refactor

csdr/chain/demodulator.py

@@ -1,12 +1,27 @@
 from csdr.chain import Chain
+from abc import ABC, abstractmethod
 
 
 class BaseDemodulatorChain(Chain):
     def getFixedIfSampleRate(self):
         return None
 
-    def getFixedAudioRate(self):
-        return None
-
     def supportsSquelch(self):
         return True
+
+
+class FixedAudioRateChain(ABC):
+    @abstractmethod
+    def getFixedAudioRate(self):
+        pass
+
+
+class FixedIfSampleRateChain(ABC):
+    @abstractmethod
+    def getFixedIfSampleRate(self):
+        return self.fixedIfSampleRate
+
+
+# marker interface
+class HdAudio:
+    pass