121 lines
3.9 KiB
C
121 lines
3.9 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* lpc10.h - LPC10 low bit rate speech 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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* $Id: lpc10.h,v 1.22 2009/04/11 18:11:19 steveu Exp $
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*/
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#if !defined(_SPANDSP_LPC10_H_)
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#define _SPANDSP_LPC10_H_
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/*! \page lpc10_page LPC10 encoding and decoding
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\section lpc10_page_sec_1 What does it do?
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The LPC10 module implements the US Department of Defense LPC10
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codec. This codec produces compressed data at 2400bps. At such
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a low rate high fidelity cannot be expected. However, the speech
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clarity is quite good, and this codec is unencumbered by patent
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or other restrictions.
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\section lpc10_page_sec_2 How does it work?
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???.
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*/
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#define LPC10_SAMPLES_PER_FRAME 180
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#define LPC10_BITS_IN_COMPRESSED_FRAME 54
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/*!
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LPC10 codec unpacked frame.
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*/
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typedef struct
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{
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/*! Pitch */
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int32_t ipitch;
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/*! Energy */
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int32_t irms;
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/*! Reflection coefficients */
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int32_t irc[10];
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} lpc10_frame_t;
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/*!
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LPC10 codec encoder state descriptor. This defines the state of
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a single working instance of the LPC10 encoder.
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*/
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typedef struct lpc10_encode_state_s lpc10_encode_state_t;
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/*!
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LPC10 codec decoder state descriptor. This defines the state of
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a single working instance of the LPC10 decoder.
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*/
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typedef struct lpc10_decode_state_s lpc10_decode_state_t;
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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 an LPC10e encode context.
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\param s The LPC10e context
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\param error_correction ???
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\return A pointer to the LPC10e context, or NULL for error. */
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SPAN_DECLARE(lpc10_encode_state_t *) lpc10_encode_init(lpc10_encode_state_t *s, int error_correction);
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SPAN_DECLARE(int) lpc10_encode_release(lpc10_encode_state_t *s);
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SPAN_DECLARE(int) lpc10_encode_free(lpc10_encode_state_t *s);
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/*! Encode a buffer of linear PCM data to LPC10e.
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\param s The LPC10e context.
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\param ima_data The LPC10e 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. This must be a multiple of 180, as
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this is the number of samples on a frame.
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\return The number of bytes of LPC10e data produced. */
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SPAN_DECLARE(int) lpc10_encode(lpc10_encode_state_t *s, uint8_t code[], const int16_t amp[], int len);
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/*! Initialise an LPC10e decode context.
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\param s The LPC10e context
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\param error_correction ???
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\return A pointer to the LPC10e context, or NULL for error. */
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SPAN_DECLARE(lpc10_decode_state_t *) lpc10_decode_init(lpc10_decode_state_t *st, int error_correction);
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SPAN_DECLARE(int) lpc10_decode_release(lpc10_decode_state_t *s);
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SPAN_DECLARE(int) lpc10_decode_free(lpc10_decode_state_t *s);
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/*! Decode a buffer of LPC10e data to linear PCM.
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\param s The LPC10e context.
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\param amp The audio sample buffer.
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\param code The LPC10e data.
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\param len The number of bytes of LPC10e data to be decoded. This must be a multiple of 7,
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as each frame is packed into 7 bytes.
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\return The number of samples returned. */
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SPAN_DECLARE(int) lpc10_decode(lpc10_decode_state_t *s, int16_t amp[], const uint8_t code[], 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 include ---------------------------------------------------------*/
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