121 lines
3.7 KiB
C
121 lines
3.7 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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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*! \file */
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#if !defined(_SPANDSP_G726_H_)
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#define _SPANDSP_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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/*!
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G.726 state
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*/
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typedef struct g726_state_s g726_state_t;
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typedef int16_t (*g726_decoder_func_t)(g726_state_t *s, uint8_t code);
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typedef uint8_t (*g726_encoder_func_t)(g726_state_t *s, int16_t amp);
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#if defined(__cplusplus)
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extern "C"
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{
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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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SPAN_DECLARE(g726_state_t *) g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing);
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/*! Release 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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SPAN_DECLARE(int) g726_release(g726_state_t *s);
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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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SPAN_DECLARE(int) g726_free(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 The audio sample buffer.
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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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SPAN_DECLARE(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 The G.726 data produced.
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\param amp The audio sample buffer.
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\param len The number of samples in the buffer.
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\return The number of bytes of G.726 data produced. */
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SPAN_DECLARE(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 len);
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#if defined(__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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