Adding channel map

First test works

pycmx/channel_map.py

@@ -0,0 +1,92 @@
+# pycmx
+# (c) 2018 Jamie Hardt
+
+from re import compile
+
+class ChannelMap:
+
+    """
+    Represents a set of all the channels to which an event applies.
+    """
+
+    chan_map = {     "V" :    (True,   False,   False),
+                "A" :    (False,  True,    False),
+                "A2" :   (False,  False,   True),
+                "AA" :   (False,  True,    True),
+                "B" :    (True,   True,    False),
+                "AA/V" : (True,   True,    True),
+                "A2/V" : (True,   False,   True)
+        }
+
+    def __init__(self, v=False, audio_channels=set()):
+        self._audio_channel_set = audio_channels 
+        self.v = v
+
+    @property
+    def video(self):
+        'True if video is included'
+        return self.v
+
+    @property
+    def channels(self):
+        'A generator for each audio channel'
+        for c in self._audio_channel_set:
+            yield c
+
+    @property
+    def a1(self):
+        return self.get_audio_channel(1)
+
+    @a1.setter
+    def a1(self,val):
+        self.set_audio_channel(1,val)
+
+    @property
+    def a2(self):
+        return self.get_audio_channel(2)
+
+    @a2.setter
+    def a2(self,val):
+        self.set_audio_channel(2,val)
+
+    @property
+    def a3(self):
+        return self.get_audio_channel(3)
+
+    @a3.setter
+    def a3(self,val):
+        self.set_audio_channel(3,val)
+    
+    @property
+    def a4(self):
+        return self.get_audio_channel(4)
+
+    @a4.setter
+    def a4(self,val):
+        self.set_audio_channel(4,val)
+
+    def get_audio_channel(self,chan_num):
+        return (chan_num in self._audio_channel_set)
+
+    def set_audio_channel(self,chan_num,enabled):
+        if enabled:
+            self._audio_channel_set.add(chan_num)
+        elif self.get_audio_channel(chan_num):
+            self._audio_channel_set.remove(chan_num)
+    
+    def append_event(self, event_str):
+        alt_channel_re = compile('^A(\d+)')
+        if event_str in self.chan_map:
+            channels = self.chan_map[event_str]
+            self.v = channels[0]
+            self.a1 = channels[1]
+            self.a2 = channels[2]
+        else:
+            matchresult = match(alt_channel_re, event_str)
+            if matchresult:
+                self.set_audio_channel(int( matchresult.group(1)), True )
+
+    def append_sxt(self, audio_ext):
+        self.a3 = ext.audio3
+        self.a4 = ext.audio4
+