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Diffstat (limited to 'audio/softsynth/mt32/SampleRateConverter.h')
-rw-r--r-- | audio/softsynth/mt32/SampleRateConverter.h | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/audio/softsynth/mt32/SampleRateConverter.h b/audio/softsynth/mt32/SampleRateConverter.h new file mode 100644 index 0000000000..24bce0891b --- /dev/null +++ b/audio/softsynth/mt32/SampleRateConverter.h @@ -0,0 +1,78 @@ +/* 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/>. + */ + +#ifndef SAMPLE_RATE_CONVERTER_H +#define SAMPLE_RATE_CONVERTER_H + +#include "globals.h" +#include "Types.h" +#include "Enumerations.h" + +namespace MT32Emu { + +class Synth; + +/* SampleRateConverter class allows to convert the synthesiser output to any desired sample rate. + * It processes the completely mixed stereo output signal as it passes the analogue circuit emulation, + * so emulating the synthesiser output signal passing further through an ADC. + * Several conversion quality options are provided which allow to trade-off the conversion speed vs. the passband width. + * All the options except FASTEST guarantee full suppression of the aliasing noise in terms of the 16-bit integer samples. + */ +class MT32EMU_EXPORT SampleRateConverter { +public: + enum Quality { + // Use this only when the speed is more important than the audio quality. + FASTEST, + FAST, + GOOD, + BEST + }; + + // Returns the value of AnalogOutputMode for which the output signal may retain its full frequency spectrum + // at the sample rate specified by the targetSampleRate argument. + static AnalogOutputMode getBestAnalogOutputMode(double targetSampleRate); + + // Creates a SampleRateConverter instance that converts output signal from the synth to the given sample rate + // with the specified conversion quality. + SampleRateConverter(Synth &synth, double targetSampleRate, Quality quality); + ~SampleRateConverter(); + + // Fills the provided output buffer with the results of the sample rate conversion. + // The input samples are automatically retrieved from the synth as necessary. + void getOutputSamples(MT32Emu::Bit16s *buffer, unsigned int length); + + // Fills the provided output buffer with the results of the sample rate conversion. + // The input samples are automatically retrieved from the synth as necessary. + void getOutputSamples(float *buffer, unsigned int length); + + // Returns the number of samples produced at the internal synth sample rate (32000 Hz) + // that correspond to the number of samples at the target sample rate. + // Intended to facilitate audio time synchronisation. + double convertOutputToSynthTimestamp(double outputTimestamp) const; + + // Returns the number of samples produced at the target sample rate + // that correspond to the number of samples at the internal synth sample rate (32000 Hz). + // Intended to facilitate audio time synchronisation. + double convertSynthToOutputTimestamp(double synthTimestamp) const; + +private: + const double synthInternalToTargetSampleRateRatio; + void * const srcDelegate; +}; // class SampleRateConverter + +} // namespace MT32Emu + +#endif // SAMPLE_RATE_CONVERTER_H |