Add enabling/disabling camera capture via MQTT

Adds new MQTT topic,

  frigate/<camera>/capture/state

to dynamically enable or disable capturing from a camera.

The ffmpeg process is terminated when the capture state is
OFF and is resumed when the capture state is ON.

docs/docs/integrations/mqtt.md

@@ -112,6 +112,14 @@ Topic to turn recordings for a camera on and off. Expected values are `ON` and `
 
 Topic with current state of recordings for a camera. Published values are `ON` and `OFF`.
 
+### `frigate/<camera_name>/capture/set`
+
+Topic to turn capture for a camera on and off. Expected values are `ON` and `OFF`.
+
+### `frigate/<camera_name>/capture/state`
+
+Topic with current state of capture for a camera. Published values are `ON` and `OFF`.
+
 ### `frigate/<camera_name>/snapshots/set`
 
 Topic to turn snapshots for a camera on and off. Expected values are `ON` and `OFF`.

frigate/app.py

@@ -109,6 +109,9 @@ class FrigateApp:
                 "camera_fps": mp.Value("d", 0.0),
                 "skipped_fps": mp.Value("d", 0.0),
                 "process_fps": mp.Value("d", 0.0),
+                "capture_enabled": mp.Value(
+                    "i", self.config.cameras[camera_name].capture_enabled
+                ),
                 "detection_enabled": mp.Value(
                     "i", self.config.cameras[camera_name].detect.enabled
                 ),

frigate/comms/dispatcher.py

@@ -1,6 +1,8 @@
 """Handle communication between Frigate and other applications."""
 
 import logging
+import os
+import signal
 from abc import ABC, abstractmethod
 from typing import Any, Callable
 
@@ -52,6 +54,7 @@ class Dispatcher:
             comm.subscribe(self._receive)
 
         self._camera_settings_handlers: dict[str, Callable] = {
+            "capture": self._on_capture_command,
             "detect": self._on_detect_command,
             "improve_contrast": self._on_motion_improve_contrast_command,
             "motion": self._on_motion_command,
@@ -92,6 +95,19 @@ class Dispatcher:
         for comm in self.comms:
             comm.stop()
 
+    def _on_capture_command(self, camera_name: str, payload: str) -> None:
+        """Callback for detect topic."""
+        logger.info(f"Received capture command [{payload}] for [{camera_name}]")
+        capture_proc = self.camera_metrics[camera_name]['capture_process']
+
+        # Send SIGUSR1 to resume, SIGUSR2 to pause
+        new_state = True if payload == "ON" else False if payload == "OFF" else None
+        if new_state is not None:
+            sig = signal.SIGUSR1 if new_state else signal.SIGUSR2
+            self.config.cameras[camera_name].capture_enabled = new_state
+            os.kill( capture_proc.pid, sig )
+            self.publish(f"{camera_name}/capture/state", payload, retain=True)
+
     def _on_detect_command(self, camera_name: str, payload: str) -> None:
         """Callback for detect topic."""
         detect_settings = self.config.cameras[camera_name].detect

frigate/comms/mqtt.py

@@ -59,6 +59,11 @@ class MqttClient(Communicator):  # type: ignore[misc]
                 "ON",
                 retain=True,
             )
+            self.publish(
+                f"{camera_name}/capture/state",
+                "ON",
+                retain=True,
+            )
             self.publish(
                 f"{camera_name}/improve_contrast/state",
                 "ON" if camera.motion.improve_contrast else "OFF",  # type: ignore[union-attr]
@@ -141,6 +146,7 @@ class MqttClient(Communicator):  # type: ignore[misc]
 
         # register callbacks
         callback_types = [
+            "capture",
             "recordings",
             "snapshots",
             "detect",

frigate/config.py

@@ -580,6 +580,7 @@ class CameraUiConfig(FrigateBaseModel):
 class CameraConfig(FrigateBaseModel):
     name: Optional[str] = Field(title="Camera name.", regex=REGEX_CAMERA_NAME)
     enabled: bool = Field(default=True, title="Enable camera.")
+    capture_enabled: bool = Field(default=True, title="Capture enabled.")
     ffmpeg: CameraFfmpegConfig = Field(title="FFmpeg configuration for the camera.")
     best_image_timeout: int = Field(
         default=60,

frigate/types.py

@@ -8,6 +8,7 @@ from frigate.object_detection import ObjectDetectProcess
 
 class CameraMetricsTypes(TypedDict):
     camera_fps: Synchronized
+    capture_enabled: Synchronized
     capture_process: Optional[Process]
     detection_enabled: Synchronized
     detection_fps: Synchronized

frigate/util.py

@@ -636,6 +636,21 @@ def restart_frigate():
     else:
         os.kill(os.getpid(), signal.SIGTERM)
 
+def terminate_process(proc: sp.Popen, logger_inst: logging.Logger = None, timeout: float = 30.0):
+    logger_inst = logger_inst or logger
+    if proc is not None and proc.poll() == None:
+        proc_name: str = proc.args[0]
+        logger_inst.info(f"Terminating the existing {proc_name} process...")
+        proc.terminate()
+        try:
+            logger_inst.info(f"Waiting for {proc_name} to exit gracefully...")
+            proc.communicate(timeout=timeout)
+        except sp.TimeoutExpired:
+            logger_inst.info(f"{proc_name}didn't exit. Force killing...")
+            proc.kill()
+            proc.communicate()
+
+
 
 class EventsPerSecond:
     def __init__(self, max_events=1000):

frigate/video.py

@@ -31,6 +31,7 @@ from frigate.util import (
     intersection,
     intersection_over_union,
     listen,
+    terminate_process,
     yuv_region_2_bgr,
     yuv_region_2_rgb,
     yuv_region_2_yuv,
@@ -112,25 +113,10 @@ def create_tensor_input(frame, model_config, region):
     # Expand dimensions since the model expects images to have shape: [1, height, width, 3]
     return np.expand_dims(cropped_frame, axis=0)
 
-
-def stop_ffmpeg(ffmpeg_process, logger):
-    logger.info("Terminating the existing ffmpeg process...")
-    ffmpeg_process.terminate()
-    try:
-        logger.info("Waiting for ffmpeg to exit gracefully...")
-        ffmpeg_process.communicate(timeout=30)
-    except sp.TimeoutExpired:
-        logger.info("FFmpeg didnt exit. Force killing...")
-        ffmpeg_process.kill()
-        ffmpeg_process.communicate()
-    ffmpeg_process = None
-
-
 def start_or_restart_ffmpeg(
     ffmpeg_cmd, logger, logpipe: LogPipe, frame_size=None, ffmpeg_process=None
 ):
-    if ffmpeg_process is not None:
-        stop_ffmpeg(ffmpeg_process, logger)
+    terminate_process( ffmpeg_process, logger_inst=logger )
 
     if frame_size is None:
         process = sp.Popen(
@@ -268,27 +254,12 @@ class CameraWatchdog(threading.Thread):
                 self.logger.info(
                     f"No frames received from {self.camera_name} in 20 seconds. Exiting ffmpeg..."
                 )
-                self.ffmpeg_detect_process.terminate()
-                try:
-                    self.logger.info("Waiting for ffmpeg to exit gracefully...")
-                    self.ffmpeg_detect_process.communicate(timeout=30)
-                except sp.TimeoutExpired:
-                    self.logger.info("FFmpeg did not exit. Force killing...")
-                    self.ffmpeg_detect_process.kill()
-                    self.ffmpeg_detect_process.communicate()
+                terminate_process(self.ffmpeg_detect_process, logger_inst=self.logger)
+                self.ffmpeg_detect_process = None
             elif self.camera_fps.value >= (self.config.detect.fps + 10):
                 self.camera_fps.value = 0
-                self.logger.info(
-                    f"{self.camera_name} exceeded fps limit. Exiting ffmpeg..."
-                )
-                self.ffmpeg_detect_process.terminate()
-                try:
-                    self.logger.info("Waiting for ffmpeg to exit gracefully...")
-                    self.ffmpeg_detect_process.communicate(timeout=30)
-                except sp.TimeoutExpired:
-                    self.logger.info("FFmpeg did not exit. Force killing...")
-                    self.ffmpeg_detect_process.kill()
-                    self.ffmpeg_detect_process.communicate()
+                terminate_process(self.ffmpeg_detect_process, logger_inst=self.logger)
+                self.ffmpeg_detect_process = None
 
             for p in self.ffmpeg_other_processes:
                 poll = p["process"].poll()
@@ -324,9 +295,11 @@ class CameraWatchdog(threading.Thread):
                     p["cmd"], self.logger, p["logpipe"], ffmpeg_process=p["process"]
                 )
 
-        stop_ffmpeg(self.ffmpeg_detect_process, self.logger)
+        terminate_process(self.ffmpeg_detect_process, logger_inst=self.logger)
+        self.ffmpeg_detect_process = None
         for p in self.ffmpeg_other_processes:
-            stop_ffmpeg(p["process"], self.logger)
+            terminate_process(p["process"], logger_inst=self.logger)
+            p["process"] = None
             p["logpipe"].close()
         self.logpipe.close()
 
@@ -405,28 +378,60 @@ class CameraCapture(threading.Thread):
 
 
 def capture_camera(name, config: CameraConfig, process_info):
+    stop_sigs = [signal.SIGTERM, signal.SIGINT]
+    pause_sigs = [signal.SIGUSR2]
+    resume_sigs = [signal.SIGUSR1]
     stop_event = mp.Event()
+    sig_queue: mp.Queue[signal.Signals] = mp.Queue()
 
     def receiveSignal(signalNumber, frame):
-        stop_event.set()
+        logger.info(f"{name} Received signal {signalNumber}")
+        sig_queue.put( signalNumber )
+        if signalNumber in (stop_sigs + pause_sigs):
+            stop_event.set()
 
     signal.signal(signal.SIGTERM, receiveSignal)
-    signal.signal(signal.SIGINT, receiveSignal)
+    signal.signal(signal.SIGINT,  receiveSignal)
+    signal.signal(signal.SIGUSR1, receiveSignal)
+    signal.signal(signal.SIGUSR2, receiveSignal)
 
-    threading.current_thread().name = f"capture:{name}"
     setproctitle(f"frigate.capture:{name}")
 
-    frame_queue = process_info["frame_queue"]
-    camera_watchdog = CameraWatchdog(
-        name,
-        config,
-        frame_queue,
-        process_info["camera_fps"],
-        process_info["ffmpeg_pid"],
-        stop_event,
-    )
-    camera_watchdog.start()
-    camera_watchdog.join()
+    def run_capture():
+        frame_queue = process_info["frame_queue"]
+        prev_sig = None
+        logger.info(f"{name}: capture starting")
+        while prev_sig not in stop_sigs:
+            camera_watchdog = CameraWatchdog(
+                name,
+                config,
+                frame_queue,
+                process_info["camera_fps"],
+                process_info["ffmpeg_pid"],
+                stop_event,
+            )
+            camera_watchdog.start()
+            camera_watchdog.join()
+            stop_event.clear()
+
+            if sig_queue.empty():
+                logger.warning(f"{name}: capture stopped without signal")
+            else:
+                logger.info(f"{name}: capture stopped")
+
+            # Go through the queued signals, aborting on any STOP or
+            # otherwise using the last state when the queue is emptied
+            while not sig_queue.empty() or prev_sig not in resume_sigs:
+                # Abort on a STOP signal
+                if( prev_sig := sig_queue.get() ) in stop_sigs:
+                    break
+
+            logger.info(f"{name}: capture resuming")
+
+    # Run a background thread to prevent deadlock in signal handlers
+    capture_thread = threading.Thread(target=run_capture)
+    capture_thread.start()
+    capture_thread.join()
 
 
 def track_camera(