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view spandsp-0.0.3/spandsp-0.0.3/src/spandsp/g726.h @ 5:f762bf195c4b
import spandsp-0.0.3
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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date | Fri, 25 Jun 2010 16:00:21 +0200 |
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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 1.13 2006/11/28 16:59:57 steveu Exp $ */ /*! \file */ #if !defined(_G726_H_) #define _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 fo 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; bitstream_state_t bs; g726_encoder_func_t enc_func; g726_decoder_func_t dec_func; } g726_state_t; #ifdef __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); #ifdef __cplusplus } #endif #endif /*- End of file ------------------------------------------------------------*/