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Diffstat (limited to 'code/libspeex/lpc.c')
| -rw-r--r-- | code/libspeex/lpc.c | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/code/libspeex/lpc.c b/code/libspeex/lpc.c new file mode 100644 index 0000000..fd5d382 --- /dev/null +++ b/code/libspeex/lpc.c @@ -0,0 +1,201 @@ +/* + Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann, + Technische Universitaet Berlin + + Any use of this software is permitted provided that this notice is not + removed and that neither the authors nor the Technische Universitaet Berlin + are deemed to have made any representations as to the suitability of this + software for any purpose nor are held responsible for any defects of + this software. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE. + + As a matter of courtesy, the authors request to be informed about uses + this software has found, about bugs in this software, and about any + improvements that may be of general interest. + + Berlin, 28.11.1994 + Jutta Degener + Carsten Bormann + + + Code modified by Jean-Marc Valin + + Speex License: + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + - Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + - Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + + - Neither the name of the Xiph.org Foundation nor the names of its + contributors may be used to endorse or promote products derived from + this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR + CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, + PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR + PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING + NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +*/ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include "lpc.h" + +#ifdef BFIN_ASM +#include "lpc_bfin.h" +#endif + +/* LPC analysis + * + * The next two functions calculate linear prediction coefficients + * and/or the related reflection coefficients from the first P_MAX+1 + * values of the autocorrelation function. + */ + +/* Invented by N. Levinson in 1947, modified by J. Durbin in 1959. + */ + +/* returns minimum mean square error */ +spx_word32_t _spx_lpc( +spx_coef_t *lpc, /* out: [0...p-1] LPC coefficients */ +const spx_word16_t *ac, /* in: [0...p] autocorrelation values */ +int p +) +{ + int i, j; + spx_word16_t r; + spx_word16_t error = ac[0]; + + if (ac[0] == 0) + { + for (i = 0; i < p; i++) + lpc[i] = 0; + return 0; + } + + for (i = 0; i < p; i++) { + + /* Sum up this iteration's reflection coefficient */ + spx_word32_t rr = NEG32(SHL32(EXTEND32(ac[i + 1]),13)); + for (j = 0; j < i; j++) + rr = SUB32(rr,MULT16_16(lpc[j],ac[i - j])); +#ifdef FIXED_POINT + r = DIV32_16(rr+PSHR32(error,1),ADD16(error,8)); +#else + r = rr/(error+.003*ac[0]); +#endif + /* Update LPC coefficients and total error */ + lpc[i] = r; + for (j = 0; j < i>>1; j++) + { + spx_word16_t tmp = lpc[j]; + lpc[j] = MAC16_16_P13(lpc[j],r,lpc[i-1-j]); + lpc[i-1-j] = MAC16_16_P13(lpc[i-1-j],r,tmp); + } + if (i & 1) + lpc[j] = MAC16_16_P13(lpc[j],lpc[j],r); + + error = SUB16(error,MULT16_16_Q13(r,MULT16_16_Q13(error,r))); + } + return error; +} + + +#ifdef FIXED_POINT + +/* Compute the autocorrelation + * ,--, + * ac(i) = > x(n) * x(n-i) for all n + * `--' + * for lags between 0 and lag-1, and x == 0 outside 0...n-1 + */ + +#ifndef OVERRIDE_SPEEX_AUTOCORR +void _spx_autocorr( +const spx_word16_t *x, /* in: [0...n-1] samples x */ +spx_word16_t *ac, /* out: [0...lag-1] ac values */ +int lag, +int n +) +{ + spx_word32_t d; + int i, j; + spx_word32_t ac0=1; + int shift, ac_shift; + + for (j=0;j<n;j++) + ac0 = ADD32(ac0,SHR32(MULT16_16(x[j],x[j]),8)); + ac0 = ADD32(ac0,n); + shift = 8; + while (shift && ac0<0x40000000) + { + shift--; + ac0 <<= 1; + } + ac_shift = 18; + while (ac_shift && ac0<0x40000000) + { + ac_shift--; + ac0 <<= 1; + } + + + for (i=0;i<lag;i++) + { + d=0; + for (j=i;j<n;j++) + { + d = ADD32(d,SHR32(MULT16_16(x[j],x[j-i]), shift)); + } + + ac[i] = SHR32(d, ac_shift); + } +} +#endif + + +#else + + + +/* Compute the autocorrelation + * ,--, + * ac(i) = > x(n) * x(n-i) for all n + * `--' + * for lags between 0 and lag-1, and x == 0 outside 0...n-1 + */ +void _spx_autocorr( +const spx_word16_t *x, /* in: [0...n-1] samples x */ +float *ac, /* out: [0...lag-1] ac values */ +int lag, +int n +) +{ + float d; + int i; + while (lag--) + { + for (i = lag, d = 0; i < n; i++) + d += x[i] * x[i-lag]; + ac[lag] = d; + } + ac[0] += 10; +} + +#endif + + |