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annotate libgsmefr/lsp_lsf.c @ 183:452c1d5a6268

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libgsmefr BFI w/o data: emit zero output after decoder reset In real-life usage, each EFR decoder session will most likely begin with lots of BFI frames before the first real frame arrives. However, because the spec-defined home state of the decoder is speech rather than CN, our regular logic for BFI w/o data would have to feed pseudorandom noise to the decoder (in the "fixed codebook excitation pulses" part), which is silly to do at the beginning of the decoder session right out of reset. Therefore, let's check reset_flag_old, and if we are still in the reset state, simply emit zero output.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 03 Jan 2023 00:12:18 +0000
parents 8d3412b7ec4e
children bcd337afa0f1
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1 /*************************************************************************
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2 *
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3 * FUNCTIONS: Lsp_lsf and Lsf_lsp
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4 *
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5 * PURPOSE:
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6 * Lsp_lsf: Transformation lsp to lsf
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7 * Lsf_lsp: Transformation lsf to lsp
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8 *
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9 * DESCRIPTION:
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10 * lsp[i] = cos(2*pi*lsf[i]) and lsf[i] = arccos(lsp[i])/(2*pi)
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11 *
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12 * The transformation from lsp[i] to lsf[i] and lsf[i] to lsp[i] are
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13 * approximated by a look-up table and interpolation.
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14 *
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15 *************************************************************************/
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16
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17 #include "gsm_efr.h"
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18 #include "typedef.h"
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19 #include "namespace.h"
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20 #include "basic_op.h"
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21 #include "no_count.h"
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22 #include "sig_proc.h"
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24 #include "lsp_lsf.tab" /* Look-up table for transformations */
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26 void Lsf_lsp (
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27 Word16 lsf[], /* (i) : lsf[m] normalized (range: 0.0<=val<=0.5) */
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28 Word16 lsp[], /* (o) : lsp[m] (range: -1<=val<1) */
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29 Word16 m /* (i) : LPC order */
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30 )
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31 {
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32 Word16 i, ind, offset;
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33 Word32 L_tmp;
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34
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35 for (i = 0; i < m; i++)
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36 {
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37 ind = shr (lsf[i], 8); /* ind = b8-b15 of lsf[i] */
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38 offset = lsf[i] & 0x00ff; logic16 (); /* offset = b0-b7 of lsf[i] */
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40 /* lsp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 256 */
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42 L_tmp = L_mult (sub (table[ind + 1], table[ind]), offset);
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43 lsp[i] = add (table[ind], extract_l (L_shr (L_tmp, 9)));
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44 move16 ();
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45 }
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46 return;
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47 }
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49 void Lsp_lsf (
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50 Word16 lsp[], /* (i) : lsp[m] (range: -1<=val<1) */
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51 Word16 lsf[], /* (o) : lsf[m] normalized (range: 0.0<=val<=0.5) */
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52 Word16 m /* (i) : LPC order */
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53 )
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54 {
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55 Word16 i, ind;
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56 Word32 L_tmp;
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58 ind = 63; /* begin at end of table -1 */
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60 for (i = m - 1; i >= 0; i--)
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61 {
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62 /* find value in table that is just greater than lsp[i] */
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63 test ();
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64 while (sub (table[ind], lsp[i]) < 0)
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65 {
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66 ind--;
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67 test ();
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68 }
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70 /* acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) *
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71 slope[ind] )/4096 */
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73 L_tmp = L_mult (sub (lsp[i], table[ind]), slope[ind]);
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74 /*(lsp[i]-table[ind])*slope[ind])>>12*/
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75 lsf[i] = round (L_shl (L_tmp, 3)); move16 ();
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76 lsf[i] = add (lsf[i], shl (ind, 8)); move16 ();
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77 }
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78 return;
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79 }