FreeCalypso > hg > gsm-codec-lib
annotate libgsmfrp/comfort_noise.c @ 242:f081a6850fb5
libgsmfrp: new refined implementation
The previous implementation exhibited the following defects,
which are now fixed:
1) The last received valid SID was cached forever for the purpose of
handling future invalid SIDs - we could have received some valid
SID ages ago, then lots of speech or NO_DATA, and if we then get
an invalid SID, we would resurrect the last valid SID from ancient
history - a bad design. In our new design, we handle invalid SID
based on the current state, much like BFI.
2) GSM 06.11 spec says clearly that after the second lost SID
(received BFI=1 && TAF=1 in CN state) we need to gradually decrease
the output level, rather than jump directly to emitting silence
frames - we previously failed to implement such logic.
3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes
in a SID frame. What should we do if we receive an otherwise valid
SID frame with different Xmaxc? Our previous approach would
replicate this Xmaxc oddity in every subsequent generated CN frame,
which is rather bad. In our new design, the very first CN frame
(which can be seen as a transformation of the SID frame itself)
retains the original 4 distinct Xmaxc, but all subsequent CN frames
are based on the Xmaxc from the last subframe of the most recent SID.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 09 May 2023 05:16:31 +0000 |
parents | 3b64f255689a |
children |
rev | line source |
---|---|
4
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
1 /* |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
2 * In this module we implement comfort noise generation per GSM 06.12 |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
3 * or 3GPP TS 46.012. |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
4 */ |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
5 |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
6 #include <stdint.h> |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
7 #include <string.h> |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
8 #include "gsm_fr_preproc.h" |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
9 #include "internal.h" |
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 static const uint8_t fold_table_8to6[24] = { |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
12 1, 2, 3, 4, 5, 6, 1, 2, |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
13 1, 2, 3, 4, 5, 6, 3, 4, |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
14 1, 2, 3, 4, 5, 6, 5, 6, |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
15 }; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
16 |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
17 static const uint8_t bc[4] = {0, 0, 0, 0}; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
18 static const uint8_t Nc[4] = {40, 120, 40, 120}; |
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 static uint8_t random_1to6(struct gsmfr_preproc_state *st) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
21 { |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
22 uint8_t range8, range6; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
23 |
108
3b64f255689a
libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents:
4
diff
changeset
|
24 range8 = gsmfr_preproc_prng(st, 3); |
4
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
25 range6 = fold_table_8to6[(st->cn_random_6fold << 3) | range8]; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
26 st->cn_random_6fold++; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
27 if (st->cn_random_6fold >= 3) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
28 st->cn_random_6fold = 0; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
29 return range6; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
30 } |
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 void gsmfr_preproc_gen_cn(struct gsmfr_preproc_state *st, gsm_byte *frame) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
33 { |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
34 unsigned sub, pulse; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
35 uint8_t Mc, xmc[13]; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
36 gsm_byte *c; |
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 /* global bytes (magic and LARc) are fixed */ |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
39 memcpy(frame, st->sid_prefix, 5); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
40 c = frame + 5; |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
41 /* now do the 4 subframes, mostly PRNG output */ |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
42 for (sub = 0; sub < 4; sub++) { |
108
3b64f255689a
libgsmfrp: factor out PRNG into its own module,
Mychaela Falconia <falcon@freecalypso.org>
parents:
4
diff
changeset
|
43 Mc = gsmfr_preproc_prng(st, 2); |
4
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
44 for (pulse = 0; pulse < 13; pulse++) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
45 xmc[pulse] = random_1to6(st); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
46 /* packing code from libgsm */ |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
47 *c++ = ((Nc[sub] & 0x7F) << 1) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
48 | ((bc[sub] >> 1) & 0x1); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
49 *c++ = ((bc[sub] & 0x1) << 7) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
50 | ((Mc & 0x3) << 5) |
242
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
51 | ((st->sid_xmaxc >> 1) & 0x1F); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
52 *c++ = ((st->sid_xmaxc & 0x1) << 7) |
4
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
53 | ((xmc[0] & 0x7) << 4) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
54 | ((xmc[1] & 0x7) << 1) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
55 | ((xmc[2] >> 2) & 0x1); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
56 *c++ = ((xmc[2] & 0x3) << 6) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
57 | ((xmc[3] & 0x7) << 3) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
58 | (xmc[4] & 0x7); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
59 *c++ = ((xmc[5] & 0x7) << 5) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
60 | ((xmc[6] & 0x7) << 2) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
61 | ((xmc[7] >> 1) & 0x3); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
62 *c++ = ((xmc[7] & 0x1) << 7) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
63 | ((xmc[8] & 0x7) << 4) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
64 | ((xmc[9] & 0x7) << 1) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
65 | ((xmc[10] >> 2) & 0x1); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
66 *c++ = ((xmc[10] & 0x3) << 6) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
67 | ((xmc[11] & 0x7) << 3) |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
68 | (xmc[12] & 0x7); |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
69 } |
286d5f097eb4
libgsmfrp: implement comfort noise generation
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
70 } |
242
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
71 |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
72 void gsmfr_preproc_sid2cn(struct gsmfr_preproc_state *st, gsm_byte *frame) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
73 { |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
74 unsigned sub, pulse; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
75 uint8_t Mc, xmc[13]; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
76 gsm_byte *c; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
77 |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
78 /* save LARc and Xmaxc from the last subframe for subsequent CN gen */ |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
79 memcpy(st->sid_prefix, frame, 5); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
80 st->sid_xmaxc = ((frame[27] & 0x1F) << 1) | (frame[28] >> 7); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
81 /* ... and turn *this* frame into very first CN output */ |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
82 c = frame + 5; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
83 for (sub = 0; sub < 4; sub++) { |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
84 Mc = gsmfr_preproc_prng(st, 2); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
85 for (pulse = 0; pulse < 13; pulse++) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
86 xmc[pulse] = random_1to6(st); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
87 /* keep each of Xmaxc and replace the rest with CN */ |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
88 *c++ = ((Nc[sub] & 0x7F) << 1) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
89 | ((bc[sub] >> 1) & 0x1); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
90 *c &= 0x1F; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
91 *c++ |= ((bc[sub] & 0x1) << 7) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
92 | ((Mc & 0x3) << 5); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
93 *c &= 0x80; |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
94 *c++ |= ((xmc[0] & 0x7) << 4) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
95 | ((xmc[1] & 0x7) << 1) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
96 | ((xmc[2] >> 2) & 0x1); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
97 *c++ = ((xmc[2] & 0x3) << 6) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
98 | ((xmc[3] & 0x7) << 3) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
99 | (xmc[4] & 0x7); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
100 *c++ = ((xmc[5] & 0x7) << 5) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
101 | ((xmc[6] & 0x7) << 2) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
102 | ((xmc[7] >> 1) & 0x3); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
103 *c++ = ((xmc[7] & 0x1) << 7) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
104 | ((xmc[8] & 0x7) << 4) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
105 | ((xmc[9] & 0x7) << 1) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
106 | ((xmc[10] >> 2) & 0x1); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
107 *c++ = ((xmc[10] & 0x3) << 6) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
108 | ((xmc[11] & 0x7) << 3) |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
109 | (xmc[12] & 0x7); |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
110 } |
f081a6850fb5
libgsmfrp: new refined implementation
Mychaela Falconia <falcon@freecalypso.org>
parents:
108
diff
changeset
|
111 } |