ComposerDesktopProject/dev/filter/filters0.c

/*
 * Copyright (c) 1983-2023 Trevor Wishart and Composers Desktop Project Ltd
 * http://www.trevorwishart.co.uk
 * http://www.composersdesktop.com
 *
 This file is part of the CDP System.

    The CDP System is free software; you can redistribute it
    and/or modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    The CDP System 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with the CDP System; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA
 *
 */

/* floatsams version*/
#include <stdio.h>
#include <stdlib.h>
#include <structures.h>
#include <tkglobals.h>
#include <globcon.h>
#include <processno.h>
#include <modeno.h>
#include <arrays.h>
#include <filters.h>
#include <cdpmain.h>
#include <sfsys.h>
/*RWD*/
#include <string.h>

#ifndef cdp_round
extern int cdp_round(double a);
#endif

#if defined unix || defined __GNUC__
#define round(x) lround((x))
#endif

#define MINUS96DB (0.000016)

static void     filtering(int n,int chans,float *buf,
                    double *a,double *b,double *y,double *z,double *d,double *e,double *ampl,dataptr dz);
static double   check_float_limits(double sum, dataptr dz);
static int      newvalue(int valno,int valincrno, int sampcntno, dataptr dz);
static int      newfval(int *fsams,dataptr dz);
static int      do_filters(dataptr dz);
static int      do_qvary_filters(dataptr dz);
static int      do_fvary_filters(dataptr dz);
static void     print_filter_frqs(dataptr dz);
static int      do_varifilter(dataptr dz);
static int      do_sweep_filter(dataptr dz);
static double   getfrq(double lfrq,double hfrq,double sfrq,dataptr dz);
static int      do_allpass_filter(dataptr dz);
static int      allpass(float *buf,int chans,double prescale,dataptr dz);
static int      varidelay_allpass(float *buf,int chans,double prescale,dataptr dz);
static int      do_eq_filter(dataptr dz);
static float    multifilter(double *dll,double *dbb,double *dnn,double *dhh,double *dpp,
                    double qfac,double coeff,float input,dataptr dz);
static int      do_lphp_filter(dataptr dz);
static int     my_modulus(int x,int y);
static void lphp_filt_chan(double *e1,double *e2,double *s1,double *s2,
                    double *den1,double *den2,double *cn,dataptr dz,int chan);

static int      do_fvary2_filters(dataptr dz);

/****************************** FILTER_PROCESS *************************/

int filter_process(dataptr dz)
{
    int exit_status = FINISHED;
    int filter_tail = 0, tail_extend = 0, was_tail_extend = 0, bufspace;
// NEW MAY 2012
    int do_norm = 0, chans = dz->infile->channels, sndendset = 0;
    double inmaxsamp = 0.0, outmaxsamp = 0.0, maxsamp = 0.0;
    float *buf = dz->sampbuf[0];
    int n, m, k, sndend = 0;
    int framend, framestart, framesize = F_SECSIZE, framecnt = dz->buflen/framesize;
    switch(dz->process) {
    case(FLTBANKV):
        if(dz->vflag[2])
            do_norm = 1;
        break;
    case(FLTBANKV2):
        if(dz->vflag[1])
            do_norm = 1;
        break;
    case(FLTBANKN):
        do_norm = 1;
        break;
    }
// MAY 2012 TO HERE
    
    if(dz->process==FLTBANKC) {
        print_filter_frqs(dz);
        return(FINISHED);
    }
    display_virtual_time(0,dz);

// NEW MAY 2012
    if(do_norm) {
        fprintf(stdout,"INFO: Assessing input level.\n");
        fflush(stdout);
        while(dz->samps_left > 0) {
            if((exit_status = read_samps(buf,dz))<0)
                return(exit_status);
            for(n = 0;n < dz->ssampsread;n++)
                inmaxsamp = max(inmaxsamp,fabs(buf[n]));
        }
        if(inmaxsamp <= 0.0) {
            sprintf(errstr,"No level found in input signal\n");
            return DATA_ERROR;
        }
        sndseekEx(dz->ifd[0],0,0);
        reset_filedata_counters(dz);
        if(dz->process==FLTBANKV) {
            if((exit_status = newfval(&(dz->iparam[FLT_FSAMS]),dz))<0)
                return(exit_status);
        } else if(dz->process==FLTBANKV2) {
            dz->iparam[FLT_FSAMS] = dz->iparam[FLT_BLOKSIZE];
            dz->param[FLT_TIMESTEP] = (double)dz->iparam[FLT_BLOKSIZE]/(double)dz->infile->srate;
            dz->param[FLT_TOTALTIME] = 0.0;
            if((exit_status = newfval2(dz->parray[FLT_FBRK],dz->parray[FLT_HBRK],dz))<0)
                return(exit_status);
        } else if(dz->process==FLTBANKN) {
            if(dz->brksize[FLT_Q])
                exit_status = do_qvary_filters(dz);
            else
                exit_status = do_filters(dz);
        }
        fprintf(stdout,"INFO: Assessing output level.\n");
        fflush(stdout);
        while(dz->samps_left > 0 || filter_tail > 0) {
            memset((char *)dz->sampbuf[0],0,(size_t) (dz->buflen * sizeof(float)));
            if(filter_tail || tail_extend) {
                dz->ssampsread = 0;
            } else {
                if((exit_status = read_samps(dz->sampbuf[0],dz))<0)
                    return(exit_status);
                if(dz->samps_left <= 0) {
                    if(dz->process==FLTBANKV || dz->process==FLTBANKV2)
                        filter_tail = round(dz->param[FILT_TAILV] * (double)dz->infile->srate) * dz->infile->channels;
                    else 
                        filter_tail = (int)round((dz->param[FILT_TAIL] * (double)dz->infile->srate) * dz->infile->channels);
                    if(filter_tail == 0) {
                        was_tail_extend = 1;
                        tail_extend = 1;
                    }
                }
            }
            if(filter_tail) {
                bufspace = dz->buflen - dz->ssampsread;
                if(bufspace >= filter_tail) {
                    dz->ssampsread += filter_tail;
                    filter_tail = 0;
                } else {
                    dz->ssampsread = dz->buflen;
                    filter_tail -= bufspace;
                }
            } else if(tail_extend) {
                bufspace = dz->buflen;
                dz->ssampsread = dz->buflen;
            }
            switch(dz->process) {
            case(FLTBANKV): exit_status = do_fvary_filters(dz);     break;
            case(FLTBANKV2):exit_status = do_fvary2_filters(dz);    break;
            case(FLTBANKN):
                if(dz->brksize[FLT_Q])  
                    exit_status = do_qvary_filters(dz);
                else
                    exit_status = do_filters(dz);
                break;
            }
            if(exit_status <0)
                return(exit_status);
            if(tail_extend) {
                sndend = dz->buflen;
                framend = dz->buflen;
                for(k = framecnt; k > 0; k--) {                 //  Search backwards thro buffer, frame by frame
                    framestart = framend - framesize;
                    maxsamp = 0.0;
                    for(n = framend-chans;n >= framestart;n-=chans) {   
                        for(m=0;m<chans;m++) {                  //  Search backwards thro frame, samp-grup by samp-group
                            if(fabs(buf[n+m]) > maxsamp) {
                                if(!sndendset) {                //  If samples cease to be zero
                                    sndend = n + chans;         //  Mark start of end-zeros in buffer
                                    sndendset = 1;              //  and flag that snd end has been found
                                }
                                maxsamp = fabs(buf[n+m]);
                            }
                        }
                        if(maxsamp < MINUS96DB) {               //  If max level in frame falls below -96dB
                            if(sndendset) {                     //  If we found a place in buffer after which samples were all zero
                                dz->ssampsread = sndend;        //  Mark this as end of output, and quit the main filtering loop
                                tail_extend = 0;                //  by setting tail_extend to zero
                                dz->samps_left = 0; // SAFETY   
                                break;
                            } else                              //  If we didn't find place ....    
                                sndend = framestart;            //  Then all samples in the frame are zero.
                        }                                       //  So move snd end to start of current frame.
                    }                                           //  .. and search backwards thro previous frame
                    if(tail_extend == 0)
                        break;
                    framend = framestart;
                }
            }
            if(tail_extend)
                tail_extend++;
            if(dz->ssampsread > 0) {
                for(n = 0;n < dz->ssampsread;n++)
                    outmaxsamp = max(outmaxsamp,(double)fabs(buf[n]));
            }
        }
        if(outmaxsamp <= 0.0) {
            sprintf(errstr,"No level found in output signal.\n");
            return DATA_ERROR;
        }

        dz->param[FLT_GAIN] *= (inmaxsamp/outmaxsamp);

        sndseekEx(dz->ifd[0],0,0);
        reset_filedata_counters(dz);
        if(dz->process==FLTBANKV || dz->process==FLTBANKV2) {
            for(n = 0;n<dz->iparam[FLT_CNT];n++) {
                dz->parray[FLT_FRQ][n]      = dz->parray[FLT_INFRQ][n];
                dz->parray[FLT_AMP][n]      = dz->parray[FLT_INAMP][n];
                dz->parray[FLT_LASTFVAL][n] = dz->parray[FLT_FRQ][n];
                dz->parray[FLT_LASTAVAL][n] = dz->parray[FLT_AMP][n];
            }
        }
        dz->iparam[FLT_FRQ_INDEX] = dz->iparam[FLT_CNT];
        dz->iparam[FLT_TIMES_CNT] = 1;
        filter_tail = 0;
        tail_extend = 0;
        sndendset   = 0;
        sndend      = 0;
        tail_extend = 0;
        was_tail_extend = 0;
        fprintf(stdout,"INFO: Running filter.\n");
        fflush(stdout);
    }
// MAY 2012, TO HERE
    if(dz->process==FLTBANKV) {
        if((exit_status = newfval(&(dz->iparam[FLT_FSAMS]),dz))<0)
            return(exit_status);
    } else  if(dz->process==FLTBANKV2) {
        dz->iparam[FLT_FSAMS] = dz->iparam[FLT_BLOKSIZE];
        dz->param[FLT_TIMESTEP] = (double)dz->iparam[FLT_BLOKSIZE]/(double)dz->infile->srate;
        dz->param[FLT_TOTALTIME] = 0.0;
        if((exit_status = newfval2(dz->parray[FLT_FBRK],dz->parray[FLT_HBRK],dz))<0)
            return(exit_status);
    }
    while(dz->samps_left > 0 || filter_tail > 0 || tail_extend) {
        memset((char *)dz->sampbuf[0],0,(size_t) (dz->buflen * sizeof(float)));
        if(filter_tail > 0 || tail_extend) {
            dz->ssampsread = 0;
        } else {
            if((exit_status = read_samps(dz->sampbuf[0],dz))<0)
                return(exit_status);
            if(dz->samps_left <= 0) {
                if(dz->process==FLTBANKV || dz->process==FLTBANKV2)
                    filter_tail = round(dz->param[FILT_TAILV] * (double)dz->infile->srate) * dz->infile->channels;
                else
                    filter_tail = (int)round((dz->param[FILT_TAIL] * (double)dz->infile->srate) * dz->infile->channels);
                if(filter_tail == 0) {
                    was_tail_extend = 1;
                    tail_extend = 1;
                    fprintf(stdout,"INFO: Writing Filter tail.\n");
                    fflush(stdout);
                }
            }
        }
        if(filter_tail) {
            bufspace = dz->buflen - dz->ssampsread;
            if(bufspace >= filter_tail) {
                dz->ssampsread += filter_tail;
                filter_tail = 0;
            } else {
                dz->ssampsread = dz->buflen;
                filter_tail -= bufspace;
            }
        } else if(tail_extend) {
            bufspace = dz->buflen;
            dz->ssampsread = dz->buflen;
        }
        switch(dz->process) {
        case(FLTBANKN):
        case(FLTBANKU):
            if(dz->brksize[FLT_Q])  
                exit_status = do_qvary_filters(dz);
            else
                exit_status = do_filters(dz);
            break;
        case(FLTBANKV): exit_status = do_fvary_filters(dz);     break;
        case(FLTBANKV2):exit_status = do_fvary2_filters(dz);    break;
        case(FLTSWEEP): exit_status = do_sweep_filter(dz);      break;
        case(FSTATVAR): exit_status = do_varifilter(dz);        break;
        case(ALLPASS):  exit_status = do_allpass_filter(dz);    break;
        case(EQ):       exit_status = do_eq_filter(dz);         break;
        case(LPHP):     exit_status = do_lphp_filter(dz);       break;
        }
        if(exit_status <0)
            return(exit_status);
        if(tail_extend) {
            sndend = dz->buflen;
            framend = dz->buflen;
            for(k = framecnt; k > 0; k--) {                 //  Search backwards thro buffer, frame by frame
                framestart = framend - framesize;
                maxsamp = 0.0;
                for(n = framend-chans;n >= framestart;n-=chans) {   
                    for(m=0;m<chans;m++) {                  //  Search backwards thro frame, samp-grup by samp-group
                        if(fabs(buf[n+m]) > maxsamp) {
                            if(!sndendset) {                //  If samples cease to be zero
                                sndend = n + chans;         //  Mark start of end-zeros in buffer
                                sndendset = 1;              //  and flag that snd end has been found
                            }
                            maxsamp = fabs(buf[n+m]);
                        }
                    }
                    if(maxsamp < MINUS96DB) {               //  If max level in frame falls below -96dB
                        if(sndendset) {                     //  If we found a place in buffer after which samples were all zero
                            dz->ssampsread = sndend;        //  Mark this as end of output, and quit the main filtering loop
                            tail_extend = 0;                //  by setting tail_extend to zero
                            dz->samps_left = 0; // SAFETY   
                            break;
                        } else                              //  If we didn't find place ....
                            sndend = framestart;            //  Then all samples in the frame are zero.
                    }                                       //  So move snd end to start of current frame.
                }                                           //  .. and search backwards thro previous frame

                if(tail_extend == 0)
                    break;
                framend = framestart;
            }
            if((maxsamp < MINUS96DB) && !sndendset) {       //  Entire buffer is "zero"
                tail_extend = 0;                            //  Force exit by seting tail_extend to zero
                dz->samps_left = 0; // SAFETY               //  DO NOT set samps_read to 0, as there may be input samples still to write
            }
        }
        if(tail_extend)
            tail_extend++;
        if(dz->ssampsread > 0) {
            if(sloom && was_tail_extend) {                  //  Force Loom progress bar to respond to tail-write
                if(!tail_extend)
                    dz->total_samps_written = dz->insams[0];
                else
                    dz->total_samps_written = (long)round((double)dz->insams[0] * ((double)(tail_extend % 8)/8.0));
                dz->total_samps_written -= dz->ssampsread;
            }
            if((exit_status = write_samps(dz->sampbuf[0],dz->ssampsread,dz))<0)
                return(exit_status);
        }
    }               
    if(dz->iparam[FLT_OVFLW] > 0)  {
        if(!sloom && !sloombatch)
            fprintf(stdout,"Number of overflows: %d\n",dz->iparam[FLT_OVFLW]);
        else
            fprintf(stdout,"INFO: Number of overflows: %d\n",dz->iparam[FLT_OVFLW]);
        fflush(stdout);
    }
    return(FINISHED);
}

/*************************** DO_FVARY_FILTERS *****************************/

int do_fvary_filters(dataptr dz)
{
    int exit_status;
    int    n, m, fno, chans = dz->infile->channels;
    float *buf = dz->sampbuf[0];

    double *fincr = dz->parray[FLT_FINCR];
    double *aincr = dz->parray[FLT_AINCR];
 
    double *ampl = dz->parray[FLT_AMPL];
    double *a = dz->parray[FLT_A];
    double *b = dz->parray[FLT_B];
    double *y = dz->parray[FLT_Y];
    double *z = dz->parray[FLT_Z];
    double *d = dz->parray[FLT_D];
    double *e = dz->parray[FLT_E];
    int fsams = dz->iparam[FLT_FSAMS];
    if (dz->vflag[DROP_OUT_AT_OVFLOW]) {
        for (n = 0; n < dz->ssampsread; n += chans) { 
            if(fsams <= 0) {
                if((exit_status = newfval(&fsams,dz))<0)
                    return(exit_status);
            }
            if(dz->brksize[FLT_Q]) {
                if((dz->iparam[FLT_SAMS] -= chans) <= 0) {
                    if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) {
                        sprintf(errstr,"Ran out of Q values: do_fvary_filters()\n");
                        return(PROGRAM_ERROR);
                    }
                    dz->iparam[FLT_SAMS] *= chans;
                }
            }
            if((dz->iparam[FLT_BLOKCNT] -= chans) <= 0) {
                for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++) {
                    get_coeffs1(fno,dz);
                    get_coeffs2(fno,dz);
                }
                if(dz->brksize[FLT_Q])
                    dz->param[FLT_Q] *= dz->param[FLT_Q_INCR];
                
                for(m=0;m<dz->iparam[FLT_CNT];m++) {
                    dz->parray[FLT_FRQ][m] *= fincr[m];
                    dz->parray[FLT_AMP][m] *= aincr[m];
                }
                dz->iparam[FLT_BLOKCNT] = dz->iparam[FLT_BLOKSIZE] * chans;
            }
            filtering(n,chans,buf,a,b,y,z,d,e,ampl,dz);
            if(dz->iparam[FLT_OVFLW] > 0) {
                sprintf(errstr,"Filter overflowed\n");
                return(GOAL_FAILED);
            }
            fsams--;
        }
    } else {
        for (n = 0; n < dz->ssampsread; n += chans) {
            if(fsams <= 0) {
                if((exit_status = newfval(&fsams,dz))<0)
                    return(exit_status);
            }
            if(dz->brksize[FLT_Q]) {
                if((dz->iparam[FLT_SAMS] -= chans) <= 0) {
                    if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) {
                        sprintf(errstr,"Ran out of Q values: do_fvary_filters()\n");
                        return(PROGRAM_ERROR);
                    }
                    dz->iparam[FLT_SAMS] *= chans;
                }
            }
            if((dz->iparam[FLT_BLOKCNT] -= chans) <= 0) {
                for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++) {
                    get_coeffs1(fno,dz);
                    get_coeffs2(fno,dz);
                }
                if(dz->brksize[FLT_Q])
                    dz->param[FLT_Q] *= dz->param[FLT_Q_INCR];

                for(m=0;m<dz->iparam[FLT_CNT];m++) {
                    dz->parray[FLT_FRQ][m] *= fincr[m];
                    dz->parray[FLT_AMP][m] *= aincr[m];
                }
                dz->iparam[FLT_BLOKCNT] = dz->iparam[FLT_BLOKSIZE] * chans;
            }
            filtering(n,chans,buf,a,b,y,z,d,e,ampl,dz);
            fsams--;
        }
    }
    dz->iparam[FLT_FSAMS] = fsams;
    return(CONTINUE);
}

/*************************** DO_FILTERS *******************************/

int do_filters(dataptr dz)
{
    int n;
    int  chans = dz->infile->channels;
    float *buf = dz->sampbuf[0];
    double *ampl = dz->parray[FLT_AMPL];
    double *a = dz->parray[FLT_A];
    double *b = dz->parray[FLT_B];
    double *y = dz->parray[FLT_Y];
    double *z = dz->parray[FLT_Z];
    double *d = dz->parray[FLT_D];
    double *e = dz->parray[FLT_E];
    for (n = 0; n < dz->ssampsread; n += chans)
        filtering(n,chans,buf,a,b,y,z,d,e,ampl,dz);
    return(CONTINUE);
}

/*************************** DO_QVARY_FILTERS *****************************/

int do_qvary_filters(dataptr dz)
{
    int   n;
    int    fno, chans = dz->infile->channels;
    float *buf = dz->sampbuf[0];
    double *ampl = dz->parray[FLT_AMPL];
    double *a = dz->parray[FLT_A];
    double *b = dz->parray[FLT_B];
    double *y = dz->parray[FLT_Y];
    double *z = dz->parray[FLT_Z];
    double *d = dz->parray[FLT_D];
    double *e = dz->parray[FLT_E];

    for (n = 0; n < dz->ssampsread; n += chans) { 
        if((dz->iparam[FLT_SAMS] -= chans) <= 0) {
            if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) {
                sprintf(errstr,"Ran out of Q values: do_qvary_filters()\n");
                return(PROGRAM_ERROR);
            }
            dz->iparam[FLT_SAMS] *= chans;
        }
        if((dz->iparam[FLT_BLOKCNT] -= chans) <= 0) {
            for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++)
                get_coeffs2(fno,dz);
            dz->param[FLT_Q] *= dz->param[FLT_Q_INCR];
            dz->iparam[FLT_BLOKCNT] = dz->iparam[FLT_BLOKSIZE] * chans;
        }
        filtering(n,chans,buf,a,b,y,z,d,e,ampl,dz);
    }
    return(CONTINUE);
}

/******************************* NEWVALUE ***************************
 *
 * VAL     is the base value from which we calculate.
 * VALINCR is the value increment per block of samples.
 * SAMPCNT is the number of samples from 1 brkpnt val to next.
 */                    

int newvalue(int valno,int valincrno, int sampcntno, dataptr dz)
{
    double *p;
    double ratio, one_over_steps;
    double thistime;
    double thisval;
    int    linear_flag = FALSE;
    if(dz->process==ALLPASS && valno==FLT_DELAY)
        linear_flag = dz->vflag[FLT_LINDELAY];
    p = dz->brkptr[valno];
    if(p - dz->brk[valno] >= dz->brksize[valno] * 2)
        return(FALSE);
    thistime = (double)round((*p++) * dz->infile->srate);
    thisval  = *p++;
    dz->iparam[sampcntno]    = round(thistime - dz->lastind[valno]);
    /* steps = no_of_samples/sampsize_of_blok: therefore.. */
    one_over_steps = (double)dz->iparam[FLT_BLOKSIZE]/(double)dz->iparam[sampcntno];
    if(linear_flag)
        dz->param[valincrno] = (thisval - dz->lastval[valno]) * one_over_steps;
    else {
        ratio                = (thisval/dz->lastval[valno]);
        dz->param[valincrno] = pow(ratio,(one_over_steps));
    }
    dz->param[valno]     = dz->lastval[valno];
    dz->lastval[valno]   = thisval;
    dz->lastind[valno]   = thistime;
    dz->brkptr[valno]    = p;
    return(TRUE);
}

/******************************* NEWFVAL ***************************
 *
 * VAL is the base value from which we calculate.
 * VALINCR is the value increment per block of samples.
 * FSAMS is the number of samples (per channel) from 1 brkpnt val to next.
 * brk is the particular table we're accessing.
 */

int newfval(int *fsams,dataptr dz)
{
    int   thistime, lasttime;
    double rratio, one_over_steps;
    int   n,m,k;
    double thisval;
    double *lastfval = dz->parray[FLT_LASTFVAL];
    double *lastaval = dz->parray[FLT_LASTAVAL];
    double *aincr    = dz->parray[FLT_AINCR];
    double *fincr    = dz->parray[FLT_FINCR];
    int total_frqcnt = dz->iparam[FLT_CNT] * dz->iparam[FLT_TIMESLOTS];
    
    if(dz->iparam[FLT_TIMES_CNT]>dz->iparam[FLT_TIMESLOTS]) {
        sprintf(errstr,"Ran off end of filter data: newfval()\n");
        return(PROGRAM_ERROR);
    }
    k = dz->iparam[FLT_TIMES_CNT];
    lasttime  = dz->lparray[FLT_SAMPTIME][k-1];
    thistime  = dz->lparray[FLT_SAMPTIME][k];
    *fsams = thistime - lasttime;
    /* steps  = fsams/FLT_BLOKSIZE: therefore ... */
    one_over_steps  = (double)dz->iparam[FLT_BLOKSIZE]/(double)(*fsams);
    if(dz->iparam[FLT_FRQ_INDEX] >= total_frqcnt)
        return(FINISHED);
    for(n=0, m= dz->iparam[FLT_FRQ_INDEX];n<dz->iparam[FLT_CNT];n++,m++) {
    /* FREQUENCY */
        thisval = dz->parray[FLT_INFRQ][m];
        if(flteq(lastfval[n],thisval))
            fincr[n] = 1.0;
        else {
            rratio = (thisval/lastfval[n]);
            fincr[n] = pow(rratio,one_over_steps);
        }
        dz->parray[FLT_FRQ][n] = lastfval[n];
        lastfval[n] = thisval;
    /* AMPLITUDE */
        thisval = dz->parray[FLT_INAMP][m];
        if(flteq(thisval,lastaval[n]))
            aincr[n] = 1.0;
        else {
            rratio = (thisval/lastaval[n]);
            aincr[n] = pow(rratio,one_over_steps);
        }
        dz->parray[FLT_AMP][n] = lastaval[n];
        lastaval[n] = thisval;
    }
    dz->iparam[FLT_FRQ_INDEX] += dz->iparam[FLT_CNT];
    dz->iparam[FLT_TIMES_CNT]++;
    return(FINISHED);
}

/************************** FILTERING ****************************/

void filtering(int n,int chans,float *buf,double *a,double *b,double *y,double *z,
                double *d,double *e,double *ampl,dataptr dz)
{
    double input, sum, xx;
    int chno, this_samp, fno, i;

    for(chno = 0; chno < chans; chno++) {
        this_samp = n + chno;
        input = (double)buf[this_samp];
        sum   = 0.0;
        for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++) {
            i    = (fno * chans) + chno;
            xx   = input + (a[fno] * y[i]) + (b[fno] * z[i]);
            z[i] = y[i];
            y[i] = xx;
            if(dz->vflag[FLT_DBLFILT]) {
                xx   += (a[fno] * d[i]) + (b[fno] * e[i]);
                e[i] = d[i];
                d[i] = xx;
            }
            sum += (xx * ampl[fno]);
        }
        sum *= dz->param[FLT_GAIN];
        sum = check_float_limits(sum,dz);
        buf[this_samp] = (float) sum;
    }
}

/************************** IO_FILTERING ****************************/

void io_filtering
(float *buf1,float *buf2,int chans,int n,
double *a,double *b,double *y,double *z,double *d,double *z1,double *ampl,dataptr dz)
{
    double input, sum, xx;
    int    chno, this_samp, fno, i;
    for(chno = 0; chno < chans; chno++) {
        this_samp = n + chno;
        input = (double)buf1[this_samp];
        sum   = 0.0;
        for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++) {
            i    = (fno * chans) + chno;
            xx   = input + (a[fno] * y[i]) + (b[fno] * z[i]);
            z[i] = y[i];
            y[i] = xx;
            if(dz->vflag[FLT_DBLFILT]) {
                xx   += (a[fno] * d[i]) + (b[fno] * z1[i]);
                z1[i] = d[i];
                d[i] = xx;
            }
            sum += (xx * ampl[fno]);
        }
        sum *= dz->param[FLT_GAIN];
        sum = check_float_limits(sum,dz);
        buf2[this_samp] = (float) sum;
    }
}

/************************ CHECK_FLOAT_LIMITS **************************/

//TODO: if shorts o/p - do clipping; if floatsams, report but don't change!
double check_float_limits(double sum,dataptr dz)
{
    double peak = fabs(sum);
#ifdef NOTDEF
    //do this when 'modify loudness' can handle floatsams!
    if(dz->true_outfile_stype== SAMP_FLOAT){
        
        if(peak > 1.0){
            dz->iparam[FLT_OVFLW]++;
            dz->peak_fval = max(dz->peak_fval,peak);
        }       
    }
    else {
#endif
        if (sum > 1.0) {
//TW SUGGEST KEEP THIS; prevents FILTER BLOWING UP: see notes
            dz->param[FLT_GAIN] *= 0.9999;
            dz->iparam[FLT_OVFLW]++;
            dz->peak_fval = max(dz->peak_fval,peak);
            //return(1.0);
            if(dz->clip_floatsams)
                sum = 1.0;
        }
        if (sum < -1.0) {
//TW SUGGEST KEEP THIS; prevents FILTER BLOWING UP: see notes

            dz->param[FLT_GAIN] *= 0.9999;
            dz->iparam[FLT_OVFLW]++;
            dz->peak_fval = max(dz->peak_fval,peak);
            //return(-1.0);
            if(dz->clip_floatsams)
                sum = -1.0;
        }
#ifdef NOTDEF
    }
#endif
    return sum;
}
/************************ PRINT_FILTER_FRQS *******************************/

void print_filter_frqs(dataptr dz)
{
    int n;
    double *frq = dz->parray[FLT_FRQ];
    for(n=0;n<dz->iparam[FLT_CNT];n++)
        fprintf(dz->fp,"%lf\n",frq[n]);
}

/******************************* DO_VARIFILTER ******************************/

int do_varifilter(dataptr dz)
{
    double *dls = dz->parray[FLT_DLS];
    double *dbs = dz->parray[FLT_DBS];
    double *dhs = dz->parray[FLT_DHS];
    double *dns = dz->parray[FLT_DNS];
    double *dops[2];
    double coeff = 0.0;
    float  *buf  = dz->sampbuf[0];
    int   n;
    int    k, chans = dz->infile->channels;
    int    is_fbrk = FALSE, is_qbrk = FALSE;
    if(dz->brksize[FLT_ONEFRQ]) is_fbrk = TRUE;
    if(dz->brksize[FLT_Q])      is_qbrk = TRUE;
    for(n=0;n<chans;n++) {
        switch(dz->mode){
        case(FSW_HIGH):     dops[n] = &(dz->parray[FLT_DHS][n]);    break;
        case(FSW_LOW):      dops[n] = &(dz->parray[FLT_DLS][n]);    break;
        case(FSW_BAND):     dops[n] = &(dz->parray[FLT_DBS][n]);    break;
        case(FSW_NOTCH):    dops[n] = &(dz->parray[FLT_DNS][n]);    break;
        }
    }
    for (n = 0 ; n < dz->ssampsread; n += chans) {
        if(is_fbrk && (--dz->iparam[FLT_FSAMS] <= 0)) {
            if(!newvalue(FLT_ONEFRQ,FLT_F_INCR,FLT_FSAMS,dz)) {
                sprintf(errstr,"Ran out of sweepfrq values: do_varifilter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(is_qbrk && (--dz->iparam[FLT_SAMS] <= 0)) {
            if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) { 
                sprintf(errstr,"Ran out of Q values: do_sweep_filter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(--dz->iparam[FLT_BLOKCNT] <= 0){
            coeff = (2.0 * PI * dz->param[FLT_ONEFRQ]) * dz->param[FLT_INV_SR];
            if(is_fbrk)    dz->param[FLT_ONEFRQ] *= dz->param[FLT_F_INCR];
            if(is_qbrk) {
                dz->param[FLT_QFAC] = 1.0/(1.0 + dz->param[FLT_Q]);
                dz->param[FLT_Q]   *= dz->param[FLT_Q_INCR];
            }
            dz->iparam[FLT_BLOKCNT] = dz->iparam[FLT_BLOKSIZE];
        }
        for(k=0;k<chans;k++)
            buf[n+k] = multifilter(&(dbs[k]),&(dls[k]),&(dhs[k]),&(dns[k]),dops[k],dz->param[FLT_Q],coeff,buf[n+k],dz);
    }
    return(CONTINUE);
}

/******************************* DO_SWEEP_FILTER ******************************/

int do_sweep_filter(dataptr dz)
{
    double *dls = dz->parray[FLT_DLS];
    double *dbs = dz->parray[FLT_DBS];
    double *dhs = dz->parray[FLT_DHS];
    double *dns = dz->parray[FLT_DNS];
    double *dops[2];
    double coeff = 0.0, frq;
    float  *buf  = dz->sampbuf[0];
    int   n;
    int    k, chans = dz->infile->channels;
    int    is_lbrk = FALSE, is_hbrk = FALSE, is_sbrk = FALSE, is_qbrk = FALSE;
    if(dz->brksize[FLT_LOFRQ])  is_lbrk = TRUE;
    if(dz->brksize[FLT_HIFRQ])  is_hbrk = TRUE;
    if(dz->brksize[FLT_SWPFRQ]) is_sbrk = TRUE;
    if(dz->brksize[FLT_Q])      is_qbrk = TRUE;
    for(n=0;n<chans;n++) {
        switch(dz->mode){
        case(FSW_HIGH):     dops[n] = &(dz->parray[FLT_DHS][n]);    break;
        case(FSW_LOW):      dops[n] = &(dz->parray[FLT_DLS][n]);    break;
        case(FSW_BAND):     dops[n] = &(dz->parray[FLT_DBS][n]);    break;
        case(FSW_NOTCH):    dops[n] = &(dz->parray[FLT_DNS][n]);    break;
        }
    }
    for (n = 0 ; n < dz->ssampsread; n += chans) {
        if(is_lbrk && (--dz->iparam[FLT_LOSAMS] <= 0)) {
            if(!newvalue(FLT_LOFRQ,FLT_LOINCR,FLT_LOSAMS,dz)) { 
                sprintf(errstr,"Ran out of lofrq values: do_sweep_filter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(is_hbrk && (--dz->iparam[FLT_HISAMS] <= 0)) {
            if(!newvalue(FLT_HIFRQ,FLT_HIINCR,FLT_HISAMS,dz)) { 
                sprintf(errstr,"Ran out of hifrq values: do_sweep_filter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(is_sbrk && (--dz->iparam[FLT_SWSAMS] <= 0)) {
            if(!newvalue(FLT_SWPFRQ,FLT_SWINCR,FLT_SWSAMS,dz)) { 
                sprintf(errstr,"Ran out of sweepfrq values: do_sweep_filter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(is_qbrk && (--dz->iparam[FLT_SAMS] <= 0)) {
            if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) { 
                sprintf(errstr,"Ran out of Q values: do_sweep_filter()\n");
                return(PROGRAM_ERROR);
            }
        }
        if(--dz->iparam[FLT_BLOKCNT] <= 0){
            frq   = getfrq(dz->param[FLT_LOFRQ],dz->param[FLT_HIFRQ],dz->param[FLT_SWPFRQ],dz);
            coeff = (2.0 * PI * frq) * dz->param[FLT_INV_SR];
            if(is_lbrk)    dz->param[FLT_LOFRQ]  *= dz->param[FLT_LOINCR];
            if(is_hbrk)    dz->param[FLT_HIFRQ]  *= dz->param[FLT_HIINCR];
            if(is_sbrk)    dz->param[FLT_SWPFRQ] *= dz->param[FLT_SWINCR];
            if(is_qbrk) {
                dz->param[FLT_QFAC] = 1.0/(1.0 + dz->param[FLT_Q]);
                dz->param[FLT_Q]   *= dz->param[FLT_Q_INCR];
            }
            dz->iparam[FLT_BLOKCNT] = dz->iparam[FLT_BLOKSIZE];
        }
        for(k=0;k<chans;k++)
            buf[n+k] = multifilter(&(dbs[k]),&(dls[k]),&(dhs[k]),&(dns[k]),dops[k],dz->param[FLT_Q],coeff,buf[n+k],dz);
    }
    return(CONTINUE);
}

/*************************** GETFRQ ****************************
 *
 * NB sfrq is already adjusted to advance over a whole flt_blok.
 */

double getfrq(double lfrq,double hfrq,double sfrq,dataptr dz)
{
    double thispos;
    double range = hfrq - lfrq;
    thispos  = (cos(dz->param[FLT_CYCPOS]) + 1.0) * 0.5;
    dz->param[FLT_CYCPOS]  =  fmod(dz->param[FLT_CYCPOS] + sfrq,TWOPI);
    return((thispos * range) + lfrq);
}

/******************************* DO_ALLPASS_FILTER ******************************/

int do_allpass_filter(dataptr dz)
{
    int exit_status;
    int    chans    = dz->infile->channels;
    float  *buf     = dz->sampbuf[0];
    double prescale = dz->param[FLT_PRESCALE];

    if(dz->brksize[FLT_DELAY])   
        exit_status = varidelay_allpass(buf,chans,prescale,dz);
    else
        exit_status = allpass(buf,chans,prescale,dz);

    return(exit_status);
}

/******************************* VARIDELAY_ALLPASS ******************************/

int varidelay_allpass(float *buf,int chans,double prescale,dataptr dz)
{
    int   n, thisdelbfpos1, thisdelbfpos2, sampno;
    int    delay, channo;
    double frac, ip, op, delval1,delval2, delval;
    double *delbuf1 = dz->parray[FLT_DELBUF1];
    double *delbuf2 = dz->parray[FLT_DELBUF2];
    int    maxdelsamps = dz->iparam[FLT_MAXDELSAMPS] * chans;
    int    delbufpos   = dz->iparam[FLT_DELBUFPOS];
    switch(dz->mode) {
    case(FLT_PHASESHIFT):
        for(n=0;n<dz->ssampsread;n+= chans){
            if(--dz->iparam[FLT_SAMS] <= 0) {
                if(!newvalue(FLT_DELAY,FLT_D_INCR,FLT_SAMS,dz)) {
                    sprintf(errstr,"Ran out of Delay vals: varidelay_allpass()\n");
                    return(PROGRAM_ERROR);
                }
            }
            delay = (int)dz->param[FLT_DELAY];
            frac  = dz->param[FLT_DELAY] - (double)delay;
            for(channo = 0;channo < chans; channo++) {
                sampno = n + channo;
                thisdelbfpos1 = my_modulus((delbufpos - (delay*chans)),maxdelsamps);
                thisdelbfpos2 = my_modulus((thisdelbfpos1 + chans)    ,maxdelsamps);
                ip = (double)buf[sampno]    * prescale;
                op = (-dz->param[FLT_GAIN]) * ip;
                delval1     = delbuf1[thisdelbfpos1];
                delval2     = delbuf1[thisdelbfpos2];
                delval      = delval1 + ((delval2 - delval1) * frac);
                op += delval;
                delval1     = delbuf2[thisdelbfpos1];
                delval2     = delbuf2[thisdelbfpos2];
                delval      = delval1 + ((delval2 - delval1) * frac);
                op += dz->param[FLT_GAIN] * delval;
                delbuf1[delbufpos] = ip;
                delbuf2[delbufpos] = op;
                if(++delbufpos >= maxdelsamps)
//                  delbufpos = 0;
                    delbufpos -= maxdelsamps;       /*RWD 9:2001 */
//TW ?????? maxdelsamps is a mutiple of channels, delbufpos is incremented by 1 each time
//   so (delbufpos -= maxdelsamps) = 0
                buf[sampno] = (float) (op);
            }
            if(dz->vflag[FLT_LINDELAY])
                dz->param[FLT_DELAY] += dz->param[FLT_D_INCR];
            else
                dz->param[FLT_DELAY] *= dz->param[FLT_D_INCR];
        }
        break;
    case(FLT_PHASER):
        for(n=0;n<dz->ssampsread;n+= chans){
            if(--dz->iparam[FLT_SAMS] <= 0) {
                if(!newvalue(FLT_DELAY,FLT_D_INCR,FLT_SAMS,dz)) {
                    sprintf(errstr,"Ran out of Delay vals: varidelay_allpass()\n");
                    return(PROGRAM_ERROR);
                }
            }
            delay = (int)dz->param[FLT_DELAY];
            frac  = dz->param[FLT_DELAY] - (double)delay;
            for(channo = 0;channo < chans; channo++) {
                sampno = n + channo;
                thisdelbfpos1 = my_modulus((delbufpos - (delay*chans)),maxdelsamps);
                thisdelbfpos2 = my_modulus((thisdelbfpos1 + chans)    ,maxdelsamps);
                ip = (double)buf[sampno]    * prescale;
                op = (-dz->param[FLT_GAIN]) * ip;
                delval1     = delbuf1[thisdelbfpos1];
                delval2     = delbuf1[thisdelbfpos2];
                delval      = delval1 + ((delval2 - delval1) * frac);
                op += delval;
                delval1     = delbuf2[thisdelbfpos1];
                delval2     = delbuf2[thisdelbfpos2];
                delval      = delval1 + ((delval2 - delval1) * frac);
                op += dz->param[FLT_GAIN] * delval;
                delbuf1[delbufpos] = ip;
                delbuf2[delbufpos] = op;
                if(++delbufpos >= maxdelsamps)
                    //delbufpos = 0;
                    delbufpos -= maxdelsamps;   /*RWD 9:2001 (see e_tmp/cdpfloat ) */
//TW ?????? maxdelsamps is a mutiple of channels, delbufpos is incremented by 1 each time
//   so (delbufpos -= maxdelsamps) = 0
                buf[sampno] = (float) ((op + (double)buf[sampno]) * 0.5);
            }
            if(dz->vflag[FLT_LINDELAY])
                dz->param[FLT_DELAY] += dz->param[FLT_D_INCR];
            else
                dz->param[FLT_DELAY] *= dz->param[FLT_D_INCR];
        }
        break;
    default:
        sprintf(errstr,"Unknown case:varidelay_allpass()\n");
        return(PROGRAM_ERROR); 
    }
    dz->iparam[FLT_DELBUFPOS] = delbufpos;
    return(FINISHED);
}

/******************************* ALLPASS ******************************/

int allpass(float *buf,int chans,double prescale,dataptr dz)
{
    int   n, sampno;
    int    channo;
    double *delbuf1 = dz->parray[FLT_DELBUF1];
    double *delbuf2 = dz->parray[FLT_DELBUF2];
    int    maxdelsamps = dz->iparam[FLT_MAXDELSAMPS] * chans;
    int    delbufpos   = dz->iparam[FLT_DELBUFPOS];
    double ip, op; 
    switch(dz->mode) {
    case(FLT_PHASESHIFT):
        for(n=0;n<dz->ssampsread;n+=chans){
            for(channo = 0;channo < chans; channo++) {
                sampno = n + channo;
                ip = (double)buf[sampno] * prescale;
                op = (-dz->param[FLT_GAIN]) * ip;
                op += delbuf1[delbufpos];
                op += dz->param[FLT_GAIN] * delbuf2[delbufpos];
                delbuf1[delbufpos] = ip;
                delbuf2[delbufpos] = op;
                if(++delbufpos >= maxdelsamps)
                    /*delbufpos = 0;*/
                    delbufpos -= maxdelsamps;           /*RWD */
//TW ?????? maxdelsamps is a mutiple of channels, delbufpos is incremented by 1 each time
//   so (delbufpos -= maxdelsamps) = 0
                buf[sampno] = (float)(op);
            }
        }
        break;
    case(FLT_PHASER):
        for(n=0;n<dz->ssampsread;n+=chans){
            for(channo = 0;channo < chans; channo++) {
                sampno = n + channo;
                ip = (double)buf[sampno] * prescale;
                op = (-dz->param[FLT_GAIN]) * ip;
                op += delbuf1[delbufpos];
                op += dz->param[FLT_GAIN] * delbuf2[delbufpos];
                delbuf1[delbufpos] = ip;
                delbuf2[delbufpos] = op;
                if(++delbufpos >= maxdelsamps)
                    /*delbufpos = 0;*/
                    delbufpos -= maxdelsamps;           /*RWD */
//TW ?????? maxdelsamps is a mutiple of channels, delbufpos is incremented by 1 each time
//   so (delbufpos -= maxdelsamps) = 0
                buf[sampno] = (float)((op + (double)buf[sampno]) * 0.5);
            }
        }
        break;
    default:
        sprintf(errstr,"Unknown case: allpass()\n");
        return(PROGRAM_ERROR);
    }
    dz->iparam[FLT_DELBUFPOS] = delbufpos;
    return(FINISHED);
}

/******************************* DO_EQ_FILTER ******************************/

int do_eq_filter(dataptr dz)
{
    double ip, op;
    int   n, sampno;
    float  *buf = dz->sampbuf[0];
    int   chans = dz->infile->channels, chno;
    double *xx1 = dz->parray[FLT_XX1];
    double *xx2 = dz->parray[FLT_XX2];
    double *yy1 = dz->parray[FLT_YY1];
    double *yy2 = dz->parray[FLT_YY2];
    double a0   = dz->param[FLT_A0];
    double a1   = dz->param[FLT_A1];
    double a2   = dz->param[FLT_A2];
    double b1   = dz->param[FLT_B1];
    double b2   = dz->param[FLT_B2];
    double prescale = dz->param[FLT_PRESCALE];
    //double inv_of_maxsamp = 1.0/(double)F_MAXSAMP;
    for(n = 0;n < dz->ssampsread; n+= chans){
        for(chno = 0;chno < chans; chno++) {
            sampno = n+chno;
            ip  = (double)buf[sampno] /* * inv_of_maxsamp*/;
            ip *= prescale;
            op  = (a0 * ip) + (a1 * xx1[chno]) + (a2 * xx2[chno]) - (b1 * yy1[chno]) - (b2 * yy2[chno]);
            xx2[chno] = xx1[chno];
            xx1[chno] = ip;
            yy2[chno] = yy1[chno];
            yy1[chno] = op;
            buf[sampno] = (float)(op);
        }
    }
    return(FINISHED);
}

/************************** MULTIFILTER **************************/

float multifilter(double *dll,double *dbb,double *dnn,double *dhh,double *dpp,
                    double qfac,double coeff,float input,dataptr dz)
{
    double dya, dsa;
    dya   = (double)input;
    *dhh  = (qfac * *dbb) - *dll - dya;
    *dbb  = *dbb - (coeff * *dhh);
    *dll  = *dll - (coeff * *dbb);
    *dnn  = *dll + *dhh;
    dsa   = (*dpp) * dz->param[FLT_GAIN]; /* dpp points to dhh,dbb,dll,dnn */
#ifdef NOTDEF
    if (fabs(dsa) > F_MAXSAMP) {
        dz->iparam[FLT_OVFLW]++;
        dz->param[FLT_GAIN] *= .9999;
        if (dsa  > 0.0) 
            dsa = (double)F_MAXSAMP;
        else 
            dsa = (double)F_MINSAMP;
    }
    return((float)dsa);  /* TRUNCATE */
#else
    return (float) check_float_limits(dsa,dz);
#endif
}

/***************************** FILTER *************************************/
/* RWD TODO: add fix for nchans */

//int do_lphp_filter(dataptr dz)
//{
//  double *e1s,*e2s,*s1s,*s2s;
//  double *e1   = dz->parray[FLT_E1];
//  double *e2   = dz->parray[FLT_E2];
//  double *s1   = dz->parray[FLT_S1];
//  double *s2   = dz->parray[FLT_S2];
//  double *den1 = dz->parray[FLT_DEN1];
//  double *den2 = dz->parray[FLT_DEN2];
//  double *cn   = dz->parray[FLT_CN];
//  switch(dz->infile->channels) {
//  case(STEREO):
//      e1s  = dz->parray[FLT_E1S];
//      e2s  = dz->parray[FLT_E2S];
//      s1s  = dz->parray[FLT_S1S];
//      s2s  = dz->parray[FLT_S2S];
//      lphp_filt_stereo(e1,e2,s1,s2,e1s,e2s,s1s,s2s,den1,den2,cn,dz);
//      break;
//  case(MONO):
//      lphp_filt(e1,e2,s1,s2,den1,den2,cn,dz);
//      break;
//  }
//  return(FINISHED);
//}
//      
// TW MULTICHAN 2010
int do_lphp_filter(dataptr dz)
{
    int i;
    int index;
    double *e1,*e2,*s1,*s2;
    double *den1 = dz->parray[FLT_DEN1];
    double *den2 = dz->parray[FLT_DEN2];
    double *cn   = dz->parray[FLT_CN];  

    for(i=0; i < dz->infile->channels; i++) {
        index = i * FLT_LPHP_ARRAYS_PER_FILTER;

        e1   = dz->parray[FLT_E1_BASE + index];
        e2   = dz->parray[FLT_E2_BASE + index];
        s1   = dz->parray[FLT_S1_BASE + index];
        s2   = dz->parray[FLT_S2_BASE + index];

        lphp_filt_chan(e1,e2,s1,s2,den1,den2,cn,dz,i);

    }
    return(FINISHED);
}

/***************************** LPHP_FILT *************************************/

void lphp_filt(double *e1,double *e2,double *s1,double *s2,
                    double *den1,double *den2,double *cn,dataptr dz)
{
    int i;
    int  k;
    float *buf = dz->sampbuf[0];
    double ip, op = 0.0, b1;
    for (i = 0 ; i < dz->ssampsread; i++) {
        ip = (double) buf[i];
        for (k = 0 ; k < dz->iparam[FLT_CNT]; k++) {
            b1    = dz->param[FLT_MUL] * cn[k];
            op    = (cn[k] * ip) + (den1[k] * s1[k]) + (den2[k] * s2[k]) + (b1 * e1[k]) + (cn[k] * e2[k]);
            s2[k] = s1[k];
            s1[k] = op;
            e2[k] = e1[k];
            e1[k] = ip;
        }
        op *= dz->param[FLT_PRESCALE];
                //RWD NB gain modification...
#ifdef NOTDEF
        if (fabs(op) > 1.0) {
            dz->iparam[FLT_OVFLW]++;
//TW SUGGEST KEEP THIS: PREVENTS FILTER BLOWING UP
            dz->param[FLT_PRESCALE] *= .9999;
            if (op  > 0.0)
                op = 1.0;
            else 
                op = -1.0;
        }
        buf[i] = (float)op;
#else
        buf[i] = (float) check_float_limits(op,dz);
#endif
    }
}

/*RWD 4:2000 */
void lphp_filt_chan(double *e1,double *e2,double *s1,double *s2,
                    double *den1,double *den2,double *cn,dataptr dz,int chan)
{
    int i;
    int  k;
    float *buf = dz->sampbuf[0];
    double ip, op = 0.0, b1;
    for (i = chan ; i < dz->ssampsread; i+= dz->infile->channels) {
        ip = (double) buf[i];
        for (k = 0 ; k < dz->iparam[FLT_CNT]; k++) {
            b1    = dz->param[FLT_MUL] * cn[k];
            op    = (cn[k] * ip) + (den1[k] * s1[k]) + (den2[k] * s2[k]) + (b1 * e1[k]) + (cn[k] * e2[k]);
            s2[k] = s1[k];
            s1[k] = op;
            e2[k] = e1[k];
            e1[k] = ip;
        }
        op *= dz->param[FLT_PRESCALE];
        //RWD NB gain modification...
#ifdef NOTDEF
        if (fabs(op) > 1.0) {
            dz->iparam[FLT_OVFLW]++;
//TW SUGGEST KEEP THIS: PREVENTS FILTER BLOWING UP
            dz->param[FLT_PRESCALE] *= .9999;
            if (op  > 0.0)
                op = 1.0;
            else 
                op = -1.0;
        }
        buf[i] = (float)op;
#else
        buf[i] = (float) check_float_limits(op,dz);
#endif
    }
}

/***************************** LPHP_FILT_STEREO *************************************/

void lphp_filt_stereo(double *e1,double *e2,double *s1,double *s2,double *e1s,double *e2s,double *s1s,double *s2s,
                    double *den1,double *den2,double *cn,dataptr dz)
{
    int i, j;
    int  k;
    float *buf = dz->sampbuf[0];
    double ip, op = 0.0, b1;
    for (i = 0 ; i < dz->ssampsread; i+=2) {
        ip = (double)buf[i];
        for (k = 0 ; k < dz->iparam[FLT_CNT]; k++) {
            b1    = dz->param[FLT_MUL] * cn[k];
            op    = (cn[k] * ip) + (den1[k] * s1[k]) + (den2[k] * s2[k]) + (b1 * e1[k]) + (cn[k] * e2[k]);
            s2[k] = s1[k];
            s1[k] = op;
            e2[k] = e1[k];
            e1[k] = ip;
        }
        op *= dz->param[FLT_PRESCALE];
#ifdef NOTDEF
        if (fabs(op) > F_MAXSAMP) {
            dz->iparam[FLT_OVFLW]++;
            dz->param[FLT_PRESCALE] *= .9999;
            if (op  > 0.0)
                op = (double)F_MAXSAMP;
            else 
                op = (double)F_MINSAMP;
        }
        buf[i] = (float)op;
#else
        buf[i] = (float) check_float_limits(op,dz);
#endif
        j = i+1;
        ip = (double)buf[j];
        for (k = 0 ; k < dz->iparam[FLT_CNT]; k++) {
            b1     = dz->param[FLT_MUL] * cn[k];
            op     = (den1[k] * s1s[k]) + (den2[k] * s2s[k]) + (cn[k] * ip) + (b1 * e1s[k]) + (cn[k] * e2s[k]);
            s2s[k] = s1s[k];
            s1s[k] = op;
            e2s[k] = e1s[k];
            e1s[k] = ip;
        }
        op *= dz->param[FLT_PRESCALE];
#ifdef NOTDEF
        if (fabs(op) > F_MAXSAMP) {
            dz->iparam[FLT_OVFLW]++;
            dz->param[FLT_PRESCALE] *= .9999;
            if (op  > 0.0)
                op = (double)F_MAXSAMP;
            else 
                op = (double)F_MINSAMP;
        }
        buf[j] = (float)op;
#else
        buf[j] = (float) check_float_limits(op,dz);
#endif
    }
}

/***************************** MY_MODULUS *************************************/

int my_modulus(int x,int y)
{
    if(x>=0)
        return(x%y);
    while(x < 0)
        x += y;
    return(x);
}

/**************************** NEWFVAL2 *******************************/

int newfval2(double *fbrk,double *hbrk,dataptr dz)
{
    int n, m, k, timepoint, nextrow;
    int entrycnt = dz->iparam[FLT_ENTRYCNT];
    int wordcnt  = dz->iparam[FLT_WORDCNT];
    int hentrycnt = dz->iparam[HRM_ENTRYCNT];
    int hwordcnt  = dz->iparam[HRM_WORDCNT];
    //long srate = dz->infile->srate;
    double lotime, hitime, timefrac, valdiff;
    double thistime = dz->param[FLT_TOTALTIME];

    memset((char *)dz->parray[FLT_INFRQ],0,dz->iparam[FLT_CNT] * sizeof(double));
    memset((char *)dz->parray[FLT_INAMP],0,dz->iparam[FLT_CNT] * sizeof(double));
    timepoint = 0;
    while(thistime >= fbrk[timepoint]) {    /* search times in frq array */
        timepoint += entrycnt;
        if(timepoint >= wordcnt)
            break;
    }
    timepoint -= entrycnt;
    lotime = fbrk[timepoint];
    nextrow = timepoint + entrycnt;
    for(n = timepoint+1,k = 0; n < nextrow;n+=2,k += dz->iparam[FLT_HARMCNT]) {
        dz->parray[FLT_INFRQ][k] = fbrk[n];     /* Get frqs of fundamentals into array, leaving space for harmonics */
        dz->parray[FLT_INAMP][k] = fbrk[n+1];   /* Get amps of fundamentals into array, leaving space for harmonics */
    }
    if(nextrow != wordcnt) {                    /* if not at end of table, do interpolation */
        nextrow += entrycnt;
        timepoint += entrycnt;
        hitime = fbrk[timepoint];
        timefrac = (thistime - lotime)/(hitime - lotime);
        k = 0;
        for(n = timepoint+1,k=0; n < nextrow;n+=2,k += dz->iparam[FLT_HARMCNT]) {
            /* FRQ */
            valdiff = fbrk[n] - dz->parray[FLT_INFRQ][k];
            valdiff *= timefrac;
            dz->parray[FLT_INFRQ][k] = dz->parray[FLT_INFRQ][k] + valdiff;
            /* AMP */
            valdiff = fbrk[n+1] - dz->parray[FLT_INAMP][k];
            valdiff *= timefrac;
            dz->parray[FLT_INAMP][k] = dz->parray[FLT_INAMP][k] + valdiff;
        }
    }
    timepoint = 0;
    while(thistime >= hbrk[timepoint]) {    /* search times in frq array */
        timepoint += hentrycnt;
        if(timepoint >= hwordcnt) {
            break;
        }
    }
    timepoint -= hentrycnt;
    lotime = hbrk[timepoint];
    nextrow = timepoint + hentrycnt;
    k = 0;
    for(n = timepoint+1,k=0; n < nextrow;n+=2,k++) {
        dz->parray[HARM_FRQ_CALC][k] = hbrk[n];
        dz->parray[HARM_AMP_CALC][k] = hbrk[n+1];
    }
    if(nextrow != hwordcnt) {                   /* if not at end of table, do interpolation */
        nextrow += hentrycnt;
        timepoint += hentrycnt;
        hitime = hbrk[timepoint];
        timefrac = (thistime - lotime)/(hitime - lotime);
        k = 0;
        for(n = timepoint+1,k=0; n < nextrow;n+=2,k++) {
            /* PARTIAL MULTIPLIER */
            valdiff = hbrk[n] - dz->parray[HARM_FRQ_CALC][k];
            valdiff *= timefrac;
            dz->parray[HARM_FRQ_CALC][k] = dz->parray[HARM_FRQ_CALC][k] + valdiff;
            /* PARTIAL AMP */
            valdiff = hbrk[n+1] - dz->parray[HARM_AMP_CALC][k];
            valdiff *= timefrac;
            dz->parray[HARM_AMP_CALC][k] = dz->parray[HARM_AMP_CALC][k] + valdiff;
        }
    }
    for(k=0;k<dz->iparam[FLT_CNT];k+=dz->iparam[FLT_HARMCNT]) {
        for(m=0; m < dz->iparam[FLT_HARMCNT];m++) { /* calc vals for partials from basefrq vals */
            dz->parray[FLT_INFRQ][k+m] = dz->parray[FLT_INFRQ][k] * dz->parray[HARM_FRQ_CALC][m];
            dz->parray[FLT_INAMP][k+m] = dz->parray[FLT_INAMP][k] * dz->parray[HARM_AMP_CALC][m];
            dz->parray[FLT_FRQ][k+m] = dz->parray[FLT_INFRQ][k+m];
            dz->parray[FLT_AMP][k+m] = dz->parray[FLT_INAMP][k+m];
        }
    }
    dz->param[FLT_TOTALTIME] += dz->param[FLT_TIMESTEP];
    return(FINISHED);
}

/*************************** DO_FVARY2_FILTERS *****************************/

int do_fvary2_filters(dataptr dz)
{
    int exit_status;
    int    n, fno, chans = dz->infile->channels;
    float *buf = dz->sampbuf[0];

    //double *fincr = dz->parray[FLT_FINCR];
    //double *aincr = dz->parray[FLT_AINCR];
 
    double *ampl = dz->parray[FLT_AMPL];
    double *a = dz->parray[FLT_A];
    double *b = dz->parray[FLT_B];
    double *y = dz->parray[FLT_Y];
    double *z = dz->parray[FLT_Z];
    double *d = dz->parray[FLT_D];
    double *e = dz->parray[FLT_E];
 
    int fsams = dz->iparam[FLT_FSAMS];
    for (n = 0; n < dz->ssampsread; n += chans) { 
        if(dz->brksize[FLT_Q]) {
            if((dz->iparam[FLT_SAMS] -= chans) <= 0) {
                if(!newvalue(FLT_Q,FLT_Q_INCR,FLT_SAMS,dz)) {
                    sprintf(errstr,"Ran out of Q values: do_fvary2_filters()\n");
                    return(PROGRAM_ERROR);
                }
                dz->iparam[FLT_SAMS] *= chans;
            }
        }
        if(fsams <= 0) {
            if((exit_status = newfval2(dz->parray[FLT_FBRK],dz->parray[FLT_HBRK],dz))<0)
                return(exit_status);
            fsams = dz->iparam[FLT_FSAMS];
            for (fno = 0; fno < dz->iparam[FLT_CNT]; fno++) {
                get_coeffs1(fno,dz);
                get_coeffs2(fno,dz);
            }
            if(dz->brksize[FLT_Q])
                dz->param[FLT_Q] *= dz->param[FLT_Q_INCR];
        }

        filtering(n,chans,buf,a,b,y,z,d,e,ampl,dz);
        fsams--;
    }
    return(CONTINUE);
}