From 91abf9937091444627836fbdb9b5f3930df5f0a8 Mon Sep 17 00:00:00 2001
From: Nicolas Mowen <nickmowen213@gmail.com>
Date: Fri, 30 Aug 2024 15:31:27 -0600
Subject: [PATCH] Handle case where camera is offline when generating previews

---
 frigate/output/output.py  | 10 ++++++++++
 frigate/output/preview.py | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/frigate/output/output.py b/frigate/output/output.py
index e0e7d0cac..cb3be844c 100644
--- a/frigate/output/output.py
+++ b/frigate/output/output.py
@@ -64,6 +64,8 @@ def output_frames(
     jsmpeg_cameras: dict[str, JsmpegCamera] = {}
     birdseye: Optional[Birdseye] = None
     preview_recorders: dict[str, PreviewRecorder] = {}
+    preview_write_times: dict[str, float] = {}
+    frame_time: float = 0
 
     move_preview_frames("cache")
 
@@ -73,6 +75,7 @@ def output_frames(
 
         jsmpeg_cameras[camera] = JsmpegCamera(cam_config, stop_event, websocket_server)
         preview_recorders[camera] = PreviewRecorder(cam_config)
+        preview_write_times[camera] = 0
 
     if config.birdseye.enabled:
         birdseye = Birdseye(config, frame_manager, stop_event, websocket_server)
@@ -83,6 +86,13 @@ def output_frames(
         (topic, data) = detection_subscriber.check_for_update(timeout=1)
 
         if not topic:
+            # all queued images have been written,
+            # check if any cameras have stale frames
+
+            for camera, time in preview_write_times.items():
+                if time != 0 and frame_time - time > 10:
+                    preview_recorders[camera].flag_offline(frame_time)
+
             continue
 
         (
diff --git a/frigate/output/preview.py b/frigate/output/preview.py
index 650805750..6d08bb785 100644
--- a/frigate/output/preview.py
+++ b/frigate/output/preview.py
@@ -3,6 +3,7 @@
 import datetime
 import logging
 import os
+import shutil
 import subprocess as sp
 import threading
 import time
@@ -326,7 +327,7 @@ class PreviewRecorder:
             )
             self.start_time = frame_time
             self.last_output_time = frame_time
-            self.output_frames = []
+            self.output_frames: list[float] = []
 
             # include first frame to ensure consistent duration
             self.output_frames.append(frame_time)
@@ -335,6 +336,35 @@ class PreviewRecorder:
             self.output_frames.append(frame_time)
             self.write_frame_to_cache(frame_time, frame)
 
+    def flag_offline(self, frame_time: float) -> None:
+        # check if PREVIEW clip should be generated and cached frames reset
+        if frame_time >= self.segment_end:
+            if len(self.output_frames) == 0:
+                return
+
+            old_frame_path = get_cache_image_name(self.config.name, self.output_frames[-1])
+            new_frame_path = get_cache_image_name(self.config.name, frame_time)
+            shutil.copy(old_frame_path, new_frame_path)
+
+            # save last frame to ensure consistent duration
+            self.output_frames.append(frame_time)
+            FFMpegConverter(
+                self.config,
+                self.output_frames,
+                self.requestor,
+            ).start()
+
+            # reset frame cache
+            self.segment_end = (
+                (datetime.datetime.now() + datetime.timedelta(hours=1))
+                .astimezone(datetime.timezone.utc)
+                .replace(minute=0, second=0, microsecond=0)
+                .timestamp()
+            )
+            self.start_time = frame_time
+            self.last_output_time = frame_time
+            self.output_frames = []
+
     def stop(self) -> None:
         self.requestor.stop()