960366cf8d
Enable support for digital audio processing capability. This module may be used for special applications that require cross connecting of bchannels, conferencing, dtmf decoding echo cancelation, tone generation, and Blowfish encryption and decryption. It may use hardware features if available. Signed-off-by: Karsten Keil <kkeil@suse.de>
110 lines
3.4 KiB
C
110 lines
3.4 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* ec_disable_detector.h - A detector which should eventually meet the
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* G.164/G.165 requirements for detecting the
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* 2100Hz echo cancellor disable tone.
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2001 Steve Underwood
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#include "dsp_biquad.h"
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struct ec_disable_detector_state {
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struct biquad2_state notch;
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int notch_level;
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int channel_level;
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int tone_present;
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int tone_cycle_duration;
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int good_cycles;
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int hit;
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};
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#define FALSE 0
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#define TRUE (!FALSE)
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static inline void
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echo_can_disable_detector_init(struct ec_disable_detector_state *det)
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{
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/* Elliptic notch */
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/* This is actually centred at 2095Hz, but gets the balance we want, due
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to the asymmetric walls of the notch */
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biquad2_init(&det->notch,
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(int32_t) (-0.7600000*32768.0),
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(int32_t) (-0.1183852*32768.0),
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(int32_t) (-0.5104039*32768.0),
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(int32_t) (0.1567596*32768.0),
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(int32_t) (1.0000000*32768.0));
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det->channel_level = 0;
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det->notch_level = 0;
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det->tone_present = FALSE;
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det->tone_cycle_duration = 0;
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det->good_cycles = 0;
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det->hit = 0;
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}
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/*- End of function --------------------------------------------------------*/
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static inline int
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echo_can_disable_detector_update(struct ec_disable_detector_state *det,
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int16_t amp)
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{
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int16_t notched;
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notched = biquad2(&det->notch, amp);
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/* Estimate the overall energy in the channel, and the energy in
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the notch (i.e. overall channel energy - tone energy => noise).
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Use abs instead of multiply for speed (is it really faster?).
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Damp the overall energy a little more for a stable result.
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Damp the notch energy a little less, so we don't damp out the
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blip every time the phase reverses */
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det->channel_level += ((abs(amp) - det->channel_level) >> 5);
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det->notch_level += ((abs(notched) - det->notch_level) >> 4);
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if (det->channel_level > 280) {
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/* There is adequate energy in the channel.
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Is it mostly at 2100Hz? */
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if (det->notch_level*6 < det->channel_level) {
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/* The notch says yes, so we have the tone. */
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if (!det->tone_present) {
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/* Do we get a kick every 450+-25ms? */
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if (det->tone_cycle_duration >= 425*8
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&& det->tone_cycle_duration <= 475*8) {
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det->good_cycles++;
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if (det->good_cycles > 2)
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det->hit = TRUE;
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}
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det->tone_cycle_duration = 0;
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}
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det->tone_present = TRUE;
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} else
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det->tone_present = FALSE;
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det->tone_cycle_duration++;
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} else {
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det->tone_present = FALSE;
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det->tone_cycle_duration = 0;
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det->good_cycles = 0;
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}
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return det->hit;
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}
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/*- End of function --------------------------------------------------------*/
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/*- End of file ------------------------------------------------------------*/
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