lpc10.h

/*
 * SpanDSP - a series of DSP components for telephony
 *
 * lpc10.h - LPC10 low bit rate speech 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 Lesser General Public License version 2.1,
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: lpc10.h,v 1.17 2008/04/17 14:27:00 steveu Exp $
 */

#if !defined(_SPANDSP_LPC10_H_)
#define _SPANDSP_LPC10_H_

/*! \page lpc10_page LPC10 encoding and decoding
\section lpc10_page_sec_1 What does it do?
The LPC10 module implements the US Department of Defense LPC10
codec. This codec produces compressed data at 2400bps. At such
a low rate high fidelity cannot be expected. However, the speech
clarity is quite good, and this codec is unencumbered by patent
or other restrictions.

\section lpc10_page_sec_2 How does it work?
???.
*/

#define LPC10_SAMPLES_PER_FRAME 180
#define LPC10_BITS_IN_COMPRESSED_FRAME 54

/*!
    LPC10 codec unpacked frame.
*/
typedef struct
{
    int32_t ipitch;
    int32_t irms;
    int32_t irc[10];
} lpc10_frame_t;

/*!
    LPC10 codec encoder state descriptor. This defines the state of
    a single working instance of the LPC10 encoder.
*/
typedef struct
{
    int error_correction;

    /* State used only by function high_pass_100hz */
    float z11;
    float z21;
    float z12;
    float z22;
    
    /* State used by function lpc10_analyse */
    float inbuf[LPC10_SAMPLES_PER_FRAME*3];
    float pebuf[LPC10_SAMPLES_PER_FRAME*3];
    float lpbuf[696];
    float ivbuf[312];
    float bias;
    int32_t osbuf[10];      /* No initial value necessary */
    int32_t osptr;          /* Initial value 1 */
    int32_t obound[3];
    int32_t vwin[3][2];     /* Initial value vwin[2][0] = 307; vwin[2][1] = 462; */
    int32_t awin[3][2];     /* Initial value awin[2][0] = 307; awin[2][1] = 462; */
    int32_t voibuf[4][2];
    float rmsbuf[3];
    float rcbuf[3][10];
    float zpre;

    /* State used by function onset */
    float n;
    float d__;          /* Initial value 1.0f */
    float fpc;          /* No initial value necessary */
    float l2buf[16];
    float l2sum1;
    int32_t l2ptr1;     /* Initial value 1 */
    int32_t l2ptr2;     /* Initial value 9 */
    int32_t lasti;      /* No initial value necessary */
    int hyst;           /* Initial value FALSE */

    /* State used by function lpc10_voicing */
    float dither;       /* Initial value 20.0f */
    float snr;
    float maxmin;
    float voice[3][2];  /* Initial value is probably unnecessary */
    int32_t lbve;
    int32_t lbue;
    int32_t fbve;
    int32_t fbue;
    int32_t ofbue;
    int32_t sfbue;
    int32_t olbue;
    int32_t slbue;

    /* State used by function dynamic_pitch_tracking */
    float s[60];
    int32_t p[2][60];
    int32_t ipoint;
    float alphax;

    /* State used by function lpc10_pack */
    int32_t isync;
} lpc10_encode_state_t;

/*!
    LPC10 codec decoder state descriptor. This defines the state of
    a single working instance of the LPC10 decoder.
*/
typedef struct
{
    int error_correction;

    /* State used by function decode */
    int32_t iptold;     /* Initial value 60 */
    int first;          /* Initial value TRUE */
    int32_t ivp2h;
    int32_t iovoic;
    int32_t iavgp;      /* Initial value 60 */
    int32_t erate;
    int32_t drc[10][3];
    int32_t dpit[3];
    int32_t drms[3];

    /* State used by function synths */
    float buf[LPC10_SAMPLES_PER_FRAME*2];
    int32_t buflen;     /* Initial value LPC10_SAMPLES_PER_FRAME */

    /* State used by function pitsyn */
    int32_t ivoico;     /* No initial value necessary as long as first_pitsyn is initially TRUE_ */
    int32_t ipito;      /* No initial value necessary as long as first_pitsyn is initially TRUE_ */
    float rmso;         /* Initial value 1.0f */
    float rco[10];      /* No initial value necessary as long as first_pitsyn is initially TRUE_ */
    int32_t jsamp;      /* Nno initial value necessary as long as first_pitsyn is initially TRUE_ */
    int first_pitsyn;   /* Initial value TRUE */

    /* State used by function bsynz */
    int32_t ipo;
    float exc[166];
    float exc2[166];
    float lpi[3];
    float hpi[3];
    float rmso_bsynz;

    /* State used by function random */
    int32_t j;
    int32_t k;
    int16_t y[5];

    /* State used by function deemp */
    float dei[2];
    float deo[3];
} lpc10_decode_state_t;

#if defined(__cplusplus)
extern "C"
{
#endif

/*! Initialise an LPC10e encode context.
    \param s The LPC10e context
    \param error_correction ???
    \return A pointer to the LPC10e context, or NULL for error. */
lpc10_encode_state_t *lpc10_encode_init(lpc10_encode_state_t *s, int error_correction);

int lpc10_encode_release(lpc10_encode_state_t *s);

/*! Encode a buffer of linear PCM data to LPC10e.
    \param s The LPC10e context.
    \param ima_data The LPC10e data produced.
    \param amp The audio sample buffer.
    \param len The number of samples in the buffer. This must be a multiple of 180, as
           this is the number of samples on a frame.
    \return The number of bytes of LPC10e data produced. */
int lpc10_encode(lpc10_encode_state_t *s, uint8_t code[], const int16_t amp[], int len);

/*! Initialise an LPC10e decode context.
    \param s The LPC10e context
    \param error_correction ???
    \return A pointer to the LPC10e context, or NULL for error. */
lpc10_decode_state_t *lpc10_decode_init(lpc10_decode_state_t *st, int error_correction);

int lpc10_decode_release(lpc10_decode_state_t *s);

/*! Decode a buffer of LPC10e data to linear PCM.
    \param s The LPC10e context.
    \param amp The audio sample buffer.
    \param code The LPC10e data.
    \param len The number of bytes of LPC10e data to be decoded. This must be a multiple of 7,
           as each frame is packed into 7 bytes.
    \return The number of samples returned. */
int lpc10_decode(lpc10_decode_state_t *s, int16_t amp[], const uint8_t code[], int len);


#if defined(__cplusplus)
}
#endif

#endif
/*- End of include ---------------------------------------------------------*/