linux/drivers/isdn/mISDN/dsp_ecdis.h
Thomas Gleixner 74ba9207e1 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61
Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not write to the free software foundation inc
  675 mass ave cambridge ma 02139 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 441 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520071858.739733335@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-24 17:36:45 +02:00

97 lines
2.8 KiB
C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* SpanDSP - a series of DSP components for telephony
*
* ec_disable_detector.h - A detector which should eventually meet the
* G.164/G.165 requirements for detecting the
* 2100Hz echo cancellor disable tone.
*
* Written by Steve Underwood <steveu@coppice.org>
*
* Copyright (C) 2001 Steve Underwood
*
* All rights reserved.
*/
#include "dsp_biquad.h"
struct ec_disable_detector_state {
struct biquad2_state notch;
int notch_level;
int channel_level;
int tone_present;
int tone_cycle_duration;
int good_cycles;
int hit;
};
#define FALSE 0
#define TRUE (!FALSE)
static inline void
echo_can_disable_detector_init(struct ec_disable_detector_state *det)
{
/* Elliptic notch */
/* This is actually centred at 2095Hz, but gets the balance we want, due
to the asymmetric walls of the notch */
biquad2_init(&det->notch,
(int32_t)(-0.7600000 * 32768.0),
(int32_t)(-0.1183852 * 32768.0),
(int32_t)(-0.5104039 * 32768.0),
(int32_t)(0.1567596 * 32768.0),
(int32_t)(1.0000000 * 32768.0));
det->channel_level = 0;
det->notch_level = 0;
det->tone_present = FALSE;
det->tone_cycle_duration = 0;
det->good_cycles = 0;
det->hit = 0;
}
/*- End of function --------------------------------------------------------*/
static inline int
echo_can_disable_detector_update(struct ec_disable_detector_state *det,
int16_t amp)
{
int16_t notched;
notched = biquad2(&det->notch, amp);
/* Estimate the overall energy in the channel, and the energy in
the notch (i.e. overall channel energy - tone energy => noise).
Use abs instead of multiply for speed (is it really faster?).
Damp the overall energy a little more for a stable result.
Damp the notch energy a little less, so we don't damp out the
blip every time the phase reverses */
det->channel_level += ((abs(amp) - det->channel_level) >> 5);
det->notch_level += ((abs(notched) - det->notch_level) >> 4);
if (det->channel_level > 280) {
/* There is adequate energy in the channel.
Is it mostly at 2100Hz? */
if (det->notch_level * 6 < det->channel_level) {
/* The notch says yes, so we have the tone. */
if (!det->tone_present) {
/* Do we get a kick every 450+-25ms? */
if (det->tone_cycle_duration >= 425 * 8
&& det->tone_cycle_duration <= 475 * 8) {
det->good_cycles++;
if (det->good_cycles > 2)
det->hit = TRUE;
}
det->tone_cycle_duration = 0;
}
det->tone_present = TRUE;
} else
det->tone_present = FALSE;
det->tone_cycle_duration++;
} else {
det->tone_present = FALSE;
det->tone_cycle_duration = 0;
det->good_cycles = 0;
}
return det->hit;
}
/*- End of function --------------------------------------------------------*/
/*- End of file ------------------------------------------------------------*/