annotate libgsmefr/d1035pf.c @ 143:195911f2211c

document PCM format conversion utilities
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 14 Dec 2022 07:04:59 +0000
parents d80e9f12a1d1
children 6ad363f7ea30
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1 /*************************************************************************
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2 *
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3 * FUNCTION: dec_10i40_35bits()
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4 *
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5 * PURPOSE: Builds the innovative codevector from the received
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6 * index of algebraic codebook.
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7 *
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8 * See c1035pf.c for more details about the algebraic codebook structure.
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9 *
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10 *************************************************************************/
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11
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12 #include "gsm_efr.h"
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13 #include "typedef.h"
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14 #include "namespace.h"
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15 #include "basic_op.h"
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16 #include "memops.h"
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17 #include "no_count.h"
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18 #include "codec.h"
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20 #define L_CODE 40 /* codevector length */
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21 #define NB_PULSE 10 /* number of pulses */
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22 #define NB_TRACK 5 /* number of track */
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24 void dec_10i40_35bits (
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25 const Word16 index[], /* (i) : index of 10 pulses (sign+position) */
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26 Word16 cod[] /* (o) : algebraic (fixed) codebook excitation */
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27 )
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28 {
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29 static const Word16 dgray[8] = {0, 1, 3, 2, 5, 6, 4, 7};
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30 Word16 i, j, pos1, pos2, sign, tmp;
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32 Set_zero (cod, L_CODE);
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34 /* decode the positions and signs of pulses and build the codeword */
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36 for (j = 0; j < NB_TRACK; j++)
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37 {
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38 /* compute index i */
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40 tmp = index[j]; move16 ();
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41 i = tmp & 7; logic16 ();
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42 i = dgray[i]; move16 ();
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44 i = extract_l (L_shr (L_mult (i, 5), 1));
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45 pos1 = add (i, j); /* position of pulse "j" */
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47 i = shr (tmp, 3) & 1; logic16 ();
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48 if (i == 0)
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49 {
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50 sign = 4096; move16 (); /* +1.0 */
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51 }
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52 else
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53 {
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54 sign = -4096; move16 (); /* -1.0 */
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55 }
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57 cod[pos1] = sign; move16 ();
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59 /* compute index i */
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61 i = index[add (j, 5)] & 7; logic16 ();
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62 i = dgray[i]; move16 ();
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63 i = extract_l (L_shr (L_mult (i, 5), 1));
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65 pos2 = add (i, j); /* position of pulse "j+5" */
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67 if (sub (pos2, pos1) < 0)
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68 {
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69 sign = negate (sign);
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70 }
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71 cod[pos2] = add (cod[pos2], sign); move16 ();
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72 }
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74 return;
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75 }