FreeCalypso > hg > gsm-codec-lib

annotate libgsmfrp/comfort_noise.c @ 282:9ee8ad3d4d30

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frtest: rm gsmfr-hand-test and gsmfr-max-out utils These hack programs were never properly documented and were written only as part of a debug chase, in pursuit of a bug that ultimately turned out to be in our then-hacky patch to osmo-bts-sysmo, before beginning of proper patches in Osmocom. These hack programs need to be dropped from the present sw package because they depend on old libgsm, and we are eliminating that dependency.
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 14 Apr 2024 05:44:47 +0000
parents f081a6850fb5
children
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1 /*
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2 * In this module we implement comfort noise generation per GSM 06.12
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3 * or 3GPP TS 46.012.
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4 */
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5
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6 #include <stdint.h>
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7 #include <string.h>
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8 #include "gsm_fr_preproc.h"
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9 #include "internal.h"
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10
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11 static const uint8_t fold_table_8to6[24] = {
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12 1, 2, 3, 4, 5, 6, 1, 2,
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13 1, 2, 3, 4, 5, 6, 3, 4,
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14 1, 2, 3, 4, 5, 6, 5, 6,
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15 };
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16
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17 static const uint8_t bc[4] = {0, 0, 0, 0};
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18 static const uint8_t Nc[4] = {40, 120, 40, 120};
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19
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20 static uint8_t random_1to6(struct gsmfr_preproc_state *st)
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21 {
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22 uint8_t range8, range6;
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23
108
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24 range8 = gsmfr_preproc_prng(st, 3);
4
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25 range6 = fold_table_8to6[(st->cn_random_6fold << 3) | range8];
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26 st->cn_random_6fold++;
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27 if (st->cn_random_6fold >= 3)
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28 st->cn_random_6fold = 0;
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29 return range6;
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30 }
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31
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32 void gsmfr_preproc_gen_cn(struct gsmfr_preproc_state *st, gsm_byte *frame)
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33 {
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34 unsigned sub, pulse;
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35 uint8_t Mc, xmc[13];
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36 gsm_byte *c;
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37
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38 /* global bytes (magic and LARc) are fixed */
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39 memcpy(frame, st->sid_prefix, 5);
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40 c = frame + 5;
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41 /* now do the 4 subframes, mostly PRNG output */
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42 for (sub = 0; sub < 4; sub++) {
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43 Mc = gsmfr_preproc_prng(st, 2);
4
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44 for (pulse = 0; pulse < 13; pulse++)
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45 xmc[pulse] = random_1to6(st);
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46 /* packing code from libgsm */
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47 *c++ = ((Nc[sub] & 0x7F) << 1)
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48 | ((bc[sub] >> 1) & 0x1);
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49 *c++ = ((bc[sub] & 0x1) << 7)
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50 | ((Mc & 0x3) << 5)
242
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51 | ((st->sid_xmaxc >> 1) & 0x1F);
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52 *c++ = ((st->sid_xmaxc & 0x1) << 7)
4
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53 | ((xmc[0] & 0x7) << 4)
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54 | ((xmc[1] & 0x7) << 1)
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55 | ((xmc[2] >> 2) & 0x1);
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56 *c++ = ((xmc[2] & 0x3) << 6)
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57 | ((xmc[3] & 0x7) << 3)
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58 | (xmc[4] & 0x7);
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59 *c++ = ((xmc[5] & 0x7) << 5)
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60 | ((xmc[6] & 0x7) << 2)
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61 | ((xmc[7] >> 1) & 0x3);
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62 *c++ = ((xmc[7] & 0x1) << 7)
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63 | ((xmc[8] & 0x7) << 4)
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64 | ((xmc[9] & 0x7) << 1)
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65 | ((xmc[10] >> 2) & 0x1);
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66 *c++ = ((xmc[10] & 0x3) << 6)
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67 | ((xmc[11] & 0x7) << 3)
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68 | (xmc[12] & 0x7);
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69 }
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70 }
242
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71
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72 void gsmfr_preproc_sid2cn(struct gsmfr_preproc_state *st, gsm_byte *frame)
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73 {
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74 unsigned sub, pulse;
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75 uint8_t Mc, xmc[13];
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76 gsm_byte *c;
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77
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78 /* save LARc and Xmaxc from the last subframe for subsequent CN gen */
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79 memcpy(st->sid_prefix, frame, 5);
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80 st->sid_xmaxc = ((frame[27] & 0x1F) << 1) | (frame[28] >> 7);
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81 /* ... and turn *this* frame into very first CN output */
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82 c = frame + 5;
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83 for (sub = 0; sub < 4; sub++) {
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84 Mc = gsmfr_preproc_prng(st, 2);
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85 for (pulse = 0; pulse < 13; pulse++)
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86 xmc[pulse] = random_1to6(st);
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87 /* keep each of Xmaxc and replace the rest with CN */
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88 *c++ = ((Nc[sub] & 0x7F) << 1)
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89 | ((bc[sub] >> 1) & 0x1);
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90 *c &= 0x1F;
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91 *c++ |= ((bc[sub] & 0x1) << 7)
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92 | ((Mc & 0x3) << 5);
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93 *c &= 0x80;
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94 *c++ |= ((xmc[0] & 0x7) << 4)
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95 | ((xmc[1] & 0x7) << 1)
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96 | ((xmc[2] >> 2) & 0x1);
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97 *c++ = ((xmc[2] & 0x3) << 6)
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98 | ((xmc[3] & 0x7) << 3)
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99 | (xmc[4] & 0x7);
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100 *c++ = ((xmc[5] & 0x7) << 5)
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101 | ((xmc[6] & 0x7) << 2)
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102 | ((xmc[7] >> 1) & 0x3);
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103 *c++ = ((xmc[7] & 0x1) << 7)
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104 | ((xmc[8] & 0x7) << 4)
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105 | ((xmc[9] & 0x7) << 1)
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106 | ((xmc[10] >> 2) & 0x1);
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107 *c++ = ((xmc[10] & 0x3) << 6)
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108 | ((xmc[11] & 0x7) << 3)
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109 | (xmc[12] & 0x7);
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110 }
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111 }