185 lines
5.7 KiB
C
185 lines
5.7 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* g726.h - ITU G.726 codec.
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2006 Steve Underwood
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*
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* Despite my general liking of the GPL, I place my own contributions
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* to this code in the public domain for the benefit of all mankind -
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* even the slimy ones who might try to proprietize my work and use it
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* to my detriment.
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*
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* Based on G.721/G.723 code which is:
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*
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* This source code is a product of Sun Microsystems, Inc. and is provided
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* for unrestricted use. Users may copy or modify this source code without
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* charge.
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*
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* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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*
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* Sun source code is provided with no support and without any obligation on
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* the part of Sun Microsystems, Inc. to assist in its use, correction,
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* modification or enhancement.
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*
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* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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* OR ANY PART THEREOF.
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*
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* In no event will Sun Microsystems, Inc. be liable for any lost revenue
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* or profits or other special, indirect and consequential damages, even if
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* Sun has been advised of the possibility of such damages.
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*
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* Sun Microsystems, Inc.
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* 2550 Garcia Avenue
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* Mountain View, California 94043
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*
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* $Id: g726.h,v 1.8 2006/09/03 04:43:46 steveu Exp $
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*/
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/*! \file */
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#if !defined(_G726_H_)
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#define _G726_H_
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/*! \page g726_page G.726 encoding and decoding
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\section g726_page_sec_1 What does it do?
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The G.726 module is a bit exact implementation of the full ITU G.726 specification.
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It supports:
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- 16 kbps, 24kbps, 32kbps, and 40kbps operation.
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- Tandem adjustment, for interworking with A-law and u-law.
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- Annex A support, for use in environments not using A-law or u-law.
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It passes the ITU tests.
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\section g726_page_sec_2 How does it work?
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???.
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*/
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enum
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{
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G726_ENCODING_LINEAR = 0, /* Interworking with 16 bit signed linear */
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G726_ENCODING_ULAW, /* Interworking with u-law */
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G726_ENCODING_ALAW /* Interworking with A-law */
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};
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enum
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{
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G726_PACKING_NONE = 0,
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G726_PACKING_LEFT = 1,
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G726_PACKING_RIGHT = 2
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};
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struct g726_state_s;
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typedef int16_t (*g726_decoder_func_t)(struct g726_state_s *s, uint8_t code);
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typedef uint8_t (*g726_encoder_func_t)(struct g726_state_s *s, int16_t amp);
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/*
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* The following is the definition of the state structure
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* used by the G.726 encoder and decoder to preserve their internal
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* state between successive calls. The meanings of the majority
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* of the state structure fields are explained in detail in the
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* CCITT Recommendation G.721. The field names are essentially indentical
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* to variable names in the bit level description of the coding algorithm
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* included in this Recommendation.
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*/
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typedef struct g726_state_s
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{
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/*! The bit rate */
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int rate;
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/*! The external coding, for tandem operation */
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int ext_coding;
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/*! The number of bits per sample */
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int bits_per_sample;
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/*! One fo the G.726_PACKING_xxx options */
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int packing;
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/*! Locked or steady state step size multiplier. */
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int32_t yl;
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/*! Unlocked or non-steady state step size multiplier. */
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int16_t yu;
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/*! int16_t term energy estimate. */
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int16_t dms;
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/*! Long term energy estimate. */
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int16_t dml;
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/*! Linear weighting coefficient of 'yl' and 'yu'. */
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int16_t ap;
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/*! Coefficients of pole portion of prediction filter. */
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int16_t a[2];
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/*! Coefficients of zero portion of prediction filter. */
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int16_t b[6];
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/*! Signs of previous two samples of a partially reconstructed signal. */
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int16_t pk[2];
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/*! Previous 6 samples of the quantized difference signal represented in
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an internal floating point format. */
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int16_t dq[6];
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/*! Previous 2 samples of the quantized difference signal represented in an
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internal floating point format. */
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int16_t sr[2];
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/*! Delayed tone detect */
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int td;
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unsigned int in_buffer;
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int in_bits;
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unsigned int out_buffer;
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int out_bits;
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g726_encoder_func_t enc_func;
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g726_decoder_func_t dec_func;
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} g726_state_t;
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*! Initialise a G.726 encode or decode context.
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\param s The G.726 context.
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\param bit_rate The required bit rate for the ADPCM data.
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The valid rates are 16000, 24000, 32000 and 40000.
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\param ext_coding The coding used outside G.726.
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\param packing One of the G.726_PACKING_xxx options.
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\return A pointer to the G.726 context, or NULL for error. */
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g726_state_t *g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing);
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/*! Free a G.726 encode or decode context.
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\param s The G.726 context.
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\return 0 for OK. */
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int g726_release(g726_state_t *s);
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/*! Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.
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\param s The G.726 context.
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\param amp
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\param g726_data
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\param g726_bytes
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\return The number of samples returned. */
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int g726_decode(g726_state_t *s,
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int16_t amp[],
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const uint8_t g726_data[],
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int g726_bytes);
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/*! Encode a buffer of linear PCM data to G.726 ADPCM.
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\param s The G.726 context.
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\param g726_data
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\param amp
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\param samples
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\return The number of bytes of G.726 data produced. */
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int g726_encode(g726_state_t *s,
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uint8_t g726_data[],
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const int16_t amp[],
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int samples);
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#ifdef __cplusplus
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}
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#endif
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#endif
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/*- End of file ------------------------------------------------------------*/
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