FreeCalypso > hg > gsm-codec-lib
view libgsmfrp/comfort_noise.c @ 75:8d63b167a5d3
libgsmefr: lag_wind.c compiles
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sat, 26 Nov 2022 06:39:36 +0000 |
parents | 286d5f097eb4 |
children | 3b64f255689a |
line wrap: on
line source
/* * In this module we implement comfort noise generation per GSM 06.12 * or 3GPP TS 46.012. */ #include <stdint.h> #include <string.h> #include "gsm_fr_preproc.h" #include "internal.h" static const uint8_t fold_table_8to6[24] = { 1, 2, 3, 4, 5, 6, 1, 2, 1, 2, 3, 4, 5, 6, 3, 4, 1, 2, 3, 4, 5, 6, 5, 6, }; static const uint8_t bc[4] = {0, 0, 0, 0}; static const uint8_t Nc[4] = {40, 120, 40, 120}; /* pseudonoise() function is based on ETSI EFR code */ static uint16_t pseudonoise(struct gsmfr_preproc_state *st, uint16_t no_bits) { uint16_t noise_bits, Sn, i; noise_bits = 0; for (i = 0; i < no_bits; i++) { /* State n == 31 */ if ((st->cn_random_lfsr & 0x00000001L) != 0) { Sn = 1; } else { Sn = 0; } /* State n == 3 */ if ((st->cn_random_lfsr & 0x10000000L) != 0) { Sn = Sn ^ 1; } else { Sn = Sn ^ 0; } noise_bits = noise_bits << 1; noise_bits = noise_bits | st->cn_random_lfsr & 1; st->cn_random_lfsr >>= 1; if (Sn & 1) { st->cn_random_lfsr |= 0x40000000L; } } return noise_bits; } static uint8_t random_1to6(struct gsmfr_preproc_state *st) { uint8_t range8, range6; range8 = pseudonoise(st, 3); range6 = fold_table_8to6[(st->cn_random_6fold << 3) | range8]; st->cn_random_6fold++; if (st->cn_random_6fold >= 3) st->cn_random_6fold = 0; return range6; } void gsmfr_preproc_gen_cn(struct gsmfr_preproc_state *st, gsm_byte *frame) { unsigned sub, pulse; uint8_t Mc, xmc[13]; gsm_byte *c; /* global bytes (magic and LARc) are fixed */ memcpy(frame, st->sid_prefix, 5); c = frame + 5; /* now do the 4 subframes, mostly PRNG output */ for (sub = 0; sub < 4; sub++) { Mc = pseudonoise(st, 2); for (pulse = 0; pulse < 13; pulse++) xmc[pulse] = random_1to6(st); /* packing code from libgsm */ *c++ = ((Nc[sub] & 0x7F) << 1) | ((bc[sub] >> 1) & 0x1); *c++ = ((bc[sub] & 0x1) << 7) | ((Mc & 0x3) << 5) | ((st->sid_xmaxc[sub] >> 1) & 0x1F); *c++ = ((st->sid_xmaxc[sub] & 0x1) << 7) | ((xmc[0] & 0x7) << 4) | ((xmc[1] & 0x7) << 1) | ((xmc[2] >> 2) & 0x1); *c++ = ((xmc[2] & 0x3) << 6) | ((xmc[3] & 0x7) << 3) | (xmc[4] & 0x7); *c++ = ((xmc[5] & 0x7) << 5) | ((xmc[6] & 0x7) << 2) | ((xmc[7] >> 1) & 0x3); *c++ = ((xmc[7] & 0x1) << 7) | ((xmc[8] & 0x7) << 4) | ((xmc[9] & 0x7) << 1) | ((xmc[10] >> 2) & 0x1); *c++ = ((xmc[10] & 0x3) << 6) | ((xmc[11] & 0x7) << 3) | (xmc[12] & 0x7); } }