diff spandsp-0.0.6pre17/src/g726.c @ 4:26cd8f1ef0b1

import spandsp-0.0.6pre17
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 15:50:58 +0200
parents
children
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.6pre17/src/g726.c	Fri Jun 25 15:50:58 2010 +0200
@@ -0,0 +1,1188 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * g726.c - The ITU G.726 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.
+ *
+ * Based on G.721/G.723 code which is:
+ *
+ * This source code is a product of Sun Microsystems, Inc. and is provided
+ * for unrestricted use.  Users may copy or modify this source code without
+ * charge.
+ *
+ * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
+ * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
+ *
+ * Sun source code is provided with no support and without any obligation on
+ * the part of Sun Microsystems, Inc. to assist in its use, correction,
+ * modification or enhancement.
+ *
+ * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
+ * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
+ * OR ANY PART THEREOF.
+ *
+ * In no event will Sun Microsystems, Inc. be liable for any lost revenue
+ * or profits or other special, indirect and consequential damages, even if
+ * Sun has been advised of the possibility of such damages.
+ *
+ * Sun Microsystems, Inc.
+ * 2550 Garcia Avenue
+ * Mountain View, California  94043
+ *
+ * $Id: g726.c,v 1.28.4.1 2009/12/28 12:20:46 steveu Exp $
+ */
+
+/*! \file */
+
+#if defined(HAVE_CONFIG_H)
+#include "config.h"
+#endif
+
+#include <inttypes.h>
+#include <memory.h>
+#include <stdlib.h>
+#if defined(HAVE_TGMATH_H)
+#include <tgmath.h>
+#endif
+#if defined(HAVE_MATH_H)
+#include <math.h>
+#endif
+#include "floating_fudge.h"
+
+#include "spandsp/telephony.h"
+#include "spandsp/dc_restore.h"
+#include "spandsp/bitstream.h"
+#include "spandsp/bit_operations.h"
+#include "spandsp/g711.h"
+#include "spandsp/g726.h"
+
+#include "spandsp/private/bitstream.h"
+#include "spandsp/private/g726.h"
+
+/*
+ * Maps G.726_16 code word to reconstructed scale factor normalized log
+ * magnitude values.
+ */
+static const int g726_16_dqlntab[4] =
+{
+    116, 365, 365, 116
+};
+
+/* Maps G.726_16 code word to log of scale factor multiplier. */
+static const int g726_16_witab[4] =
+{
+    -704, 14048, 14048, -704
+};
+
+/*
+ * Maps G.726_16 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 const int g726_16_fitab[4] =
+{
+    0x000, 0xE00, 0xE00, 0x000
+};
+
+static const int qtab_726_16[1] =
+{
+    261
+};
+
+/*
+ * Maps G.726_24 code word to reconstructed scale factor normalized log
+ * magnitude values.
+ */
+static const int g726_24_dqlntab[8] =
+{
+    -2048, 135, 273, 373, 373, 273, 135, -2048
+};
+
+/* Maps G.726_24 code word to log of scale factor multiplier. */
+static const int g726_24_witab[8] =
+{
+    -128, 960, 4384, 18624, 18624, 4384, 960, -128
+};
+
+/*
+ * Maps G.726_24 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 const int g726_24_fitab[8] =
+{
+    0x000, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0x000
+};
+
+static const int qtab_726_24[3] =
+{
+    8, 218, 331
+};
+
+/*
+ * Maps G.726_32 code word to reconstructed scale factor normalized log
+ * magnitude values.
+ */
+static const int g726_32_dqlntab[16] =
+{
+    -2048,   4, 135, 213, 273, 323, 373,   425,
+      425, 373, 323, 273, 213, 135,   4, -2048
+};
+
+/* Maps G.726_32 code word to log of scale factor multiplier. */
+static const int g726_32_witab[16] =
+{
+     -384,   576,  1312,  2048,  3584,  6336, 11360, 35904,
+    35904, 11360,  6336,  3584,  2048,  1312,   576,  -384
+};
+
+/*
+ * Maps G.726_32 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 const int g726_32_fitab[16] =
+{
+    0x000, 0x000, 0x000, 0x200, 0x200, 0x200, 0x600, 0xE00,
+    0xE00, 0x600, 0x200, 0x200, 0x200, 0x000, 0x000, 0x000
+};
+
+static const int qtab_726_32[7] =
+{
+    -124, 80, 178, 246, 300, 349, 400
+};
+
+/*
+ * Maps G.726_40 code word to ructeconstructed scale factor normalized log
+ * magnitude values.
+ */
+static const int g726_40_dqlntab[32] =
+{
+    -2048, -66, 28, 104, 169, 224, 274, 318,
+      358, 395, 429, 459, 488, 514, 539, 566,
+      566, 539, 514, 488, 459, 429, 395, 358,
+      318, 274, 224, 169, 104, 28, -66, -2048
+};
+
+/* Maps G.726_40 code word to log of scale factor multiplier. */
+static const int g726_40_witab[32] =
+{
+      448,   448,   768,  1248,  1280,  1312,  1856,  3200,
+     4512,  5728,  7008,  8960, 11456, 14080, 16928, 22272,
+    22272, 16928, 14080, 11456,  8960,  7008,  5728,  4512,
+     3200,  1856,  1312,  1280,  1248,   768,   448,   448
+};
+
+/*
+ * Maps G.726_40 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 const int g726_40_fitab[32] =
+{
+    0x000, 0x000, 0x000, 0x000, 0x000, 0x200, 0x200, 0x200,
+    0x200, 0x200, 0x400, 0x600, 0x800, 0xA00, 0xC00, 0xC00,
+    0xC00, 0xC00, 0xA00, 0x800, 0x600, 0x400, 0x200, 0x200,
+    0x200, 0x200, 0x200, 0x000, 0x000, 0x000, 0x000, 0x000
+};
+
+static const int qtab_726_40[15] =
+{
+    -122, -16,  68, 139, 198, 250, 298, 339,
+     378, 413, 445, 475, 502, 528, 553
+};
+
+/*
+ * returns the integer product of the 14-bit integer "an" and
+ * "floating point" representation (4-bit exponent, 6-bit mantessa) "srn".
+ */
+static int16_t fmult(int16_t an, int16_t srn)
+{
+    int16_t anmag;
+    int16_t anexp;
+    int16_t anmant;
+    int16_t wanexp;
+    int16_t wanmant;
+    int16_t retval;
+
+    anmag = (an > 0)  ?  an  :  ((-an) & 0x1FFF);
+    anexp = (int16_t) (top_bit(anmag) - 5);
+    anmant = (anmag == 0)  ?  32  :  (anexp >= 0)  ?  (anmag >> anexp)  :  (anmag << -anexp);
+    wanexp = anexp + ((srn >> 6) & 0xF) - 13;
+
+    wanmant = (anmant*(srn & 0x3F) + 0x30) >> 4;
+    retval = (wanexp >= 0)  ?  ((wanmant << wanexp) & 0x7FFF)  :  (wanmant >> -wanexp);
+
+    return (((an ^ srn) < 0)  ?  -retval  :  retval);
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Compute the estimated signal from the 6-zero predictor.
+ */
+static __inline__ int16_t predictor_zero(g726_state_t *s)
+{
+    int i;
+    int sezi;
+
+    sezi = fmult(s->b[0] >> 2, s->dq[0]);
+    /* ACCUM */
+    for (i = 1;  i < 6;  i++)
+        sezi += fmult(s->b[i] >> 2, s->dq[i]);
+    return (int16_t) sezi;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Computes the estimated signal from the 2-pole predictor.
+ */
+static __inline__ int16_t predictor_pole(g726_state_t *s)
+{
+    return (fmult(s->a[1] >> 2, s->sr[1]) + fmult(s->a[0] >> 2, s->sr[0]));
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Computes the quantization step size of the adaptive quantizer.
+ */
+static int step_size(g726_state_t *s)
+{
+    int y;
+    int dif;
+    int al;
+
+    if (s->ap >= 256)
+        return s->yu;
+    y = s->yl >> 6;
+    dif = s->yu - y;
+    al = s->ap >> 2;
+    if (dif > 0)
+        y += (dif*al) >> 6;
+    else if (dif < 0)
+        y += (dif*al + 0x3F) >> 6;
+    return y;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * 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 int16_t quantize(int d,                  /* Raw difference signal sample */
+                        int y,                  /* Step size multiplier */
+                        const int table[],     /* quantization table */
+                        int quantizer_states)   /* table size of int16_t integers */
+{
+    int16_t dqm;    /* Magnitude of 'd' */
+    int16_t exp;    /* Integer part of base 2 log of 'd' */
+    int16_t mant;   /* Fractional part of base 2 log */
+    int16_t dl;     /* Log of magnitude of 'd' */
+    int16_t dln;    /* Step size scale factor normalized log */
+    int i;
+    int size;
+
+    /*
+     * LOG
+     *
+     * Compute base 2 log of 'd', and store in 'dl'.
+     */
+    dqm = (int16_t) abs(d);
+    exp = (int16_t) (top_bit(dqm >> 1) + 1);
+    /* Fractional portion. */
+    mant = ((dqm << 7) >> exp) & 0x7F;
+    dl = (exp << 7) + mant;
+
+    /*
+     * SUBTB
+     *
+     * "Divide" by step size multiplier.
+     */
+    dln = dl - (int16_t) (y >> 2);
+
+    /*
+     * QUAN
+     *
+     * Search for codword i for 'dln'.
+     */
+    size = (quantizer_states - 1) >> 1;
+    for (i = 0;  i < size;  i++)
+    {
+        if (dln < table[i])
+            break;
+    }
+    if (d < 0)
+    {
+        /* Take 1's complement of i */
+        return (int16_t) ((size << 1) + 1 - i);
+    }
+    if (i == 0  &&  (quantizer_states & 1))
+    {
+        /* Zero is only valid if there are an even number of states, so
+           take the 1's complement if the code is zero. */
+        return (int16_t) quantizer_states;
+    }
+    return (int16_t) i;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * 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 int16_t reconstruct(int sign,    /* 0 for non-negative value */
+                           int dqln,    /* G.72x codeword */
+                           int y)       /* Step size multiplier */
+{
+    int16_t dql;    /* Log of 'dq' magnitude */
+    int16_t dex;    /* Integer part of log */
+    int16_t dqt;
+    int16_t dq;     /* Reconstructed difference signal sample */
+
+    dql = (int16_t) (dqln + (y >> 2));  /* ADDA */
+
+    if (dql < 0)
+        return ((sign)  ?  -0x8000  :  0);
+    /* ANTILOG */
+    dex = (dql >> 7) & 15;
+    dqt = 128 + (dql & 127);
+    dq = (dqt << 7) >> (14 - dex);
+    return ((sign)  ?  (dq - 0x8000)  :  dq);
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * updates the state variables for each output code
+ */
+static void update(g726_state_t *s,
+                   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 */
+{
+    int16_t mag;
+    int16_t exp;
+    int16_t a2p;        /* LIMC */
+    int16_t a1ul;       /* UPA1 */
+    int16_t pks1;       /* UPA2 */
+    int16_t fa1;
+    int16_t ylint;
+    int16_t dqthr;
+    int16_t ylfrac;
+    int16_t thr;
+    int16_t pk0;
+    int i;
+    int tr;
+
+    a2p = 0;
+    /* Needed in updating predictor poles */
+    pk0 = (dqsez < 0)  ?  1  :  0;
+
+    /* prediction difference magnitude */
+    mag = (int16_t) (dq & 0x7FFF);
+    /* TRANS */
+    ylint = (int16_t) (s->yl >> 15);            /* exponent part of yl */
+    ylfrac = (int16_t) ((s->yl >> 10) & 0x1F);  /* fractional part of yl */
+    /* Limit threshold to 31 << 10 */
+    thr = (ylint > 9)  ?  (31 << 10)  :  ((32 + ylfrac) << ylint);
+    dqthr = (thr + (thr >> 1)) >> 1;            /* dqthr = 0.75 * thr */
+    if (!s->td)                                 /* signal supposed voice */
+        tr = FALSE;
+    else if (mag <= dqthr)                      /* supposed data, but small mag */
+        tr = FALSE;                             /* treated as voice */
+    else                                        /* signal is data (modem) */
+        tr = TRUE;
+
+    /*
+     * Quantizer scale factor adaptation.
+     */
+
+    /* FUNCTW & FILTD & DELAY */
+    /* update non-steady state step size multiplier */
+    s->yu = (int16_t) (y + ((wi - y) >> 5));
+
+    /* LIMB */
+    if (s->yu < 544)
+        s->yu = 544;
+    else if (s->yu > 5120)
+        s->yu = 5120;
+
+    /* FILTE & DELAY */
+    /* update steady state step size multiplier */
+    s->yl += s->yu + ((-s->yl) >> 6);
+
+    /*
+     * Adaptive predictor coefficients.
+     */
+    if (tr)
+    {
+        /* Reset the a's and b's for a modem signal */
+        s->a[0] = 0;
+        s->a[1] = 0;
+        s->b[0] = 0;
+        s->b[1] = 0;
+        s->b[2] = 0;
+        s->b[3] = 0;
+        s->b[4] = 0;
+        s->b[5] = 0;
+    }
+    else
+    {
+        /* Update the a's and b's */
+        /* UPA2 */
+        pks1 = pk0 ^ s->pk[0];
+
+        /* Update predictor pole a[1] */
+        a2p = s->a[1] - (s->a[1] >> 7);
+        if (dqsez != 0)
+        {
+            fa1 = (pks1)  ?  s->a[0]  :  -s->a[0];
+            /* a2p = function of fa1 */
+            if (fa1 < -8191)
+                a2p -= 0x100;
+            else if (fa1 > 8191)
+                a2p += 0xFF;
+            else
+                a2p += fa1 >> 5;
+
+            if (pk0 ^ s->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 */
+        s->a[1] = a2p;
+
+        /* UPA1 */
+        /* Update predictor pole a[0] */
+        s->a[0] -= s->a[0] >> 8;
+        if (dqsez != 0)
+        {
+            if (pks1 == 0)
+                s->a[0] += 192;
+            else
+                s->a[0] -= 192;
+        }
+        /* LIMD */
+        a1ul = 15360 - a2p;
+        if (s->a[0] < -a1ul)
+            s->a[0] = -a1ul;
+        else if (s->a[0] > a1ul)
+            s->a[0] = a1ul;
+
+        /* UPB : update predictor zeros b[6] */
+        for (i = 0;  i < 6;  i++)
+        {
+            /* Distinguish 40Kbps mode from the others */
+            s->b[i] -= s->b[i] >> ((s->bits_per_sample == 5)  ?  9  :  8);
+            if (dq & 0x7FFF)
+            {
+                /* XOR */
+                if ((dq ^ s->dq[i]) >= 0)
+                    s->b[i] += 128;
+                else
+                    s->b[i] -= 128;
+            }
+        }
+    }
+
+    for (i = 5;  i > 0;  i--)
+        s->dq[i] = s->dq[i - 1];
+    /* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
+    if (mag == 0)
+    {
+        s->dq[0] = (dq >= 0)  ?  0x20  :  0xFC20;
+    }
+    else
+    {
+        exp = (int16_t) (top_bit(mag) + 1);
+        s->dq[0] = (dq >= 0)
+                 ?  ((exp << 6) + ((mag << 6) >> exp))
+                 :  ((exp << 6) + ((mag << 6) >> exp) - 0x400);
+    }
+
+    s->sr[1] = s->sr[0];
+    /* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */
+    if (sr == 0)
+    {
+        s->sr[0] = 0x20;
+    }
+    else if (sr > 0)
+    {
+        exp = (int16_t) (top_bit(sr) + 1);
+        s->sr[0] = (int16_t) ((exp << 6) + ((sr << 6) >> exp));
+    }
+    else if (sr > -32768)
+    {
+        mag = (int16_t) -sr;
+        exp = (int16_t) (top_bit(mag) + 1);
+        s->sr[0] =  (exp << 6) + ((mag << 6) >> exp) - 0x400;
+    }
+    else
+    {
+        s->sr[0] = (uint16_t) 0xFC20;
+    }
+
+    /* DELAY A */
+    s->pk[1] = s->pk[0];
+    s->pk[0] = pk0;
+
+    /* TONE */
+    if (tr)                 /* this sample has been treated as data */
+        s->td = FALSE;      /* next one will be treated as voice */
+    else if (a2p < -11776)  /* small sample-to-sample correlation */
+        s->td = TRUE;       /* signal may be data */
+    else                    /* signal is voice */
+        s->td = FALSE;
+
+    /* Adaptation speed control. */
+    /* FILTA */
+    s->dms += ((int16_t) fi - s->dms) >> 5;
+    /* FILTB */
+    s->dml += (((int16_t) (fi << 2) - s->dml) >> 7);
+
+    if (tr)
+        s->ap = 256;
+    else if (y < 1536)                      /* SUBTC */
+        s->ap += (0x200 - s->ap) >> 4;
+    else if (s->td)
+        s->ap += (0x200 - s->ap) >> 4;
+    else if (abs((s->dms << 2) - s->dml) >= (s->dml >> 3))
+        s->ap += (0x200 - s->ap) >> 4;
+    else
+        s->ap += (-s->ap) >> 4;
+}
+/*- End of function --------------------------------------------------------*/
+
+static int16_t tandem_adjust_alaw(int16_t sr,   /* decoder output linear PCM sample */
+                                  int se,       /* predictor estimate sample */
+                                  int y,        /* quantizer step size */
+                                  int i,        /* decoder input code */
+                                  int sign,
+                                  const int qtab[],
+                                  int quantizer_states)
+{
+    uint8_t sp; /* A-law compressed 8-bit code */
+    int16_t dx; /* prediction error */
+    int id;     /* quantized prediction error */
+    int sd;     /* adjusted A-law decoded sample value */
+
+    if (sr <= -32768)
+        sr = -1;
+    sp = linear_to_alaw((sr >> 1) << 3);
+    /* 16-bit prediction error */
+    dx = (int16_t) ((alaw_to_linear(sp) >> 2) - se);
+    id = quantize(dx, y, qtab, quantizer_states);
+    if (id == i)
+    {
+        /* No adjustment of sp required */
+        return (int16_t) sp;
+    }
+    /* sp adjustment needed */
+    /* ADPCM codes : 8, 9, ... F, 0, 1, ... , 6, 7 */
+    /* 2's complement to biased unsigned */
+    if ((id ^ sign) > (i ^ sign))
+    {
+        /* sp adjusted to next lower value */
+        if (sp & 0x80)
+            sd = (sp == 0xD5)  ?  0x55  :  (((sp ^ 0x55) - 1) ^ 0x55);
+        else
+            sd = (sp == 0x2A)  ?  0x2A  :  (((sp ^ 0x55) + 1) ^ 0x55);
+    }
+    else
+    {
+        /* sp adjusted to next higher value */
+        if (sp & 0x80)
+            sd = (sp == 0xAA)  ?  0xAA  :  (((sp ^ 0x55) + 1) ^ 0x55);
+        else
+            sd = (sp == 0x55)  ?  0xD5  :  (((sp ^ 0x55) - 1) ^ 0x55);
+    }
+    return (int16_t) sd;
+}
+/*- End of function --------------------------------------------------------*/
+
+static int16_t tandem_adjust_ulaw(int16_t sr,   /* decoder output linear PCM sample */
+                                  int se,       /* predictor estimate sample */
+                                  int y,        /* quantizer step size */
+                                  int i,        /* decoder input code */
+                                  int sign,
+                                  const int qtab[],
+                                  int quantizer_states)
+{
+    uint8_t sp; /* u-law compressed 8-bit code */
+    int16_t dx; /* prediction error */
+    int id;     /* quantized prediction error */
+    int sd;     /* adjusted u-law decoded sample value */
+
+    if (sr <= -32768)
+        sr = 0;
+    sp = linear_to_ulaw(sr << 2);
+    /* 16-bit prediction error */
+    dx = (int16_t) ((ulaw_to_linear(sp) >> 2) - se);
+    id = quantize(dx, y, qtab, quantizer_states);
+    if (id == i)
+    {
+        /* No adjustment of sp required. */
+        return (int16_t) sp;
+    }
+    /* ADPCM codes : 8, 9, ... F, 0, 1, ... , 6, 7 */
+    /* 2's complement to biased unsigned */
+    if ((id ^ sign) > (i ^ sign))
+    {
+        /* sp adjusted to next lower value */
+        if (sp & 0x80)
+            sd = (sp == 0xFF)  ?  0x7E  :  (sp + 1);
+        else
+            sd = (sp == 0x00)  ?  0x00  :  (sp - 1);
+    }
+    else
+    {
+        /* sp adjusted to next higher value */
+        if (sp & 0x80)
+            sd = (sp == 0x80)  ?  0x80  :  (sp - 1);
+        else
+            sd = (sp == 0x7F)  ?  0xFE  :  (sp + 1);
+    }
+    return (int16_t) sd;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
+ */
+static uint8_t g726_16_encoder(g726_state_t *s, int16_t amp)
+{
+    int y;
+    int16_t sei;
+    int16_t sezi;
+    int16_t se;
+    int16_t d;
+    int16_t sr;
+    int16_t dqsez;
+    int16_t dq;
+    int16_t i;
+    
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+    se = sei >> 1;
+    d = amp - se;
+
+    /* Quantize prediction difference */
+    y = step_size(s);
+    i = quantize(d, y, qtab_726_16, 4);
+    dq = reconstruct(i & 2, g726_16_dqlntab[i], y);
+
+    /* Reconstruct the signal */
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+    
+    update(s, y, g726_16_witab[i], g726_16_fitab[i], dq, sr, dqsez);
+    return (uint8_t) i;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Decodes a 2-bit CCITT G.726_16 ADPCM code and returns
+ * the resulting 16-bit linear PCM, A-law or u-law sample value.
+ */
+static int16_t g726_16_decoder(g726_state_t *s, uint8_t code)
+{
+    int16_t sezi;
+    int16_t sei;
+    int16_t se;
+    int16_t sr;
+    int16_t dq;
+    int16_t dqsez;
+    int y;
+
+    /* Mask to get proper bits */
+    code &= 0x03;
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+
+    y = step_size(s);
+    dq = reconstruct(code & 2, g726_16_dqlntab[code], y);
+
+    /* Reconstruct the signal */
+    se = sei >> 1;
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_16_witab[code], g726_16_fitab[code], dq, sr, dqsez);
+
+    switch (s->ext_coding)
+    {
+    case G726_ENCODING_ALAW:
+        return tandem_adjust_alaw(sr, se, y, code, 2, qtab_726_16, 4);
+    case G726_ENCODING_ULAW:
+        return tandem_adjust_ulaw(sr, se, y, code, 2, qtab_726_16, 4);
+    }
+    return (sr << 2);
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
+ */
+static uint8_t g726_24_encoder(g726_state_t *s, int16_t amp)
+{
+    int16_t sei;
+    int16_t sezi;
+    int16_t se;
+    int16_t d;
+    int16_t sr;
+    int16_t dqsez;
+    int16_t dq;
+    int16_t i;
+    int y;
+    
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+    se = sei >> 1;
+    d = amp - se;
+
+    /* Quantize prediction difference */
+    y = step_size(s);
+    i = quantize(d, y, qtab_726_24, 7);
+    dq = reconstruct(i & 4, g726_24_dqlntab[i], y);
+
+    /* Reconstruct the signal */
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+    
+    update(s, y, g726_24_witab[i], g726_24_fitab[i], dq, sr, dqsez);
+    return (uint8_t) i;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Decodes a 3-bit CCITT G.726_24 ADPCM code and returns
+ * the resulting 16-bit linear PCM, A-law or u-law sample value.
+ */
+static int16_t g726_24_decoder(g726_state_t *s, uint8_t code)
+{
+    int16_t sezi;
+    int16_t sei;
+    int16_t se;
+    int16_t sr;
+    int16_t dq;
+    int16_t dqsez;
+    int y;
+
+    /* Mask to get proper bits */
+    code &= 0x07;
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+
+    y = step_size(s);
+    dq = reconstruct(code & 4, g726_24_dqlntab[code], y);
+
+    /* Reconstruct the signal */
+    se = sei >> 1;
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_24_witab[code], g726_24_fitab[code], dq, sr, dqsez);
+
+    switch (s->ext_coding)
+    {
+    case G726_ENCODING_ALAW:
+        return tandem_adjust_alaw(sr, se, y, code, 4, qtab_726_24, 7);
+    case G726_ENCODING_ULAW:
+        return tandem_adjust_ulaw(sr, se, y, code, 4, qtab_726_24, 7);
+    }
+    return (sr << 2);
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Encodes a linear input sample and returns its 4-bit code.
+ */
+static uint8_t g726_32_encoder(g726_state_t *s, int16_t amp)
+{
+    int16_t sei;
+    int16_t sezi;
+    int16_t se;
+    int16_t d;
+    int16_t sr;
+    int16_t dqsez;
+    int16_t dq;
+    int16_t i;
+    int y;
+    
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+    se = sei >> 1;
+    d = amp - se;
+
+    /* Quantize the prediction difference */
+    y = step_size(s);
+    i = quantize(d, y, qtab_726_32, 15);
+    dq = reconstruct(i & 8, g726_32_dqlntab[i], y);
+
+    /* Reconstruct the signal */
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_32_witab[i], g726_32_fitab[i], dq, sr, dqsez);
+    return (uint8_t) i;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Decodes a 4-bit CCITT G.726_32 ADPCM code and returns
+ * the resulting 16-bit linear PCM, A-law or u-law sample value.
+ */
+static int16_t g726_32_decoder(g726_state_t *s, uint8_t code)
+{
+    int16_t sezi;
+    int16_t sei;
+    int16_t se;
+    int16_t sr;
+    int16_t dq;
+    int16_t dqsez;
+    int y;
+
+    /* Mask to get proper bits */
+    code &= 0x0F;
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+
+    y = step_size(s);
+    dq = reconstruct(code & 8, g726_32_dqlntab[code], y);
+
+    /* Reconstruct the signal */
+    se = sei >> 1;
+    sr = (dq < 0)  ?  (se - (dq & 0x3FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_32_witab[code], g726_32_fitab[code], dq, sr, dqsez);
+
+    switch (s->ext_coding)
+    {
+    case G726_ENCODING_ALAW:
+        return tandem_adjust_alaw(sr, se, y, code, 8, qtab_726_32, 15);
+    case G726_ENCODING_ULAW:
+        return tandem_adjust_ulaw(sr, se, y, code, 8, qtab_726_32, 15);
+    }
+    return (sr << 2);
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Encodes a 16-bit linear PCM, A-law or u-law input sample and retuens
+ * the resulting 5-bit CCITT G.726 40Kbps code.
+ */
+static uint8_t g726_40_encoder(g726_state_t *s, int16_t amp)
+{
+    int16_t sei;
+    int16_t sezi;
+    int16_t se;
+    int16_t d;
+    int16_t sr;
+    int16_t dqsez;
+    int16_t dq;
+    int16_t i;
+    int y;
+    
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+    se = sei >> 1;
+    d = amp - se;
+
+    /* Quantize prediction difference */
+    y = step_size(s);
+    i = quantize(d, y, qtab_726_40, 31);
+    dq = reconstruct(i & 0x10, g726_40_dqlntab[i], y);
+
+    /* Reconstruct the signal */
+    sr = (dq < 0)  ?  (se - (dq & 0x7FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_40_witab[i], g726_40_fitab[i], dq, sr, dqsez);
+    return (uint8_t) i;
+}
+/*- End of function --------------------------------------------------------*/
+
+/*
+ * Decodes a 5-bit CCITT G.726 40Kbps code and returns
+ * the resulting 16-bit linear PCM, A-law or u-law sample value.
+ */
+static int16_t g726_40_decoder(g726_state_t *s, uint8_t code)
+{
+    int16_t sezi;
+    int16_t sei;
+    int16_t se;
+    int16_t sr;
+    int16_t dq;
+    int16_t dqsez;
+    int y;
+
+    /* Mask to get proper bits */
+    code &= 0x1F;
+    sezi = predictor_zero(s);
+    sei = sezi + predictor_pole(s);
+        
+    y = step_size(s);
+    dq = reconstruct(code & 0x10, g726_40_dqlntab[code], y);
+
+    /* Reconstruct the signal */
+    se = sei >> 1;
+    sr = (dq < 0)  ?  (se - (dq & 0x7FFF))  :  (se + dq);
+
+    /* Pole prediction difference */
+    dqsez = sr + (sezi >> 1) - se;
+
+    update(s, y, g726_40_witab[code], g726_40_fitab[code], dq, sr, dqsez);
+
+    switch (s->ext_coding)
+    {
+    case G726_ENCODING_ALAW:
+        return tandem_adjust_alaw(sr, se, y, code, 0x10, qtab_726_40, 31);
+    case G726_ENCODING_ULAW:
+        return tandem_adjust_ulaw(sr, se, y, code, 0x10, qtab_726_40, 31);
+    }
+    return (sr << 2);
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(g726_state_t *) g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing)
+{
+    int i;
+
+    if (bit_rate != 16000  &&  bit_rate != 24000  &&  bit_rate != 32000  &&  bit_rate != 40000)
+        return NULL;
+    if (s == NULL)
+    {
+        if ((s = (g726_state_t *) malloc(sizeof(*s))) == NULL)
+            return  NULL;
+    }
+    s->yl = 34816;
+    s->yu = 544;
+    s->dms = 0;
+    s->dml = 0;
+    s->ap = 0;
+    s->rate = bit_rate;
+    s->ext_coding = ext_coding;
+    s->packing = packing;
+    for (i = 0; i < 2; i++)
+    {
+        s->a[i] = 0;
+        s->pk[i] = 0;
+        s->sr[i] = 32;
+    }
+    for (i = 0; i < 6; i++)
+    {
+        s->b[i] = 0;
+        s->dq[i] = 32;
+    }
+    s->td = FALSE;
+    switch (bit_rate)
+    {
+    case 16000:
+        s->enc_func = g726_16_encoder;
+        s->dec_func = g726_16_decoder;
+        s->bits_per_sample = 2;
+        break;
+    case 24000:
+        s->enc_func = g726_24_encoder;
+        s->dec_func = g726_24_decoder;
+        s->bits_per_sample = 3;
+        break;
+    case 32000:
+    default:
+        s->enc_func = g726_32_encoder;
+        s->dec_func = g726_32_decoder;
+        s->bits_per_sample = 4;
+        break;
+    case 40000:
+        s->enc_func = g726_40_encoder;
+        s->dec_func = g726_40_decoder;
+        s->bits_per_sample = 5;
+        break;
+    }
+    bitstream_init(&s->bs, (s->packing != G726_PACKING_LEFT));
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) g726_release(g726_state_t *s)
+{
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) g726_free(g726_state_t *s)
+{
+    free(s);
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) g726_decode(g726_state_t *s,
+                              int16_t amp[],
+                              const uint8_t g726_data[],
+                              int g726_bytes)
+{
+    int i;
+    int samples;
+    uint8_t code;
+    int sl;
+
+    for (samples = i = 0;  ;  )
+    {
+        if (s->packing != G726_PACKING_NONE)
+        {
+            /* Unpack the code bits */
+            if (s->packing != G726_PACKING_LEFT)
+            {
+                if (s->bs.residue < s->bits_per_sample)
+                {
+                    if (i >= g726_bytes)
+                        break;
+                    s->bs.bitstream |= (g726_data[i++] << s->bs.residue);
+                    s->bs.residue += 8;
+                }
+                code = (uint8_t) (s->bs.bitstream & ((1 << s->bits_per_sample) - 1));
+                s->bs.bitstream >>= s->bits_per_sample;
+            }
+            else
+            {
+                if (s->bs.residue < s->bits_per_sample)
+                {
+                    if (i >= g726_bytes)
+                        break;
+                    s->bs.bitstream = (s->bs.bitstream << 8) | g726_data[i++];
+                    s->bs.residue += 8;
+                }
+                code = (uint8_t) ((s->bs.bitstream >> (s->bs.residue - s->bits_per_sample)) & ((1 << s->bits_per_sample) - 1));
+            }
+            s->bs.residue -= s->bits_per_sample;
+        }
+        else
+        {
+            if (i >= g726_bytes)
+                break;
+            code = g726_data[i++];
+        }
+        sl = s->dec_func(s, code);
+        if (s->ext_coding != G726_ENCODING_LINEAR)
+            ((uint8_t *) amp)[samples++] = (uint8_t) sl;
+        else
+            amp[samples++] = (int16_t) sl;
+    }
+    return samples;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) g726_encode(g726_state_t *s,
+                              uint8_t g726_data[],
+                              const int16_t amp[],
+                              int len)
+{
+    int i;
+    int g726_bytes;
+    int16_t sl;
+    uint8_t code;
+
+    for (g726_bytes = i = 0;  i < len;  i++)
+    {
+        /* Linearize the input sample to 14-bit PCM */
+        switch (s->ext_coding)
+        {
+        case G726_ENCODING_ALAW:
+            sl = alaw_to_linear(((const uint8_t *) amp)[i]) >> 2;
+            break;
+        case G726_ENCODING_ULAW:
+            sl = ulaw_to_linear(((const uint8_t *) amp)[i]) >> 2;
+            break;
+        default:
+            sl = amp[i] >> 2;
+            break;
+        }
+        code = s->enc_func(s, sl);
+        if (s->packing != G726_PACKING_NONE)
+        {
+            /* Pack the code bits */
+            if (s->packing != G726_PACKING_LEFT)
+            {
+                s->bs.bitstream |= (code << s->bs.residue);
+                s->bs.residue += s->bits_per_sample;
+                if (s->bs.residue >= 8)
+                {
+                    g726_data[g726_bytes++] = (uint8_t) (s->bs.bitstream & 0xFF);
+                    s->bs.bitstream >>= 8;
+                    s->bs.residue -= 8;
+                }
+            }
+            else
+            {
+                s->bs.bitstream = (s->bs.bitstream << s->bits_per_sample) | code;
+                s->bs.residue += s->bits_per_sample;
+                if (s->bs.residue >= 8)
+                {
+                    g726_data[g726_bytes++] = (uint8_t) ((s->bs.bitstream >> (s->bs.residue - 8)) & 0xFF);
+                    s->bs.residue -= 8;
+                }
+            }
+        }
+        else
+        {
+            g726_data[g726_bytes++] = (uint8_t) code;
+        }
+    }
+    return g726_bytes;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/

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