reverse.cpp

Audacity是一款用於錄音和編輯聲音的、免費的開放源碼軟體。它可以執行於Mac OS X、Microsoft Windows、GNU/Linux和其它作業系統

/**********************************************************************

  Audacity: A Digital Audio Editor

  Reverse.cpp

  Mark Phillips

  This class reverses the selected audio.

**********************************************************************/

#include <math.h>

#include "Reverse.h"
#include "../WaveTrack.h"

//
// EffectReverse
//

EffectReverse::EffectReverse()
{
}

bool EffectReverse::Process()
{
   TrackListIterator iter(mWaveTracks);
   WaveTrack *track = (WaveTrack *) iter.First();
   int count = 0;
   while (track) {
      double trackStart = track->GetStartTime();
      double trackEnd = track->GetEndTime();
      double t0 = mT0 < trackStart? trackStart: mT0;
      double t1 = mT1 > trackEnd? trackEnd: mT1;

      if (t1 > t0) {
         longSampleCount start = track->TimeToLongSamples(t0);
         longSampleCount end = track->TimeToLongSamples(t1);
         sampleCount len = (sampleCount)(end - start);

         if (!ProcessOne(count, track, start, len))
            return false;
      }

      track = (WaveTrack *) iter.Next();
      count++;
   }

   return true;
}

bool EffectReverse::ProcessOne(int count, WaveTrack *track,
                               longSampleCount start, sampleCount len)
{
   // keep track of two blocks whose data we will swap
   longSampleCount first = start;
   longSampleCount second;

   sampleCount blockSize = track->GetMaxBlockSize();
   float tmp;
   float *buffer1 = new float[blockSize];
   float *buffer2 = new float[blockSize];
   
   sampleCount originalLen = len;

   while (len > 1) {
      sampleCount block = track->GetBestBlockSize(first);
      if (block > len / 2)
         block = len / 2;
      second = first + (len - block);

      track->Get((samplePtr)buffer1, floatSample, first, block);
      track->Get((samplePtr)buffer2, floatSample, second, block);
      for (int i = 0; i < block; i++) {
         tmp = buffer1[i];
         buffer1[i] = buffer2[block-i-1];
         buffer2[block-i-1] = tmp;
      }
      track->Set((samplePtr)buffer1, floatSample, first, block);
      track->Set((samplePtr)buffer2, floatSample, second, block);

      len -= 2 * block;
      first += block;
      
      TrackProgress(count, 2*(first-start) / (double) originalLen);
   }

   delete[] buffer1;
   delete[] buffer2;

   return true;
}


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