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cx_g726.c

/*
 * 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
 */
 
#ifndef HIDE_SOURCE_STRINGS
static const char cvsid[] = 
      "$Id: cx_g726.c,v 1.7 2000/01/27 17:11:32 ucacoxh Exp $";
#endif /* HIDE_SOURCE_STRINGS */

/*
 * g72x.c
 *
 * Common routines for G.726_32 and G.726 conversions.
 */

/* 
 * Small tweaks made to fix compiler warnings i.e. prototypes and
 * unused variables 
 */

#define _PRIVATE_G726_
#include "cx_g726.h"
#include "math.h"
#include "stdlib.h" /* abs */

static short power2[15] = {1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80,
                  0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000};

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

      for (i = 0; i < size; i++)
            if (val < *table++)
                  break;
      return (i);
}

/*
 * fmult()
 *
 * returns the integer product of the 14-bit integer "an" and
 * "floating point" representation (4-bit exponent, 6-bit mantessa) "srn".
 */
static int
fmult(
      int         an,
      int         srn)
{
      short       anmag, anexp, anmant;
      short       wanexp, wanmant;
      short       retval;

      anmag = (an > 0) ? an : ((-an) & 0x1FFF);
      anexp = quan(anmag, power2, 15) - 6;
      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);
}

/*
 * g726_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.726_32 document.
 */
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;
            state_ptr->sr[cnta] = 32;
      }
      for (cnta = 0; cnta < 6; cnta++) {
            state_ptr->b[cnta] = 0;
            state_ptr->dq[cnta] = 32;
      }
      state_ptr->td = 0;
}

/*
 * predictor_zero()
 *
 * computes the estimated signal from 6-zero predictor.
 */
int
predictor_zero(
      struct g726_state *state_ptr)
{
      int         i;
      int         sezi;

      sezi = fmult(state_ptr->b[0] >> 2, state_ptr->dq[0]);
      for (i = 1; i < 6; i++)             /* ACCUM */
            sezi += fmult(state_ptr->b[i] >> 2, state_ptr->dq[i]);
      return (sezi);
}
/*
 * predictor_pole()
 *
 * computes the estimated signal from 2-pole predictor.
 */
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]));
}
/*
 * step_size()
 *
 * computes the quantization step size of the adaptive quantizer.
 */
int
step_size(
      struct g726_state *state_ptr)
{
      int         y;
      int         dif;
      int         al;

      if (state_ptr->ap >= 256)
            return (state_ptr->yu);
      else {
            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.
 */
int
quantize(
      int         d,    /* Raw difference signal sample */
      int         y,    /* Step size multiplier */
      short       *table,     /* quantization table */
      int         size) /* table size of short integers */
{
      short       dqm;  /* Magnitude of 'd' */
      short       exp;  /* Integer part of base 2 log of 'd' */
      short       mant; /* Fractional part of base 2 log */
      short       dl;   /* Log of magnitude of 'd' */
      short       dln;  /* Step size scale factor normalized log */
      int         i;

      /*
       * LOG
       *
       * Compute base 2 log of 'd', and store in 'dl'.
       */
      dqm = abs(d);
      exp = quan(dqm >> 1, power2, 15);
      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.
 */
int
reconstruct(
      int         sign, /* 0 for non-negative value */
      int         dqln, /* G.72x codeword */
      int         y)    /* Step size multiplier */
{
      short       dql;  /* Log of 'dq' magnitude */
      short       dex;  /* Integer part of log */
      short       dqt;
      short       dq;   /* Reconstructed difference signal sample */

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

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


/*
 * update()
 *
 * updates the state variables for each output code
 */
void
update(
      int         code_size,  /* distinguish 726_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;
      short       mag, exp;   /* Adaptive predictor, FLOAT A */
      short       a2p=0;            /* LIMC */
      short       a1ul;       /* UPA1 */
      short       pks1;  /* UPA2 */
      short       fa1;
      char        tr;         /* tone/transition detector */
      short       ylint, thr2, dqthr;
      short             ylfrac, thr1;
      short       pk0;

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

      mag = dq & 0x7FFF;            /* prediction difference magnitude */
      /* TRANS */
      ylint = (short)(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.726 */
                        state_ptr->b[cnt] -= state_ptr->b[cnt] >> 9;
                  else              /* for G.726_32 and 24Kbps G.726 */
                        state_ptr->b[cnt] -= state_ptr->b[cnt] >> 8;
                  if (dq & 0x7FFF) {                  /* 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];
      /* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
      if (mag == 0) {
            state_ptr->dq[0] = (dq >= 0) ? 0x20 : 0xFC20;
      } else {
            exp = quan(mag, power2, 15);
            state_ptr->dq[0] = (dq >= 0) ?
                (exp << 6) + ((mag << 6) >> exp) :
                (exp << 6) + ((mag << 6) >> exp) - 0x400;
      }

      state_ptr->sr[1] = state_ptr->sr[0];
      /* 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 = quan(sr, power2, 15);
            state_ptr->sr[0] = (exp << 6) + ((sr << 6) >> exp);
      } else if (sr > -32768) {
            mag = -sr;
            exp = quan(mag, power2, 15);
            state_ptr->sr[0] =  (exp << 6) + ((mag << 6) >> exp) - 0x400;
      } else
            state_ptr->sr[0] = (short)0xFC20;

      /* 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;
}


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