Thu Apr 28 2011 17:16:02

Asterisk developer's documentation


codec_g726.c File Reference

codec_g726.c - translate between signed linear and ITU G.726-32kbps (both RFC3551 and AAL2 codeword packing) More...

#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"
#include "log2comp.h"
#include "asterisk/slin.h"
#include "ex_g726.h"
Include dependency graph for codec_g726.c:

Go to the source code of this file.

Data Structures

struct  g726_coder_pvt
struct  g726_state

Defines

#define BUF_SHIFT   5
#define BUFFER_SAMPLES   8096
#define WANT_ASM

Functions

static void __reg_module (void)
static void __unreg_module (void)
static int fmult (int an, int srn)
static int g726_decode (int i, struct g726_state *state_ptr)
static int g726_encode (int sl, struct g726_state *state_ptr)
static void g726_init_state (struct g726_state *state_ptr)
static int g726aal2tolin_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
 decode packed 4-bit G726 values (AAL2 packing) and store in buffer.
static int g726tolin_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
 decode packed 4-bit G726 values (RFC3551 packing) and store in buffer.
static int lintog726_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
 compress and store data (4-bit G726 samples, RFC3551 packing) in outbuf
static int lintog726_new (struct ast_trans_pvt *pvt)
 init a new instance of g726_coder_pvt.
static int lintog726aal2_framein (struct ast_trans_pvt *pvt, struct ast_frame *f)
 compress and store data (4-bit G726 samples, AAL2 packing) in outbuf
static int load_module (void)
static int predictor_pole (struct g726_state *state_ptr)
static int predictor_zero (struct g726_state *state_ptr)
static int quan (int val, int *table, int size)
static int quantize (int d, int y, int *table, int size)
static int reconstruct (int sign, int dqln, int y)
static int reload (void)
static int step_size (struct g726_state *state_ptr)
static int unload_module (void)
static void update (int code_size, int y, int wi, int fi, int dq, int sr, int dqsez, struct g726_state *state_ptr)

Variables

static struct ast_module_info
__MODULE_INFO_SECTION 
__mod_info = { __MODULE_INFO_GLOBALS .name = AST_MODULE, .flags = AST_MODFLAG_DEFAULT , .description = "ITU G.726-32kbps G726 Transcoder" , .key = ASTERISK_GPL_KEY , .buildopt_sum = AST_BUILDOPT_SUM, .load = load_module, .unload = unload_module, .reload = reload, }
static int _dqlntab [16]
static int _fitab [16]
static int _witab [16]
static struct ast_module_infoast_module_info = &__mod_info
static struct ast_translator g726aal2tolin
static struct ast_translator g726tolin
static struct ast_translator lintog726
static struct ast_translator lintog726aal2
static int qtab_721 [7] = {-124, 80, 178, 246, 300, 349, 400}

Detailed Description

codec_g726.c - translate between signed linear and ITU G.726-32kbps (both RFC3551 and AAL2 codeword packing)

Definition in file codec_g726.c.


Define Documentation

#define BUF_SHIFT   5

Definition at line 58 of file codec_g726.c.

#define BUFFER_SAMPLES   8096

Definition at line 57 of file codec_g726.c.

#define WANT_ASM

Definition at line 41 of file codec_g726.c.


Function Documentation

static void __reg_module ( void  ) [static]

Definition at line 860 of file codec_g726.c.

static void __unreg_module ( void  ) [static]

Definition at line 860 of file codec_g726.c.

static int fmult ( int  an,
int  srn 
) [static]

Definition at line 203 of file codec_g726.c.

References ilog2().

Referenced by predictor_pole(), and predictor_zero().

{
   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 g726_decode ( int  i,
struct g726_state state_ptr 
) [static]

Definition at line 576 of file codec_g726.c.

References predictor_pole(), predictor_zero(), reconstruct(), step_size(), and update().

Referenced by g726aal2tolin_framein(), and g726tolin_framein().

{
   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
}
static int g726_encode ( int  sl,
struct g726_state state_ptr 
) [static]

Definition at line 622 of file codec_g726.c.

References predictor_pole(), predictor_zero(), quantize(), reconstruct(), step_size(), and update().

Referenced by lintog726_framein(), and lintog726aal2_framein().

{
   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);
}
static void g726_init_state ( struct g726_state state_ptr) [static]

Definition at line 121 of file codec_g726.c.

References g726_state::a, g726_state::ap, g726_state::b, g726_state::dml, g726_state::dms, g726_state::dq, g726_state::pk, g726_state::sr, g726_state::td, g726_state::yl, and g726_state::yu.

Referenced by lintog726_new().

{
   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;
}
static int g726aal2tolin_framein ( struct ast_trans_pvt pvt,
struct ast_frame f 
) [static]

decode packed 4-bit G726 values (AAL2 packing) and store in buffer.

Definition at line 691 of file codec_g726.c.

References ast_frame::data, ast_trans_pvt::datalen, ast_frame::datalen, g726_coder_pvt::g726, g726_decode(), ast_trans_pvt::i16, ast_trans_pvt::outbuf, ast_frame::ptr, ast_trans_pvt::pvt, ast_frame::samples, and ast_trans_pvt::samples.

{
   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;
}
static int g726tolin_framein ( struct ast_trans_pvt pvt,
struct ast_frame f 
) [static]

decode packed 4-bit G726 values (RFC3551 packing) and store in buffer.

Definition at line 732 of file codec_g726.c.

References ast_frame::data, ast_trans_pvt::datalen, ast_frame::datalen, g726_coder_pvt::g726, g726_decode(), ast_trans_pvt::i16, ast_trans_pvt::outbuf, ast_frame::ptr, ast_trans_pvt::pvt, ast_frame::samples, and ast_trans_pvt::samples.

{
   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;
}
static int lintog726_framein ( struct ast_trans_pvt pvt,
struct ast_frame f 
) [static]

compress and store data (4-bit G726 samples, RFC3551 packing) in outbuf

Definition at line 751 of file codec_g726.c.

References ast_trans_pvt::c, ast_frame::data, ast_trans_pvt::datalen, g726_coder_pvt::g726, g726_encode(), g726_coder_pvt::next_flag, ast_trans_pvt::outbuf, ast_frame::ptr, ast_trans_pvt::pvt, ast_trans_pvt::samples, and ast_frame::samples.

{
   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 int lintog726_new ( struct ast_trans_pvt pvt) [static]

init a new instance of g726_coder_pvt.

Definition at line 681 of file codec_g726.c.

References g726_coder_pvt::g726, g726_init_state(), and ast_trans_pvt::pvt.

{
   struct g726_coder_pvt *tmp = pvt->pvt;

   g726_init_state(&tmp->g726);

   return 0;
}
static int lintog726aal2_framein ( struct ast_trans_pvt pvt,
struct ast_frame f 
) [static]

compress and store data (4-bit G726 samples, AAL2 packing) in outbuf

Definition at line 710 of file codec_g726.c.

References ast_trans_pvt::c, ast_frame::data, ast_trans_pvt::datalen, g726_coder_pvt::g726, g726_encode(), g726_coder_pvt::next_flag, ast_trans_pvt::outbuf, ast_frame::ptr, ast_trans_pvt::pvt, ast_trans_pvt::samples, and ast_frame::samples.

{
   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;
}
static int load_module ( void  ) [static]
static int predictor_pole ( struct g726_state state_ptr) [static]

Definition at line 231 of file codec_g726.c.

References g726_state::a, fmult(), and g726_state::sr.

Referenced by g726_decode(), and g726_encode().

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

Definition at line 222 of file codec_g726.c.

References g726_state::b, g726_state::dq, and fmult().

Referenced by g726_decode(), and g726_encode().

{
   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 quan ( int  val,
int *  table,
int  size 
) [static]

Definition at line 158 of file codec_g726.c.

References table.

Referenced by quantize().

{
   int      i;

   for (i = 0; i < size && val >= *table; ++i, ++table)
      ;
   return (i);
}
static int quantize ( int  d,
int  y,
int *  table,
int  size 
) [static]

Definition at line 274 of file codec_g726.c.

References ilog2(), and quan().

Referenced by g726_encode().

{
   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);
}
static int reconstruct ( int  sign,
int  dqln,
int  y 
) [static]

Definition at line 327 of file codec_g726.c.

Referenced by bridge_p2p_rtp_write(), g726_decode(), and g726_encode().

{
   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
   }
}
static int reload ( void  ) [static]

Definition at line 820 of file codec_g726.c.

References AST_MODULE_LOAD_SUCCESS.

static int step_size ( struct g726_state state_ptr) [static]

Definition at line 245 of file codec_g726.c.

References g726_state::ap, g726_state::yl, and g726_state::yu.

Referenced by g726_decode(), and g726_encode().

{
   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);
   }
}
static int unload_module ( void  ) [static]

Definition at line 825 of file codec_g726.c.

References ast_unregister_translator().

Referenced by load_module().

static void update ( int  code_size,
int  y,
int  wi,
int  fi,
int  dq,
int  sr,
int  dqsez,
struct g726_state state_ptr 
) [static]

Definition at line 363 of file codec_g726.c.

References g726_state::a, g726_state::ap, g726_state::b, g726_state::dml, g726_state::dms, g726_state::dq, ilog2(), g726_state::pk, g726_state::sr, g726_state::td, g726_state::yl, and g726_state::yu.

Referenced by config_device(), config_line(), g726_decode(), and g726_encode().

{
   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;
}

Variable Documentation

struct ast_module_info __MODULE_INFO_SECTION __mod_info = { __MODULE_INFO_GLOBALS .name = AST_MODULE, .flags = AST_MODFLAG_DEFAULT , .description = "ITU G.726-32kbps G726 Transcoder" , .key = ASTERISK_GPL_KEY , .buildopt_sum = AST_BUILDOPT_SUM, .load = load_module, .unload = unload_module, .reload = reload, } [static]

Definition at line 860 of file codec_g726.c.

int _dqlntab[16] [static]
Initial value:
 {-2048, 4, 135, 213, 273, 323, 373, 425,
            425, 373, 323, 273, 213, 135, 4, -2048}

Definition at line 99 of file codec_g726.c.

int _fitab[16] [static]
Initial value:
 {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
            0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0}

Definition at line 110 of file codec_g726.c.

int _witab[16] [static]
Initial value:
 {-12, 18, 41, 64, 112, 198, 355, 1122,
            1122, 355, 198, 112, 64, 41, 18, -12}

Definition at line 103 of file codec_g726.c.

Definition at line 860 of file codec_g726.c.

struct ast_translator g726aal2tolin [static]

Definition at line 796 of file codec_g726.c.

struct ast_translator g726tolin [static]

Definition at line 772 of file codec_g726.c.

struct ast_translator lintog726 [static]

Definition at line 784 of file codec_g726.c.

struct ast_translator lintog726aal2 [static]

Definition at line 808 of file codec_g726.c.

int qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400} [static]

Definition at line 94 of file codec_g726.c.