dsp.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * Goertzel routines are borrowed from Steve Underwood's tremendous work on the
 * DTMF detector.
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Convenience Signal Processing routines
 *
 * \author Mark Spencer <markster@digium.com>
 * \author Steve Underwood <steveu@coppice.org>
 */

/*! \li \ref dsp.c uses the configuration file \ref dsp.conf
 * \addtogroup configuration_file Configuration Files
 */

/*!
 * \page dsp.conf dsp.conf
 * \verbinclude dsp.conf.sample
 */

/* Some routines from tone_detect.c by Steven Underwood as published under the zapata library */
/*
	tone_detect.c - General telephony tone detection, and specific
					detection of DTMF.

	Copyright (C) 2001  Steve Underwood <steveu@coppice.org>

	Despite my general liking of the GPL, I place this code in the
	public domain for the benefit of all mankind - even the slimy
	ones who might try to proprietize my work and use it to my
	detriment.
*/

/*** MODULEINFO
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

ASTERISK_REGISTER_FILE()

#include <math.h>

#include "asterisk/frame.h"
#include "asterisk/format_cache.h"
#include "asterisk/channel.h"
#include "asterisk/dsp.h"
#include "asterisk/ulaw.h"
#include "asterisk/alaw.h"
#include "asterisk/utils.h"
#include "asterisk/options.h"
#include "asterisk/config.h"

/*! Number of goertzels for progress detect */
enum gsamp_size {
	GSAMP_SIZE_NA = 183,			/*!< North America - 350, 440, 480, 620, 950, 1400, 1800 Hz */
	GSAMP_SIZE_CR = 188,			/*!< Costa Rica, Brazil - Only care about 425 Hz */
	GSAMP_SIZE_UK = 160			/*!< UK disconnect goertzel feed - should trigger 400hz */
};

enum prog_mode {
	PROG_MODE_NA = 0,
	PROG_MODE_CR,
	PROG_MODE_UK
};

enum freq_index {
	/*! For US modes { */
	HZ_350 = 0,
	HZ_440,
	HZ_480,
	HZ_620,
	HZ_950,
	HZ_1400,
	HZ_1800, /*!< } */

	/*! For CR/BR modes */
	HZ_425 = 0,

	/*! For UK mode */
	HZ_350UK = 0,
	HZ_400UK,
	HZ_440UK
};

static struct progalias {
	char *name;
	enum prog_mode mode;
} aliases[] = {
	{ "us", PROG_MODE_NA },
	{ "ca", PROG_MODE_NA },
	{ "cr", PROG_MODE_CR },
	{ "br", PROG_MODE_CR },
	{ "uk", PROG_MODE_UK },
};

#define FREQ_ARRAY_SIZE 7

static struct progress {
	enum gsamp_size size;
	int freqs[FREQ_ARRAY_SIZE];
} modes[] = {
	{ GSAMP_SIZE_NA, { 350, 440, 480, 620, 950, 1400, 1800 } },	/*!< North America */
	{ GSAMP_SIZE_CR, { 425 } },					/*!< Costa Rica, Brazil */
	{ GSAMP_SIZE_UK, { 350, 400, 440 } },				/*!< UK */
};

/*!\brief This value is the minimum threshold, calculated by averaging all
 * of the samples within a frame, for which a frame is determined to either
 * be silence (below the threshold) or noise (above the threshold).  Please
 * note that while the default threshold is an even exponent of 2, there is
 * no requirement that it be so.  The threshold will accept any value between
 * 0 and 32767.
 */
#define DEFAULT_THRESHOLD	512

enum busy_detect {
	BUSY_PERCENT = 10,	/*!< The percentage difference between the two last silence periods */
	BUSY_PAT_PERCENT = 7,	/*!< The percentage difference between measured and actual pattern */
	BUSY_THRESHOLD = 100,	/*!< Max number of ms difference between max and min times in busy */
	BUSY_MIN = 75,		/*!< Busy must be at least 80 ms in half-cadence */
	BUSY_MAX = 3100		/*!< Busy can't be longer than 3100 ms in half-cadence */
};

/*! Remember last 15 units */
#define DSP_HISTORY		15

#define TONE_THRESH		10.0	/*!< How much louder the tone should be than channel energy */
#define TONE_MIN_THRESH		1e8	/*!< How much tone there should be at least to attempt */

/*! All THRESH_XXX values are in GSAMP_SIZE chunks (us = 22ms) */
enum gsamp_thresh {
	THRESH_RING = 8,		/*!< Need at least 150ms ring to accept */
	THRESH_TALK = 2,		/*!< Talk detection does not work continuously */
	THRESH_BUSY = 4,		/*!< Need at least 80ms to accept */
	THRESH_CONGESTION = 4,		/*!< Need at least 80ms to accept */
	THRESH_HANGUP = 60,		/*!< Need at least 1300ms to accept hangup */
	THRESH_RING2ANSWER = 300	/*!< Timeout from start of ring to answer (about 6600 ms) */
};

#define	MAX_DTMF_DIGITS		128

/* Basic DTMF (AT&T) specs:
 *
 * Minimum tone on = 40ms
 * Minimum tone off = 50ms
 * Maximum digit rate = 10 per second
 * Normal twist <= 8dB accepted
 * Reverse twist <= 4dB accepted
 * S/N >= 15dB will detect OK
 * Attenuation <= 26dB will detect OK
 * Frequency tolerance +- 1.5% will detect, +-3.5% will reject
 */

#define DTMF_THRESHOLD		8.0e7
#define FAX_THRESHOLD		8.0e7
#define FAX_2ND_HARMONIC	2.0     /* 4dB */

#define DEF_DTMF_NORMAL_TWIST		6.31	 /* 8.0dB */
#define DEF_RELAX_DTMF_NORMAL_TWIST	6.31	 /* 8.0dB */

#ifdef	RADIO_RELAX
#define DEF_DTMF_REVERSE_TWIST		2.51	 /* 4.01dB */
#define DEF_RELAX_DTMF_REVERSE_TWIST	6.61	 /* 8.2dB */
#else
#define DEF_DTMF_REVERSE_TWIST		2.51	 /* 4.01dB */
#define DEF_RELAX_DTMF_REVERSE_TWIST	3.98	 /* 6.0dB */
#endif

#define DTMF_RELATIVE_PEAK_ROW	6.3     /* 8dB */
#define DTMF_RELATIVE_PEAK_COL	6.3     /* 8dB */
#define DTMF_2ND_HARMONIC_ROW       (relax ? 1.7 : 2.5)     /* 4dB normal */
#define DTMF_2ND_HARMONIC_COL	63.1    /* 18dB */
#define DTMF_TO_TOTAL_ENERGY	42.0

#define BELL_MF_THRESHOLD	1.6e9
#define BELL_MF_TWIST		4.0     /* 6dB */
#define BELL_MF_RELATIVE_PEAK	12.6    /* 11dB */

#if defined(BUSYDETECT_TONEONLY) && defined(BUSYDETECT_COMPARE_TONE_AND_SILENCE)
#error You cant use BUSYDETECT_TONEONLY together with BUSYDETECT_COMPARE_TONE_AND_SILENCE
#endif

/* The CNG signal consists of the transmission of 1100 Hz for 1/2 second,
 * followed by a 3 second silent (2100 Hz OFF) period.
 */
#define FAX_TONE_CNG_FREQ	1100
#define FAX_TONE_CNG_DURATION	500
#define FAX_TONE_CNG_DB		16

/* This signal may be sent by the Terminating FAX machine anywhere between
 * 1.8 to 2.5 seconds AFTER answering the call.  The CED signal consists
 * of a 2100 Hz tone that is from 2.6 to 4 seconds in duration.
*/
#define FAX_TONE_CED_FREQ	2100
#define FAX_TONE_CED_DURATION	2600
#define FAX_TONE_CED_DB		16

#define DEFAULT_SAMPLE_RATE		8000

/* MF goertzel size */
#define MF_GSIZE		120

/* DTMF goertzel size */
#define DTMF_GSIZE		102

/* How many successive hits needed to consider begin of a digit
 * IE. Override with dtmf_hits_to_begin=4 in dsp.conf
 */
#define DEF_DTMF_HITS_TO_BEGIN	2

/* How many successive misses needed to consider end of a digit
 * IE. Override with dtmf_misses_to_end=4 in dsp.conf
 */
#define DEF_DTMF_MISSES_TO_END	3

/*!
 * \brief The default silence threshold we will use if an alternate
 * configured value is not present or is invalid.
 */
static const int DEFAULT_SILENCE_THRESHOLD = 256;

#define CONFIG_FILE_NAME "dsp.conf"

typedef struct {
	int v2;
	int v3;
	int chunky;
	int fac;
} goertzel_state_t;

typedef struct {
	int value;
	int power;
} goertzel_result_t;

typedef struct
{
	int freq;
	int block_size;
	int squelch;		/* Remove (squelch) tone */
	goertzel_state_t tone;
	float energy;		/* Accumulated energy of the current block */
	int samples_pending;	/* Samples remain to complete the current block */
	int mute_samples;	/* How many additional samples needs to be muted to suppress already detected tone */

	int hits_required;	/* How many successive blocks with tone we are looking for */
	float threshold;	/* Energy of the tone relative to energy from all other signals to consider a hit */

	int hit_count;		/* How many successive blocks we consider tone present */
	int last_hit;		/* Indicates if the last processed block was a hit */

} tone_detect_state_t;

typedef struct
{
	goertzel_state_t row_out[4];
	goertzel_state_t col_out[4];
	int hits;			/* How many successive hits we have seen already */
	int misses;			/* How many successive misses we have seen already */
	int lasthit;
	int current_hit;
	float energy;
	int current_sample;
	int mute_samples;
} dtmf_detect_state_t;

typedef struct
{
	goertzel_state_t tone_out[6];
	int current_hit;
	int hits[5];
	int current_sample;
	int mute_samples;
} mf_detect_state_t;

typedef struct
{
	char digits[MAX_DTMF_DIGITS + 1];
	int digitlen[MAX_DTMF_DIGITS + 1];
	int current_digits;
	int detected_digits;
	int lost_digits;

	union {
		dtmf_detect_state_t dtmf;
		mf_detect_state_t mf;
	} td;
} digit_detect_state_t;

static const float dtmf_row[] = {
	697.0,  770.0,  852.0,  941.0
};
static const float dtmf_col[] = {
	1209.0, 1336.0, 1477.0, 1633.0
};
static const float mf_tones[] = {
	700.0, 900.0, 1100.0, 1300.0, 1500.0, 1700.0
};
static const char dtmf_positions[] = "123A" "456B" "789C" "*0#D";
static const char bell_mf_positions[] = "1247C-358A--69*---0B----#";
static int thresholds[THRESHOLD_MAX];
static float dtmf_normal_twist;		/* AT&T = 8dB */
static float dtmf_reverse_twist;	/* AT&T = 4dB */
static float relax_dtmf_normal_twist;	/* AT&T = 8dB */
static float relax_dtmf_reverse_twist;	/* AT&T = 6dB */
static int dtmf_hits_to_begin;		/* How many successive hits needed to consider begin of a digit */
static int dtmf_misses_to_end;		/* How many successive misses needed to consider end of a digit */

static inline void goertzel_sample(goertzel_state_t *s, short sample)
{
	int v1;

	v1 = s->v2;
	s->v2 = s->v3;

	s->v3 = (s->fac * s->v2) >> 15;
	s->v3 = s->v3 - v1 + (sample >> s->chunky);
	if (abs(s->v3) > 32768) {
		s->chunky++;
		s->v3 = s->v3 >> 1;
		s->v2 = s->v2 >> 1;
	}
}

static inline float goertzel_result(goertzel_state_t *s)
{
	goertzel_result_t r;
	r.value = (s->v3 * s->v3) + (s->v2 * s->v2);
	r.value -= ((s->v2 * s->v3) >> 15) * s->fac;
	r.power = s->chunky * 2;
	return (float)r.value * (float)(1 << r.power);
}

static inline void goertzel_init(goertzel_state_t *s, float freq, unsigned int sample_rate)
{
	s->v2 = s->v3 = s->chunky = 0.0;
	s->fac = (int)(32768.0 * 2.0 * cos(2.0 * M_PI * freq / sample_rate));
}

static inline void goertzel_reset(goertzel_state_t *s)
{
	s->v2 = s->v3 = s->chunky = 0.0;
}

typedef struct {
	int start;
	int end;
} fragment_t;

/* Note on tone suppression (squelching). Individual detectors (DTMF/MF/generic tone)
 * report fragments of the frame in which detected tone resides and which needs
 * to be "muted" in order to suppress the tone. To mark fragment for muting,
 * detectors call mute_fragment passing fragment_t there. Multiple fragments
 * can be marked and ast_dsp_process later will mute all of them.
 *
 * Note: When tone starts in the middle of a Goertzel block, it won't be properly
 * detected in that block, only in the next. If we only mute the next block
 * where tone is actually detected, the user will still hear beginning
 * of the tone in preceeding block. This is why we usually want to mute some amount
 * of samples preceeding and following the block where tone was detected.
*/

struct ast_dsp {
	struct ast_frame f;
	int threshold;
	int totalsilence;
	int totalnoise;
	int features;
	int ringtimeout;
	int busymaybe;
	int busycount;
	struct ast_dsp_busy_pattern busy_cadence;
	int historicnoise[DSP_HISTORY];
	int historicsilence[DSP_HISTORY];
	goertzel_state_t freqs[FREQ_ARRAY_SIZE];
	int freqcount;
	int gsamps;
	enum gsamp_size gsamp_size;
	enum prog_mode progmode;
	int tstate;
	int tcount;
	int digitmode;
	int faxmode;
	int dtmf_began;
	int display_inband_dtmf_warning;
	float genergy;
	int mute_fragments;
	unsigned int sample_rate;
	fragment_t mute_data[5];
	digit_detect_state_t digit_state;
	tone_detect_state_t cng_tone_state;
	tone_detect_state_t ced_tone_state;
};

static void mute_fragment(struct ast_dsp *dsp, fragment_t *fragment)
{
	if (dsp->mute_fragments >= ARRAY_LEN(dsp->mute_data)) {
		ast_log(LOG_ERROR, "Too many fragments to mute. Ignoring\n");
		return;
	}

	dsp->mute_data[dsp->mute_fragments++] = *fragment;
}

static void ast_tone_detect_init(tone_detect_state_t *s, int freq, int duration, int amp, unsigned int sample_rate)
{
	int duration_samples;
	float x;
	int periods_in_block;

	s->freq = freq;

	/* Desired tone duration in samples */
	duration_samples = duration * sample_rate / 1000;
	/* We want to allow 10% deviation of tone duration */
	duration_samples = duration_samples * 9 / 10;

	/* If we want to remove tone, it is important to have block size not
	   to exceed frame size. Otherwise by the moment tone is detected it is too late
	   to squelch it from previous frames. Block size is 20ms at the given sample rate.*/
	s->block_size = (20 * sample_rate) / 1000;

	periods_in_block = s->block_size * freq / sample_rate;

	/* Make sure we will have at least 5 periods at target frequency for analisys.
	   This may make block larger than expected packet and will make squelching impossible
	   but at least we will be detecting the tone */
	if (periods_in_block < 5) {
		periods_in_block = 5;
	}

	/* Now calculate final block size. It will contain integer number of periods */
	s->block_size = periods_in_block * sample_rate / freq;

	/* tone_detect is currently only used to detect fax tones and we
	   do not need squelching the fax tones */
	s->squelch = 0;

	/* Account for the first and the last block to be incomplete
	   and thus no tone will be detected in them */
	s->hits_required = (duration_samples - (s->block_size - 1)) / s->block_size;

	goertzel_init(&s->tone, freq, sample_rate);

	s->samples_pending = s->block_size;
	s->hit_count = 0;
	s->last_hit = 0;
	s->energy = 0.0;

	/* We want tone energy to be amp decibels above the rest of the signal (the noise).
	   According to Parseval's theorem the energy computed in time domain equals to energy
	   computed in frequency domain. So subtracting energy in the frequency domain (Goertzel result)
	   from the energy in the time domain we will get energy of the remaining signal (without the tone
	   we are detecting). We will be checking that
		10*log(Ew / (Et - Ew)) > amp
	   Calculate threshold so that we will be actually checking
		Ew > Et * threshold
	*/

	x = pow(10.0, amp / 10.0);
	s->threshold = x / (x + 1);

	ast_debug(1, "Setup tone %d Hz, %d ms, block_size=%d, hits_required=%d\n", freq, duration, s->block_size, s->hits_required);
}

static void ast_fax_detect_init(struct ast_dsp *s)
{
	ast_tone_detect_init(&s->cng_tone_state, FAX_TONE_CNG_FREQ, FAX_TONE_CNG_DURATION, FAX_TONE_CNG_DB, s->sample_rate);
	ast_tone_detect_init(&s->ced_tone_state, FAX_TONE_CED_FREQ, FAX_TONE_CED_DURATION, FAX_TONE_CED_DB, s->sample_rate);
	if (s->faxmode & DSP_FAXMODE_DETECT_SQUELCH) {
		s->cng_tone_state.squelch = 1;
		s->ced_tone_state.squelch = 1;
	}

}

static void ast_dtmf_detect_init(dtmf_detect_state_t *s, unsigned int sample_rate)
{
	int i;

	for (i = 0; i < 4; i++) {
		goertzel_init(&s->row_out[i], dtmf_row[i], sample_rate);
		goertzel_init(&s->col_out[i], dtmf_col[i], sample_rate);
	}
	s->lasthit = 0;
	s->current_hit = 0;
	s->energy = 0.0;
	s->current_sample = 0;
	s->hits = 0;
	s->misses = 0;
}

static void ast_mf_detect_init(mf_detect_state_t *s, unsigned int sample_rate)
{
	int i;

	for (i = 0; i < 6; i++) {
		goertzel_init(&s->tone_out[i], mf_tones[i], sample_rate);
	}
	s->hits[0] = s->hits[1] = s->hits[2] = s->hits[3] = s->hits[4] = 0;
	s->current_sample = 0;
	s->current_hit = 0;
}

static void ast_digit_detect_init(digit_detect_state_t *s, int mf, unsigned int sample_rate)
{
	s->current_digits = 0;
	s->detected_digits = 0;
	s->lost_digits = 0;
	s->digits[0] = '\0';

	if (mf) {
		ast_mf_detect_init(&s->td.mf, sample_rate);
	} else {
		ast_dtmf_detect_init(&s->td.dtmf, sample_rate);
	}
}

static int tone_detect(struct ast_dsp *dsp, tone_detect_state_t *s, int16_t *amp, int samples)
{
	float tone_energy;
	int i;
	int hit = 0;
	int limit;
	int res = 0;
	int16_t *ptr;
	short samp;
	int start, end;
	fragment_t mute = {0, 0};

	if (s->squelch && s->mute_samples > 0) {
		mute.end = (s->mute_samples < samples) ? s->mute_samples : samples;
		s->mute_samples -= mute.end;
	}

	for (start = 0; start < samples; start = end) {
		/* Process in blocks. */
		limit = samples - start;
		if (limit > s->samples_pending) {
			limit = s->samples_pending;
		}
		end = start + limit;

		for (i = limit, ptr = amp ; i > 0; i--, ptr++) {
			samp = *ptr;
			/* signed 32 bit int should be enough to square any possible signed 16 bit value */
			s->energy += (int32_t) samp * (int32_t) samp;

			goertzel_sample(&s->tone, samp);
		}

		s->samples_pending -= limit;

		if (s->samples_pending) {
			/* Finished incomplete (last) block */
			break;
		}

		tone_energy = goertzel_result(&s->tone);

		/* Scale to make comparable */
		tone_energy *= 2.0;
		s->energy *= s->block_size;

		ast_debug(10, "tone %d, Ew=%.2E, Et=%.2E, s/n=%10.2f\n", s->freq, tone_energy, s->energy, tone_energy / (s->energy - tone_energy));
		hit = 0;
		if (tone_energy > s->energy * s->threshold) {
			ast_debug(10, "Hit! count=%d\n", s->hit_count);
			hit = 1;
		}

		if (s->hit_count) {
			s->hit_count++;
		}

		if (hit == s->last_hit) {
			if (!hit) {
				/* Two successive misses. Tone ended */
				s->hit_count = 0;
			} else if (!s->hit_count) {
				s->hit_count++;
			}

		}

		if (s->hit_count == s->hits_required) {
			ast_debug(1, "%d Hz done detected\n", s->freq);
			res = 1;
		}

		s->last_hit = hit;

		/* If we had a hit in this block, include it into mute fragment */
		if (s->squelch && hit) {
			if (mute.end < start - s->block_size) {
				/* There is a gap between fragments */
				mute_fragment(dsp, &mute);
				mute.start = (start > s->block_size) ? (start - s->block_size) : 0;
			}
			mute.end = end + s->block_size;
		}

		/* Reinitialise the detector for the next block */
		/* Reset for the next block */
		goertzel_reset(&s->tone);

		/* Advance to the next block */
		s->energy = 0.0;
		s->samples_pending = s->block_size;

		amp += limit;
	}

	if (s->squelch && mute.end) {
		if (mute.end > samples) {
			s->mute_samples = mute.end - samples;
			mute.end = samples;
		}
		mute_fragment(dsp, &mute);
	}

	return res;
}

static void store_digit(digit_detect_state_t *s, char digit)
{
	s->detected_digits++;
	if (s->current_digits < MAX_DTMF_DIGITS) {
		s->digitlen[s->current_digits] = 0;
		s->digits[s->current_digits++] = digit;
		s->digits[s->current_digits] = '\0';
	} else {
		ast_log(LOG_WARNING, "Digit lost due to full buffer\n");
		s->lost_digits++;
	}
}

static int dtmf_detect(struct ast_dsp *dsp, digit_detect_state_t *s, int16_t amp[], int samples, int squelch, int relax)
{
	float row_energy[4];
	float col_energy[4];
	int i;
	int j;
	int sample;
	short samp;
	int best_row;
	int best_col;
	int hit;
	int limit;
	fragment_t mute = {0, 0};

	if (squelch && s->td.dtmf.mute_samples > 0) {
		mute.end = (s->td.dtmf.mute_samples < samples) ? s->td.dtmf.mute_samples : samples;
		s->td.dtmf.mute_samples -= mute.end;
	}

	hit = 0;
	for (sample = 0; sample < samples; sample = limit) {
		/* DTMF_GSIZE is optimised to meet the DTMF specs. */
		if ((samples - sample) >= (DTMF_GSIZE - s->td.dtmf.current_sample)) {
			limit = sample + (DTMF_GSIZE - s->td.dtmf.current_sample);
		} else {
			limit = samples;
		}
		/* The following unrolled loop takes only 35% (rough estimate) of the
		   time of a rolled loop on the machine on which it was developed */
		for (j = sample; j < limit; j++) {
			samp = amp[j];
			s->td.dtmf.energy += (int32_t) samp * (int32_t) samp;
			/* With GCC 2.95, the following unrolled code seems to take about 35%
			   (rough estimate) as long as a neat little 0-3 loop */
			goertzel_sample(s->td.dtmf.row_out, samp);
			goertzel_sample(s->td.dtmf.col_out, samp);
			goertzel_sample(s->td.dtmf.row_out + 1, samp);
			goertzel_sample(s->td.dtmf.col_out + 1, samp);
			goertzel_sample(s->td.dtmf.row_out + 2, samp);
			goertzel_sample(s->td.dtmf.col_out + 2, samp);
			goertzel_sample(s->td.dtmf.row_out + 3, samp);
			goertzel_sample(s->td.dtmf.col_out + 3, samp);
		}
		s->td.dtmf.current_sample += (limit - sample);
		if (s->td.dtmf.current_sample < DTMF_GSIZE) {
			continue;
		}
		/* We are at the end of a DTMF detection block */
		/* Find the peak row and the peak column */
		row_energy[0] = goertzel_result(&s->td.dtmf.row_out[0]);
		col_energy[0] = goertzel_result(&s->td.dtmf.col_out[0]);

		for (best_row = best_col = 0, i = 1; i < 4; i++) {
			row_energy[i] = goertzel_result(&s->td.dtmf.row_out[i]);
			if (row_energy[i] > row_energy[best_row]) {
				best_row = i;
			}
			col_energy[i] = goertzel_result(&s->td.dtmf.col_out[i]);
			if (col_energy[i] > col_energy[best_col]) {
				best_col = i;
			}
		}
		hit = 0;
		/* Basic signal level test and the twist test */
		if (row_energy[best_row] >= DTMF_THRESHOLD &&
		    col_energy[best_col] >= DTMF_THRESHOLD &&
		    col_energy[best_col] < row_energy[best_row] * (relax ? relax_dtmf_reverse_twist : dtmf_reverse_twist) &&
		    row_energy[best_row] < col_energy[best_col] * (relax ? relax_dtmf_normal_twist : dtmf_normal_twist)) {
			/* Relative peak test */
			for (i = 0; i < 4; i++) {
				if ((i != best_col &&
				    col_energy[i] * DTMF_RELATIVE_PEAK_COL > col_energy[best_col]) ||
				    (i != best_row
				     && row_energy[i] * DTMF_RELATIVE_PEAK_ROW > row_energy[best_row])) {
					break;
				}
			}
			/* ... and fraction of total energy test */
			if (i >= 4 &&
			    (row_energy[best_row] + col_energy[best_col]) > DTMF_TO_TOTAL_ENERGY * s->td.dtmf.energy) {
				/* Got a hit */
				hit = dtmf_positions[(best_row << 2) + best_col];
			}
		}

/*
 * Adapted from ETSI ES 201 235-3 V1.3.1 (2006-03)
 * (40ms reference is tunable with hits_to_begin and misses_to_end)
 * each hit/miss is 12.75ms with DTMF_GSIZE at 102
 *
 * Character recognition: When not DRC *(1) and then
 *      Shall exist VSC > 40 ms (hits_to_begin)
 *      May exist 20 ms <= VSC <= 40 ms
 *      Shall not exist VSC < 20 ms
 *
 * Character recognition: When DRC and then
 *      Shall cease Not VSC > 40 ms (misses_to_end)
 *      May cease 20 ms >= Not VSC >= 40 ms
 *      Shall not cease Not VSC < 20 ms
 *
 * *(1) or optionally a different digit recognition condition
 *
 * Legend: VSC The continuous existence of a valid signal condition.
 *      Not VSC The continuous non-existence of valid signal condition.
 *      DRC The existence of digit recognition condition.
 *      Not DRC The non-existence of digit recognition condition.
 */

/*
 * Example: hits_to_begin=2 misses_to_end=3
 * -------A last_hit=A hits=0&1
 * ------AA hits=2 current_hit=A misses=0       BEGIN A
 * -----AA- misses=1 last_hit=' ' hits=0
 * ----AA-- misses=2
 * ---AA--- misses=3 current_hit=' '            END A
 * --AA---B last_hit=B hits=0&1
 * -AA---BC last_hit=C hits=0&1
 * AA---BCC hits=2 current_hit=C misses=0       BEGIN C
 * A---BCC- misses=1 last_hit=' ' hits=0
 * ---BCC-C misses=0 last_hit=C hits=0&1
 * --BCC-CC misses=0
 *
 * Example: hits_to_begin=3 misses_to_end=2
 * -------A last_hit=A hits=0&1
 * ------AA hits=2
 * -----AAA hits=3 current_hit=A misses=0       BEGIN A
 * ----AAAB misses=1 last_hit=B hits=0&1
 * ---AAABB misses=2 current_hit=' ' hits=2     END A
 * --AAABBB hits=3 current_hit=B misses=0       BEGIN B
 * -AAABBBB misses=0
 *
 * Example: hits_to_begin=2 misses_to_end=2
 * -------A last_hit=A hits=0&1
 * ------AA hits=2 current_hit=A misses=0       BEGIN A
 * -----AAB misses=1 hits=0&1
 * ----AABB misses=2 current_hit=' ' hits=2 current_hit=B misses=0 BEGIN B
 * ---AABBB misses=0
 */

		if (s->td.dtmf.current_hit) {
			/* We are in the middle of a digit already */
			if (hit != s->td.dtmf.current_hit) {
				s->td.dtmf.misses++;
				if (s->td.dtmf.misses == dtmf_misses_to_end) {
					/* There were enough misses to consider digit ended */
					s->td.dtmf.current_hit = 0;
				}
			} else {
				s->td.dtmf.misses = 0;
				/* Current hit was same as last, so increment digit duration (of last digit) */
				s->digitlen[s->current_digits - 1] += DTMF_GSIZE;
			}
		}

		/* Look for a start of a new digit no matter if we are already in the middle of some
		   digit or not. This is because hits_to_begin may be smaller than misses_to_end
		   and we may find begin of new digit before we consider last one ended. */

		if (hit != s->td.dtmf.lasthit) {
			s->td.dtmf.lasthit = hit;
			s->td.dtmf.hits = 0;
		}
		if (hit && hit != s->td.dtmf.current_hit) {
			s->td.dtmf.hits++;
			if (s->td.dtmf.hits == dtmf_hits_to_begin) {
				store_digit(s, hit);
				s->digitlen[s->current_digits - 1] = dtmf_hits_to_begin * DTMF_GSIZE;
				s->td.dtmf.current_hit = hit;
				s->td.dtmf.misses = 0;
			}
		}

		/* If we had a hit in this block, include it into mute fragment */
		if (squelch && hit) {
			if (mute.end < sample - DTMF_GSIZE) {
				/* There is a gap between fragments */
				mute_fragment(dsp, &mute);
				mute.start = (sample > DTMF_GSIZE) ? (sample - DTMF_GSIZE) : 0;
			}
			mute.end = limit + DTMF_GSIZE;
		}

		/* Reinitialise the detector for the next block */
		for (i = 0; i < 4; i++) {
			goertzel_reset(&s->td.dtmf.row_out[i]);
			goertzel_reset(&s->td.dtmf.col_out[i]);
		}
		s->td.dtmf.energy = 0.0;
		s->td.dtmf.current_sample = 0;
	}

	if (squelch && mute.end) {
		if (mute.end > samples) {
			s->td.dtmf.mute_samples = mute.end - samples;
			mute.end = samples;
		}
		mute_fragment(dsp, &mute);
	}

	return (s->td.dtmf.current_hit);	/* return the debounced hit */
}

static int mf_detect(struct ast_dsp *dsp, digit_detect_state_t *s, int16_t amp[],
		int samples, int squelch, int relax)
{
	float energy[6];
	int best;
	int second_best;
	int i;
	int j;
	int sample;
	short samp;
	int hit;
	int limit;
	fragment_t mute = {0, 0};

	if (squelch && s->td.mf.mute_samples > 0) {
		mute.end = (s->td.mf.mute_samples < samples) ? s->td.mf.mute_samples : samples;
		s->td.mf.mute_samples -= mute.end;
	}

	hit = 0;
	for (sample = 0; sample < samples; sample = limit) {
		/* 80 is optimised to meet the MF specs. */
		/* XXX So then why is MF_GSIZE defined as 120? */
		if ((samples - sample) >= (MF_GSIZE - s->td.mf.current_sample)) {
			limit = sample + (MF_GSIZE - s->td.mf.current_sample);
		} else {
			limit = samples;
		}
		/* The following unrolled loop takes only 35% (rough estimate) of the
		   time of a rolled loop on the machine on which it was developed */
		for (j = sample; j < limit; j++) {
			/* With GCC 2.95, the following unrolled code seems to take about 35%
			   (rough estimate) as long as a neat little 0-3 loop */
			samp = amp[j];
			goertzel_sample(s->td.mf.tone_out, samp);
			goertzel_sample(s->td.mf.tone_out + 1, samp);
			goertzel_sample(s->td.mf.tone_out + 2, samp);
			goertzel_sample(s->td.mf.tone_out + 3, samp);
			goertzel_sample(s->td.mf.tone_out + 4, samp);
			goertzel_sample(s->td.mf.tone_out + 5, samp);
		}
		s->td.mf.current_sample += (limit - sample);
		if (s->td.mf.current_sample < MF_GSIZE) {
			continue;
		}
		/* We're at the end of an MF detection block.  */
		/* Find the two highest energies. The spec says to look for
		   two tones and two tones only. Taking this literally -ie
		   only two tones pass the minimum threshold - doesn't work
		   well. The sinc function mess, due to rectangular windowing
		   ensure that! Find the two highest energies and ensure they
		   are considerably stronger than any of the others. */
		energy[0] = goertzel_result(&s->td.mf.tone_out[0]);
		energy[1] = goertzel_result(&s->td.mf.tone_out[1]);
		if (energy[0] > energy[1]) {
			best = 0;
			second_best = 1;
		} else {
			best = 1;
			second_best = 0;
		}
		/*endif*/
		for (i = 2; i < 6; i++) {
			energy[i] = goertzel_result(&s->td.mf.tone_out[i]);
			if (energy[i] >= energy[best]) {
				second_best = best;
				best = i;
			} else if (energy[i] >= energy[second_best]) {
				second_best = i;
			}
		}
		/* Basic signal level and twist tests */
		hit = 0;
		if (energy[best] >= BELL_MF_THRESHOLD && energy[second_best] >= BELL_MF_THRESHOLD
		    && energy[best] < energy[second_best]*BELL_MF_TWIST
		    && energy[best] * BELL_MF_TWIST > energy[second_best]) {
			/* Relative peak test */
			hit = -1;
			for (i = 0; i < 6; i++) {
				if (i != best && i != second_best) {
					if (energy[i]*BELL_MF_RELATIVE_PEAK >= energy[second_best]) {
						/* The best two are not clearly the best */
						hit = 0;
						break;
					}
				}
			}
		}
		if (hit) {
			/* Get the values into ascending order */
			if (second_best < best) {
				i = best;
				best = second_best;
				second_best = i;
			}
			best = best * 5 + second_best - 1;
			hit = bell_mf_positions[best];
			/* Look for two successive similar results */
			/* The logic in the next test is:
			   For KP we need 4 successive identical clean detects, with
			   two blocks of something different preceeding it. For anything
			   else we need two successive identical clean detects, with
			   two blocks of something different preceeding it. */
			if (hit == s->td.mf.hits[4] && hit == s->td.mf.hits[3] &&
			   ((hit != '*' && hit != s->td.mf.hits[2] && hit != s->td.mf.hits[1])||
			    (hit == '*' && hit == s->td.mf.hits[2] && hit != s->td.mf.hits[1] &&
			    hit != s->td.mf.hits[0]))) {
				store_digit(s, hit);
			}
		}


		if (hit != s->td.mf.hits[4] && hit != s->td.mf.hits[3]) {
			/* Two successive block without a hit terminate current digit */
			s->td.mf.current_hit = 0;
		}

		s->td.mf.hits[0] = s->td.mf.hits[1];
		s->td.mf.hits[1] = s->td.mf.hits[2];
		s->td.mf.hits[2] = s->td.mf.hits[3];
		s->td.mf.hits[3] = s->td.mf.hits[4];
		s->td.mf.hits[4] = hit;

		/* If we had a hit in this block, include it into mute fragment */
		if (squelch && hit) {
			if (mute.end < sample - MF_GSIZE) {
				/* There is a gap between fragments */
				mute_fragment(dsp, &mute);
				mute.start = (sample > MF_GSIZE) ? (sample - MF_GSIZE) : 0;
			}
			mute.end = limit + MF_GSIZE;
		}

		/* Reinitialise the detector for the next block */
		for (i = 0; i < 6; i++) {
			goertzel_reset(&s->td.mf.tone_out[i]);
		}
		s->td.mf.current_sample = 0;
	}

	if (squelch && mute.end) {
		if (mute.end > samples) {