codec_g726.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 * Kevin P. Fleming <[email protected]>
 *
 * Based on frompcm.c and topcm.c from the Emiliano MIPL browser/
 * interpreter. See http://www.bsdtelephony.com.mx
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief codec_g726.c - translate between signed linear and ITU G.726-32kbps (both RFC3551 and AAL2 codeword packing)
 *
 * \ingroup codecs
 */

/*** MODULEINFO
 <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/lock.h"
#include "asterisk/linkedlists.h"
#include "asterisk/module.h"
#include "asterisk/config.h"
#include "asterisk/translate.h"
#include "asterisk/utils.h"

#define WANT_ASM
#include "log2comp.h"

/* define NOT_BLI to use a faster but not bit-level identical version */
/* #define NOT_BLI */

#if defined(NOT_BLI)
# if defined(_MSC_VER)
typedef __int64 sint64;
# elif defined(__GNUC__)
typedef long long sint64;
# else
# error 64-bit integer type is not defined for your compiler/platform
# endif
#endif

#define BUFFER_SAMPLES 8096 /* size for the translation buffers */
#define BUF_SHIFT 5

/* Sample frame data */
#include "asterisk/slin.h"
#include "ex_g726.h"

/*
 * 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 identical
 * to variable names in the bit level description of the coding algorithm
 * included in this Recommendation.
 */
struct g726_state {
 long yl; /* Locked or steady state step size multiplier. */
 int yu; /* Unlocked or non-steady state step size multiplier. */
 int dms; /* Short term energy estimate. */
 int dml; /* Long term energy estimate. */
 int ap; /* Linear weighting coefficient of 'yl' and 'yu'. */
 int a[2]; /* Coefficients of pole portion of prediction filter.
 * stored as fixed-point 1==2^14 */
 int b[6]; /* Coefficients of zero portion of prediction filter.
 * stored as fixed-point 1==2^14 */
 int pk[2]; /* Signs of previous two samples of a partially
 * reconstructed signal. */
 int dq[6]; /* Previous 6 samples of the quantized difference signal
 * stored as fixed point 1==2^12,
 * or in internal floating point format */
 int sr[2]; /* Previous 2 samples of the quantized difference signal
 * stored as fixed point 1==2^12,
 * or in internal floating point format */
 int td; /* delayed tone detect, new in 1988 version */
};

static int qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
/*
 * Maps G.721 code word to reconstructed scale factor normalized log
 * magnitude values.
 */
static int _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
 425, 373, 323, 273, 213, 135, 4, -2048};

/* Maps G.721 code word to log of scale factor multiplier. */
static int _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
 1122, 355, 198, 112, 64, 41, 18, -12};
/*
 * Maps G.721 code words to a set of values whose long and short
 * term averages are computed and then compared to give an indication
 * how stationary (steady state) the signal is.
 */
static int _fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};


/*
 * g72x_init_state()
 *
 * This routine initializes and/or resets the g726_state structure
 * pointed to by 'state_ptr'.
 * All the initial state values are specified in the CCITT G.721 document.
 */
static void g726_init_state(struct g726_state *state_ptr)
{
 int cnta;

 state_ptr->yl = 34816;
 state_ptr->yu = 544;
 state_ptr->dms = 0;
 state_ptr->dml = 0;
 state_ptr->ap = 0;
 for (cnta = 0; cnta < 2; cnta++) {
 state_ptr->a[cnta] = 0;
 state_ptr->pk[cnta] = 0;
#ifdef NOT_BLI
 state_ptr->sr[cnta] = 1;
#else
 state_ptr->sr[cnta] = 32;
#endif
 }
 for (cnta = 0; cnta < 6; cnta++) {
 state_ptr->b[cnta] = 0;
#ifdef NOT_BLI
 state_ptr->dq[cnta] = 1;
#else
 state_ptr->dq[cnta] = 32;
#endif
 }
 state_ptr->td = 0;
}

/*
 * quan()
 *
 * quantizes the input val against the table of integers.
 * It returns i if table[i - 1] <= val < table[i].
 *
 * Using linear search for simple coding.
 */
static int quan(int val, int *table, int size)
{
 int i;

 for (i = 0; i < size && val >= *table; ++i, ++table)
 ;
 return i;
}

#ifdef NOT_BLI /* faster non-identical version */

/*
 * predictor_zero()
 *
 * computes the estimated signal from 6-zero predictor.
 *
 */
static int predictor_zero(struct g726_state *state_ptr)
{ /* divide by 2 is necessary here to handle negative numbers correctly */
 int i;
 sint64 sezi;
 for (sezi = 0, i = 0; i < 6; i++) /* ACCUM */
 sezi += (sint64)state_ptr->b[i] * state_ptr->dq[i];
 return (int)(sezi >> 13) / 2 /* 2^14 */;
}

/*
 * predictor_pole()
 *
 * computes the estimated signal from 2-pole predictor.
 *
 */
static int predictor_pole(struct g726_state *state_ptr)
{ /* divide by 2 is necessary here to handle negative numbers correctly */
 return (int)(((sint64)state_ptr->a[1] * state_ptr->sr[1] +
 (sint64)state_ptr->a[0] * state_ptr->sr[0]) >> 13) / 2 /* 2^14 */;
}

#else /* NOT_BLI - identical version */
/*
 * fmult()
 *
 * returns the integer product of the fixed-point number "an" (1==2^12) and
 * "floating point" representation (4-bit exponent, 6-bit mantessa) "srn".
 */
static int fmult(int an, int srn)
{
 int anmag, anexp, anmant;
 int wanexp, wanmant;
 int retval;

 anmag = (an > 0) ? an : ((-an) & 0x1FFF);
 anexp = ilog2(anmag) - 5;
 anmant = (anmag == 0) ? 32 :
 (anexp >= 0) ? anmag >> anexp : anmag << -anexp;
 wanexp = anexp + ((srn >> 6) & 0xF) - 13;

 wanmant = (anmant * (srn & 077) + 0x30) >> 4;
 retval = (wanexp >= 0) ? ((wanmant << wanexp) & 0x7FFF) :
 (wanmant >> -wanexp);

 return (((an ^ srn) < 0) ? -retval : retval);
}

static int predictor_zero(struct g726_state *state_ptr)
{
 int i;
 int sezi;
 for (sezi = 0, i = 0; i < 6; i++) /* ACCUM */
 sezi += fmult(state_ptr->b[i] >> 2, state_ptr->dq[i]);
 return sezi;
}

static int predictor_pole(struct g726_state *state_ptr)
{
 return (fmult(state_ptr->a[1] >> 2, state_ptr->sr[1]) +
 fmult(state_ptr->a[0] >> 2, state_ptr->sr[0]));
}

#endif /* NOT_BLI */

/*
 * step_size()
 *
 * computes the quantization step size of the adaptive quantizer.
 *
 */
static int step_size(struct g726_state *state_ptr)
{
 int y, dif, al;

 if (state_ptr->ap >= 256) {
 return state_ptr->yu;
 }

 y = state_ptr->yl >> 6;
 dif = state_ptr->yu - y;
 al = state_ptr->ap >> 2;

 if (dif > 0) {
 y += (dif * al) >> 6;
 } else if (dif < 0) {
 y += (dif * al + 0x3F) >> 6;
 }
 return y;
}

/*
 * quantize()
 *
 * Given a raw sample, 'd', of the difference signal and a
 * quantization step size scale factor, 'y', this routine returns the
 * ADPCM codeword to which that sample gets quantized. The step
 * size scale factor division operation is done in the log base 2 domain
 * as a subtraction.
 */
static int quantize(
 int d, /* Raw difference signal sample */
 int y, /* Step size multiplier */
 int *table, /* quantization table */
 int size) /* table size of integers */
{
 int dqm; /* Magnitude of 'd' */
 int exp; /* Integer part of base 2 log of 'd' */
 int mant; /* Fractional part of base 2 log */
 int dl; /* Log of magnitude of 'd' */
 int dln; /* Step size scale factor normalized log */
 int i;

 /*
 * LOG
 *
 * Compute base 2 log of 'd', and store in 'dl'.
 */
 dqm = abs(d);
 exp = ilog2(dqm);
 if (exp < 0) {
 exp = 0;
 }
 mant = ((dqm << 7) >> exp) & 0x7F; /* Fractional portion. */
 dl = (exp << 7) | mant;

 /*
 * SUBTB
 *
 * "Divide" by step size multiplier.
 */
 dln = dl - (y >> 2);

 /*
 * QUAN
 *
 * Obtain codword i for 'd'.
 */
 i = quan(dln, table, size);
 if (d < 0) { /* take 1's complement of i */
 return ((size << 1) + 1 - i);
 } else if (i == 0) { /* take 1's complement of 0 */
 return ((size << 1) + 1); /* new in 1988 */
 } else {
 return i;
 }
}

/*
 * reconstruct()
 *
 * Returns reconstructed difference signal 'dq' obtained from
 * codeword 'i' and quantization step size scale factor 'y'.
 * Multiplication is performed in log base 2 domain as addition.
 */
static int reconstruct(
 int sign, /* 0 for non-negative value */
 int dqln, /* G.72x codeword */
 int y) /* Step size multiplier */
{
 int dql; /* Log of 'dq' magnitude */
 int dex; /* Integer part of log */
 int dqt;
 int dq; /* Reconstructed difference signal sample */

 dql = dqln + (y >> 2); /* ADDA */

 if (dql < 0) {
#ifdef NOT_BLI
 return (sign) ? -1 : 1;
#else
 return (sign) ? -0x8000 : 0;
#endif
 } else { /* ANTILOG */
 dex = (dql >> 7) & 15;
 dqt = 128 + (dql & 127);
#ifdef NOT_BLI
 dq = ((dqt << 19) >> (14 - dex));
 return (sign) ? -dq : dq;
#else
 dq = (dqt << 7) >> (14 - dex);
 return (sign) ? (dq - 0x8000) : dq;
#endif
 }
}

/*
 * update()
 *
 * updates the state variables for each output code
 */
static void update(
 int code_size, /* distinguish 723_40 with others */
 int y, /* quantizer step size */
 int wi, /* scale factor multiplier */
 int fi, /* for long/short term energies */
 int dq, /* quantized prediction difference */
 int sr, /* reconstructed signal */
 int dqsez, /* difference from 2-pole predictor */
 struct g726_state *state_ptr) /* coder state pointer */
{
 int cnt;
 int mag; /* Adaptive predictor, FLOAT A */
#ifndef NOT_BLI
 int exp;
#endif
 int a2p=0; /* LIMC */
 int a1ul; /* UPA1 */
 int pks1; /* UPA2 */
 int fa1;
 int tr; /* tone/transition detector */
 int ylint, thr2, dqthr;
 int ylfrac, thr1;
 int pk0;

 pk0 = (dqsez < 0) ? 1 : 0; /* needed in updating predictor poles */

#ifdef NOT_BLI
 mag = abs(dq / 0x1000); /* prediction difference magnitude */
#else
 mag = dq & 0x7FFF; /* prediction difference magnitude */
#endif
 /* TRANS */
 ylint = state_ptr->yl >> 15; /* exponent part of yl */
 ylfrac = (state_ptr->yl >> 10) & 0x1F; /* fractional part of yl */
 thr1 = (32 + ylfrac) << ylint; /* threshold */
 thr2 = (ylint > 9) ? 31 << 10 : thr1; /* limit thr2 to 31 << 10 */
 dqthr = (thr2 + (thr2 >> 1)) >> 1; /* dqthr = 0.75 * thr2 */
 if (state_ptr->td == 0) { /* signal supposed voice */
 tr = 0;
 } else if (mag <= dqthr) { /* supposed data, but small mag */
 tr = 0; /* treated as voice */
 } else { /* signal is data (modem) */
 tr = 1;
 }
 /*
 * Quantizer scale factor adaptation.
 */

 /* FUNCTW & FILTD & DELAY */
 /* update non-steady state step size multiplier */
 state_ptr->yu = y + ((wi - y) >> 5);

 /* LIMB */
 if (state_ptr->yu < 544) { /* 544 <= yu <= 5120 */
 state_ptr->yu = 544;
 } else if (state_ptr->yu > 5120) {
 state_ptr->yu = 5120;
 }

 /* FILTE & DELAY */
 /* update steady state step size multiplier */
 state_ptr->yl += state_ptr->yu + ((-state_ptr->yl) >> 6);

 /*
 * Adaptive predictor coefficients.
 */
 if (tr == 1) { /* reset a's and b's for modem signal */
 state_ptr->a[0] = 0;
 state_ptr->a[1] = 0;
 state_ptr->b[0] = 0;
 state_ptr->b[1] = 0;
 state_ptr->b[2] = 0;
 state_ptr->b[3] = 0;
 state_ptr->b[4] = 0;
 state_ptr->b[5] = 0;
 } else { /* update a's and b's */
 pks1 = pk0 ^ state_ptr->pk[0]; /* UPA2 */

 /* update predictor pole a[1] */
 a2p = state_ptr->a[1] - (state_ptr->a[1] >> 7);
 if (dqsez != 0) {
 fa1 = (pks1) ? state_ptr->a[0] : -state_ptr->a[0];
 if (fa1 < -8191) { /* a2p = function of fa1 */
 a2p -= 0x100;
 } else if (fa1 > 8191) {
 a2p += 0xFF;
 } else {
 a2p += fa1 >> 5;
 }

 if (pk0 ^ state_ptr->pk[1]) {
 /* LIMC */
 if (a2p <= -12160) {
 a2p = -12288;
 } else if (a2p >= 12416) {
 a2p = 12288;
 } else {
 a2p -= 0x80;
 }
 } else if (a2p <= -12416) {
 a2p = -12288;
 } else if (a2p >= 12160) {
 a2p = 12288;
 } else {
 a2p += 0x80;
 }
 }

 /* TRIGB & DELAY */
 state_ptr->a[1] = a2p;

 /* UPA1 */
 /* update predictor pole a[0] */
 state_ptr->a[0] -= state_ptr->a[0] >> 8;
 if (dqsez != 0) {
 if (pks1 == 0)
 state_ptr->a[0] += 192;
 else
 state_ptr->a[0] -= 192;
 }
 /* LIMD */
 a1ul = 15360 - a2p;
 if (state_ptr->a[0] < -a1ul) {
 state_ptr->a[0] = -a1ul;
 } else if (state_ptr->a[0] > a1ul) {
 state_ptr->a[0] = a1ul;
 }

 /* UPB : update predictor zeros b[6] */
 for (cnt = 0; cnt < 6; cnt++) {
 if (code_size == 5) { /* for 40Kbps G.723 */
 state_ptr->b[cnt] -= state_ptr->b[cnt] >> 9;
 } else { /* for G.721 and 24Kbps G.723 */
 state_ptr->b[cnt] -= state_ptr->b[cnt] >> 8;
 }
 if (mag) { /* XOR */
 if ((dq ^ state_ptr->dq[cnt]) >= 0) {
 state_ptr->b[cnt] += 128;
 } else {
 state_ptr->b[cnt] -= 128;
 }
 }
 }
 }

 for (cnt = 5; cnt > 0; cnt--)
 state_ptr->dq[cnt] = state_ptr->dq[cnt-1];
#ifdef NOT_BLI
 state_ptr->dq[0] = dq;
#else
 /* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
 if (mag == 0) {
 state_ptr->dq[0] = (dq >= 0) ? 0x20 : 0x20 - 0x400;
 } else {
 exp = ilog2(mag) + 1;
 state_ptr->dq[0] = (dq >= 0) ?
 (exp << 6) + ((mag << 6) >> exp) :
 (exp << 6) + ((mag << 6) >> exp) - 0x400;
 }
#endif

 state_ptr->sr[1] = state_ptr->sr[0];
#ifdef NOT_BLI
 state_ptr->sr[0] = sr;
#else
 /* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */
 if (sr == 0) {
 state_ptr->sr[0] = 0x20;
 } else if (sr > 0) {
 exp = ilog2(sr) + 1;
 state_ptr->sr[0] = (exp << 6) + ((sr << 6) >> exp);
 } else if (sr > -0x8000) {
 mag = -sr;
 exp = ilog2(mag) + 1;
 state_ptr->sr[0] = (exp << 6) + ((mag << 6) >> exp) - 0x400;
 } else
 state_ptr->sr[0] = 0x20 - 0x400;
#endif

 /* DELAY A */
 state_ptr->pk[1] = state_ptr->pk[0];
 state_ptr->pk[0] = pk0;

 /* TONE */
 if (tr == 1) { /* this sample has been treated as data */
 state_ptr->td = 0; /* next one will be treated as voice */
 } else if (a2p < -11776) { /* small sample-to-sample correlation */
 state_ptr->td = 1; /* signal may be data */
 } else { /* signal is voice */
 state_ptr->td = 0;
 }

 /*
 * Adaptation speed control.
 */
 state_ptr->dms += (fi - state_ptr->dms) >> 5; /* FILTA */
 state_ptr->dml += (((fi << 2) - state_ptr->dml) >> 7); /* FILTB */

 if (tr == 1) {
 state_ptr->ap = 256;
 } else if (y < 1536) { /* SUBTC */
 state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
 } else if (state_ptr->td == 1) {
 state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
 } else if (abs((state_ptr->dms << 2) - state_ptr->dml) >=
 (state_ptr->dml >> 3)) {
 state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
 } else {
 state_ptr->ap += (-state_ptr->ap) >> 4;
 }
}

/*
 * g726_decode()
 *
 * Description:
 *
 * Decodes a 4-bit code of G.726-32 encoded data of i and
 * returns the resulting linear PCM, A-law or u-law value.
 * return -1 for unknown out_coding value.
 */
static int g726_decode(int i, struct g726_state *state_ptr)
{
 int sezi, sez, se; /* ACCUM */
 int y; /* MIX */
 int sr; /* ADDB */
 int dq;
 int dqsez;

 i &= 0x0f; /* mask to get proper bits */
#ifdef NOT_BLI
 sezi = predictor_zero(state_ptr);
 sez = sezi;
 se = sezi + predictor_pole(state_ptr); /* estimated signal */
#else
 sezi = predictor_zero(state_ptr);
 sez = sezi >> 1;
 se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */
#endif

 y = step_size(state_ptr); /* dynamic quantizer step size */

 dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized diff. */

#ifdef NOT_BLI
 sr = se + dq; /* reconst. signal */
 dqsez = dq + sez; /* pole prediction diff. */
#else
 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */
 dqsez = sr - se + sez; /* pole prediction diff. */
#endif

 update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);

#ifdef NOT_BLI
 return (sr >> 10); /* sr was 26-bit dynamic range */
#else
 return (sr << 2); /* sr was 14-bit dynamic range */
#endif
}

/*
 * g726_encode()
 *
 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
 * the resulting code. -1 is returned for unknown input coding value.
 */
static int g726_encode(int sl, struct g726_state *state_ptr)
{
 int sezi, se, sez; /* ACCUM */
 int d; /* SUBTA */
 int sr; /* ADDB */
 int y; /* MIX */
 int dqsez; /* ADDC */
 int dq, i;

#ifdef NOT_BLI
 sl <<= 10; /* 26-bit dynamic range */

 sezi = predictor_zero(state_ptr);
 sez = sezi;
 se = sezi + predictor_pole(state_ptr); /* estimated signal */
#else
 sl >>= 2; /* 14-bit dynamic range */

 sezi = predictor_zero(state_ptr);
 sez = sezi >> 1;
 se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */
#endif

 d = sl - se; /* estimation difference */

 /* quantize the prediction difference */
 y = step_size(state_ptr); /* quantizer step size */
#ifdef NOT_BLI
 d /= 0x1000;
#endif
 i = quantize(d, y, qtab_721, 7); /* i = G726 code */

 dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */

#ifdef NOT_BLI
 sr = se + dq; /* reconst. signal */
 dqsez = dq + sez; /* pole prediction diff. */
#else
 sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */
 dqsez = sr - se + sez; /* pole prediction diff. */
#endif

 update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);

 return i;
}

/*
 * Private workspace for translating signed linear signals to G726.
 * Don't bother to define two distinct structs.
 */

struct g726_coder_pvt {
 /* buffer any odd byte in input - 0x80 + (value & 0xf) if present */
 unsigned char next_flag;
 struct g726_state g726;
};

/*! \brief init a new instance of g726_coder_pvt. */
static int lintog726_new(struct ast_trans_pvt *pvt)
{
 struct g726_coder_pvt *tmp = pvt->pvt;

 g726_init_state(&tmp->g726);

 return 0;
}

/*! \brief decode packed 4-bit G726 values (AAL2 packing) and store in buffer. */
static int g726aal2tolin_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct g726_coder_pvt *tmp = pvt->pvt;
 unsigned char *src = f->data.ptr;
 int16_t *dst = pvt->outbuf.i16 + pvt->samples;
 unsigned int i;

 for (i = 0; i < f->datalen; i++) {
 *dst++ = g726_decode((src[i] >> 4) & 0xf, &tmp->g726);
 *dst++ = g726_decode(src[i] & 0x0f, &tmp->g726);
 }

 pvt->samples += f->samples;
 pvt->datalen += 2 * f->samples; /* 2 bytes/sample */

 return 0;
}

/*! \brief compress and store data (4-bit G726 samples, AAL2 packing) in outbuf */
static int lintog726aal2_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct g726_coder_pvt *tmp = pvt->pvt;
 int16_t *src = f->data.ptr;
 unsigned int i;

 for (i = 0; i < f->samples; i++) {
 unsigned char d = g726_encode(src[i], &tmp->g726); /* this sample */

 if (tmp->next_flag & 0x80) { /* merge with leftover sample */
 pvt->outbuf.c[pvt->datalen++] = ((tmp->next_flag & 0xf)<< 4) | d;
 pvt->samples += 2; /* 2 samples per byte */
 tmp->next_flag = 0;
 } else {
 tmp->next_flag = 0x80 | d;
 }
 }

 return 0;
}

/*! \brief decode packed 4-bit G726 values (RFC3551 packing) and store in buffer. */
static int g726tolin_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct g726_coder_pvt *tmp = pvt->pvt;
 unsigned char *src = f->data.ptr;
 int16_t *dst = pvt->outbuf.i16 + pvt->samples;
 unsigned int i;

 for (i = 0; i < f->datalen; i++) {
 *dst++ = g726_decode(src[i] & 0x0f, &tmp->g726);
 *dst++ = g726_decode((src[i] >> 4) & 0xf, &tmp->g726);
 }

 pvt->samples += f->samples;
 pvt->datalen += 2 * f->samples; /* 2 bytes/sample */

 return 0;
}

/*! \brief compress and store data (4-bit G726 samples, RFC3551 packing) in outbuf */
static int lintog726_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
{
 struct g726_coder_pvt *tmp = pvt->pvt;
 int16_t *src = f->data.ptr;
 unsigned int i;

 for (i = 0; i < f->samples; i++) {
 unsigned char d = g726_encode(src[i], &tmp->g726); /* this sample */

 if (tmp->next_flag & 0x80) { /* merge with leftover sample */
 pvt->outbuf.c[pvt->datalen++] = (d << 4) | (tmp->next_flag & 0xf);
 pvt->samples += 2; /* 2 samples per byte */
 tmp->next_flag = 0;
 } else {
 tmp->next_flag = 0x80 | d;
 }
 }

 return 0;
}

static struct ast_translator g726tolin = {
 .name = "g726tolin",
 .src_codec = {
 .name = "g726",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .dst_codec = {
 .name = "slin",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .format = "slin",
 .newpvt = lintog726_new, /* same for both directions */
 .framein = g726tolin_framein,
 .sample = g726_sample,
 .desc_size = sizeof(struct g726_coder_pvt),
 .buffer_samples = BUFFER_SAMPLES,
 .buf_size = BUFFER_SAMPLES * 2,
};

static struct ast_translator lintog726 = {
 .name = "lintog726",
 .src_codec = {
 .name = "slin",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .dst_codec = {
 .name = "g726",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .format = "g726",
 .newpvt = lintog726_new, /* same for both directions */
 .framein = lintog726_framein,
 .sample = slin8_sample,
 .desc_size = sizeof(struct g726_coder_pvt),
 .buffer_samples = BUFFER_SAMPLES,
 .buf_size = BUFFER_SAMPLES/2,
};

static struct ast_translator g726aal2tolin = {
 .name = "g726aal2tolin",
 .src_codec = {
 .name = "g726aal2",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .dst_codec = {
 .name = "slin",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .format = "slin",
 .newpvt = lintog726_new, /* same for both directions */
 .framein = g726aal2tolin_framein,
 .sample = g726_sample,
 .desc_size = sizeof(struct g726_coder_pvt),
 .buffer_samples = BUFFER_SAMPLES,
 .buf_size = BUFFER_SAMPLES * 2,
};

static struct ast_translator lintog726aal2 = {
 .name = "lintog726aal2",
 .src_codec = {
 .name = "slin",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .dst_codec = {
 .name = "g726aal2",
 .type = AST_MEDIA_TYPE_AUDIO,
 .sample_rate = 8000,
 },
 .format = "g726aal2",
 .newpvt = lintog726_new, /* same for both directions */
 .framein = lintog726aal2_framein,
 .sample = slin8_sample,
 .desc_size = sizeof(struct g726_coder_pvt),
 .buffer_samples = BUFFER_SAMPLES,
 .buf_size = BUFFER_SAMPLES / 2,
};

static int unload_module(void)
{
 int res = 0;

 res |= ast_unregister_translator(&g726tolin);
 res |= ast_unregister_translator(&lintog726);

 res |= ast_unregister_translator(&g726aal2tolin);
 res |= ast_unregister_translator(&lintog726aal2);

 return res;
}

static int load_module(void)
{
 int res = 0;

 res |= ast_register_translator(&g726tolin);
 res |= ast_register_translator(&lintog726);

 res |= ast_register_translator(&g726aal2tolin);
 res |= ast_register_translator(&lintog726aal2);

 if (res) {
 unload_module();
 return AST_MODULE_LOAD_DECLINE;
 }

 return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "ITU G.726-32kbps G726 Transcoder",
 .support_level = AST_MODULE_SUPPORT_CORE,
 .load = load_module,
 .unload = unload_module,
);