Allow modems to limit/control input rate

- Modems can now over-ride user rate input and lock/step as needed
- Separate digital code defs a bit more so it’s not required when
disabled
- Testing FSK based on @andresv ’s example at
https://github.com/jgaeddert/liquid-dsp/issues/9

src/modules/modem/analog/ModemFMStereo.cpp

@@ -30,6 +30,14 @@ Modem *ModemFMStereo::factory() {
     return new ModemFMStereo;
 }
 
+int ModemFMStereo::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate < 100000) {
+        return 100000;
+    } else {
+        return sampleRate;
+    }
+}
+
 ModemKit *ModemFMStereo::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKitFMStereo *kit = new ModemKitFMStereo;
     

src/modules/modem/analog/ModemFMStereo.h

@@ -23,6 +23,7 @@ public:
     std::string getType();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     ModemKit *buildKit(long long sampleRate, int audioSampleRate);
     void disposeKit(ModemKit *kit);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);

src/modules/modem/analog/ModemIQ.cpp

@@ -10,6 +10,8 @@ Modem *ModemIQ::factory() {
 
 ModemKit *ModemIQ::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKit *kit = new ModemKit;
+    kit->sampleRate = sampleRate;
+    kit->audioSampleRate = audioSampleRate;
     return kit;
 }
 
@@ -25,6 +27,10 @@ void ModemIQ::disposeKit(ModemKit *kit) {
     delete kit;
 }
 
+int ModemIQ::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    return audioSampleRate;
+}
+
 void ModemIQ::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     int bufSize = input->data.size();
     

src/modules/modem/analog/ModemIQ.h

@@ -8,6 +8,7 @@ public:
     std::string getName();
     Modem *factory();
     ModemKit *buildKit(long long sampleRate, int audioSampleRate);
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void disposeKit(ModemKit *kit);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     

src/modules/modem/analog/ModemLSB.cpp

@@ -19,6 +19,13 @@ ModemLSB::~ModemLSB() {
     ampmodem_destroy(demodAM_LSB);
 }
 
+int ModemLSB::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate % 2 == 0) {
+        return sampleRate;
+    }
+    return sampleRate+1;
+}
+
 void ModemLSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     ModemKitAnalog *akit = (ModemKitAnalog *)kit;
     

src/modules/modem/analog/ModemLSB.h

@@ -8,6 +8,7 @@ public:
     ~ModemLSB();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     
 private:

src/modules/modem/analog/ModemUSB.cpp

@@ -19,6 +19,13 @@ ModemUSB::~ModemUSB() {
     ampmodem_destroy(demodAM_USB);
 }
 
+int ModemUSB::checkSampleRate(long long sampleRate, int audioSampleRate) {
+    if (sampleRate % 2 == 0) {
+        return sampleRate;
+    }
+    return sampleRate+1;
+}
+
 void ModemUSB::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
     ModemKitAnalog *akit = (ModemKitAnalog *)kit;
     

src/modules/modem/analog/ModemUSB.h

@@ -7,6 +7,7 @@ public:
     ~ModemUSB();
     std::string getName();
     Modem *factory();
+    int checkSampleRate(long long sampleRate, int audioSampleRate);
     void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut);
     
 private: