Point people to where active development is taking placesvn_trunk

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@10748 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 0 insertions, 890 deletions

diff --git a/drivers/dahdi/dahdi_echocan_mg2.c b/drivers/dahdi/dahdi_echocan_mg2.c
deleted file mode 100644
index 4038ff2..0000000
--- a/drivers/dahdi/dahdi_echocan_mg2.c
+++ /dev/null
@@ -1,890 +0,0 @@
-/*
- * ECHO_CAN_MG2
- *
- * by Michael Gernoth
- *
- * Based upon kb1ec.h and mec2.h
- * 
- * Copyright (C) 2002-2012, Digium, Inc.
- *
- * Additional background on the techniques used in this code can be found in:
- *
- *  Messerschmitt, David; Hedberg, David; Cole, Christopher; Haoui, Amine; 
- *  Winship, Peter; "Digital Voice Echo Canceller with a TMS32020," 
- *  in Digital Signal Processing Applications with the TMS320 Family, 
- *  pp. 415-437, Texas Instruments, Inc., 1986. 
- *
- * A pdf of which is available by searching on the document title at http://www.ti.com/
- *
- */
-
-/*
- * 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 as published by the
- * Free Software Foundation. See the LICENSE file included with
- * this program for more details.
- */
-
-#include <linux/kernel.h>
-#include <linux/slab.h>
-#include <linux/errno.h>
-#include <linux/module.h>
-#include <linux/init.h>
-#include <linux/ctype.h>
-#include <linux/moduleparam.h>
-
-#include <dahdi/kernel.h>
-
-static int debug;
-static int aggressive;
-
-#define ABS(a) abs(a!=-32768?a:-32767)
-
-#define RESTORE_COEFFS {\
-				int x;\
-				memcpy(pvt->a_i, pvt->c_i, pvt->N_d*sizeof(int));\
-				for (x = 0; x < pvt->N_d; x++) {\
-					pvt->a_s[x] = pvt->a_i[x] >> 16;\
-				}\
-				pvt->backup = BACKUP;\
-			}
-
-/* Uncomment to provide summary statistics for overall echo can performance every 4000 samples */ 
-/* #define MEC2_STATS 4000 */
-
-/* Uncomment to generate per-sample statistics - this will severely degrade system performance and audio quality */
-/* #define MEC2_STATS_DETAILED */
-
-/* Uncomment to generate per-call DC bias offset messages */
-/* #define MEC2_DCBIAS_MESSAGE */
-
-/* Get optimized routines for math */
-#include "arith.h"
-
-/*
-   Important constants for tuning mg2 echo can
- */
-
-/* Convergence (aka. adaptation) speed -- higher means slower */
-#define DEFAULT_BETA1_I 2048
-
-/* Constants for various power computations */
-#define DEFAULT_SIGMA_LY_I 7
-#define DEFAULT_SIGMA_LU_I 7
-#define DEFAULT_ALPHA_ST_I 5 		/* near-end speech detection sensitivity factor */
-#define DEFAULT_ALPHA_YT_I 5
-
-#define DEFAULT_CUTOFF_I 128
-
-/* Define the near-end speech hangover counter: if near-end speech 
- *  is declared, hcntr is set equal to hangt (see pg. 432)
- */
-#define DEFAULT_HANGT 600  		/* in samples, so 600 samples = 75ms */
-
-/* define the residual error suppression threshold */
-#define DEFAULT_SUPPR_I 16		/* 16 = -24db */
-
-/* This is the minimum reference signal power estimate level 
- *  that will result in filter adaptation.
- * If this is too low then background noise will cause the filter 
- *  coefficients to constantly be updated.
- */
-#define MIN_UPDATE_THRESH_I 2048
-
-/* The number of samples used to update coefficients using the
- *  the block update method (M). It should be related back to the 
- *  length of the echo can.
- * ie. it only updates coefficients when (sample number MOD default_m) = 0
- *
- *  Getting this wrong may cause an oops. Consider yourself warned!
- */
-#define DEFAULT_M 16		  	/* every 16th sample */
-
-/* If AGGRESSIVE supression is enabled, then we start cancelling residual 
- * echos again even while there is potentially the very end of a near-side 
- *  signal present.
- * This defines how many samples of DEFAULT_HANGT can remain before we
- *  kick back in
- */
-#define AGGRESSIVE_HCNTR 160		/* in samples, so 160 samples = 20ms */
-
-/* Treat sample as error if it has a different sign as the
- * input signal and is this number larger in ABS() as
- * the input-signal */
-#define MAX_SIGN_ERROR 3000
-
-/* Number of coefficients really used for calculating the
- * simulated echo. The value specifies how many of the
- * biggest coefficients are used for calculating rs.
- * This helps on long echo-tails by artificially limiting
- * the number of coefficients for the calculation and
- * preventing overflows.
- * Comment this to deactivate the code */
-#define USED_COEFFS 64
-
-/* Backup coefficients every this number of samples */
-#define BACKUP 256
-
-/***************************************************************/
-/* The following knobs are not implemented in the current code */
-
-/* we need a dynamic level of suppression varying with the ratio of the 
-   power of the echo to the power of the reference signal this is 
-   done so that we have a  smoother background. 		
-   we have a higher suppression when the power ratio is closer to
-   suppr_ceil and reduces logarithmically as we approach suppr_floor.
- */
-#define SUPPR_FLOOR -64
-#define SUPPR_CEIL -24
-
-/* in a second departure, we calculate the residual error suppression
- * as a percentage of the reference signal energy level. The threshold
- * is defined in terms of dB below the reference signal.
- */
-#define RES_SUPR_FACTOR -20
-
-#define DC_NORMALIZE
-
-#ifndef NULL
-#define NULL 0
-#endif
-#ifndef FALSE
-#define FALSE 0
-#endif
-#ifndef TRUE
-#define TRUE (!FALSE)
-#endif
-
-/* Generic circular buffer definition */
-typedef struct {
-	/* Pointer to the relative 'start' of the buffer */
-	int idx_d;
-	/* The absolute size of the buffer */
-	int size_d;			 
-	/* The actual sample -  twice as large as we need, however we do store values at idx_d and idx_d+size_d */
-	short *buf_d;			
-} echo_can_cb_s;
-
-static int echo_can_create(struct dahdi_chan *chan, struct dahdi_echocanparams *ecp,
-			   struct dahdi_echocanparam *p, struct dahdi_echocan_state **ec);
-static void echo_can_free(struct dahdi_chan *chan, struct dahdi_echocan_state *ec);
-static void echo_can_process(struct dahdi_echocan_state *ec, short *isig, const short *iref, u32 size);
-static int echo_can_traintap(struct dahdi_echocan_state *ec, int pos, short val);
-static void echocan_NLP_toggle(struct dahdi_echocan_state *ec, unsigned int enable);
-static const char *name = "MG2";
-static const char *ec_name(const struct dahdi_chan *chan) { return name; }
-
-static const struct dahdi_echocan_factory my_factory = {
-	.get_name = ec_name,
-	.owner = THIS_MODULE,
-	.echocan_create = echo_can_create,
-};
-
-static const struct dahdi_echocan_features my_features = {
-	.NLP_toggle = 1,
-};
-
-static const struct dahdi_echocan_ops my_ops = {
-	.echocan_free = echo_can_free,
-	.echocan_process = echo_can_process,
-	.echocan_traintap = echo_can_traintap,
-	.echocan_NLP_toggle = echocan_NLP_toggle,
-};
-
-struct ec_pvt {
-	struct dahdi_echocan_state dahdi;
-	/* an arbitrary ID for this echo can - this really should be settable from the calling channel... */
-	int id;
-
-	/* absolute time - aka. sample number index - essentially the number of samples since this can was init'ed */
-	int i_d;
-  
-	/* Pre-computed constants */
-	/* ---------------------- */
-	/* Number of filter coefficents */
-	int N_d;
-	/* Rate of adaptation of filter */
-	int beta2_i;
-
-	/* Accumulators for power computations */
-	/* ----------------------------------- */
-	/* reference signal power estimate - aka. Average absolute value of y(k) */
-	int Ly_i;			
-	/* ... */
-	int Lu_i;
-
-	/* Accumulators for signal detectors */
-	/* --------------------------------- */
-	/* Power estimate of the recent past of the near-end hybrid signal - aka. Short-time average of: 2 x |s(i)| */
-	int s_tilde_i;		
-	/* Power estimate of the recent past of the far-end receive signal - aka. Short-time average of:     |y(i)| */
-	int y_tilde_i;
-
-	/* Near end speech detection counter - stores Hangover counter time remaining, in samples */
-	int HCNTR_d;			
-  
-	/* Circular buffers and coefficients */
-	/* --------------------------------- */
-	/* ... */
-	int *a_i;
-	/* ... */
-	short *a_s;
-	/* Backups */
-	int *b_i;
-	int *c_i;
-	/* Reference samples of far-end receive signal */
-	echo_can_cb_s y_s;
-	/* Reference samples of near-end signal */
-	echo_can_cb_s s_s;
-	/* Reference samples of near-end signal minus echo estimate */
-	echo_can_cb_s u_s;
-	/* Reference samples of far-end receive signal used to calculate short-time average */
-	echo_can_cb_s y_tilde_s;
-
-	/* Peak far-end receive signal */
-	/* --------------------------- */
-	/* Highest y_tilde value in the sample buffer */
-	short max_y_tilde;
-	/* Index of the sample containing the max_y_tilde value */
-	int max_y_tilde_pos;
-
-#ifdef MEC2_STATS
-	/* Storage for performance statistics */
-	int cntr_nearend_speech_frames;
-	int cntr_residualcorrected_frames;
-	int cntr_residualcorrected_framesskipped;
-	int cntr_coeff_updates;
-	int cntr_coeff_missedupdates;
- 
-	int avg_Lu_i_toolow; 
-	int avg_Lu_i_ok;
-#endif 
-	unsigned int aggressive:1;
-	short lastsig;
-	int lastcount;
-	int backup;
-#ifdef DC_NORMALIZE
-	int dc_estimate;
-#endif
-	int use_nlp;
-};
-
-#define dahdi_to_pvt(a) container_of(a, struct ec_pvt, dahdi)
-
-static inline void init_cb_s(echo_can_cb_s *cb, int len, void *where)
-{
-	cb->buf_d = (short *)where;
-	cb->idx_d = 0;
-	cb->size_d = len;
-}
-
-static inline void add_cc_s(echo_can_cb_s *cb, short newval)
-{
-	/* Can't use modulus because N+M isn't a power of two (generally) */
-	cb->idx_d--;
-	if (cb->idx_d < (int)0) 
-		/* Whoops - the pointer to the 'start' wrapped around so reset it to the top of the buffer */
-	 	cb->idx_d += cb->size_d;
-  	
-	/* Load two copies into memory */
-	cb->buf_d[cb->idx_d] = newval;
-	cb->buf_d[cb->idx_d + cb->size_d] = newval;
-}
-
-static inline short get_cc_s(echo_can_cb_s *cb, int pos)
-{
-	/* Load two copies into memory */
-	return cb->buf_d[cb->idx_d + pos];
-}
-
-static inline void init_cc(struct ec_pvt *pvt, int N, int maxy, int maxu)
-{
-	char *ptr = (char *) pvt;
-	unsigned long tmp;
-
-	/* Double-word align past end of state */
-	ptr += sizeof(*pvt);
-	tmp = (unsigned long)ptr;
-	tmp += 3;
-	tmp &= ~3L;
-	ptr = (void *)tmp;
-
-	/* Reset parameters */
-	pvt->N_d = N;
-	pvt->beta2_i = DEFAULT_BETA1_I;
-  
-	/* Allocate coefficient memory */
-	pvt->a_i = (int *) ptr;
-	ptr += (sizeof(int) * pvt->N_d);
-	pvt->a_s = (short *) ptr;
-	ptr += (sizeof(short) * pvt->N_d);
-
-	/* Allocate backup memory */
-	pvt->b_i = (int *) ptr;
-	ptr += (sizeof(int) * pvt->N_d);
-	pvt->c_i = (int *) ptr;
-	ptr += (sizeof(int) * pvt->N_d);
-
-	/* Reset Y circular buffer (short version) */
-	init_cb_s(&pvt->y_s, maxy, ptr);
-	ptr += (sizeof(short) * (maxy) * 2);
-  
-	/* Reset Sigma circular buffer (short version for FIR filter) */
-	init_cb_s(&pvt->s_s, (1 << DEFAULT_ALPHA_ST_I), ptr);
-	ptr += (sizeof(short) * (1 << DEFAULT_ALPHA_ST_I) * 2);
-
-	init_cb_s(&pvt->u_s, maxu, ptr);
-	ptr += (sizeof(short) * maxu * 2);
-
-	/* Allocate a buffer for the reference signal power computation */
-	init_cb_s(&pvt->y_tilde_s, pvt->N_d, ptr);
-
-	/* Reset the absolute time index */
-	pvt->i_d = (int)0;
-  
-	/* Reset the power computations (for y and u) */
-	pvt->Ly_i = DEFAULT_CUTOFF_I;
-	pvt->Lu_i = DEFAULT_CUTOFF_I;
-
-#ifdef MEC2_STATS
-	/* set the identity */
-	pvt->id = (int)&ptr;
-  
-	/* Reset performance stats */
-	pvt->cntr_nearend_speech_frames = (int)0;
-	pvt->cntr_residualcorrected_frames = (int)0;
-	pvt->cntr_residualcorrected_framesskipped = (int)0;
-	pvt->cntr_coeff_updates = (int)0;
-	pvt->cntr_coeff_missedupdates = (int)0;
-
-	pvt->avg_Lu_i_toolow = (int)0;
-	pvt->avg_Lu_i_ok = (int)0;
-#endif
-
-	/* Reset the near-end speech detector */
-	pvt->s_tilde_i = (int)0;
-	pvt->y_tilde_i = (int)0;
-	pvt->HCNTR_d = (int)0;
-
-}
-
-static void echo_can_free(struct dahdi_chan *chan, struct dahdi_echocan_state *ec)
-{
-	struct ec_pvt *pvt = dahdi_to_pvt(ec);
-
-#if defined(DC_NORMALIZE) && defined(MEC2_DCBIAS_MESSAGE)
-	printk(KERN_INFO "EC: DC bias calculated: %d V\n", pvt->dc_estimate >> 15);
-#endif
-	kfree(pvt);
-}
-
-#ifdef DC_NORMALIZE
-static inline short dc_removal(int *dc_estimate, short samp)
-{
-	*dc_estimate += ((((int)samp << 15) - *dc_estimate) >> 9);
-	return samp - (*dc_estimate >> 15);
-}
-#endif
-
-static inline short sample_update(struct ec_pvt *pvt, short iref, short isig)
-{
-	/* Declare local variables that are used more than once */
-	/* ... */
-	int k;
-	/* ... */
-	int rs;
-	/* ... */
-	short u;
-	/* ... */
-	int Py_i;
-	/* ... */
-	int two_beta_i;
-
-#ifdef DC_NORMALIZE
-	isig = dc_removal(&pvt->dc_estimate, isig);
-#endif
-	
-	/* flow A on pg. 428 */
-	/* eq. (16): high-pass filter the input to generate the next value;
-	 *           push the current value into the circular buffer
-	 *
-	 * sdc_im1_d = sdc_d;
-	 *     sdc_d = sig;
-	 *     s_i_d = sdc_d;
-	 *       s_d = s_i_d;
-	 *     s_i_d = (float)(1.0 - gamma_d) * s_i_d
-	 *	+ (float)(0.5 * (1.0 - gamma_d)) * (sdc_d - sdc_im1_d); 
-	 */
-
-	/* Update the Far-end receive signal circular buffers and accumulators */
-	/* ------------------------------------------------------------------- */
-	/* Delete the oldest sample from the power estimate accumulator */
-	pvt->y_tilde_i -= abs(get_cc_s(&pvt->y_s, (1 << DEFAULT_ALPHA_YT_I) - 1)) >> DEFAULT_ALPHA_YT_I;
-	/* Add the new sample to the power estimate accumulator */
-	pvt->y_tilde_i += abs(iref) >> DEFAULT_ALPHA_ST_I;
-	/* Push a copy of the new sample into its circular buffer */
-	add_cc_s(&pvt->y_s, iref);
- 
-
-	/* eq. (2): compute r in fixed-point */
-	rs = CONVOLVE2(pvt->a_s,
-		       pvt->y_s.buf_d + pvt->y_s.idx_d,
-		       pvt->N_d);
-	rs >>= 15;
-
-	if (pvt->lastsig == isig) {
-		pvt->lastcount++;
-	} else {
-		pvt->lastcount = 0;
-		pvt->lastsig = isig;
-	}
-
-	if (isig == 0) {
-		u = 0;
-	} else if (pvt->lastcount > 255) {
-		/* We have seen the same input-signal more than 255 times,
-		 * we should pass it through uncancelled, as we are likely on hold */
-		u = isig;
-	} else {
-		int sign_error;
-
-		if (rs < -32768) {
-			rs = -32768;
-			pvt->HCNTR_d = DEFAULT_HANGT;
-			RESTORE_COEFFS;
-		} else if (rs > 32767) {
-			rs = 32767;
-			pvt->HCNTR_d = DEFAULT_HANGT;
-			RESTORE_COEFFS;
-		}
-
-		sign_error = ABS(rs) - ABS(isig);
-
-		if (ABS(sign_error) > MAX_SIGN_ERROR)
-		{
-			rs = 0;
-			RESTORE_COEFFS;
-		}
-
-		/* eq. (3): compute the output value (see figure 3) and the error
-		 * note: the error is the same as the output signal when near-end
-		 * speech is not present
-		 */
-		u = isig - rs;
-
-		if (u / isig < 0)
-			u = isig - (rs >> 1);
-	}
-
-	/* Push a copy of the output value sample into its circular buffer */
-	add_cc_s(&pvt->u_s, u);
-
-	if (!pvt->backup) {
-		/* Backup coefficients periodically */
-		pvt->backup = BACKUP;
-		memcpy(pvt->c_i, pvt->b_i, pvt->N_d*sizeof(int));
-		memcpy(pvt->b_i, pvt->a_i, pvt->N_d*sizeof(int));
-	} else
-		pvt->backup--;
-
-
-	/* Update the Near-end hybrid signal circular buffers and accumulators */
-	/* ------------------------------------------------------------------- */
-	/* Delete the oldest sample from the power estimate accumulator */
-	pvt->s_tilde_i -= abs(get_cc_s(&pvt->s_s, (1 << DEFAULT_ALPHA_ST_I) - 1));
-	/* Add the new sample to the power estimate accumulator */
-	pvt->s_tilde_i += abs(isig);
-	/* Push a copy of the new sample into it's circular buffer */
-	add_cc_s(&pvt->s_s, isig);
-
-
-	/* Push a copy of the current short-time average of the far-end receive signal into it's circular buffer */
-	add_cc_s(&pvt->y_tilde_s, pvt->y_tilde_i);
-
-	/* flow B on pg. 428 */
-  
-	/* If the hangover timer isn't running then compute the new convergence factor, otherwise set Py_i to 32768 */
-	if (!pvt->HCNTR_d) {
-		Py_i = (pvt->Ly_i >> DEFAULT_SIGMA_LY_I) * (pvt->Ly_i >> DEFAULT_SIGMA_LY_I);
-		Py_i >>= 15;
-	} else {
-	  	Py_i = (1 << 15);
-	}
-  
-#if 0
-	/* Vary rate of adaptation depending on position in the file
-	 *  Do not do this for the first (DEFAULT_UPDATE_TIME) secs after speech
-	 *  has begun of the file to allow the echo cancellor to estimate the
-	 *  channel accurately
-	 * Still needs conversion!
-	 */
-
-	if (pvt->start_speech_d != 0) {
-		if (pvt->i_d > (DEFAULT_T0 + pvt->start_speech_d)*(SAMPLE_FREQ)) {
-			pvt->beta2_d = max_cc_float(MIN_BETA, DEFAULT_BETA1 * exp((-1/DEFAULT_TAU)*((pvt->i_d/(float)SAMPLE_FREQ) - DEFAULT_T0 - pvt->start_speech_d)));
-		}
-	} else {
-		pvt->beta2_d = DEFAULT_BETA1;
-	}
-#endif
-  
-	/* Fixed point, inverted */
-	pvt->beta2_i = DEFAULT_BETA1_I;
-  
-	/* Fixed point version, inverted */
-	two_beta_i = (pvt->beta2_i * Py_i) >> 15;
-	if (!two_beta_i)
-		two_beta_i++;
-
-	/* Update the Suppressed signal power estimate accumulator */
-        /* ------------------------------------------------------- */
-        /* Delete the oldest sample from the power estimate accumulator */
-	pvt->Lu_i -= abs(get_cc_s(&pvt->u_s, (1 << DEFAULT_SIGMA_LU_I) - 1));
-        /* Add the new sample to the power estimate accumulator */
-	pvt->Lu_i += abs(u);
-
-	/* Update the Far-end reference signal power estimate accumulator */
-        /* -------------------------------------------------------------- */
-	/* eq. (10): update power estimate of the reference */
-        /* Delete the oldest sample from the power estimate accumulator */
-	pvt->Ly_i -= abs(get_cc_s(&pvt->y_s, (1 << DEFAULT_SIGMA_LY_I) - 1)) ;
-        /* Add the new sample to the power estimate accumulator */
-	pvt->Ly_i += abs(iref);
-
-	if (pvt->Ly_i < DEFAULT_CUTOFF_I)
-		pvt->Ly_i = DEFAULT_CUTOFF_I;
-
-
-	/* Update the Peak far-end receive signal detected */
-        /* ----------------------------------------------- */
-	if (pvt->y_tilde_i > pvt->max_y_tilde) {
-		/* New highest y_tilde with full life */
-		pvt->max_y_tilde = pvt->y_tilde_i;
-		pvt->max_y_tilde_pos = pvt->N_d - 1;
-	} else if (--pvt->max_y_tilde_pos < 0) {
-		/* Time to find new max y tilde... */
-		pvt->max_y_tilde = MAX16(pvt->y_tilde_s.buf_d + pvt->y_tilde_s.idx_d, pvt->N_d, &pvt->max_y_tilde_pos);
-	}
-
-	/* Determine if near end speech was detected in this sample */
-	/* -------------------------------------------------------- */
-	if (((pvt->s_tilde_i >> (DEFAULT_ALPHA_ST_I - 1)) > pvt->max_y_tilde)
-	    && (pvt->max_y_tilde > 0))  {
-		/* Then start the Hangover counter */
-		pvt->HCNTR_d = DEFAULT_HANGT;
-		RESTORE_COEFFS;
-#ifdef MEC2_STATS_DETAILED
-		printk(KERN_INFO "Reset near end speech timer with: s_tilde_i %d, stmnt %d, max_y_tilde %d\n", pvt->s_tilde_i, (pvt->s_tilde_i >> (DEFAULT_ALPHA_ST_I - 1)), pvt->max_y_tilde);
-#endif
-#ifdef MEC2_STATS
-		++pvt->cntr_nearend_speech_frames;
-#endif
-	} else if (pvt->HCNTR_d > (int)0) {
-  		/* otherwise, if it's still non-zero, decrement the Hangover counter by one sample */
-#ifdef MEC2_STATS
-		++pvt->cntr_nearend_speech_frames;
-#endif
-		pvt->HCNTR_d--;
-	} 
-
-	/* Update coefficients if no near-end speech in this sample (ie. HCNTR_d = 0)
-	 * and we have enough signal to bother trying to update.
-	 * --------------------------------------------------------------------------
-	 */
-	if (!pvt->HCNTR_d && 				/* no near-end speech present */
-	    !(pvt->i_d % DEFAULT_M)) {		/* we only update on every DEFAULM_M'th sample from the stream */
-		if (pvt->Lu_i > MIN_UPDATE_THRESH_I) {	/* there is sufficient energy above the noise floor to contain meaningful data */
-  							/* so loop over all the filter coefficients */
-#ifdef USED_COEFFS
-			int max_coeffs[USED_COEFFS];
-			int *pos;
-
-			if (pvt->N_d > USED_COEFFS)
-				memset(max_coeffs, 0, USED_COEFFS*sizeof(int));
-#endif
-#ifdef MEC2_STATS_DETAILED
-			printk(KERN_INFO "updating coefficients with: pvt->Lu_i %9d\n", pvt->Lu_i);
-#endif
-#ifdef MEC2_STATS
-			pvt->avg_Lu_i_ok = pvt->avg_Lu_i_ok + pvt->Lu_i;
-			++pvt->cntr_coeff_updates;
-#endif
-			for (k = 0; k < pvt->N_d; k++) {
-				/* eq. (7): compute an expectation over M_d samples */
-				int grad2;
-				grad2 = CONVOLVE2(pvt->u_s.buf_d + pvt->u_s.idx_d,
-						  pvt->y_s.buf_d + pvt->y_s.idx_d + k,
-						  DEFAULT_M);
-				/* eq. (7): update the coefficient */
-				pvt->a_i[k] += grad2 / two_beta_i;
-				pvt->a_s[k] = pvt->a_i[k] >> 16;
-
-#ifdef USED_COEFFS
-				if (pvt->N_d > USED_COEFFS) {
-					if (abs(pvt->a_i[k]) > max_coeffs[USED_COEFFS-1]) {
-						/* More or less insertion-sort... */
-						pos = max_coeffs;
-						while (*pos > abs(pvt->a_i[k]))
-							pos++;
-
-						if (*pos > max_coeffs[USED_COEFFS-1])
-							memmove(pos+1, pos, (USED_COEFFS-(pos-max_coeffs)-1)*sizeof(int));
-
-						*pos = abs(pvt->a_i[k]);
-					}
-				}
-#endif
-			}
-
-#ifdef USED_COEFFS
-			/* Filter out irrelevant coefficients */
-			if (pvt->N_d > USED_COEFFS)
-				for (k = 0; k < pvt->N_d; k++)
-					if (abs(pvt->a_i[k]) < max_coeffs[USED_COEFFS-1])
-						pvt->a_i[k] = pvt->a_s[k] = 0;
-#endif
-		} else {
-#ifdef MEC2_STATS_DETAILED
-			printk(KERN_INFO "insufficient signal to update coefficients pvt->Lu_i %5d < %5d\n", pvt->Lu_i, MIN_UPDATE_THRESH_I);
-#endif
-#ifdef MEC2_STATS
-			pvt->avg_Lu_i_toolow = pvt->avg_Lu_i_toolow + pvt->Lu_i;
-			++pvt->cntr_coeff_missedupdates;
-#endif
-		}
-	}
-  
-	/* paragraph below eq. (15): if no near-end speech in the sample and 
-	 * the reference signal power estimate > cutoff threshold
-	 * then perform residual error suppression
-	 */
-#ifdef MEC2_STATS_DETAILED
-	if (pvt->HCNTR_d == 0)
-		printk(KERN_INFO "possibly correcting frame with pvt->Ly_i %9d pvt->Lu_i %9d and expression %d\n", pvt->Ly_i, pvt->Lu_i, (pvt->Ly_i/(pvt->Lu_i + 1)));
-#endif
-
-#ifndef NO_ECHO_SUPPRESSOR
-	if (pvt->use_nlp) {
-		if (pvt->aggressive) {
-			if ((pvt->HCNTR_d < AGGRESSIVE_HCNTR) && (pvt->Ly_i > (pvt->Lu_i << 1))) {
-				for (k = 0; k < 2; k++) {
-					u = u * (pvt->Lu_i >> DEFAULT_SIGMA_LU_I) / ((pvt->Ly_i >> (DEFAULT_SIGMA_LY_I)) + 1);
-				}
-#ifdef MEC2_STATS_DETAILED
-				printk(KERN_INFO "aggresively correcting frame with pvt->Ly_i %9d pvt->Lu_i %9d expression %d\n", pvt->Ly_i, pvt->Lu_i, (pvt->Ly_i/(pvt->Lu_i + 1)));
-#endif
-#ifdef MEC2_STATS
-				++pvt->cntr_residualcorrected_frames;
-#endif
-			}
-		} else {
-			if (pvt->HCNTR_d == 0) {
-				if ((pvt->Ly_i/(pvt->Lu_i + 1)) > DEFAULT_SUPPR_I) {
-					for (k = 0; k < 1; k++) {
-						u = u * (pvt->Lu_i >> DEFAULT_SIGMA_LU_I) / ((pvt->Ly_i >> (DEFAULT_SIGMA_LY_I + 2)) + 1);
-					}
-#ifdef MEC2_STATS_DETAILED
-					printk(KERN_INFO "correcting frame with pvt->Ly_i %9d pvt->Lu_i %9d expression %d\n", pvt->Ly_i, pvt->Lu_i, (pvt->Ly_i/(pvt->Lu_i + 1)));
-#endif
-#ifdef MEC2_STATS
-					++pvt->cntr_residualcorrected_frames;
-#endif
-				}
-#ifdef MEC2_STATS
-				else {
-					++pvt->cntr_residualcorrected_framesskipped;
-				}
-#endif
-			}
-		}
-	}
-#endif  
-
-#if 0
-	/* This will generate a non-linear supression factor, once converted */
-	if ((pvt->HCNTR_d == 0) &&
-		((pvt->Lu_d/pvt->Ly_d) < DEFAULT_SUPPR) &&
-		(pvt->Lu_d/pvt->Ly_d > EC_MIN_DB_VALUE)) {
-		suppr_factor = (10 / (float)(SUPPR_FLOOR - SUPPR_CEIL)) * log(pvt->Lu_d/pvt->Ly_d)
-			- SUPPR_CEIL / (float)(SUPPR_FLOOR - SUPPR_CEIL);
-		u_suppr = pow(10.0, (suppr_factor) * RES_SUPR_FACTOR / 10.0) * u_suppr;
-	}
-#endif  
-
-#ifdef MEC2_STATS
-	/* Periodically dump performance stats */
-	if ((pvt->i_d % MEC2_STATS) == 0) {
-		/* make sure to avoid div0's! */
-		if (pvt->cntr_coeff_missedupdates > 0)
-			pvt->avg_Lu_i_toolow = (int)(pvt->avg_Lu_i_toolow / pvt->cntr_coeff_missedupdates);
-		else
-			pvt->avg_Lu_i_toolow = -1;
-
-		if (pvt->cntr_coeff_updates > 0)
-			pvt->avg_Lu_i_ok = (pvt->avg_Lu_i_ok / pvt->cntr_coeff_updates);
-		else
-			pvt->avg_Lu_i_ok = -1;
-
-		printk(KERN_INFO "%d: Near end speech: %5d Residuals corrected/skipped: %5d/%5d Coefficients updated ok/low sig: %3d/%3d Lu_i avg ok/low sig %6d/%5d\n", 
-		       pvt->id,
-		       pvt->cntr_nearend_speech_frames,
-		       pvt->cntr_residualcorrected_frames, pvt->cntr_residualcorrected_framesskipped,
-		       pvt->cntr_coeff_updates, pvt->cntr_coeff_missedupdates,
-		       pvt->avg_Lu_i_ok, pvt->avg_Lu_i_toolow);
-
-		pvt->cntr_nearend_speech_frames = 0;
-		pvt->cntr_residualcorrected_frames = 0;
-		pvt->cntr_residualcorrected_framesskipped = 0;
-		pvt->cntr_coeff_updates = 0;
-		pvt->cntr_coeff_missedupdates = 0;
-		pvt->avg_Lu_i_ok = 0;
-		pvt->avg_Lu_i_toolow = 0;
-	}
-#endif
-
-	/* Increment the sample index and return the corrected sample */
-	pvt->i_d++;
-	return u;
-}
-
-static void echo_can_process(struct dahdi_echocan_state *ec, short *isig, const short *iref, u32 size)
-{
-	struct ec_pvt *pvt = dahdi_to_pvt(ec);
-	u32 x;
-	short result;
-
-	for (x = 0; x < size; x++) {
-		result = sample_update(pvt, *iref, *isig);
-		*isig++ = result;
-		++iref;
-	}
-}
-
-static int echo_can_create(struct dahdi_chan *chan, struct dahdi_echocanparams *ecp,
-			   struct dahdi_echocanparam *p, struct dahdi_echocan_state **ec)
-{
-	int maxy;
-	int maxu;
-	size_t size;
-	unsigned int x;
-	char *c;
-	struct ec_pvt *pvt;
-
-	maxy = ecp->tap_length + DEFAULT_M;
-	maxu = DEFAULT_M;
-	if (maxy < (1 << DEFAULT_ALPHA_YT_I))
-		maxy = (1 << DEFAULT_ALPHA_YT_I);
-	if (maxy < (1 << DEFAULT_SIGMA_LY_I))
-		maxy = (1 << DEFAULT_SIGMA_LY_I);
-	if (maxu < (1 << DEFAULT_SIGMA_LU_I))
-		maxu = (1 << DEFAULT_SIGMA_LU_I);
-	size = sizeof(**ec) +
-		4 + 						/* align */
-		sizeof(int) * ecp->tap_length +			/* a_i */
-		sizeof(short) * ecp->tap_length + 		/* a_s */
-		sizeof(int) * ecp->tap_length +			/* b_i */
-		sizeof(int) * ecp->tap_length +			/* c_i */
-		2 * sizeof(short) * (maxy) +			/* y_s */
-		2 * sizeof(short) * (1 << DEFAULT_ALPHA_ST_I) + /* s_s */
-		2 * sizeof(short) * (maxu) +			/* u_s */
-		2 * sizeof(short) * ecp->tap_length;		/* y_tilde_s */
-
-	pvt = kzalloc(size, GFP_KERNEL);
-	if (!pvt)
-		return -ENOMEM;
-
-	pvt->dahdi.ops = &my_ops;
-
-	pvt->aggressive = aggressive;
-	pvt->dahdi.features = my_features;
-
-	for (x = 0; x < ecp->param_count; x++) {
-		for (c = p[x].name; *c; c++)
-			*c = tolower(*c);
-		if (!strcmp(p[x].name, "aggressive")) {
-			pvt->aggressive = p[x].value ? 1 : 0;
-		} else {
-			printk(KERN_WARNING "Unknown parameter supplied to MG2 echo canceler: '%s'\n", p[x].name);
-			kfree(pvt);
-
-			return -EINVAL;
-		}
-	}
-
-	init_cc(pvt, ecp->tap_length, maxy, maxu);
-	/* Non-linear processor - a fancy way to say "zap small signals, to avoid
-	   accumulating noise". */
-	pvt->use_nlp = TRUE;
-
-	*ec = &pvt->dahdi;
-	return 0;
-}
-
-static int echo_can_traintap(struct dahdi_echocan_state *ec, int pos, short val)
-{
-	struct ec_pvt *pvt = dahdi_to_pvt(ec);
-
-	/* Set the hangover counter to the length of the can to 
-	 * avoid adjustments occuring immediately after initial forced training 
-	 */
-	pvt->HCNTR_d = pvt->N_d << 1;
-
-	if (pos >= pvt->N_d) {
-		memcpy(pvt->b_i, pvt->a_i, pvt->N_d*sizeof(int));
-		memcpy(pvt->c_i, pvt->a_i, pvt->N_d*sizeof(int));
-		return 1;
-	}
-
-	pvt->a_i[pos] = val << 17;
-	pvt->a_s[pos] = val << 1;
-
-	if (++pos >= pvt->N_d) {
-		memcpy(pvt->b_i, pvt->a_i, pvt->N_d*sizeof(int));
-		memcpy(pvt->c_i, pvt->a_i, pvt->N_d*sizeof(int));
-		return 1;
-	}
-
-	return 0;
-}
-
-static void echocan_NLP_toggle(struct dahdi_echocan_state *ec, unsigned int enable)
-{
-	struct ec_pvt *pvt = dahdi_to_pvt(ec);
-
-	pvt->use_nlp = enable ? 1 : 0;
-}
-
-static int __init mod_init(void)
-{
-	if (dahdi_register_echocan_factory(&my_factory)) {
-		module_printk(KERN_ERR, "could not register with DAHDI core\n");
-
-		return -EPERM;
-	}
-
-	module_printk(KERN_NOTICE, "Registered echo canceler '%s'\n",
-		      my_factory.get_name(NULL));
-
-	return 0;
-}
-
-static void __exit mod_exit(void)
-{
-	dahdi_unregister_echocan_factory(&my_factory);
-}
-
-module_param(debug, int, S_IRUGO | S_IWUSR);
-module_param(aggressive, int, S_IRUGO | S_IWUSR);
-
-MODULE_DESCRIPTION("DAHDI 'MG2' Echo Canceler");
-MODULE_AUTHOR("Michael Gernoth");
-MODULE_LICENSE("GPL v2");
-
-module_init(mod_init);
-module_exit(mod_exit);