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/ptz/autotrack.py

@@ -99,6 +99,10 @@ class PtzMotionEstimator:
                 frame_id, self.camera_config.frame_shape_yuv
             )
 
+            if yuv_frame is None:
+                self.coord_transformations = None
+                return None
+
             frame = cv2.cvtColor(yuv_frame, cv2.COLOR_YUV2GRAY_I420)
 
             # mask out detections for better motion estimation