feat: integrate RTL-TCP server support

android/app/src/main/cpp/dsp/fftfilt.h

@@ -0,0 +1,153 @@
+///////////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany     //
+// written by Christian Daniel                                                       //
+// Copyright (C) 2014-2015 John Greb <hexameron@spam.no>                             //
+// Copyright (C) 2015-2018, 2022-2023 Edouard Griffiths, F4EXB <f4exb06@gmail.com>   //
+// Copyright (C) 2020 Kacper Michajłow <kasper93@gmail.com>                          //
+//                                                                                   //
+// This program 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 as version 3 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 General Public License V3 for more details.                                   //
+//                                                                                   //
+// You should have received a copy of the GNU General Public License                 //
+// along with this program. If not, see <http://www.gnu.org/licenses/>.              //
+///////////////////////////////////////////////////////////////////////////////////////
+/*
+ * Filters from Fldigi.
+*/
+
+#ifndef	_FFTFILT_H
+#define	_FFTFILT_H
+
+#include <complex>
+#include <cmath>
+
+#include "gfft.h"
+#include "fftwindow.h"
+#include "fftnr.h"
+#include "export.h"
+
+//----------------------------------------------------------------------
+
+class SDRBASE_API fftfilt {
+enum {NONE, BLACKMAN, HAMMING, HANNING};
+
+public:
+	typedef std::complex<float> cmplx;
+
+	fftfilt(int len);
+	fftfilt(float f1, float f2, int len);
+	fftfilt(float f2, int len);
+	~fftfilt();
+// f1 < f2 ==> bandpass
+// f1 > f2 ==> band reject
+	void create_filter(float f1, float f2, FFTWindow::Function wf = FFTWindow::Blackman);
+    void create_filter(const std::vector<std::pair<float, float>>& limits, bool pass = true, FFTWindow::Function wf = FFTWindow::Blackman);
+    void create_filter(const std::vector<std::pair<float, float>>& limits, bool pass = true); //!< Windowless version
+	void create_dsb_filter(float f2, FFTWindow::Function wf = FFTWindow::Blackman);
+    void create_asym_filter(float fopp, float fin, FFTWindow::Function wf = FFTWindow::Blackman); //!< two different filters for in band and opposite band
+    void create_rrc_filter(float fb, float a); //!< root raised cosine. fb is half the band pass
+
+	int noFilt(const cmplx& in, cmplx **out);
+	int runFilt(const cmplx& in, cmplx **out);
+	int runSSB(const cmplx& in, cmplx **out, bool usb, bool getDC = true);
+	int runDSB(const cmplx& in, cmplx **out, bool getDC = true);
+	int runAsym(const cmplx & in, cmplx **out, bool usb); //!< Asymmetrical filtering can be used for vestigial sideband
+
+    void setDNR(bool dnr) { m_dnr = dnr; }
+    void setDNRScheme(FFTNoiseReduction::Scheme scheme) { m_dnrScheme = scheme; }
+    void setDNRAboveAvgFactor(float aboveAvgFactor) { m_dnrAboveAvgFactor = aboveAvgFactor; }
+    void setDNRSigmaFactor(float sigmaFactor) { m_dnrSigmaFactor = sigmaFactor; }
+    void setDNRNbPeaks(int nbPeaks) { m_dnrNbPeaks = nbPeaks; }
+    void setDNRAlpha(float alpha) { m_noiseReduction.setAlpha(alpha); }
+
+protected:
+    // helper class for FFT based noise reduction
+	int flen;
+	int flen2;
+	g_fft<float> *fft;
+	cmplx *filter;
+    cmplx *filterOpp;
+	cmplx *data;
+	cmplx *ovlbuf;
+	cmplx *output;
+	int inptr;
+	int pass;
+	int window;
+    bool m_dnr;
+    FFTNoiseReduction::Scheme m_dnrScheme;
+    float m_dnrAboveAvgFactor; //!< above average factor
+    float m_dnrSigmaFactor; //!< sigma multiplicator for average + std deviation
+    int m_dnrNbPeaks; //!< number of peaks (peaks scheme)
+    FFTNoiseReduction m_noiseReduction;
+
+	inline float fsinc(float fc, int i, int len)
+	{
+	    int len2 = len/2;
+		return (i == len2) ? 2.0 * fc:
+				sin(2 * M_PI * fc * (i - len2)) / (M_PI * (i - len2));
+	}
+
+	inline float _blackman(int i, int len)
+	{
+		return (0.42 -
+				 0.50 * cos(2.0 * M_PI * i / len) +
+				 0.08 * cos(4.0 * M_PI * i / len));
+	}
+
+	/** RRC function in the frequency domain. Zero frequency is on the sides with first half in positive frequencies
+	 * and second half in negative frequencies */
+	inline cmplx frrc(float fb, float a, int i, int len)
+	{
+        float x = i/(float)len; // normalize to [0..1]
+        x = 0.5-fabs(x-0.5); // apply symmetry: now both halves overlap near 0
+        float tr = fb*a; // half the transition zone
+
+        if (x < fb-tr)
+        {
+            return 1.0; // in band
+        }
+        else if (x < fb+tr) // transition
+        {
+            float y = ((x-(fb-tr)) / (2.0*tr))*M_PI;
+            return (cos(y) + 1.0f)/2.0f;
+        }
+        else
+        {
+            return 0.0; // out of band
+        }
+	}
+
+	void init_filter();
+	void init_dsb_filter();
+};
+
+
+
+/* Sliding FFT filter from Fldigi */
+class SDRBASE_API sfft {
+#define K1 0.99999
+public:
+	typedef std::complex<float> cmplx;
+	sfft(int len);
+	~sfft();
+	void run(const cmplx& input);
+	void fetch(float *result);
+private:
+	int fftlen;
+	int first;
+	int last;
+	int ptr;
+	struct vrot_bins_pair;
+	vrot_bins_pair *vrot_bins;
+	cmplx *delay;
+	float k2;
+};
+
+#endif