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1 /*
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2 * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
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3 * Universitaet Berlin. See the accompanying file "COPYRIGHT" for
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4 * details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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5 */
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6
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7 /* $Header: /home/kbs/jutta/src/gsm/gsm-1.0/src/RCS/decode.c,v 1.1 1992/10/28 00:15:50 jutta Exp $ */
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8
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9 #include <stdio.h>
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10
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11 #include "private.h"
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12 #include "gsm.h"
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13 #include "proto.h"
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14
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15 /*
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16 * 4.3 FIXED POINT IMPLEMENTATION OF THE RPE-LTP DECODER
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17 */
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18
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19 static void Postprocessing P2((S, s),
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20 struct gsm_state *S, register word * s)
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21 {
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22 register int k;
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23 register word msr = S->msr;
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24 register longword ltmp; /* for GSM_ADD */
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25 register word tmp;
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26
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27 for (k = 160; k--; s++) {
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28 tmp = GSM_MULT_R(msr, 28180);
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29 msr = GSM_ADD(*s, tmp); /* Deemphasis */
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30 #ifdef USE_ROUNDING_INSTEAD_OF_TRUNCATION
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31 *s = GSM_ADD(msr, msr); /* Upscaling by 2 */
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32 *s = GSM_ADD(*s, 4) & 0xFFF8; /* Truncation */
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33 #else
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34 *s = GSM_ADD(msr, msr) & 0xFFF8; /* Upscaling & Truncation */
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35 #endif
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36 }
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37 S->msr = msr;
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38 }
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39
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40 void Gsm_Decoder P8((S, LARcr, Ncr, bcr, Mcr, xmaxcr, xMcr, s), struct gsm_state *S, word * LARcr, /* [0..7] IN */
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41 word * Ncr, /* [0..3] IN */
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42 word * bcr, /* [0..3] IN */
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43 word * Mcr, /* [0..3] IN */
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44 word * xmaxcr, /* [0..3] IN */
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45 word * xMcr, /* [0..13*4] IN */
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46 word * s)
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47 { /* [0..159] OUT */
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48 int j, k;
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49 word erp[40], wt[160];
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50 word *drp = S->dp0 + 120;
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51
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52 for (j = 0; j <= 3; j++, xmaxcr++, bcr++, Ncr++, Mcr++, xMcr += 13) {
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53
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54 Gsm_RPE_Decoding(S, *xmaxcr, *Mcr, xMcr, erp);
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55 Gsm_Long_Term_Synthesis_Filtering(S, *Ncr, *bcr, erp, drp);
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56
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57 for (k = 0; k <= 39; k++)
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58 wt[j * 40 + k] = drp[k];
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59 }
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60
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61 Gsm_Short_Term_Synthesis_Filter(S, LARcr, wt, s);
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62 Postprocessing(S, s);
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63 }
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