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audio/softsynth/mt32/srchelper/srctools/include/FIRResampler.h

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+/* Copyright (C) 2015-2022 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 SRCTOOLS_FIR_RESAMPLER_H
+#define SRCTOOLS_FIR_RESAMPLER_H
+
+#include "ResamplerStage.h"
+
+namespace SRCTools {
+
+typedef FloatSample FIRCoefficient;
+
+static const unsigned int FIR_INTERPOLATOR_CHANNEL_COUNT = 2;
+
+class FIRResampler : public ResamplerStage {
+public:
+	FIRResampler(const unsigned int upsampleFactor, const double downsampleFactor, const FIRCoefficient kernel[], const unsigned int kernelLength);
+	~FIRResampler();
+
+	void process(const FloatSample *&inSamples, unsigned int &inLength, FloatSample *&outSamples, unsigned int &outLength);
+	unsigned int estimateInLength(const unsigned int outLength) const;
+
+private:
+	const struct Constants {
+		// Filter coefficients
+		const FIRCoefficient *taps;
+		// Indicates whether to interpolate filter taps
+		bool usePhaseInterpolation;
+		// Size of array of filter coefficients
+		unsigned int numberOfTaps;
+		// Upsampling factor
+		unsigned int numberOfPhases;
+		// Downsampling factor
+		double phaseIncrement;
+		// Index of last delay line element, generally greater than numberOfTaps to form a proper binary mask
+		unsigned int delayLineMask;
+		// Delay line
+		FloatSample(*ringBuffer)[FIR_INTERPOLATOR_CHANNEL_COUNT];
+
+		Constants(const unsigned int upsampleFactor, const double downsampleFactor, const FIRCoefficient kernel[], const unsigned int kernelLength);
+	} constants;
+	// Index of current sample in delay line
+	unsigned int ringBufferPosition;
+	// Current phase
+	double phase;
+
+	bool needNextInSample() const;
+	void addInSamples(const FloatSample *&inSamples);
+	void getOutSamplesStereo(FloatSample *&outSamples);
+}; // class FIRResampler
+
+} // namespace SRCTools
+
+#endif // SRCTOOLS_FIR_RESAMPLER_H