Bug fix for stream ticking in OS-X if using two different devices.

RtAudio.cpp

@@ -1905,7 +1905,10 @@ bool RtApiCore :: callbackEvent( AudioDeviceID deviceId,
  unlock:
   //MUTEX_UNLOCK( &stream_.mutex );
 
-  RtApi::tickStreamTime();
+  // Make sure to only tick duplex stream time once if using two devices
+  if ( stream_.mode != DUPLEX || (stream_.mode == DUPLEX && handle->id[0] != handle->id[1] && deviceId == handle->id[0] ) )
+    RtApi::tickStreamTime();
+  
   return SUCCESS;
 }