added OQPSK mode to the meteor demodulator

Author: AlexandreRouma

decoder_modules/meteor_demodulator/src/main.cpp

@@ -57,9 +57,12 @@ class MeteorDemodulatorModule : public ModuleManager::Instance {
         if (config.conf[name].contains("brokenModulation")) {
             brokenModulation = config.conf[name]["brokenModulation"];
         }
+        if (config.conf[name].contains("oqpsk")) {
+            oqpsk = config.conf[name]["oqpsk"];
+        }
         config.release();
 
-        vfo = sigpath::vfoManager.createVFO(name, ImGui::WaterfallVFO::REF_CENTER, 0, 150000, INPUT_SAMPLE_RATE, 150000, 150000, true);
+        vfo = sigpath::vfoManager.createVFO(name, ImGui::WaterfallVFO::REF_CENTER, 0, INPUT_SAMPLE_RATE, INPUT_SAMPLE_RATE, INPUT_SAMPLE_RATE, INPUT_SAMPLE_RATE, true);
         demod.init(vfo->output, 72000.0f, INPUT_SAMPLE_RATE, 33, 0.6f, 0.1f, 0.005f, brokenModulation, 1e-6, 0.01);
         split.init(&demod.out);
         split.bindStream(&symSinkStream);
@@ -151,6 +154,13 @@ class MeteorDemodulatorModule : public ModuleManager::Instance {
             config.release(true);
         }
 
+        if (ImGui::Checkbox(CONCAT("OQPSK##oqpsk", _this->name), &_this->oqpsk)) {
+            _this->demod.setOQPSK(_this->oqpsk);
+            config.acquire();
+            config.conf[_this->name]["oqpsk"] = _this->oqpsk;
+            config.release(true);
+        }
+
         if (!_this->folderSelect.pathIsValid() && _this->enabled) { style::beginDisabled(); }
 
         if (_this->recording) {
@@ -245,7 +255,7 @@ class MeteorDemodulatorModule : public ModuleManager::Instance {
     uint64_t dataWritten = 0;
     std::ofstream recFile;
     bool brokenModulation = false;
-
+    bool oqpsk = false;
     int8_t* writeBuffer;
 };
 

decoder_modules/meteor_demodulator/src/meteor_demod.h

@@ -129,6 +129,12 @@ namespace dsp::demod {
             costas.setBrokenModulation(enabled);
         }
 
+        void setOQPSK(bool enabled) {
+            assert(base_type::_block_init);
+            std::lock_guard<std::recursive_mutex> lck(base_type::ctrlMtx);
+            oqpsk = enabled;
+        }
+
         void reset() {
             assert(base_type::_block_init);
             std::lock_guard<std::recursive_mutex> lck(base_type::ctrlMtx);
@@ -144,6 +150,18 @@ namespace dsp::demod {
             rrc.process(count, in, out);
             agc.process(count, out, out);
             costas.process(count, out, out);
+
+            if (oqpsk) {
+                // Single sample delay + deinterleave
+                for (int i = 0; i < count; i++) {
+                    float tmp = out[i].im;
+                    out[i].im = lastI;
+                    lastI = tmp;
+                }
+
+                // TODO: Additional 1/24th sample delay
+            }
+
             return recov.process(count, out, out);
         }
 
@@ -166,6 +184,8 @@ namespace dsp::demod {
         double _samplerate;
         int _rrcTapCount;
         double _rrcBeta;
+        float lastI = 0.0f;
+        bool oqpsk = false;
 
         tap<float> rrcTaps;
         filter::FIR<complex_t, float> rrc;