Expose dBFS when doing audio analysis (#6979)

* Expose dBFS when doing audio analysis

* Implement metadata communicator

* revert test changes

* Reverting the tests changes. For real this time

* Address feedback

* Address feedback

* Address feedback

* Address feedback

frigate/comms/inter_process.py

@@ -0,0 +1,40 @@
+import multiprocessing as mp
+import queue
+import threading
+from multiprocessing.synchronize import Event as MpEvent
+from typing import Callable
+
+from faster_fifo import Queue
+
+from frigate.comms.dispatcher import Communicator
+
+
+class InterProcessCommunicator(Communicator):
+    def __init__(self, queue: Queue) -> None:
+        self.queue = queue
+        self.stop_event: MpEvent = mp.Event()
+
+    def publish(self, topic: str, payload: str, retain: bool) -> None:
+        """There is no communication back to the processes."""
+        pass
+
+    def subscribe(self, receiver: Callable) -> None:
+        self._dispatcher = receiver
+        self.reader_thread = threading.Thread(target=self.read)
+        self.reader_thread.start()
+
+    def read(self) -> None:
+        while not self.stop_event.is_set():
+            try:
+                (
+                    topic,
+                    value,
+                ) = self.queue.get(True, 1)
+            except queue.Empty:
+                continue
+
+            self._dispatcher(topic, value)
+
+    def stop(self) -> None:
+        self.stop_event.set()
+        self.reader_thread.join()