lpc.c revision 98913fed6520d8849fb2e246be943e04474aefa4 
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.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    */
73spx_word32_t _spx_lpc(
74spx_coef_t       *lpc, /* out: [0...p-1] LPC coefficients      */
75const spx_word16_t *ac,  /* in:  [0...p] autocorrelation values  */
76int          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
128void _spx_autocorr(
129const spx_word16_t *x,   /*  in: [0...n-1] samples x   */
130spx_word16_t       *ac,  /* out: [0...lag-1] ac values */
131int          lag,
132int          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 */
181void _spx_autocorr(
182const spx_word16_t *x,   /*  in: [0...n-1] samples x   */
183float       *ac,  /* out: [0...lag-1] ac values */
184int          lag,
185int          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
202