apps/codecs/libspeex/lpc.c

   1 /*
   2   Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann,
   3   Technische Universitaet Berlin
   4
   5   Any use of this software is permitted provided that this notice is not
   6   removed and that neither the authors nor the Technische Universitaet Berlin
   7   are deemed to have made any representations as to the suitability of this
   8   software for any purpose nor are held responsible for any defects of
   9   this software.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
  10
  11   As a matter of courtesy, the authors request to be informed about uses
  12   this software has found, about bugs in this software, and about any
  13   improvements that may be of general interest.
  14
  15   Berlin, 28.11.1994
  16   Jutta Degener
  17   Carsten Bormann
  18
  19
  20    Code modified by Jean-Marc Valin
  21
  22    Speex License:
  23
  24    Redistribution and use in source and binary forms, with or without
  25    modification, are permitted provided that the following conditions
  26    are met:
  27
  28    - Redistributions of source code must retain the above copyright
  29    notice, this list of conditions and the following disclaimer.
  30
  31    - Redistributions in binary form must reproduce the above copyright
  32    notice, this list of conditions and the following disclaimer in the
  33    documentation and/or other materials provided with the distribution.
  34
  35    - Neither the name of the Xiph.org Foundation nor the names of its
  36    contributors may be used to endorse or promote products derived from
  37    this software without specific prior written permission.
  38
  39    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  40    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  41    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  42    A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
  43    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  44    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  45    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  46    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  47    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  48    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  49    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  50 */
  51
  52 #ifdef HAVE_CONFIG_H
  53 #include "config-speex.h"
  54 #endif
  55
  56 #include "lpc.h"
  57
  58 #ifdef BFIN_ASM
  59 #include "lpc_bfin.h"
  60 #endif
  61
  62 /* LPC analysis
  63  *
  64  * The next two functions calculate linear prediction coefficients
  65  * and/or the related reflection coefficients from the first P_MAX+1
  66  * values of the autocorrelation function.
  67  */
  68
  69 /* Invented by N. Levinson in 1947, modified by J. Durbin in 1959.
  70  */
  71
  72 /* returns minimum mean square error    */
  73 spx_word32_t _spx_lpc(
  74 spx_coef_t       *lpc, /* out: [0...p-1] LPC coefficients      */
  75 const spx_word16_t *ac,  /* in:  [0...p] autocorrelation values  */
  76 int          p
  77 )
  78 {
  79    int i, j;
  80    spx_word16_t r;
  81    spx_word16_t error = ac[0];
  82
  83    if (ac[0] == 0)
  84    {
  85       for (i = 0; i < p; i++)
  86          lpc[i] = 0;
  87       return 0;
  88    }
  89
  90    for (i = 0; i < p; i++) {
  91
  92       /* Sum up this iteration's reflection coefficient */
  93       spx_word32_t rr = NEG32(SHL32(EXTEND32(ac[i + 1]),13));
  94       for (j = 0; j < i; j++)
  95          rr = SUB32(rr,MULT16_16(lpc[j],ac[i - j]));
  96 #ifdef FIXED_POINT
  97       r = DIV32_16(rr+PSHR32(error,1),ADD16(error,8));
  98 #else
  99       r = rr/(error+.003*ac[0]);
 100 #endif
 101       /*  Update LPC coefficients and total error */
 102       lpc[i] = r;
 103       for (j = 0; j < i>>1; j++)
 104       {
 105          spx_word16_t tmp  = lpc[j];
 106          lpc[j]     = MAC16_16_P13(lpc[j],r,lpc[i-1-j]);
 107          lpc[i-1-j] = MAC16_16_P13(lpc[i-1-j],r,tmp);
 108       }
 109       if (i & 1)
 110          lpc[j] = MAC16_16_P13(lpc[j],lpc[j],r);
 111
 112       error = SUB16(error,MULT16_16_Q13(r,MULT16_16_Q13(error,r)));
 113    }
 114    return error;
 115 }
 116
 117
 118 #ifdef FIXED_POINT
 119
 120 /* Compute the autocorrelation
 121  *                      ,--,
 122  *              ac(i) = >  x(n) * x(n-i)  for all n
 123  *                      `--'
 124  * for lags between 0 and lag-1, and x == 0 outside 0...n-1
 125  */
 126
 127 #ifndef OVERRIDE_SPEEX_AUTOCORR
 128 void _spx_autocorr(
 129 const spx_word16_t *x,   /*  in: [0...n-1] samples x   */
 130 spx_word16_t       *ac,  /* out: [0...lag-1] ac values */
 131 int          lag,
 132 int          n
 133 )
 134 {
 135    spx_word32_t d;
 136    int i, j;
 137    spx_word32_t ac0=1;
 138    int shift, ac_shift;
 139
 140    for (j=0;j<n;j++)
 141       ac0 = ADD32(ac0,SHR32(MULT16_16(x[j],x[j]),8));
 142    ac0 = ADD32(ac0,n);
 143    shift = 8;
 144    while (shift && ac0<0x40000000)
 145    {
 146       shift--;
 147       ac0 <<= 1;
 148    }
 149    ac_shift = 18;
 150    while (ac_shift && ac0<0x40000000)
 151    {
 152       ac_shift--;
 153       ac0 <<= 1;
 154    }
 155
 156
 157    for (i=0;i<lag;i++)
 158    {
 159       d=0;
 160       for (j=i;j<n;j++)
 161       {
 162          d = ADD32(d,SHR32(MULT16_16(x[j],x[j-i]), shift));
 163       }
 164
 165       ac[i] = SHR32(d, ac_shift);
 166    }
 167 }
 168 #endif
 169
 170
 171 #else
 172
 173
 174
 175 /* Compute the autocorrelation
 176  *                      ,--,
 177  *              ac(i) = >  x(n) * x(n-i)  for all n
 178  *                      `--'
 179  * for lags between 0 and lag-1, and x == 0 outside 0...n-1
 180  */
 181 void _spx_autocorr(
 182 const spx_word16_t *x,   /*  in: [0...n-1] samples x   */
 183 float       *ac,  /* out: [0...lag-1] ac values */
 184 int          lag,
 185 int          n
 186 )
 187 {
 188    float d;
 189    int i;
 190    while (lag--)
 191    {
 192       for (i = lag, d = 0; i < n; i++)
 193          d += x[i] * x[i-lag];
 194       ac[lag] = d;
 195    }
 196    ac[0] += 10;
 197 }
 198
 199 #endif
 200
 201