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filter.cc

/*
 * Copyright (c) 1991-1993 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the Computer Systems
 *    Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
static const char rcsid[] =
    "@(#) $Header: filter.cc,v 1.7 96/03/16 13:12:51 van Exp $ (LBL)";

#include "config.h"
#include <math.h>
#include <sys/types.h>

#include "filter.h"
#include "mulaw.h"
#include "wiener.h"

Filter::Filter(Audio *a)
{
      taps = 0;
      ntaps = 0;
      audio = a;
}

Filter::~Filter()
{
      delete taps;
      taps = 0;
}

void Filter::Compute(SampleStream *in, u_char *out, int n)
{
      FilterTap* tap = taps;
      register u_char* blk = in->CurBlk();
      if (in->BlkBack(-tap[0].tapno) - blk != tap[0].tapno) {
            // convolution spans buffer wrap.
      } else {
            while (--n >= 0) {
                  register u_long sum = 0;
                  register int t;
                  for ( ; (t = tap->tapno) != 0; ++tap)
                        sum += tap->product[blk[t]];

                  *out++ = lintomulaw[sum & 0xffff];
                  ++blk;
                  tap = taps;
            }
      }
}

struct Tap {
      double val;
      int tap;
};

static int tapCompareV(struct Tap* a, struct Tap* b)
{
      if (a->val > b->val)
            return (1);
      return (a->val == b->val? 0 : -1);
}

static int tapCompareT(struct Tap* a, struct Tap* b)
{
      return (b->tap - a->tap);
}

void Filter::Create(double *d, int n, int m)
{
      struct Tap wrk[4096];
      register int i;
      for (i = 0; i < n; ++i) {
            wrk[i].tap = i;
            wrk[i].val = d[i];
      }
      qsort(wrk, n, sizeof(wrk[0]),
            (int(*)(const void*, const void*))tapCompareV);
      qsort(wrk, m, sizeof(wrk[0]),
            (int(*)(const void*, const void*))tapCompareT);

      if (taps)
            delete taps;
      taps = new FilterTap[m + 1];
      ntaps = m;

      wrk[m].tap = 0;
      wrk[m].val = 0.;

      for (i = 0; i <= m; ++i) {
            taps[i].tapno = -wrk[i].tap;
            double c = wrk[i].val;
            taps[i].mod = c >= 0 ? c : -c;
            for (int u = 0; u < 256; ++u)
                  taps[i].product[u] = (int)(c * (double)mulawtolin[u]);
      }
}

static inline void GenerateNoise(u_char *cp, int len)
{
      double phi = 0;
      double delta = M_PI / len;
      srandom(u_int(time(0)));
      while (--len >= 0) {
            int x = int((random() & (32768 - 1)) - 16384);
            double cphi = cos(phi);
            x = (int)((double)x * (1 - cphi * cphi));
            phi += delta;
            *cp++ = lintomulaw[x & 0xffff];
      }
}

static inline void ulawtoreal(u_char *u, double *r, int len)
{
      while (--len >= 0)
            *r++ = double(mulawtolin[*u++]);
}

void Filter::Train(int len, int maxtaps)
{
      u_char x[3584], y[3584];
      GenerateNoise(x, 3584);
      int playlen = audio->PlayRec(x, y, sizeof(x));
      double rx[sizeof(x)], ry[sizeof(x)];
      ulawtoreal(x, rx, playlen);
      ulawtoreal(y, ry, playlen);
      Wiener wf(rx, ry, playlen, len);
      if (maxtaps > len)
            maxtaps = len;
      Create(wf.Coeffs(), len, maxtaps);
}

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