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annotate libgsmefr/enc_lag6.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 e109d8752d60
children f151d6c18b31
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Enc_lag6
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4 *
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5 * PURPOSE: Encoding of fractional pitch lag with 1/6 resolution.
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6 *
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7 * DESCRIPTION:
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8 * First and third subframes:
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9 * --------------------------
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10 * The pitch range is divided as follows:
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11 * 17 3/6 to 94 3/6 resolution 1/6
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12 * 95 to 143 resolution 1
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13 *
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14 * The period is encoded with 9 bits.
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15 * For the range with fractions:
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16 * index = (T-17)*6 + frac - 3;
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17 * where T=[17..94] and frac=[-2,-1,0,1,2,3]
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18 * and for the integer only range
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19 * index = (T - 95) + 463; where T=[95..143]
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20 *
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21 * Second and fourth subframes:
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22 * ----------------------------
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23 * For the 2nd and 4th subframes a resolution of 1/6 is always used,
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24 * and the search range is relative to the lag in previous subframe.
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25 * If t0 is the lag in the previous subframe then
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26 * t_min=t0-5 and t_max=t0+4 and the range is given by
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27 * (t_min-1) 3/6 to (t_max) 3/6
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28 *
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29 * The period in the 2nd (and 4th) subframe is encoded with 6 bits:
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30 * index = (T-(t_min-1))*6 + frac - 3;
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31 * where T=[t_min-1..t_max] and frac=[-2,-1,0,1,2,3]
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32 *
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33 * Note that only 61 values are used. If the decoder receives 61, 62,
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34 * or 63 as the relative pitch index, it means that a transmission
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35 * error occurred and the pitch from previous subframe should be used.
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36 *
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37 *************************************************************************/
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38
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39 #include "gsm_efr.h"
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40 #include "typedef.h"
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41 #include "namespace.h"
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42 #include "basic_op.h"
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43 #include "no_count.h"
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44 #include "codec.h"
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46 Word16 Enc_lag6 ( /* output: Return index of encoding */
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47 Word16 T0, /* input : Pitch delay */
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48 Word16 *T0_frac, /* in/out: Fractional pitch delay */
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49 Word16 *T0_min, /* in/out: Minimum search delay */
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50 Word16 *T0_max, /* in/out: Maximum search delay */
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51 Word16 pit_min, /* input : Minimum pitch delay */
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52 Word16 pit_max, /* input : Maximum pitch delay */
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53 Word16 pit_flag /* input : Flag for 1st or 3rd subframe */
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54 )
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55 {
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56 Word16 index, i;
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57
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58 test ();
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59 if (pit_flag == 0) /* if 1st or 3rd subframe */
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60 {
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61 /* encode pitch delay (with fraction) */
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62
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63 test ();
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64 if (sub (T0, 94) <= 0)
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65 {
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66 /* index = T0*6 - 105 + *T0_frac */
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67 i = add (add (T0, T0), T0);
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68 index = add (sub (add (i, i), 105), *T0_frac);
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69 } else
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70 { /* set fraction to 0 for delays > 94 */
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71 *T0_frac = 0; move16 ();
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72 index = add (T0, 368);
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73 }
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74
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75 /* find T0_min and T0_max for second (or fourth) subframe */
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76
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77 *T0_min = sub (T0, 5); move16 ();
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78 test ();
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79 if (sub (*T0_min, pit_min) < 0)
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80 {
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81 *T0_min = pit_min; move16 ();
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82 }
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83 *T0_max = add (*T0_min, 9);
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84 test ();
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85 if (sub (*T0_max, pit_max) > 0)
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86 {
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87 *T0_max = pit_max; move16 ();
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88 *T0_min = sub (*T0_max, 9); move16 ();
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89 }
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90 } else
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91 /* if second or fourth subframe */
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92 {
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93 /* index = 6*(T0-*T0_min) + 3 + *T0_frac */
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94 i = sub (T0, *T0_min);
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95 i = add (add (i, i), i);
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96 index = add (add (add (i, i), 3), *T0_frac);
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97 }
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98
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99 return index;
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100 }