Limit shm frame count (#12363)

* Limited shm frame count (#12346)

* Only keep 2x detect fps frames in SHM

* Don't delete previous shm frames in output

* Catch case where images do not exist

* Ensure files are closed

* Clear out all frames when shutting down

* Correct the number of frames saved

* Simplify empty shm error handling

* Improve frame safety

* Add handler logs when frame is None

* Don't fail on cleanup

* Cleanup logging

* Update docs

* Update calculation

* Restore condition

* Fix case where thumbnail is saved without frame

* Adjust debug logs

* Calculate best shm frame count

* Fix shm count calculation

* Catch missing frame

* Formatting

* Clarify docs

* Catch none frame in autotracking

frigate/output/output.py

@@ -45,7 +45,6 @@ def output_frames(
     signal.signal(signal.SIGINT, receiveSignal)
 
     frame_manager = SharedMemoryFrameManager()
-    previous_frames = {}
 
     # start a websocket server on 8082
     WebSocketWSGIHandler.http_version = "1.1"
@@ -99,6 +98,10 @@ def output_frames(
 
         frame = frame_manager.get(frame_id, config.cameras[camera].frame_shape_yuv)
 
+        if frame is None:
+            logger.debug(f"Failed to get frame {frame_id} from SHM")
+            continue
+
         # send camera frame to ffmpeg process if websockets are connected
         if any(
             ws.environ["PATH_INFO"].endswith(camera) for ws in websocket_server.manager
@@ -128,10 +131,6 @@ def output_frames(
         )
         preview_write_times[camera] = frame_time
 
-        # delete frames after they have been used for output
-        if camera in previous_frames:
-            frame_manager.delete(f"{camera}{previous_frames[camera]}")
-
         # if another camera generated a preview,
         # check for any cameras that are currently offline
         # and need to generate a preview
@@ -141,7 +140,7 @@ def output_frames(
                     preview_recorders[camera].flag_offline(frame_time)
                     preview_write_times[camera] = frame_time
 
-        previous_frames[camera] = frame_time
+        frame_manager.close(frame_id)
 
     move_preview_frames("clips")
 
@@ -161,7 +160,7 @@ def output_frames(
 
         frame_id = f"{camera}{frame_time}"
         frame = frame_manager.get(frame_id, config.cameras[camera].frame_shape_yuv)
-        frame_manager.delete(frame_id)
+        frame_manager.close(frame_id)
 
     detection_subscriber.stop()