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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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/* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/rpe.c,v 1.3 1994/05/10 20:18:46 jutta Exp $ */
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/* 4.2.13 .. 4.2.17 RPE ENCODING SECTION
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static void Weighting_filter P2((e, x),
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register word * e, /* signal [-5..0.39.44] IN */
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word * x /* signal [0..39] OUT */
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* The coefficients of the weighting filter are stored in a table
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* (see table 4.4). The following scaling is used:
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* H[0..10] = integer( real_H[ 0..10] * 8192 );
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register longword L_result;
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register int k /* , i */ ;
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/* Initialization of a temporary working array wt[0...49]
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/* for (k = 0; k <= 4; k++) wt[k] = 0;
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* for (k = 5; k <= 44; k++) wt[k] = *e++;
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* for (k = 45; k <= 49; k++) wt[k] = 0;
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* (e[-5..-1] and e[40..44] are allocated by the caller,
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* are initially zero and are not written anywhere.)
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/* Compute the signal x[0..39]
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for (k = 0; k <= 39; k++) {
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/* for (i = 0; i <= 10; i++) {
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* L_temp = GSM_L_MULT( wt[k+i], gsm_H[i] );
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* L_result = GSM_L_ADD( L_result, L_temp );
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#define STEP( i, H ) (e[ k + i ] * (longword)H)
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/* Every one of these multiplications is done twice --
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* but I don't see an elegant way to optimize this.
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#ifdef STUPID_COMPILER
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L_result += STEP( 0, -134 ) ;
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L_result += STEP( 1, -374 ) ;
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L_result += STEP( 3, 2054 ) ;
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L_result += STEP( 4, 5741 ) ;
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L_result += STEP( 5, 8192 ) ;
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L_result += STEP( 6, 5741 ) ;
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L_result += STEP( 7, 2054 ) ;
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L_result += STEP( 9, -374 ) ;
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L_result += STEP( 10, -134 ) ;
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/* L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x2) *)
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* L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x4) *)
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* x[k] = SASR( L_result, 16 );
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/* 2 adds vs. >>16 => 14, minus one shift to compensate for
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* those we lost when replacing L_MULT by '*'.
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L_result = SASR( L_result, 13 );
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x[k] = ( L_result < MIN_WORD ? MIN_WORD
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: (L_result > MAX_WORD ? MAX_WORD : L_result ));
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static void RPE_grid_selection P3((x,xM,Mc_out),
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word * x, /* [0..39] IN */
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word * xM, /* [0..12] OUT */
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word * Mc_out /* OUT */
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* The signal x[0..39] is used to select the RPE grid which is
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/* register word temp1; */
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register int /* m, */ i;
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register longword L_result, L_temp;
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longword EM; /* xxx should be L_EM? */
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longword L_common_0_3;
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/* for (m = 0; m <= 3; m++) {
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* for (i = 0; i <= 12; i++) {
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* temp1 = SASR( x[m + 3*i], 2 );
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* assert(temp1 != MIN_WORD);
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* L_temp = GSM_L_MULT( temp1, temp1 );
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* L_result = GSM_L_ADD( L_temp, L_result );
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* if (L_result > EM) {
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#define STEP( m, i ) L_temp = SASR( x[m + 3 * i], 2 ); \
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L_result += L_temp * L_temp;
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/* common part of 0 and 3 */
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STEP( 0, 1 ); STEP( 0, 2 ); STEP( 0, 3 ); STEP( 0, 4 );
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STEP( 0, 5 ); STEP( 0, 6 ); STEP( 0, 7 ); STEP( 0, 8 );
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STEP( 0, 9 ); STEP( 0, 10); STEP( 0, 11); STEP( 0, 12);
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L_common_0_3 = L_result;
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L_result <<= 1; /* implicit in L_MULT */
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STEP( 1, 1 ); STEP( 1, 2 ); STEP( 1, 3 ); STEP( 1, 4 );
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STEP( 1, 5 ); STEP( 1, 6 ); STEP( 1, 7 ); STEP( 1, 8 );
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STEP( 1, 9 ); STEP( 1, 10); STEP( 1, 11); STEP( 1, 12);
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STEP( 2, 1 ); STEP( 2, 2 ); STEP( 2, 3 ); STEP( 2, 4 );
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STEP( 2, 5 ); STEP( 2, 6 ); STEP( 2, 7 ); STEP( 2, 8 );
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STEP( 2, 9 ); STEP( 2, 10); STEP( 2, 11); STEP( 2, 12);
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L_result = L_common_0_3;
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/* Down-sampling by a factor 3 to get the selected xM[0..12]
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for (i = 0; i <= 12; i ++) xM[i] = x[Mc + 3*i];
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static void APCM_quantization_xmaxc_to_exp_mant P3((xmaxc,exp_out,mant_out),
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word * exp_out, /* OUT */
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word * mant_out ) /* OUT */
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/* Compute exponent and mantissa of the decoded version of xmaxc
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if (xmaxc > 15) exp = SASR(xmaxc, 3) - 1;
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mant = xmaxc - (exp << 3);
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mant = mant << 1 | 1;
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assert( exp >= -4 && exp <= 6 );
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assert( mant >= 0 && mant <= 7 );
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static void APCM_quantization P5((xM,xMc,mant_out,exp_out,xmaxc_out),
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word * xM, /* [0..12] IN */
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word * xMc, /* [0..12] OUT */
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word * mant_out, /* OUT */
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word * exp_out, /* OUT */
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word * xmaxc_out /* OUT */
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word xmax, xmaxc, temp, temp1, temp2;
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/* Find the maximum absolute value xmax of xM[0..12].
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for (i = 0; i <= 12; i++) {
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temp = GSM_ABS(temp);
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if (temp > xmax) xmax = temp;
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/* Qantizing and coding of xmax to get xmaxc.
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temp = SASR( xmax, 9 );
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for (i = 0; i <= 5; i++) {
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itest |= (temp <= 0);
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temp = SASR( temp, 1 );
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if (itest == 0) exp++; /* exp = add (exp, 1) */
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assert(exp <= 6 && exp >= 0);
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assert(temp <= 11 && temp >= 0);
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xmaxc = gsm_add( SASR(xmax, temp), exp << 3 );
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/* Quantizing and coding of the xM[0..12] RPE sequence
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* to get the xMc[0..12]
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APCM_quantization_xmaxc_to_exp_mant( xmaxc, &exp, &mant );
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/* This computation uses the fact that the decoded version of xmaxc
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* can be calculated by using the exponent and the mantissa part of
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* xmaxc (logarithmic table).
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* So, this method avoids any division and uses only a scaling
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* of the RPE samples by a function of the exponent. A direct
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* multiplication by the inverse of the mantissa (NRFAC[0..7]
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* found in table 4.5) gives the 3 bit coded version xMc[0..12]
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* of the RPE samples.
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/* Direct computation of xMc[0..12] using table 4.5
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assert( exp <= 4096 && exp >= -4096);
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assert( mant >= 0 && mant <= 7 );
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temp1 = 6 - exp; /* normalization by the exponent */
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temp2 = gsm_NRFAC[ mant ]; /* inverse mantissa */
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for (i = 0; i <= 12; i++) {
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assert(temp1 >= 0 && temp1 < 16);
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temp = xM[i] << temp1;
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temp = GSM_MULT( temp, temp2 );
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temp = SASR(temp, 12);
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xMc[i] = temp + 4; /* see note below */
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/* NOTE: This equation is used to make all the xMc[i] positive.
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static void APCM_inverse_quantization P4((xMc,mant,exp,xMp),
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register word * xMc, /* [0..12] IN */
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register word * xMp) /* [0..12] OUT */
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* This part is for decoding the RPE sequence of coded xMc[0..12]
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* samples to obtain the xMp[0..12] array. Table 4.6 is used to get
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* the mantissa of xmaxc (FAC[0..7]).
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word temp, temp1, temp2, temp3;
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assert( mant >= 0 && mant <= 7 );
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temp1 = gsm_FAC[ mant ]; /* see 4.2-15 for mant */
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temp2 = gsm_sub( 6, exp ); /* see 4.2-15 for exp */
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temp3 = gsm_asl( 1, gsm_sub( temp2, 1 ));
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assert( *xMc <= 7 && *xMc >= 0 ); /* 3 bit unsigned */
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/* temp = gsm_sub( *xMc++ << 1, 7 ); */
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temp = (*xMc++ << 1) - 7; /* restore sign */
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assert( temp <= 7 && temp >= -7 ); /* 4 bit signed */
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temp <<= 12; /* 16 bit signed */
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temp = GSM_MULT_R( temp1, temp );
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temp = GSM_ADD( temp, temp3 );
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*xMp++ = gsm_asr( temp, temp2 );
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static void RPE_grid_positioning P3((Mc,xMp,ep),
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word Mc, /* grid position IN */
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register word * xMp, /* [0..12] IN */
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register word * ep /* [0..39] OUT */
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* This procedure computes the reconstructed long term residual signal
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* ep[0..39] for the LTP analysis filter. The inputs are the Mc
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* which is the grid position selection and the xMp[0..12] decoded
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* RPE samples which are upsampled by a factor of 3 by inserting zero
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assert(0 <= Mc && Mc <= 3);
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case 0: *ep++ = *xMp++;
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while (++Mc < 4) *ep++ = 0;
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for (k = 0; k <= 39; k++) ep[k] = 0;
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for (i = 0; i <= 12; i++) {
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ep[ Mc + (3*i) ] = xMp[i];
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/* This procedure adds the reconstructed long term residual signal
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* ep[0..39] to the estimated signal dpp[0..39] from the long term
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* analysis filter to compute the reconstructed short term residual
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* signal dp[-40..-1]; also the reconstructed short term residual
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* array dp[-120..-41] is updated.
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#if 0 /* Has been inlined in code.c */
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void Gsm_Update_of_reconstructed_short_time_residual_signal P3((dpp, ep, dp),
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word * dpp, /* [0...39] IN */
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word * ep, /* [0...39] IN */
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word * dp) /* [-120...-1] IN/OUT */
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for (k = 0; k <= 79; k++)
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dp[ -120 + k ] = dp[ -80 + k ];
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for (k = 0; k <= 39; k++)
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dp[ -40 + k ] = gsm_add( ep[k], dpp[k] );
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#endif /* Has been inlined in code.c */
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void Gsm_RPE_Encoding P5((S,e,xmaxc,Mc,xMc),
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struct gsm_state * S,
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word * e, /* -5..-1][0..39][40..44 IN/OUT */
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word * xmaxc, /* OUT */
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word * xMc) /* [0..12] OUT */
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word xM[13], xMp[13];
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Weighting_filter(e, x);
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RPE_grid_selection(x, xM, Mc);
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APCM_quantization( xM, xMc, &mant, &exp, xmaxc);
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APCM_inverse_quantization( xMc, mant, exp, xMp);
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RPE_grid_positioning( *Mc, xMp, e );
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void Gsm_RPE_Decoding P5((S, xmaxcr, Mcr, xMcr, erp),
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struct gsm_state * S,
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word * xMcr, /* [0..12], 3 bits IN */
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word * erp /* [0..39] OUT */
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APCM_quantization_xmaxc_to_exp_mant( xmaxcr, &exp, &mant );
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APCM_inverse_quantization( xMcr, mant, exp, xMp );
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RPE_grid_positioning( Mcr, xMp, erp );