FreeCalypso > hg > gsm-codec-lib

annotate libgsmfr2/prng.c @ 529:79cd992de3ad

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
libgsmfr2: API definitions for TFO transform
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 19 Sep 2024 08:07:26 +0000
parents 573afa985df6
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
4
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
1 /*
108
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
2 * We use a pseudorandom sequence generator function in two places:
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
3 * when generating comfort noise (GSM 06.12 section 6.1), and when
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
4 * randomizing grid position parameters as part of speech muting
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
5 * during error handling (GSM 06.11 section 6).
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
6 *
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
7 * Our PRNG is a copy of the pseudonoise() function from ETSI EFR code,
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
8 * where it is used for similar purposes.
4
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
9 */
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
10
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
11 #include <stdint.h>
256
a33edf624061 libgsmfr2: start with API definition and port of libgsmfrp code
Mychaela Falconia <falcon@freecalypso.org>
parents: 108
diff changeset
12 #include "tw_gsmfr.h"
262
573afa985df6 libgsmfr2: split pp_state.h from pp_internal.h
Mychaela Falconia <falcon@freecalypso.org>
parents: 256
diff changeset
13 #include "pp_state.h"
256
a33edf624061 libgsmfr2: start with API definition and port of libgsmfrp code
Mychaela Falconia <falcon@freecalypso.org>
parents: 108
diff changeset
14 #include "pp_internal.h"
4
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
15
108
3b64f255689a libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents: 4
diff changeset
16 uint16_t gsmfr_preproc_prng(struct gsmfr_preproc_state *st, uint16_t no_bits)
4
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
18 uint16_t noise_bits, Sn, i;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
19
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
20 noise_bits = 0;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
21 for (i = 0; i < no_bits; i++)
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
22 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
23 /* State n == 31 */
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
24 if ((st->cn_random_lfsr & 0x00000001L) != 0)
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
25 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
26 Sn = 1;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
27 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
28 else
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
29 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
30 Sn = 0;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
31 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
32
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
33 /* State n == 3 */
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
34 if ((st->cn_random_lfsr & 0x10000000L) != 0)
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
35 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
36 Sn = Sn ^ 1;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
37 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
38 else
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
39 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
40 Sn = Sn ^ 0;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
41 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
42
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
43 noise_bits = noise_bits << 1;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
44 noise_bits = noise_bits | st->cn_random_lfsr & 1;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
45
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
46 st->cn_random_lfsr >>= 1;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
47 if (Sn & 1)
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
48 {
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
49 st->cn_random_lfsr |= 0x40000000L;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
50 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
51 }
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
52
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
53 return noise_bits;
286d5f097eb4 libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
54 }