/src/fdk-aac/libAACdec/src/usacdec_lpc.cpp

Source
/* -----------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

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 1.    INTRODUCTION
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that implements the MPEG Advanced Audio Coding ("AAC") encoding and decoding
scheme for digital audio. This FDK AAC Codec software is intended to be used on
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AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient
general perceptual audio codecs. AAC-ELD is considered the best-performing
full-bandwidth communications codec by independent studies and is widely
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Patent licenses for necessary patent claims for the FDK AAC Codec (including
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already be covered under those patent licenses when it is used for those
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Commercially-licensed AAC software libraries, including floating-point versions
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5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------- */

/**************************** AAC decoder library ******************************

   Author(s):   Matthias Hildenbrand, Manuel Jander

   Description: USAC LPC/AVQ decode

*******************************************************************************/

#include "usacdec_lpc.h"

#include "usacdec_rom.h"
#include "FDK_trigFcts.h"

#define NQ_MAX 36

/*
 * Helper functions.
 */

/**
 * \brief Read unary code.
 * \param hBs bitstream handle as data source.
 * \return decoded value.
 */
static int get_vlclbf(HANDLE_FDK_BITSTREAM hBs) {
  int result = 0;

  while (FDKreadBits(hBs, 1) && result <= NQ_MAX) {
    result++;
  }
  return result;
}

/**
 * \brief Read bit count limited unary code.
 * \param hBs bitstream handle as data source
 * \param n max amount of bits to be read.
 * \return decoded value.
 */
static int get_vlclbf_n(HANDLE_FDK_BITSTREAM hBs, int n) {
  int result = 0;

  while (FDKreadBits(hBs, 1)) {
    result++;
    n--;
    if (n <= 0) {
      break;
    }
  }

  return result;
}

/*
 * Algebraic Vector Quantizer
 */

/* ZF_SCALE must be greater than (number of FIXP_ZF)/2
   because the loss of precision caused by fPow2Div2 in RE8_PPV() */
//#define ZF_SCALE ((NQ_MAX-3)>>1)
#define ZF_SCALE ((DFRACT_BITS / 2))
#define FIXP_ZF FIXP_DBL
#define INT2ZF(x, s) (FIXP_ZF)((x) << (ZF_SCALE - (s)))
#define ZF2INT(x) (INT)((x) >> ZF_SCALE)

/* 1.0 in ZF format format */
#define ONEZF ((FIXP_ZF)INT2ZF(1, 0))

/* static */
void nearest_neighbor_2D8(FIXP_ZF x[8], int y[8]) {
  FIXP_ZF s, em, e[8];
  int i, j, sum;

  /* round x into 2Z^8 i.e. compute y=(y1,...,y8) such that yi = 2[xi/2]
     where [.] is the nearest integer operator
     in the mean time, compute sum = y1+...+y8
  */
  sum = 0;
  for (i = 0; i < 8; i++) {
    FIXP_ZF tmp;
    /* round to ..., -2, 0, 2, ... ([-1..1[ --> 0) */
    if (x[i] < (FIXP_ZF)0) {
      tmp = ONEZF - x[i];
      y[i] = -2 * ((ZF2INT(tmp)) >> 1);
    } else {
      tmp = ONEZF + x[i];
      y[i] = 2 * ((ZF2INT(tmp)) >> 1);
    }
    sum += y[i];
  }
  /* check if y1+...+y8 is a multiple of 4
     if not, y is not round xj in the wrong way where j is defined by
        j = arg max_i | xi -yi|
     (this is called the Wagner rule)
  */
  if (sum % 4) {
    /* find j = arg max_i | xi -yi| */
    em = (FIXP_SGL)0;
    j = 0;
    for (i = 0; i < 8; i++) {
      /* compute ei = xi-yi */
      e[i] = x[i] - INT2ZF(y[i], 0);
    }
    for (i = 0; i < 8; i++) {
      /* compute |ei| = | xi-yi | */
      if (e[i] < (FIXP_ZF)0) {
        s = -e[i];
      } else {
        s = e[i];
      }
      /* check if |ei| is maximal, if so, set j=i */
      if (em < s) {
        em = s;
        j = i;
      }
    }
    /* round xj in the "wrong way" */
    if (e[j] < (FIXP_ZF)0) {
      y[j] -= 2;
    } else {
      y[j] += 2;
    }
  }
}

/*--------------------------------------------------------------
  RE8_PPV(x,y)
  NEAREST NEIGHBOR SEARCH IN INFINITE LATTICE RE8
  the algorithm is based on the definition of RE8 as
      RE8 = (2D8) U (2D8+[1,1,1,1,1,1,1,1])
  it applies the coset decoding of Sloane and Conway
  (i) x: point in R^8 in 32-ZF_SCALE.ZF_SCALE format
  (o) y: point in RE8 (8-dimensional integer vector)
  --------------------------------------------------------------
*/
/* static */
void RE8_PPV(FIXP_ZF x[], SHORT y[], int r) {
  int i, y0[8], y1[8];
  FIXP_ZF x1[8], tmp;
  INT64 e;

  /* find the nearest neighbor y0 of x in 2D8 */
  nearest_neighbor_2D8(x, y0);
  /* find the nearest neighbor y1 of x in 2D8+(1,...,1) (by coset decoding) */
  for (i = 0; i < 8; i++) {
    x1[i] = x[i] - ONEZF;
  }
  nearest_neighbor_2D8(x1, y1);
  for (i = 0; i < 8; i++) {
    y1[i] += 1;
  }

  /* compute e0=||x-y0||^2 and e1=||x-y1||^2 */
  e = 0;
  for (i = 0; i < 8; i++) {
    tmp = x[i] - INT2ZF(y0[i], 0);
    e += (INT64)fPow2Div2(
        tmp << r); /* shift left to ensure that no fract part bits get lost. */
    tmp = x[i] - INT2ZF(y1[i], 0);
    e -= (INT64)fPow2Div2(tmp << r);
  }
  /* select best candidate y0 or y1 to minimize distortion */
  if (e < 0) {
    for (i = 0; i < 8; i++) {
      y[i] = y0[i];
    }
  } else {
    for (i = 0; i < 8; i++) {
      y[i] = y1[i];
    }
  }
}

/* table look-up of unsigned value: find i where index >= table[i]
   Note: range must be >= 2, index must be >= table[0] */
static int table_lookup(const USHORT *table, unsigned int index, int range) {
  int i;

  for (i = 4; i < range; i += 4) {
    if (index < table[i]) {
      break;
    }
  }
  if (i > range) {
    i = range;
  }

  if (index < table[i - 2]) {
    i -= 2;
  }
  if (index < table[i - 1]) {
    i--;
  }
  i--;

  return (i); /* index >= table[i] */
}

/*--------------------------------------------------------------------------
  re8_decode_rank_of_permutation(rank, xs, x)
  DECODING OF THE RANK OF THE PERMUTATION OF xs
  (i) rank: index (rank) of a permutation
  (i) xs:   signed leader in RE8 (8-dimensional integer vector)
  (o) x:    point in RE8 (8-dimensional integer vector)
  --------------------------------------------------------------------------
 */
static void re8_decode_rank_of_permutation(int rank, int *xs, SHORT x[8]) {
  INT a[8], w[8], B, fac, fac_B, target;
  int i, j;

  /* --- pre-processing based on the signed leader xs ---
     - compute the alphabet a=[a[0] ... a[q-1]] of x (q elements)
       such that a[0]!=...!=a[q-1]
       it is assumed that xs is sorted in the form of a signed leader
       which can be summarized in 2 requirements:
          a) |xs[0]| >= |xs[1]| >= |xs[2]| >= ... >= |xs[7]|
          b) if |xs[i]|=|xs[i-1]|, xs[i]>=xs[i+1]
       where |.| indicates the absolute value operator
     - compute q (the number of symbols in the alphabet)
     - compute w[0..q-1] where w[j] counts the number of occurences of
       the symbol a[j] in xs
     - compute B = prod_j=0..q-1 (w[j]!) where .! is the factorial */
  /* xs[i], xs[i-1] and ptr_w/a*/
  j = 0;
  w[j] = 1;
  a[j] = xs[0];
  B = 1;
  for (i = 1; i < 8; i++) {
    if (xs[i] != xs[i - 1]) {
      j++;
      w[j] = 1;
      a[j] = xs[i];
    } else {
      w[j]++;
      B *= w[j];
    }
  }

  /* --- actual rank decoding ---
     the rank of x (where x is a permutation of xs) is based on
     Schalkwijk's formula
     it is given by rank=sum_{k=0..7} (A_k * fac_k/B_k)
     the decoding of this rank is sequential and reconstructs x[0..7]
     element by element from x[0] to x[7]
     [the tricky part is the inference of A_k for each k...]
   */

  if (w[0] == 8) {
    for (i = 0; i < 8; i++) {
      x[i] = a[0]; /* avoid fac of 40320 */
    }
  } else {
    target = rank * B;
    fac_B = 1;
    /* decode x element by element */
    for (i = 0; i < 8; i++) {
      fac = fac_B * fdk_dec_tab_factorial[i]; /* fac = 1..5040 */
      j = -1;
      do {
        target -= w[++j] * fac;
      } while (target >= 0); /* max of 30 tests / SV */
      x[i] = a[j];
      /* update rank, denominator B (B_k) and counter w[j] */
      target += w[j] * fac; /* target = fac_B*B*rank */
      fac_B *= w[j];
      w[j]--;
    }
  }
}

/*--------------------------------------------------------------------------
  re8_decode_base_index(n, I, y)
  DECODING OF AN INDEX IN Qn (n=0,2,3 or 4)
  (i) n: codebook number (*n is an integer defined in {0,2,3,4})
  (i) I: index of c (pointer to unsigned 16-bit word)
  (o) y: point in RE8 (8-dimensional integer vector)
  note: the index I is defined as a 32-bit word, but only
  16 bits are required (long can be replaced by unsigned integer)
  --------------------------------------------------------------------------
 */
static void re8_decode_base_index(int *n, UINT index, SHORT y[8]) {
  int i, im, t, sign_code, ka, ks, rank, leader[8];

  if (*n < 2) {
    for (i = 0; i < 8; i++) {
      y[i] = 0;
    }
  } else {
    // index = (unsigned int)*I;
    /* search for the identifier ka of the absolute leader (table-lookup)
       Q2 is a subset of Q3 - the two cases are considered in the same branch
     */
    switch (*n) {
      case 2:
      case 3:
        i = table_lookup(fdk_dec_I3, index, NB_LDQ3);
        ka = fdk_dec_A3[i];
        break;
      case 4:
        i = table_lookup(fdk_dec_I4, index, NB_LDQ4);
        ka = fdk_dec_A4[i];
        break;
      default:
        FDK_ASSERT(0);
        return;
    }
    /* reconstruct the absolute leader */
    for (i = 0; i < 8; i++) {
      leader[i] = fdk_dec_Da[ka][i];
    }
    /* search for the identifier ks of the signed leader (table look-up)
       (this search is focused based on the identifier ka of the absolute
        leader)*/
    t = fdk_dec_Ia[ka];
    im = fdk_dec_Ns[ka];
    ks = table_lookup(fdk_dec_Is + t, index, im);

    /* reconstruct the signed leader from its sign code */
    sign_code = 2 * fdk_dec_Ds[t + ks];
    for (i = 7; i >= 0; i--) {
      leader[i] *= (1 - (sign_code & 2));
      sign_code >>= 1;
    }

    /* compute and decode the rank of the permutation */
    rank = index - fdk_dec_Is[t + ks]; /* rank = index - cardinality offset */

    re8_decode_rank_of_permutation(rank, leader, y);
  }
  return;
}

/* re8_y2k(y,m,k)
   VORONOI INDEXING (INDEX DECODING) k -> y
   (i) k: Voronoi index k[0..7]
   (i) m: Voronoi modulo (m = 2^r = 1<<r, where r is integer >=2)
   (i) r: Voronoi order  (m = 2^r = 1<<r, where r is integer >=2)
   (o) y: 8-dimensional point y[0..7] in RE8
 */
static void re8_k2y(int *k, int r, SHORT *y) {
  int i, tmp, sum;
  SHORT v[8];
  FIXP_ZF zf[8];

  FDK_ASSERT(r <= ZF_SCALE);

  /* compute y = k M and z=(y-a)/m, where
     M = [4        ]
         [2 2      ]
         [|   \    ]
         [2     2  ]
         [1 1 _ 1 1]
     a=(2,0,...,0)
     m = 1<<r
  */
  for (i = 0; i < 8; i++) {
    y[i] = k[7];
  }
  zf[7] = INT2ZF(y[7], r);
  sum = 0;
  for (i = 6; i >= 1; i--) {
    tmp = 2 * k[i];
    sum += tmp;
    y[i] += tmp;
    zf[i] = INT2ZF(y[i], r);
  }
  y[0] += (4 * k[0] + sum);
  zf[0] = INT2ZF(y[0] - 2, r);
  /* find nearest neighbor v of z in infinite RE8 */
  RE8_PPV(zf, v, r);
  /* compute y -= m v */
  for (i = 0; i < 8; i++) {
    y[i] -= (SHORT)(v[i] << r);
  }
}

/*--------------------------------------------------------------------------
  RE8_dec(n, I, k, y)
  MULTI-RATE INDEXING OF A POINT y in THE LATTICE RE8 (INDEX DECODING)
  (i) n: codebook number (*n is an integer defined in {0,2,3,4,..,n_max}). n_max
  = 36 (i) I: index of c (pointer to unsigned 16-bit word) (i) k: index of v
  (8-dimensional vector of binary indices) = Voronoi index (o) y: point in RE8
  (8-dimensional integer vector) note: the index I is defined as a 32-bit word,
  but only 16 bits are required (long can be replaced by unsigned integer)

  return 0 on success, -1 on error.
  --------------------------------------------------------------------------
 */
static int RE8_dec(int n, int I, int *k, FIXP_DBL *y) {
  SHORT v[8];
  SHORT _y[8];
  UINT r;
  int i;

  /* Check bound of codebook qn */
  if (n > NQ_MAX) {
    return -1;
  }

  /* decode the sub-indices I and kv[] according to the codebook number n:
     if n=0,2,3,4, decode I (no Voronoi extension)
     if n>4, Voronoi extension is used, decode I and kv[] */
  if (n <= 4) {
    re8_decode_base_index(&n, I, _y);
    for (i = 0; i < 8; i++) {
      y[i] = (LONG)_y[i];
    }
  } else {
    /* compute the Voronoi modulo m = 2^r where r is extension order */
    r = ((n - 3) >> 1);

    while (n > 4) {
      n -= 2;
    }
    /* decode base codebook index I into c (c is an element of Q3 or Q4)
       [here c is stored in y to save memory] */
    re8_decode_base_index(&n, I, _y);
    /* decode Voronoi index k[] into v */
    re8_k2y(k, r, v);
    /* reconstruct y as y = m c + v (with m=2^r, r integer >=1) */
    for (i = 0; i < 8; i++) {
      y[i] = (LONG)((_y[i] << r) + v[i]);
    }
  }
  return 0;
}

/**************************/
/* start LPC decode stuff */
/**************************/
//#define M         16
#define FREQ_MAX 6400.0f
#define FREQ_DIV 400.0f
#define LSF_GAP 50.0f

/**
 * \brief calculate inverse weighting factor and add non-weighted residual
 *        LSF vector to first stage LSF approximation
 * \param lsfq first stage LSF approximation values.
 * \param xq weighted residual LSF vector
 * \param nk_mode code book number coding mode.
 */
static void lsf_weight_2st(FIXP_LPC *lsfq, FIXP_DBL *xq, int nk_mode) {
  FIXP_LPC d[M_LP_FILTER_ORDER + 1];
  FIXP_SGL factor;
  LONG w; /* inverse weight factor */
  int i;

  /* compute lsf distance */
  d[0] = lsfq[0];
  d[M_LP_FILTER_ORDER] =
      FL2FXCONST_LPC(FREQ_MAX / (1 << LSF_SCALE)) - lsfq[M_LP_FILTER_ORDER - 1];
  for (i = 1; i < M_LP_FILTER_ORDER; i++) {
    d[i] = lsfq[i] - lsfq[i - 1];
  }

  switch (nk_mode) {
    case 0:
      factor = FL2FXCONST_SGL(2.0f * 60.0f / FREQ_DIV);
      break; /* abs */
    case 1:
      factor = FL2FXCONST_SGL(2.0f * 65.0f / FREQ_DIV);
      break; /* mid */
    case 2:
      factor = FL2FXCONST_SGL(2.0f * 64.0f / FREQ_DIV);
      break; /* rel1 */
    default:
      factor = FL2FXCONST_SGL(2.0f * 63.0f / FREQ_DIV);
      break; /* rel2 */
  }
  /* add non-weighted residual LSF vector to LSF1st */
  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    w = (LONG)fMultDiv2(factor, sqrtFixp(fMult(d[i], d[i + 1])));
    lsfq[i] = fAddSaturate(lsfq[i],
                           FX_DBL2FX_LPC((FIXP_DBL)((INT64)w * (LONG)xq[i])));
  }

  return;
}

/**
 * \brief decode nqn amount of code book numbers. These values determine the
 * amount of following bits for nqn AVQ RE8 vectors.
 * \param nk_mode quantization mode.
 * \param nqn amount code book number to read.
 * \param qn pointer to output buffer to hold decoded code book numbers qn.
 */
static void decode_qn(HANDLE_FDK_BITSTREAM hBs, int nk_mode, int nqn,
                      int qn[]) {
  int n;

  if (nk_mode == 1) { /* nk mode 1 */
    /* Unary code for mid LPC1/LPC3 */
    /* Q0=0, Q2=10, Q3=110, ... */
    for (n = 0; n < nqn; n++) {
      qn[n] = get_vlclbf(hBs);
      if (qn[n] > 0) {
        qn[n]++;
      }
    }
  } else { /* nk_mode 0, 3 and 2 */
    /* 2 bits to specify Q2,Q3,Q4,ext */
    for (n = 0; n < nqn; n++) {
      qn[n] = 2 + FDKreadBits(hBs, 2);
    }
    if (nk_mode == 2) {
      /* Unary code for rel LPC1/LPC3 */
      /* Q0 = 0, Q5=10, Q6=110, ... */
      for (n = 0; n < nqn; n++) {
        if (qn[n] > 4) {
          qn[n] = get_vlclbf(hBs);
          if (qn[n] > 0) qn[n] += 4;
        }
      }
    } else { /* nk_mode == (0 and 3) */
      /* Unary code for abs and rel LPC0/LPC2 */
      /* Q5 = 0, Q6=10, Q0=110, Q7=1110, ... */
      for (n = 0; n < nqn; n++) {
        if (qn[n] > 4) {
          qn[n] = get_vlclbf(hBs);
          switch (qn[n]) {
            case 0:
              qn[n] = 5;
              break;
            case 1:
              qn[n] = 6;
              break;
            case 2:
              qn[n] = 0;
              break;
            default:
              qn[n] += 4;
              break;
          }
        }
      }
    }
  }
}

/**
 * \brief reorder LSF coefficients to minimum distance.
 * \param lsf pointer to buffer containing LSF coefficients and where reordered
 * LSF coefficients will be stored into, scaled by LSF_SCALE.
 * \param min_dist min distance scaled by LSF_SCALE
 * \param n number of LSF/LSP coefficients.
 */
static void reorder_lsf(FIXP_LPC *lsf, FIXP_LPC min_dist, int n) {
  FIXP_LPC lsf_min;
  int i;

  lsf_min = min_dist;
  for (i = 0; i < n; i++) {
    if (lsf[i] < lsf_min) {
      lsf[i] = lsf_min;
    }
    lsf_min = fAddSaturate(lsf[i], min_dist);
  }

  /* reverse */
  lsf_min = FL2FXCONST_LPC(FREQ_MAX / (1 << LSF_SCALE)) - min_dist;
  for (i = n - 1; i >= 0; i--) {
    if (lsf[i] > lsf_min) {
      lsf[i] = lsf_min;
    }

    lsf_min = lsf[i] - min_dist;
  }
}

/**
 * \brief First stage approximation
 * \param hBs bitstream handle as data source
 * \param lsfq pointer to output buffer to hold LPC coefficients scaled by
 * LSF_SCALE.
 */
static void vlpc_1st_dec(
    HANDLE_FDK_BITSTREAM hBs, /* input:  codebook index                  */
    FIXP_LPC *lsfq            /* i/o:    i:prediction   o:quantized lsf  */
) {
  const FIXP_LPC *p_dico;
  int i, index;

  index = FDKreadBits(hBs, 8);
  p_dico = &fdk_dec_dico_lsf_abs_8b[index * M_LP_FILTER_ORDER];
  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    lsfq[i] = p_dico[i];
  }
}

/**
 * \brief Do first stage approximation weighting and multiply with AVQ
 * refinement.
 * \param hBs bitstream handle data ssource.
 * \param lsfq buffer holding 1st stage approx, 2nd stage approx is added to
 * this values.
 * \param nk_mode quantization mode.
 * \return 0 on success, -1 on error.
 */
static int vlpc_2st_dec(
    HANDLE_FDK_BITSTREAM hBs,
    FIXP_LPC *lsfq, /* i/o:    i:1st stage   o:1st+2nd stage   */
    int nk_mode     /* input:  0=abs, >0=rel                   */
) {
  int err;
  FIXP_DBL xq[M_LP_FILTER_ORDER]; /* weighted residual LSF vector */

  /* Decode AVQ refinement */
  { err = CLpc_DecodeAVQ(hBs, xq, nk_mode, 2, 8); }
  if (err != 0) {
    return -1;
  }

  /* add non-weighted residual LSF vector to LSF1st */
  lsf_weight_2st(lsfq, xq, nk_mode);

  /* reorder */
  reorder_lsf(lsfq, FL2FXCONST_LPC(LSF_GAP / (1 << LSF_SCALE)),
              M_LP_FILTER_ORDER);

  return 0;
}

/*
 * Externally visible functions
 */

int CLpc_DecodeAVQ(HANDLE_FDK_BITSTREAM hBs, FIXP_DBL *pOutput, int nk_mode,
                   int no_qn, int length) {
  int i, l;

  for (i = 0; i < length; i += 8 * no_qn) {
    int qn[2], nk, n, I;
    int kv[8] = {0};

    decode_qn(hBs, nk_mode, no_qn, qn);

    for (l = 0; l < no_qn; l++) {
      if (qn[l] == 0) {
        FDKmemclear(&pOutput[i + l * 8], 8 * sizeof(FIXP_DBL));
      }

      /* Voronoi extension order ( nk ) */
      nk = 0;
      n = qn[l];
      if (qn[l] > 4) {
        nk = (qn[l] - 3) >> 1;
        n = qn[l] - nk * 2;
      }

      /* Base codebook index, in reverse bit group order (!) */
      I = FDKreadBits(hBs, 4 * n);

      if (nk > 0) {
        int j;

        for (j = 0; j < 8; j++) {
          kv[j] = FDKreadBits(hBs, nk);
        }
      }

      if (RE8_dec(qn[l], I, kv, &pOutput[i + l * 8]) != 0) {
        return -1;
      }
    }
  }
  return 0;
}

int CLpc_Read(HANDLE_FDK_BITSTREAM hBs, FIXP_LPC lsp[][M_LP_FILTER_ORDER],
              FIXP_LPC lpc4_lsf[M_LP_FILTER_ORDER],
              FIXP_LPC lsf_adaptive_mean_cand[M_LP_FILTER_ORDER],
              FIXP_SGL pStability[], UCHAR *mod, int first_lpd_flag,
              int last_lpc_lost, int last_frame_ok) {
  int i, k, err;
  int mode_lpc_bin = 0; /* mode_lpc bitstream representation */
  int lpc_present[5] = {0, 0, 0, 0, 0};
  int lpc0_available = 1;
  int s = 0;
  int l = 3;
  const int nbDiv = NB_DIV;

  lpc_present[4 >> s] = 1; /* LPC4 */

  /* Decode LPC filters in the following order: LPC 4,0,2,1,3 */

  /*** Decode LPC4 ***/
  vlpc_1st_dec(hBs, lsp[4 >> s]);
  err = vlpc_2st_dec(hBs, lsp[4 >> s], 0); /* nk_mode = 0 */
  if (err != 0) {
    return err;
  }

  /*** Decode LPC0 and LPC2 ***/
  k = 0;
  if (!first_lpd_flag) {
    lpc_present[0] = 1;
    lpc0_available = !last_lpc_lost;
    /* old LPC4 is new LPC0 */
    for (i = 0; i < M_LP_FILTER_ORDER; i++) {
      lsp[0][i] = lpc4_lsf[i];
    }
    /* skip LPC0 and continue with LPC2 */
    k = 2;
  }

  for (; k < l; k += 2) {
    int nk_mode = 0;

    if ((k == 2) && (mod[0] == 3)) {
      break; /* skip LPC2 */
    }

    lpc_present[k >> s] = 1;

    mode_lpc_bin = FDKreadBit(hBs);

    if (mode_lpc_bin == 0) {
      /* LPC0/LPC2: Abs */
      vlpc_1st_dec(hBs, lsp[k >> s]);
    } else {
      /* LPC0/LPC2: RelR */
      for (i = 0; i < M_LP_FILTER_ORDER; i++) {
        lsp[k >> s][i] = lsp[4 >> s][i];
      }
      nk_mode = 3;
    }

    err = vlpc_2st_dec(hBs, lsp[k >> s], nk_mode);
    if (err != 0) {
      return err;
    }
  }

  /*** Decode LPC1 ***/
  if (mod[0] < 2) { /* else: skip LPC1 */
    lpc_present[1] = 1;
    mode_lpc_bin = get_vlclbf_n(hBs, 2);

    switch (mode_lpc_bin) {
      case 1:
        /* LPC1: abs */
        vlpc_1st_dec(hBs, lsp[1]);
        err = vlpc_2st_dec(hBs, lsp[1], 0);
        if (err != 0) {
          return err;
        }
        break;
      case 2:
        /* LPC1: mid0 (no second stage AVQ quantizer in this case) */
        if (lpc0_available) { /* LPC0/lsf[0] might be zero some times */
          for (i = 0; i < M_LP_FILTER_ORDER; i++) {
            lsp[1][i] = (lsp[0][i] >> 1) + (lsp[2][i] >> 1);
          }
        } else {
          for (i = 0; i < M_LP_FILTER_ORDER; i++) {
            lsp[1][i] = lsp[2][i];
          }
        }
        break;
      case 0:
        /* LPC1: RelR */
        for (i = 0; i < M_LP_FILTER_ORDER; i++) {
          lsp[1][i] = lsp[2][i];
        }
        err = vlpc_2st_dec(hBs, lsp[1], 2 << s);
        if (err != 0) {
          return err;
        }
        break;
    }
  }

  /*** Decode LPC3 ***/
  if ((mod[2] < 2)) { /* else: skip LPC3 */
    int nk_mode = 0;
    lpc_present[3] = 1;

    mode_lpc_bin = get_vlclbf_n(hBs, 3);

    switch (mode_lpc_bin) {
      case 1:
        /* LPC3: abs */
        vlpc_1st_dec(hBs, lsp[3]);
        break;
      case 0:
        /* LPC3: mid */
        for (i = 0; i < M_LP_FILTER_ORDER; i++) {
          lsp[3][i] = (lsp[2][i] >> 1) + (lsp[4][i] >> 1);
        }
        nk_mode = 1;
        break;
      case 2:
        /* LPC3: relL */
        for (i = 0; i < M_LP_FILTER_ORDER; i++) {
          lsp[3][i] = lsp[2][i];
        }
        nk_mode = 2;
        break;
      case 3:
        /* LPC3: relR */
        for (i = 0; i < M_LP_FILTER_ORDER; i++) {
          lsp[3][i] = lsp[4][i];
        }
        nk_mode = 2;
        break;
    }
    err = vlpc_2st_dec(hBs, lsp[3], nk_mode);
    if (err != 0) {
      return err;
    }
  }

  if (!lpc0_available && !last_frame_ok) {
    /* LPC(0) was lost. Use next available LPC(k) instead */
    for (k = 1; k < (nbDiv + 1); k++) {
      if (lpc_present[k]) {
        for (i = 0; i < M_LP_FILTER_ORDER; i++) {
#define LSF_INIT_TILT (0.25f)
          if (mod[0] > 0) {
            lsp[0][i] = FX_DBL2FX_LPC(
                fMult(lsp[k][i], FL2FXCONST_SGL(1.0f - LSF_INIT_TILT)) +
                fMult(fdk_dec_lsf_init[i], FL2FXCONST_SGL(LSF_INIT_TILT)));
          } else {
            lsp[0][i] = lsp[k][i];
          }
        }
        break;
      }
    }
  }

  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    lpc4_lsf[i] = lsp[4 >> s][i];
  }

  {
    FIXP_DBL divFac;
    int last, numLpc = 0;

    i = nbDiv;
    do {
      numLpc += lpc_present[i--];
    } while (i >= 0 && numLpc < 3);

    last = i;

    switch (numLpc) {
      case 3:
        divFac = FL2FXCONST_DBL(1.0f / 3.0f);
        break;
      case 2:
        divFac = FL2FXCONST_DBL(1.0f / 2.0f);
        break;
      default:
        divFac = FL2FXCONST_DBL(1.0f);
        break;
    }

    /* get the adaptive mean for the next (bad) frame */
    for (k = 0; k < M_LP_FILTER_ORDER; k++) {
      FIXP_DBL tmp = (FIXP_DBL)0;
      for (i = nbDiv; i > last; i--) {
        if (lpc_present[i]) {
          tmp = fMultAdd(tmp >> 1, lsp[i][k], divFac);
        }
      }
      lsf_adaptive_mean_cand[k] = FX_DBL2FX_LPC(tmp);
    }
  }

  /* calculate stability factor Theta. Needed for ACELP decoder and concealment
   */
  {
    FIXP_LPC *lsf_prev, *lsf_curr;
    k = 0;

    FDK_ASSERT(lpc_present[0] == 1 && lpc_present[4 >> s] == 1);
    lsf_prev = lsp[0];
    for (i = 1; i < (nbDiv + 1); i++) {
      if (lpc_present[i]) {
        FIXP_DBL tmp = (FIXP_DBL)0;
        int j;
        lsf_curr = lsp[i];

        /* sum = tmp * 2^(LSF_SCALE*2 + 4) */
        for (j = 0; j < M_LP_FILTER_ORDER; j++) {
          tmp += fPow2Div2((FIXP_SGL)(lsf_curr[j] - lsf_prev[j])) >> 3;
        }

        /* tmp = (float)(FL2FXCONST_DBL(1.25f) - fMult(tmp,
         * FL2FXCONST_DBL(1/400000.0f))); */
        tmp = FL2FXCONST_DBL(1.25f / (1 << LSF_SCALE)) -
              fMult(tmp, FL2FXCONST_DBL((1 << (LSF_SCALE + 4)) / 400000.0f));
        if (tmp >= FL2FXCONST_DBL(1.0f / (1 << LSF_SCALE))) {
          pStability[k] = FL2FXCONST_SGL(1.0f / 2.0f);
        } else if (tmp < FL2FXCONST_DBL(0.0f)) {
          pStability[k] = FL2FXCONST_SGL(0.0f);
        } else {
          pStability[k] = FX_DBL2FX_SGL(tmp << (LSF_SCALE - 1));
        }

        lsf_prev = lsf_curr;
        k = i;
      } else {
        /* Mark stability value as undefined. */
        pStability[i] = (FIXP_SGL)-1;
      }
    }
  }

  /* convert into LSP domain */
  for (i = 0; i < (nbDiv + 1); i++) {
    if (lpc_present[i]) {
      for (k = 0; k < M_LP_FILTER_ORDER; k++) {
        lsp[i][k] = FX_DBL2FX_LPC(
            fixp_cos(fMult(lsp[i][k],
                           FL2FXCONST_SGL((1 << LSPARG_SCALE) * M_PI / 6400.0)),
                     LSF_SCALE - LSPARG_SCALE));
      }
    }
  }

  return 0;
}

void CLpc_Conceal(FIXP_LPC lsp[][M_LP_FILTER_ORDER],
                  FIXP_LPC lpc4_lsf[M_LP_FILTER_ORDER],
                  FIXP_LPC lsf_adaptive_mean[M_LP_FILTER_ORDER],
                  const int first_lpd_flag) {
  int i, j;

#define BETA (FL2FXCONST_SGL(0.25f))
#define ONE_BETA (FL2FXCONST_SGL(0.75f))
#define BFI_FAC (FL2FXCONST_SGL(0.90f))
#define ONE_BFI_FAC (FL2FXCONST_SGL(0.10f))

  /* Frame loss concealment (could be improved) */

  if (first_lpd_flag) {
    /* Reset past LSF values */
    for (i = 0; i < M_LP_FILTER_ORDER; i++) {
      lsp[0][i] = lpc4_lsf[i] = fdk_dec_lsf_init[i];
    }
  } else {
    /* old LPC4 is new LPC0 */
    for (i = 0; i < M_LP_FILTER_ORDER; i++) {
      lsp[0][i] = lpc4_lsf[i];
    }
  }

  /* LPC1 */
  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    FIXP_LPC lsf_mean = FX_DBL2FX_LPC(fMult(BETA, fdk_dec_lsf_init[i]) +
                                      fMult(ONE_BETA, lsf_adaptive_mean[i]));

    lsp[1][i] = FX_DBL2FX_LPC(fMult(BFI_FAC, lpc4_lsf[i]) +
                              fMult(ONE_BFI_FAC, lsf_mean));
  }

  /* LPC2 - LPC4 */
  for (j = 2; j <= 4; j++) {
    for (i = 0; i < M_LP_FILTER_ORDER; i++) {
      /* lsf_mean[i] =  FX_DBL2FX_LPC(fMult((FIXP_LPC)(BETA + j *
         FL2FXCONST_LPC(0.1f)), fdk_dec_lsf_init[i])
                                    + fMult((FIXP_LPC)(ONE_BETA - j *
         FL2FXCONST_LPC(0.1f)), lsf_adaptive_mean[i])); */

      FIXP_LPC lsf_mean = FX_DBL2FX_LPC(
          fMult((FIXP_SGL)(BETA + (FIXP_SGL)(j * (INT)FL2FXCONST_SGL(0.1f))),
                (FIXP_SGL)fdk_dec_lsf_init[i]) +
          fMult(
              (FIXP_SGL)(ONE_BETA - (FIXP_SGL)(j * (INT)FL2FXCONST_SGL(0.1f))),
              lsf_adaptive_mean[i]));

      lsp[j][i] = FX_DBL2FX_LPC(fMult(BFI_FAC, lsp[j - 1][i]) +
                                fMult(ONE_BFI_FAC, lsf_mean));
    }
  }

  /* Update past values for the future */
  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    lpc4_lsf[i] = lsp[4][i];
  }

  /* convert into LSP domain */
  for (j = 0; j < 5; j++) {
    for (i = 0; i < M_LP_FILTER_ORDER; i++) {
      lsp[j][i] = FX_DBL2FX_LPC(fixp_cos(
          fMult(lsp[j][i], FL2FXCONST_SGL((1 << LSPARG_SCALE) * M_PI / 6400.0)),
          LSF_SCALE - LSPARG_SCALE));
    }
  }
}

void E_LPC_a_weight(FIXP_LPC *wA, const FIXP_LPC *A, int m) {
  FIXP_DBL f;
  int i;

  f = FL2FXCONST_DBL(0.92f);
  for (i = 0; i < m; i++) {
    wA[i] = FX_DBL2FX_LPC(fMult(A[i], f));
    f = fMult(f, FL2FXCONST_DBL(0.92f));
  }
}

void CLpd_DecodeGain(FIXP_DBL *gain, INT *gain_e, int gain_code) {
  /* gain * 2^(gain_e) = 10^(gain_code/28) */
  *gain = fLdPow(
      FL2FXCONST_DBL(3.3219280948873623478703194294894 / 4.0), /* log2(10)*/
      2,
      fMultDiv2((FIXP_DBL)gain_code << (DFRACT_BITS - 1 - 7),
                FL2FXCONST_DBL(2.0f / 28.0f)),
      7, gain_e);
}

  /**
   * \brief *   Find the polynomial F1(z) or F2(z) from the LSPs.
   * This is performed by expanding the product polynomials:
   *
   * F1(z) =   product   ( 1 - 2 LSP_i z^-1 + z^-2 )
   *         i=0,2,4,6,8
   * F2(z) =   product   ( 1 - 2 LSP_i z^-1 + z^-2 )
   *         i=1,3,5,7,9
   *
   * where LSP_i are the LSPs in the cosine domain.
   * R.A.Salami    October 1990
   * \param lsp input, line spectral freq. (cosine domain)
   * \param f output, the coefficients of F1 or F2, scaled by 8 bits
   * \param n no of coefficients (m/2)
   * \param flag 1 : F1(z) ; 2 : F2(z)
   */

#define SF_F 8

static void get_lsppol(FIXP_LPC lsp[], FIXP_DBL f[], int n, int flag) {
  FIXP_DBL b;
  FIXP_LPC *plsp;
  int i, j;

  plsp = lsp + flag - 1;
  f[0] = FL2FXCONST_DBL(1.0f / (1 << SF_F));
  b = -FX_LPC2FX_DBL(*plsp);
  f[1] = b >> (SF_F - 1);
  for (i = 2; i <= n; i++) {
    plsp += 2;
    b = -FX_LPC2FX_DBL(*plsp);
    f[i] = SATURATE_LEFT_SHIFT((fMultDiv2(b, f[i - 1]) + (f[i - 2] >> 1)), 2,
                               DFRACT_BITS);
    for (j = i - 1; j > 1; j--) {
      f[j] = SATURATE_LEFT_SHIFT(
          ((f[j] >> 2) + fMultDiv2(b, f[j - 1]) + (f[j - 2] >> 2)), 2,
          DFRACT_BITS);
    }
    f[1] = f[1] + (b >> (SF_F - 1));
  }
  return;
}

#define NC M_LP_FILTER_ORDER / 2

/**
 * \brief lsp input LSP vector
 * \brief a output LP filter coefficient vector scaled by SF_A_COEFFS.
 */
void E_LPC_f_lsp_a_conversion(FIXP_LPC *lsp, FIXP_LPC *a, INT *a_exp) {
  FIXP_DBL f1[NC + 1], f2[NC + 1];
  int i, k;

  /*-----------------------------------------------------*
   *  Find the polynomials F1(z) and F2(z)               *
   *-----------------------------------------------------*/

  get_lsppol(lsp, f1, NC, 1);
  get_lsppol(lsp, f2, NC, 2);

  /*-----------------------------------------------------*
   *  Multiply F1(z) by (1+z^-1) and F2(z) by (1-z^-1)   *
   *-----------------------------------------------------*/
  scaleValues(f1, NC + 1, -2);
  scaleValues(f2, NC + 1, -2);

  for (i = NC; i > 0; i--) {
    f1[i] += f1[i - 1];
    f2[i] -= f2[i - 1];
  }

  FIXP_DBL aDBL[M_LP_FILTER_ORDER];

  for (i = 1, k = M_LP_FILTER_ORDER - 1; i <= NC; i++, k--) {
    aDBL[i - 1] = f1[i] + f2[i];
    aDBL[k] = f1[i] - f2[i];
  }

  int headroom_a = getScalefactor(aDBL, M_LP_FILTER_ORDER);

  for (i = 0; i < M_LP_FILTER_ORDER; i++) {
    a[i] = FX_DBL2FX_LPC(aDBL[i] << headroom_a);
  }

  *a_exp = SF_F + (2 - 1) - headroom_a;
}

Coverage Report

Created: 2026-04-01 07:42