Add software

Software/CubicSDR/src/modules/modem/analog/ModemLSB.cpp

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+// Copyright (c) Charles J. Cliffe
+// SPDX-License-Identifier: GPL-2.0+
+
+#include "ModemLSB.h"
+
+ModemLSB::ModemLSB() : ModemAnalog() {
+    // half band filter used for side-band elimination
+    ssbFilt = iirfilt_crcf_create_lowpass(6, 0.25);
+	ssbShift = nco_crcf_create(LIQUID_NCO);
+    nco_crcf_set_frequency(ssbShift,  (float)((2.0 * M_PI) * 0.25));
+    c2rFilt = firhilbf_create(5, 90.0);
+    useSignalOutput(true);
+}
+
+ModemBase *ModemLSB::factory() {
+    return new ModemLSB;
+}
+
+std::string ModemLSB::getName() {
+    return "LSB";
+}
+
+ModemLSB::~ModemLSB() {
+	iirfilt_crcf_destroy(ssbFilt);
+	nco_crcf_destroy(ssbShift);
+    firhilbf_destroy(c2rFilt);
+}
+
+int ModemLSB::checkSampleRate(long long sampleRate, int /* audioSampleRate */) {
+    if (sampleRate < MIN_BANDWIDTH) {
+        return MIN_BANDWIDTH;
+    }
+    if (sampleRate % 2 == 0) {
+        return (int)sampleRate;
+    }
+    return (int)(sampleRate+1);
+}
+
+int ModemLSB::getDefaultSampleRate() {
+    return 5400;
+}
+
+void ModemLSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
+    auto *akit = (ModemKitAnalog *)kit;
+    
+    initOutputBuffers(akit,input);
+    
+    if (!bufSize) {
+       
+        return;
+    }
+    
+    liquid_float_complex x, y;
+    for (size_t i = 0; i < bufSize; i++) { // Reject upper band
+        nco_crcf_step(ssbShift);
+        nco_crcf_mix_up(ssbShift, input->data[i], &x);
+		iirfilt_crcf_execute(ssbFilt, x, &y);
+        nco_crcf_mix_down(ssbShift, y, &x);
+        float usb_discard;
+        firhilbf_c2r_execute(c2rFilt, x, &demodOutputData[i], &usb_discard);
+    }
+    
+    buildAudioOutput(akit, audioOut, true);
+}