annotate libgsmefr/autocorr.c @ 183:452c1d5a6268

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 92dc7f0082a3
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: autocorr
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4 *
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5 * PURPOSE: Compute autocorrelations of signal with windowing
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6 *
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7 * DESCRIPTION:
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8 * - Windowing of input speech: s'[n] = s[n] * w[n]
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9 * - Autocorrelations of input speech:
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10 * r[k] = sum_{i=k}^{239} s'[i]*s'[i-k] k=0,...,10
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11 * The autocorrelations are expressed in normalized double precision
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12 * format.
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13 *
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14 *************************************************************************/
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15
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16 #include "gsm_efr.h"
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17 #include "typedef.h"
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18 #include "namespace.h"
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19 #include "basic_op.h"
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20 #include "oper_32b.h"
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21 #include "no_count.h"
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22 #include "cnst.h"
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23 #include "sig_proc.h"
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25 Word16 Autocorr (
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26 Word16 x[], /* (i) : Input signal */
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27 Word16 m, /* (i) : LPC order */
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28 Word16 r_h[], /* (o) : Autocorrelations (msb) */
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29 Word16 r_l[], /* (o) : Autocorrelations (lsb) */
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30 const Word16 wind[] /* (i) : window for LPC analysis */
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31 )
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32 {
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33 Word16 i, j, norm;
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34 Word16 y[L_WINDOW];
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35 Word32 sum;
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36 Word16 overfl, overfl_shft;
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37
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38 /* Windowing of signal */
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39
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40 for (i = 0; i < L_WINDOW; i++)
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41 {
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42 y[i] = mult_r (x[i], wind[i]); move16 ();
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43 }
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45 /* Compute r[0] and test for overflow */
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47 overfl_shft = 0; move16 ();
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49 do
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50 {
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51 overfl = 0; move16 ();
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52 sum = 0L; move32 ();
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54 for (i = 0; i < L_WINDOW; i++)
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55 {
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56 sum = L_mac (sum, y[i], y[i]);
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57 }
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59 /* If overflow divide y[] by 4 */
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61 test ();
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62 if (L_sub (sum, MAX_32) == 0L)
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63 {
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64 overfl_shft = add (overfl_shft, 4);
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65 overfl = 1; move16 (); /* Set the overflow flag */
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67 for (i = 0; i < L_WINDOW; i++)
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68 {
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69 y[i] = shr (y[i], 2); move16 ();
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70 }
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71 }
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72 test ();
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73 }
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74 while (overfl != 0);
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76 sum = L_add (sum, 1L); /* Avoid the case of all zeros */
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78 /* Normalization of r[0] */
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80 norm = norm_l (sum);
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81 sum = L_shl (sum, norm);
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82 L_Extract (sum, &r_h[0], &r_l[0]); /* Put in DPF format (see oper_32b) */
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83
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84 /* r[1] to r[m] */
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86 for (i = 1; i <= m; i++)
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87 {
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88 sum = 0; move32 ();
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89
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90 for (j = 0; j < L_WINDOW - i; j++)
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91 {
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92 sum = L_mac (sum, y[j], y[j + i]);
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93 }
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95 sum = L_shl (sum, norm);
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96 L_Extract (sum, &r_h[i], &r_l[i]);
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97 }
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99 norm = sub (norm, overfl_shft);
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100
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101 return norm;
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102 }