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278 lines
7.8 KiB
C++
278 lines
7.8 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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///
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/// Peak detection routine.
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///
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/// The routine detects highest value on an array of values and calculates the
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/// precise peak location as a mass-center of the 'hump' around the peak value.
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///
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/// Author : Copyright (c) Olli Parviainen
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/// Author e-mail : oparviai 'at' iki.fi
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/// SoundTouch WWW: http://www.surina.net/soundtouch
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///
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////////////////////////////////////////////////////////////////////////////////
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//
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// License :
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//
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// SoundTouch audio processing library
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// Copyright (c) Olli Parviainen
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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////////////////////////////////////////////////////////////////////////////////
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#include <math.h>
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#include <assert.h>
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#include "PeakFinder.h"
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using namespace soundtouch;
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#define max(x, y) (((x) > (y)) ? (x) : (y))
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PeakFinder::PeakFinder()
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{
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minPos = maxPos = 0;
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}
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// Finds real 'top' of a peak hump from neighnourhood of the given 'peakpos'.
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int PeakFinder::findTop(const float *data, int peakpos) const
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{
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int i;
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int start, end;
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float refvalue;
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refvalue = data[peakpos];
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// seek within ±10 points
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start = peakpos - 10;
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if (start < minPos) start = minPos;
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end = peakpos + 10;
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if (end > maxPos) end = maxPos;
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for (i = start; i <= end; i ++)
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{
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if (data[i] > refvalue)
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{
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peakpos = i;
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refvalue = data[i];
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}
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}
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// failure if max value is at edges of seek range => it's not peak, it's at slope.
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if ((peakpos == start) || (peakpos == end)) return 0;
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return peakpos;
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}
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// Finds 'ground level' of a peak hump by starting from 'peakpos' and proceeding
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// to direction defined by 'direction' until next 'hump' after minimum value will
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// begin
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int PeakFinder::findGround(const float *data, int peakpos, int direction) const
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{
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int lowpos;
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int pos;
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int climb_count;
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float refvalue;
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float delta;
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climb_count = 0;
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refvalue = data[peakpos];
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lowpos = peakpos;
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pos = peakpos;
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while ((pos > minPos+1) && (pos < maxPos-1))
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{
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int prevpos;
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prevpos = pos;
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pos += direction;
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// calculate derivate
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delta = data[pos] - data[prevpos];
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if (delta <= 0)
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{
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// going downhill, ok
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if (climb_count)
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{
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climb_count --; // decrease climb count
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}
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// check if new minimum found
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if (data[pos] < refvalue)
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{
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// new minimum found
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lowpos = pos;
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refvalue = data[pos];
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}
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}
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else
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{
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// going uphill, increase climbing counter
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climb_count ++;
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if (climb_count > 5) break; // we've been climbing too long => it's next uphill => quit
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}
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}
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return lowpos;
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}
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// Find offset where the value crosses the given level, when starting from 'peakpos' and
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// proceeds to direction defined in 'direction'
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int PeakFinder::findCrossingLevel(const float *data, float level, int peakpos, int direction) const
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{
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float peaklevel;
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int pos;
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peaklevel = data[peakpos];
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assert(peaklevel >= level);
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pos = peakpos;
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while ((pos >= minPos) && (pos + direction < maxPos))
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{
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if (data[pos + direction] < level) return pos; // crossing found
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pos += direction;
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}
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return -1; // not found
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}
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// Calculates the center of mass location of 'data' array items between 'firstPos' and 'lastPos'
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double PeakFinder::calcMassCenter(const float *data, int firstPos, int lastPos) const
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{
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int i;
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float sum;
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float wsum;
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sum = 0;
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wsum = 0;
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for (i = firstPos; i <= lastPos; i ++)
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{
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sum += (float)i * data[i];
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wsum += data[i];
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}
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if (wsum < 1e-6) return 0;
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return sum / wsum;
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}
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/// get exact center of peak near given position by calculating local mass of center
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double PeakFinder::getPeakCenter(const float *data, int peakpos) const
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{
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float peakLevel; // peak level
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int crosspos1, crosspos2; // position where the peak 'hump' crosses cutting level
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float cutLevel; // cutting value
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float groundLevel; // ground level of the peak
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int gp1, gp2; // bottom positions of the peak 'hump'
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// find ground positions.
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gp1 = findGround(data, peakpos, -1);
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gp2 = findGround(data, peakpos, 1);
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peakLevel = data[peakpos];
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if (gp1 == gp2)
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{
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// avoid rounding errors when all are equal
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assert(gp1 == peakpos);
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cutLevel = groundLevel = peakLevel;
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} else {
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// get average of the ground levels
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groundLevel = 0.5f * (data[gp1] + data[gp2]);
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// calculate 70%-level of the peak
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cutLevel = 0.70f * peakLevel + 0.30f * groundLevel;
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}
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// find mid-level crossings
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crosspos1 = findCrossingLevel(data, cutLevel, peakpos, -1);
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crosspos2 = findCrossingLevel(data, cutLevel, peakpos, 1);
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if ((crosspos1 < 0) || (crosspos2 < 0)) return 0; // no crossing, no peak..
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// calculate mass center of the peak surroundings
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return calcMassCenter(data, crosspos1, crosspos2);
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}
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double PeakFinder::detectPeak(const float *data, int aminPos, int amaxPos)
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{
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int i;
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int peakpos; // position of peak level
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double highPeak, peak;
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this->minPos = aminPos;
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this->maxPos = amaxPos;
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// find absolute peak
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peakpos = minPos;
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peak = data[minPos];
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for (i = minPos + 1; i < maxPos; i ++)
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{
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if (data[i] > peak)
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{
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peak = data[i];
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peakpos = i;
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}
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}
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// Calculate exact location of the highest peak mass center
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highPeak = getPeakCenter(data, peakpos);
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peak = highPeak;
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// Now check if the highest peak were in fact harmonic of the true base beat peak
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// - sometimes the highest peak can be Nth harmonic of the true base peak yet
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// just a slightly higher than the true base
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for (i = 1; i < 3; i ++)
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{
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double peaktmp, harmonic;
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int i1,i2;
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harmonic = (double)pow(2.0, i);
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peakpos = (int)(highPeak / harmonic + 0.5f);
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if (peakpos < minPos) break;
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peakpos = findTop(data, peakpos); // seek true local maximum index
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if (peakpos == 0) continue; // no local max here
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// calculate mass-center of possible harmonic peak
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peaktmp = getPeakCenter(data, peakpos);
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// accept harmonic peak if
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// (a) it is found
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// (b) is within ±4% of the expected harmonic interval
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// (c) has at least half x-corr value of the max. peak
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double diff = harmonic * peaktmp / highPeak;
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if ((diff < 0.96) || (diff > 1.04)) continue; // peak too afar from expected
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// now compare to highest detected peak
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i1 = (int)(highPeak + 0.5);
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i2 = (int)(peaktmp + 0.5);
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if (data[i2] >= 0.4*data[i1])
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{
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// The harmonic is at least half as high primary peak,
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// thus use the harmonic peak instead
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peak = peaktmp;
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}
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}
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return peak;
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}
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