Commit | Line | Data |
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74ba9207 | 1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
960366cf KK |
2 | /* |
3 | * SpanDSP - a series of DSP components for telephony | |
4 | * | |
5 | * ec_disable_detector.h - A detector which should eventually meet the | |
6 | * G.164/G.165 requirements for detecting the | |
7 | * 2100Hz echo cancellor disable tone. | |
8 | * | |
9 | * Written by Steve Underwood <steveu@coppice.org> | |
10 | * | |
11 | * Copyright (C) 2001 Steve Underwood | |
12 | * | |
13 | * All rights reserved. | |
960366cf KK |
14 | */ |
15 | ||
16 | #include "dsp_biquad.h" | |
17 | ||
18 | struct ec_disable_detector_state { | |
19 | struct biquad2_state notch; | |
20 | int notch_level; | |
21 | int channel_level; | |
22 | int tone_present; | |
23 | int tone_cycle_duration; | |
24 | int good_cycles; | |
25 | int hit; | |
26 | }; | |
27 | ||
28 | ||
29 | #define FALSE 0 | |
30 | #define TRUE (!FALSE) | |
31 | ||
32 | static inline void | |
33 | echo_can_disable_detector_init(struct ec_disable_detector_state *det) | |
34 | { | |
475be4d8 JP |
35 | /* Elliptic notch */ |
36 | /* This is actually centred at 2095Hz, but gets the balance we want, due | |
37 | to the asymmetric walls of the notch */ | |
960366cf | 38 | biquad2_init(&det->notch, |
475be4d8 JP |
39 | (int32_t)(-0.7600000 * 32768.0), |
40 | (int32_t)(-0.1183852 * 32768.0), | |
41 | (int32_t)(-0.5104039 * 32768.0), | |
42 | (int32_t)(0.1567596 * 32768.0), | |
43 | (int32_t)(1.0000000 * 32768.0)); | |
960366cf KK |
44 | |
45 | det->channel_level = 0; | |
46 | det->notch_level = 0; | |
47 | det->tone_present = FALSE; | |
48 | det->tone_cycle_duration = 0; | |
49 | det->good_cycles = 0; | |
50 | det->hit = 0; | |
51 | } | |
52 | /*- End of function --------------------------------------------------------*/ | |
53 | ||
54 | static inline int | |
55 | echo_can_disable_detector_update(struct ec_disable_detector_state *det, | |
475be4d8 | 56 | int16_t amp) |
960366cf KK |
57 | { |
58 | int16_t notched; | |
59 | ||
60 | notched = biquad2(&det->notch, amp); | |
61 | /* Estimate the overall energy in the channel, and the energy in | |
62 | the notch (i.e. overall channel energy - tone energy => noise). | |
63 | Use abs instead of multiply for speed (is it really faster?). | |
64 | Damp the overall energy a little more for a stable result. | |
65 | Damp the notch energy a little less, so we don't damp out the | |
66 | blip every time the phase reverses */ | |
67 | det->channel_level += ((abs(amp) - det->channel_level) >> 5); | |
68 | det->notch_level += ((abs(notched) - det->notch_level) >> 4); | |
69 | if (det->channel_level > 280) { | |
70 | /* There is adequate energy in the channel. | |
475be4d8 JP |
71 | Is it mostly at 2100Hz? */ |
72 | if (det->notch_level * 6 < det->channel_level) { | |
960366cf KK |
73 | /* The notch says yes, so we have the tone. */ |
74 | if (!det->tone_present) { | |
75 | /* Do we get a kick every 450+-25ms? */ | |
475be4d8 JP |
76 | if (det->tone_cycle_duration >= 425 * 8 |
77 | && det->tone_cycle_duration <= 475 * 8) { | |
960366cf KK |
78 | det->good_cycles++; |
79 | if (det->good_cycles > 2) | |
eac74af9 | 80 | det->hit = TRUE; |
960366cf KK |
81 | } |
82 | det->tone_cycle_duration = 0; | |
83 | } | |
84 | det->tone_present = TRUE; | |
85 | } else | |
86 | det->tone_present = FALSE; | |
87 | det->tone_cycle_duration++; | |
88 | } else { | |
89 | det->tone_present = FALSE; | |
90 | det->tone_cycle_duration = 0; | |
91 | det->good_cycles = 0; | |
92 | } | |
93 | return det->hit; | |
94 | } | |
95 | /*- End of function --------------------------------------------------------*/ | |
96 | /*- End of file ------------------------------------------------------------*/ |