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Diffstat (limited to 'audio/softsynth/mt32/srchelper/InternalResampler.cpp')
-rw-r--r-- | audio/softsynth/mt32/srchelper/InternalResampler.cpp | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/audio/softsynth/mt32/srchelper/InternalResampler.cpp b/audio/softsynth/mt32/srchelper/InternalResampler.cpp new file mode 100644 index 0000000000..f76c7d117e --- /dev/null +++ b/audio/softsynth/mt32/srchelper/InternalResampler.cpp @@ -0,0 +1,74 @@ +/* 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 <SincResampler.h> +#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, SampleRateConverter::Quality quality) { + static const double MAX_AUDIBLE_FREQUENCY = 20000.0; + + const double sourceSampleRate = synth.getStereoOutputSampleRate(); + if (quality != SampleRateConverter::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, SampleRateConverter::Quality 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); +} |