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/* Copyright (C) 2015-2017 Sergey V. Mikayev
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 2.1 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "InternalResampler.h"
#include "srctools/include/SincResampler.h"
#include "srctools/include/ResamplerModel.h"
#include "../Synth.h"
using namespace SRCTools;
namespace MT32Emu {
class SynthWrapper : public FloatSampleProvider {
Synth &synth;
public:
SynthWrapper(Synth &useSynth) : synth(useSynth)
{}
void getOutputSamples(FloatSample *outBuffer, unsigned int size) {
synth.render(outBuffer, size);
}
};
static FloatSampleProvider &createModel(Synth &synth, SRCTools::FloatSampleProvider &synthSource, double targetSampleRate, SamplerateConversionQuality quality) {
static const double MAX_AUDIBLE_FREQUENCY = 20000.0;
const double sourceSampleRate = synth.getStereoOutputSampleRate();
if (quality != SamplerateConversionQuality_FASTEST) {
const bool oversampledMode = synth.getStereoOutputSampleRate() == Synth::getStereoOutputSampleRate(AnalogOutputMode_OVERSAMPLED);
// Oversampled input allows to bypass IIR interpolation stage and, in some cases, IIR decimation stage
if (oversampledMode && (0.5 * sourceSampleRate) <= targetSampleRate) {
// NOTE: In the oversampled mode, the transition band starts at 20kHz and ends at 28kHz
double passband = MAX_AUDIBLE_FREQUENCY;
double stopband = 0.5 * sourceSampleRate + MAX_AUDIBLE_FREQUENCY;
ResamplerStage &resamplerStage = *SincResampler::createSincResampler(sourceSampleRate, targetSampleRate, passband, stopband, ResamplerModel::DEFAULT_DB_SNR, ResamplerModel::DEFAULT_WINDOWED_SINC_MAX_UPSAMPLE_FACTOR);
return ResamplerModel::createResamplerModel(synthSource, resamplerStage);
}
}
return ResamplerModel::createResamplerModel(synthSource, sourceSampleRate, targetSampleRate, static_cast<ResamplerModel::Quality>(quality));
}
} // namespace MT32Emu
using namespace MT32Emu;
InternalResampler::InternalResampler(Synth &synth, double targetSampleRate, SamplerateConversionQuality quality) :
synthSource(*new SynthWrapper(synth)),
model(createModel(synth, synthSource, targetSampleRate, quality))
{}
InternalResampler::~InternalResampler() {
ResamplerModel::freeResamplerModel(model, synthSource);
delete &synthSource;
}
void InternalResampler::getOutputSamples(float *buffer, unsigned int length) {
model.getOutputSamples(buffer, length);
}
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