downsamplerlibsrc.cpp

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

  Copyright 2011 Ibrahim Sha'ath

  This file is part of KeyFinder.

  KeyFinder 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 3 of the License, or
  (at your option) any later version.

  KeyFinder 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 KeyFinder.  If not, see <http://www.gnu.org/licenses/>.

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

#include "downsamplerlibsrc.h"
#include <samplerate.h>

KeyFinder::AudioData* SecretRabbitDownsampler::downsample(KeyFinder::AudioData* audioIn, unsigned int factor){
  if(factor == 1) return audioIn;
  KeyFinder::AudioData* audioOut = new KeyFinder::AudioData();
  audioOut->setFrameRate(audioIn->getFrameRate() / factor);
  audioOut->setChannels(audioIn->getChannels());
  try{
    audioOut->addToSampleCount(audioIn->getSampleCount() / factor);
  }catch(const KeyFinder::Exception& e){
    throw e;
  }
  SRC_DATA srcData;
  srcData.data_in = &audioIn->getSamples().front();
  srcData.data_out = &audioOut->getSamples().front();
  srcData.input_frames = (long)(audioIn->getSampleCount() / audioIn->getChannels());
  srcData.output_frames = (long)(audioOut->getSampleCount() / audioOut->getChannels());
  srcData.src_ratio = 1.0/factor;
  // second parameter = converter type.
  // 0-2 quite slow but they anti-alias roughly the same amount, based on a visual inspection.
  // 3-4 super fast but the aliasing is worse than a simple discard. Don't use.
  int result = src_simple(&srcData,2,audioIn->getChannels());
  if(result != 0){
    throw KeyFinder::Exception("Error in LibSRC sample rate conversion");
  }
  delete audioIn;
  return audioOut;
}