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https://github.com/signalwire/freeswitch.git
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d92ee88a8b
git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@966 d0543943-73ff-0310-b7d9-9358b9ac24b2
343 lines
6.9 KiB
C
343 lines
6.9 KiB
C
/*
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* gsm_lpc.c
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*
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* Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
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* Universitaet Berlin. See the accompanying file "COPYRIGHT" for
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* details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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*/
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#include <stdio.h>
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#include <assert.h>
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#include "private.h"
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#include "gsm.h"
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#include "proto.h"
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#undef P
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/*
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* 4.2.4 .. 4.2.7 LPC ANALYSIS SECTION
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*/
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/* 4.2.4 */
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static void Autocorrelation P2((s, L_ACF),
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word * s, /* [0..159] IN/OUT */
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longword * L_ACF) /* [0..8] OUT */
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/*
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* The goal is to compute the array L_ACF[k]. The signal s[i] must
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* be scaled in order to avoid an overflow situation.
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*/
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{
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register int k, i;
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word temp, smax, scalauto;
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#ifdef USE_FLOAT_MUL
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float float_s[160];
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#endif
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/* Dynamic scaling of the array s[0..159]
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*/
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/* Search for the maximum.
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*/
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smax = 0;
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for (k = 0; k <= 159; k++) {
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temp = GSM_ABS( s[k] );
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if (temp > smax) smax = temp;
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}
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/* Computation of the scaling factor.
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*/
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if (smax == 0) scalauto = 0;
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else {
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assert(smax > 0);
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scalauto = 4 - gsm_norm( (longword)smax << 16 );/* sub(4,..) */
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}
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/* Scaling of the array s[0...159]
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*/
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if (scalauto > 0) {
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# ifdef USE_FLOAT_MUL
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# define SCALE(n) \
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case n: for (k = 0; k <= 159; k++) \
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float_s[k] = (float) \
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(s[k] = GSM_MULT_R(s[k], 16384 >> (n-1)));\
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break;
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# else
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# define SCALE(n) \
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case n: for (k = 0; k <= 159; k++) \
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s[k] = (word) GSM_MULT_R( s[k], 16384 >> (n-1) );\
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break;
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# endif /* USE_FLOAT_MUL */
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switch (scalauto) {
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SCALE(1)
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SCALE(2)
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SCALE(3)
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SCALE(4)
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}
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# undef SCALE
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}
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# ifdef USE_FLOAT_MUL
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else for (k = 0; k <= 159; k++) float_s[k] = (float) s[k];
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# endif
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/* Compute the L_ACF[..].
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*/
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{
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# ifdef USE_FLOAT_MUL
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register float * sp = float_s;
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register float sl = *sp;
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# define STEP(k) L_ACF[k] += (longword)(sl * sp[ -(k) ]);
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# else
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word * sp = s;
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word sl = *sp;
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# define STEP(k) L_ACF[k] += ((longword)sl * sp[ -(k) ]);
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# endif
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# define NEXTI sl = *++sp
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for (k = 9; k--; L_ACF[k] = 0) ;
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STEP (0);
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NEXTI;
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STEP(0); STEP(1);
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NEXTI;
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STEP(0); STEP(1); STEP(2);
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NEXTI;
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STEP(0); STEP(1); STEP(2); STEP(3);
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NEXTI;
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STEP(0); STEP(1); STEP(2); STEP(3); STEP(4);
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NEXTI;
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STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5);
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NEXTI;
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STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6);
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NEXTI;
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STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6); STEP(7);
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for (i = 8; i <= 159; i++) {
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NEXTI;
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STEP(0);
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STEP(1); STEP(2); STEP(3); STEP(4);
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STEP(5); STEP(6); STEP(7); STEP(8);
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}
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for (k = 9; k--; L_ACF[k] <<= 1) ;
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}
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/* Rescaling of the array s[0..159]
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*/
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if (scalauto > 0) {
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assert(scalauto <= 4);
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for (k = 160; k--; *s++ <<= scalauto) ;
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}
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}
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#if defined(USE_FLOAT_MUL) && defined(FAST)
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static void Fast_Autocorrelation P2((s, L_ACF),
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word * s, /* [0..159] IN/OUT */
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longword * L_ACF) /* [0..8] OUT */
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{
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register int k, i;
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float f_L_ACF[9];
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float scale;
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float s_f[160];
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register float *sf = s_f;
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for (i = 0; i < 160; ++i) sf[i] = s[i];
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for (k = 0; k <= 8; k++) {
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register float L_temp2 = 0;
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register float *sfl = sf - k;
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for (i = k; i < 160; ++i) L_temp2 += sf[i] * sfl[i];
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f_L_ACF[k] = L_temp2;
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}
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scale = MAX_LONGWORD / f_L_ACF[0];
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for (k = 0; k <= 8; k++) {
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L_ACF[k] = f_L_ACF[k] * scale;
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}
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}
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#endif /* defined (USE_FLOAT_MUL) && defined (FAST) */
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/* 4.2.5 */
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static void Reflection_coefficients P2( (L_ACF, r),
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longword * L_ACF, /* 0...8 IN */
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register word * r /* 0...7 OUT */
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)
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{
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register int i, m, n;
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register word temp;
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register longword ltmp;
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word ACF[9]; /* 0..8 */
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word P[ 9]; /* 0..8 */
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word K[ 9]; /* 2..8 */
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/* Schur recursion with 16 bits arithmetic.
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*/
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if (L_ACF[0] == 0) {
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for (i = 8; i--; *r++ = 0) ;
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return;
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}
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assert( L_ACF[0] != 0 );
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temp = gsm_norm( L_ACF[0] );
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assert(temp >= 0 && temp < 32);
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/* ? overflow ? */
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for (i = 0; i <= 8; i++) ACF[i] = (word) SASR( L_ACF[i] << temp, 16 );
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/* Initialize array P[..] and K[..] for the recursion.
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*/
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for (i = 1; i <= 7; i++) K[ i ] = ACF[ i ];
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for (i = 0; i <= 8; i++) P[ i ] = ACF[ i ];
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/* Compute reflection coefficients
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*/
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for (n = 1; n <= 8; n++, r++) {
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temp = P[1];
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temp = GSM_ABS(temp);
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if (P[0] < temp) {
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for (i = n; i <= 8; i++) *r++ = 0;
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return;
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}
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*r = gsm_div( temp, P[0] );
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assert(*r >= 0);
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if (P[1] > 0) *r = -*r; /* r[n] = sub(0, r[n]) */
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assert (*r != MIN_WORD);
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if (n == 8) return;
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/* Schur recursion
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*/
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temp = (word) GSM_MULT_R( P[1], *r );
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P[0] = (word) GSM_ADD( P[0], temp );
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for (m = 1; m <= 8 - n; m++) {
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temp = (word) GSM_MULT_R( K[ m ], *r );
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P[m] = (word) GSM_ADD( P[ m+1 ], temp );
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temp = (word) GSM_MULT_R( P[ m+1 ], *r );
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K[m] = (word) GSM_ADD( K[ m ], temp );
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}
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}
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}
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/* 4.2.6 */
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static void Transformation_to_Log_Area_Ratios P1((r),
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register word * r /* 0..7 IN/OUT */
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)
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/*
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* The following scaling for r[..] and LAR[..] has been used:
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*
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* r[..] = integer( real_r[..]*32768. ); -1 <= real_r < 1.
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* LAR[..] = integer( real_LAR[..] * 16384 );
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* with -1.625 <= real_LAR <= 1.625
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*/
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{
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register word temp;
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register int i;
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/* Computation of the LAR[0..7] from the r[0..7]
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*/
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for (i = 1; i <= 8; i++, r++) {
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temp = *r;
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temp = GSM_ABS(temp);
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assert(temp >= 0);
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if (temp < 22118) {
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temp >>= 1;
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} else if (temp < 31130) {
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assert( temp >= 11059 );
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temp -= 11059;
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} else {
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assert( temp >= 26112 );
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temp -= 26112;
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temp <<= 2;
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}
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*r = *r < 0 ? -temp : temp;
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assert( *r != MIN_WORD );
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}
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}
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/* 4.2.7 */
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static void Quantization_and_coding P1((LAR),
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register word * LAR /* [0..7] IN/OUT */
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)
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{
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register word temp;
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longword ltmp;
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/* This procedure needs four tables; the following equations
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* give the optimum scaling for the constants:
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*
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* A[0..7] = integer( real_A[0..7] * 1024 )
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* B[0..7] = integer( real_B[0..7] * 512 )
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* MAC[0..7] = maximum of the LARc[0..7]
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* MIC[0..7] = minimum of the LARc[0..7]
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*/
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# undef STEP
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# define STEP( A, B, MAC, MIC ) \
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temp = (word)GSM_MULT( A, *LAR ); \
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temp = (word) GSM_ADD( temp, B ); \
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temp = (word) GSM_ADD( temp, 256 ); \
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temp = (word)SASR( temp, 9 ); \
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*LAR = temp>MAC ? MAC - MIC : (temp<MIC ? 0 : temp - MIC); \
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LAR++;
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STEP( 20480, 0, 31, -32 );
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STEP( 20480, 0, 31, -32 );
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STEP( 20480, 2048, 15, -16 );
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STEP( 20480, -2560, 15, -16 );
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STEP( 13964, 94, 7, -8 );
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STEP( 15360, -1792, 7, -8 );
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STEP( 8534, -341, 3, -4 );
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STEP( 9036, -1144, 3, -4 );
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# undef STEP
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}
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void Gsm_LPC_Analysis P3((S, s,LARc),
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struct gsm_state *S,
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word * s, /* 0..159 signals IN/OUT */
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word * LARc) /* 0..7 LARc's OUT */
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{
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longword L_ACF[9];
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#if defined(USE_FLOAT_MUL) && defined(FAST)
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if (S->fast) Fast_Autocorrelation (s, L_ACF );
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else
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#endif
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Autocorrelation (s, L_ACF );
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Reflection_coefficients (L_ACF, LARc );
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Transformation_to_Log_Area_Ratios (LARc);
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Quantization_and_coding (LARc);
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}
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