| Karsten Keil | 960366c | 2008-07-27 01:56:38 +0200 | [diff] [blame] | 1 | /* |
| 2 | * SpanDSP - a series of DSP components for telephony |
| 3 | * |
| 4 | * ec_disable_detector.h - A detector which should eventually meet the |
| 5 | * G.164/G.165 requirements for detecting the |
| 6 | * 2100Hz echo cancellor disable tone. |
| 7 | * |
| 8 | * Written by Steve Underwood <steveu@coppice.org> |
| 9 | * |
| 10 | * Copyright (C) 2001 Steve Underwood |
| 11 | * |
| 12 | * All rights reserved. |
| 13 | * |
| 14 | * This program is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * This program is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with this program; if not, write to the Free Software |
| 26 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| 27 | * |
| 28 | */ |
| 29 | |
| 30 | #include "dsp_biquad.h" |
| 31 | |
| 32 | struct ec_disable_detector_state { |
| 33 | struct biquad2_state notch; |
| 34 | int notch_level; |
| 35 | int channel_level; |
| 36 | int tone_present; |
| 37 | int tone_cycle_duration; |
| 38 | int good_cycles; |
| 39 | int hit; |
| 40 | }; |
| 41 | |
| 42 | |
| 43 | #define FALSE 0 |
| 44 | #define TRUE (!FALSE) |
| 45 | |
| 46 | static inline void |
| 47 | echo_can_disable_detector_init(struct ec_disable_detector_state *det) |
| 48 | { |
| 49 | /* Elliptic notch */ |
| 50 | /* This is actually centred at 2095Hz, but gets the balance we want, due |
| 51 | to the asymmetric walls of the notch */ |
| 52 | biquad2_init(&det->notch, |
| 53 | (int32_t) (-0.7600000*32768.0), |
| 54 | (int32_t) (-0.1183852*32768.0), |
| 55 | (int32_t) (-0.5104039*32768.0), |
| 56 | (int32_t) (0.1567596*32768.0), |
| 57 | (int32_t) (1.0000000*32768.0)); |
| 58 | |
| 59 | det->channel_level = 0; |
| 60 | det->notch_level = 0; |
| 61 | det->tone_present = FALSE; |
| 62 | det->tone_cycle_duration = 0; |
| 63 | det->good_cycles = 0; |
| 64 | det->hit = 0; |
| 65 | } |
| 66 | /*- End of function --------------------------------------------------------*/ |
| 67 | |
| 68 | static inline int |
| 69 | echo_can_disable_detector_update(struct ec_disable_detector_state *det, |
| 70 | int16_t amp) |
| 71 | { |
| 72 | int16_t notched; |
| 73 | |
| 74 | notched = biquad2(&det->notch, amp); |
| 75 | /* Estimate the overall energy in the channel, and the energy in |
| 76 | the notch (i.e. overall channel energy - tone energy => noise). |
| 77 | Use abs instead of multiply for speed (is it really faster?). |
| 78 | Damp the overall energy a little more for a stable result. |
| 79 | Damp the notch energy a little less, so we don't damp out the |
| 80 | blip every time the phase reverses */ |
| 81 | det->channel_level += ((abs(amp) - det->channel_level) >> 5); |
| 82 | det->notch_level += ((abs(notched) - det->notch_level) >> 4); |
| 83 | if (det->channel_level > 280) { |
| 84 | /* There is adequate energy in the channel. |
| 85 | Is it mostly at 2100Hz? */ |
| 86 | if (det->notch_level*6 < det->channel_level) { |
| 87 | /* The notch says yes, so we have the tone. */ |
| 88 | if (!det->tone_present) { |
| 89 | /* Do we get a kick every 450+-25ms? */ |
| 90 | if (det->tone_cycle_duration >= 425*8 |
| 91 | && det->tone_cycle_duration <= 475*8) { |
| 92 | det->good_cycles++; |
| 93 | if (det->good_cycles > 2) |
| 94 | det->hit = TRUE; |
| 95 | } |
| 96 | det->tone_cycle_duration = 0; |
| 97 | } |
| 98 | det->tone_present = TRUE; |
| 99 | } else |
| 100 | det->tone_present = FALSE; |
| 101 | det->tone_cycle_duration++; |
| 102 | } else { |
| 103 | det->tone_present = FALSE; |
| 104 | det->tone_cycle_duration = 0; |
| 105 | det->good_cycles = 0; |
| 106 | } |
| 107 | return det->hit; |
| 108 | } |
| 109 | /*- End of function --------------------------------------------------------*/ |
| 110 | /*- End of file ------------------------------------------------------------*/ |