder_func_t)(struct g726_state_s *s, uint8_t code);
typedef uint8_t (*g726_encoder_func_t)(struct g726_state_s *s, int16_t amp);
/*!
* The following is the definition of the state structure
* used by the G.726 encoder and decoder to preserve their internal
* state between successive calls. The meanings of the majority
* of the state structure fields are explained in detail in the
* CCITT Recommendation G.721. The field names are essentially indentical
* to variable names in the bit level description of the coding algorithm
* included in this Recommendation.
*/
typedef struct g726_state_s
{
/*! The bit rate */
int rate;
/*! The external coding, for tandem operation */
int ext_coding;
/*! The number of bits per sample */
unsigned int bits_per_sample;
/*! One of the G.726_PACKING_xxx options */
int packing;
/*! Locked or steady state step size multiplier. */
int32_t yl;
/*! Unlocked or non-steady state step size multiplier. */
int16_t yu;
/*! int16_t term energy estimate. */
int16_t dms;
/*! Long term energy estimate. */
int16_t dml;
/*! Linear weighting coefficient of 'yl' and 'yu'. */
int16_t ap;
/*! Coefficients of pole portion of prediction filter. */
int16_t a[2];
/*! Coefficients of zero portion of prediction filter. */
int16_t b[6];
/*! Signs of previous two samples of a partially reconstructed signal. */
int16_t pk[2];
/*! Previous 6 samples of the quantized difference signal represented in
an internal floating point format. */
int16_t dq[6];
/*! Previous 2 samples of the quantized difference signal represented in an
internal floating point format. */
int16_t sr[2];
/*! Delayed tone detect */
int td;
/*! \brief The bit stream processing context. */
bitstream_state_t bs;
/*! \brief The current encoder function. */
g726_encoder_func_t enc_func;
/*! \brief The current decoder function. */
g726_decoder_func_t dec_func;
} g726_state_t;
#if defined(__cplusplus)
extern "C"
{
#endif
/*! Initialise a G.726 encode or decode context.
\param s The G.726 context.
\param bit_rate The required bit rate for the ADPCM data.
The valid rates are 16000, 24000, 32000 and 40000.
\param ext_coding The coding used outside G.726.
\param packing One of the G.726_PACKING_xxx options.
\return A pointer to the G.726 context, or NULL for error. */
g726_state_t *g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing);
/*! Free a G.726 encode or decode context.
\param s The G.726 context.
\return 0 for OK. */
int g726_release(g726_state_t *s);
/*! Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.
\param s The G.726 context.
\param amp The audio sample buffer.
\param g726_data
\param g726_bytes
\return The number of samples returned. */
int g726_decode(g726_state_t *s,
int16_t amp[],
const uint8_t g726_data[],
int g726_bytes);
/*! Encode a buffer of linear PCM data to G.726 ADPCM.
\param s The G.726 context.
\param g726_data The G.726 data produced.
\param amp The audio sample buffer.
\param len The number of samples in the buffer.
\return The number of bytes of G.726 data produced. */
int g726_encode(g726_state_t *s,
uint8_t g726_data[],
const int16_t amp[],
int len);
#if defined(__cplusplus)
}
#endif
#endif
/*- End of file ------------------------------------------------------------*/
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