strawberry-audio-player-windows-mac-linux/src/analyzer/fht.cpp

// FHT - Fast Hartley Transform Class
//
// Copyright (C) 2004  Melchior FRANZ - mfranz@kde.org
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, 51 Franklin Steet, Fifth Floor, Boston, MA 02110-1301, USA
//
// $Id$

#include <math.h>
#include <string.h>

#include "fht.h"

FHT::FHT(int n) : m_buf(0), m_tab(0), m_log(0) {
  if (n < 3) {
    m_num = 0;
    m_exp2 = -1;
    return;
  }
  m_exp2 = n;
  m_num = 1 << n;
  if (n > 3) {
    m_buf = new float[m_num];
    m_tab = new float[m_num * 2];
    makeCasTable();
  }
}

FHT::~FHT() {
  delete[] m_buf;
  delete[] m_tab;
  delete[] m_log;
}

void FHT::makeCasTable(void) {
  float d, *costab, *sintab;
  int ul, ndiv2 = m_num / 2;

    for (costab = m_tab, sintab = m_tab + m_num / 2 + 1, ul = 0; ul < m_num; ul++) {
    d = M_PI * ul / ndiv2;
    *costab = *sintab = cos(d);

    costab += 2, sintab += 2;
    if (sintab > m_tab + m_num * 2) sintab = m_tab + 1;
  }
}

float* FHT::copy(float* d, float* s) {
  return (float*)memcpy(d, s, m_num * sizeof(float));
}

float* FHT::clear(float* d) {
  return (float*)memset(d, 0, m_num * sizeof(float));
}

void FHT::scale(float* p, float d) {
  for (int i = 0; i < (m_num / 2); i++) *p++ *= d;
}

void FHT::ewma(float* d, float* s, float w) {
  for (int i = 0; i < (m_num / 2); i++, d++, s++) *d = *d * w + *s * (1 - w);
}

void FHT::logSpectrum(float* out, float* p) {
  int n = m_num / 2, i, j, k, *r;
  if (!m_log) {
    m_log = new int[n];
    float f = n / log10((double)n);
    for (i = 0, r = m_log; i < n; i++, r++) {
      j = int(rint(log10(i + 1.0) * f));
      *r = j >= n ? n - 1 : j;
    }
  }
  semiLogSpectrum(p);
  *out++ = *p = *p / 100;
  for (k = i = 1, r = m_log; i < n; i++) {
    j = *r++;
    if (i == j)
      *out++ = p[i];
    else {
      float base = p[k - 1];
      float step = (p[j] - base) / (j - (k - 1));
      for (float corr = 0; k <= j; k++, corr += step) *out++ = base + corr;
    }
  }
}

void FHT::semiLogSpectrum(float* p) {
  float e;
  power2(p);
  for (int i = 0; i < (m_num / 2); i++, p++) {
    e = 10.0 * log10(sqrt(*p * .5));
    *p = e < 0 ? 0 : e;
  }
}

void FHT::spectrum(float* p) {
  power2(p);
  for (int i = 0; i < (m_num / 2); i++, p++) *p = (float)sqrt(*p * .5);
}

void FHT::power(float* p) {
  power2(p);
  for (int i = 0; i < (m_num / 2); i++) *p++ *= .5;
}

void FHT::power2(float* p) {
  int i;
  float* q;
  _transform(p, m_num, 0);

  *p = (*p * *p), *p += *p, p++;

  for (i = 1, q = p + m_num - 2; i < (m_num / 2); i++, --q)
    *p = (*p * *p) + (*q * *q), p++;
}

void FHT::transform(float* p) {
  if (m_num == 8)
    transform8(p);
  else
    _transform(p, m_num, 0);
}

void FHT::transform8(float* p) {
  float a, b, c, d, e, f, g, h, b_f2, d_h2;
  float a_c_eg, a_ce_g, ac_e_g, aceg, b_df_h, bdfh;

  a = *p++, b = *p++, c = *p++, d = *p++;
  e = *p++, f = *p++, g = *p++, h = *p;
  b_f2 = (b - f) * M_SQRT2;
  d_h2 = (d - h) * M_SQRT2;

  a_c_eg = a - c - e + g;
  a_ce_g = a - c + e - g;
  ac_e_g = a + c - e - g;
  aceg = a + c + e + g;

  b_df_h = b - d + f - h;
  bdfh = b + d + f + h;

  *p = a_c_eg - d_h2;
  *--p = a_ce_g - b_df_h;
  *--p = ac_e_g - b_f2;
  *--p = aceg - bdfh;
  *--p = a_c_eg + d_h2;
  *--p = a_ce_g + b_df_h;
  *--p = ac_e_g + b_f2;
  *--p = aceg + bdfh;
}

void FHT::_transform(float* p, int n, int k) {

  if (n == 8) {
    transform8(p + k);
    return;
  }

  int i, j, ndiv2 = n / 2;
  float a, *t1, *t2, *t3, *t4, *ptab, *pp;

  for (i = 0, t1 = m_buf, t2 = m_buf + ndiv2, pp = &p[k]; i < ndiv2; i++)
    *t1++ = *pp++, *t2++ = *pp++;

  memcpy(p + k, m_buf, sizeof(float) * n);

  _transform(p, ndiv2, k);
  _transform(p, ndiv2, k + ndiv2);

  j = m_num / ndiv2 - 1;
  t1 = m_buf;
  t2 = t1 + ndiv2;
  t3 = p + k + ndiv2;
  ptab = m_tab;
  pp = p + k;

  a = *ptab++ * *t3++;
  a += *ptab * *pp;
  ptab += j;

  *t1++ = *pp + a;
  *t2++ = *pp++ - a;

  for (i = 1, t4 = p + k + n; i < ndiv2; i++, ptab += j) {
    a = *ptab++ * *t3++;
    a += *ptab * *--t4;

    *t1++ = *pp + a;
    *t2++ = *pp++ - a;
  }
  memcpy(p + k, m_buf, sizeof(float) * n);
}