Catch camera event

gistfile1.txt

#!/bin/bash

# Catch the system log events for when a camera turns on for conferencing. Should work on Zoom, Teams, etc. Your
# specific logging may vary. Also this sends API requests to the Elgato Key Light specifically.

# Begin looking at the system log via the steam sub-command. Using a --predicate and filtering by the correct
# subsystem first improves CPU performance DRASTICALLY. Then just pull out the camera event and shot a POST
# to the Elgato key light controller. It helps to create a static IP mapping in your DHCP setup so the IP of the light
# controller remains consistent. 
log stream --predicate 'subsystem == "com.apple.cameracapture" && eventMessage CONTAINS[c] "posting notification"'| while read line; do
  
  # If we catch a camera start event, turn the light on
  if echo "$line" | grep -q "AVCaptureSessionDidStartRunningNotification"; then
    echo "Camera has been activated, turn on the light."
    curl --location --request PUT 'http://[IP ADDRESS]:9123/elgato/lights' --header 'Accept: application/json' --data-raw '{"numberOfLights": 1, "lights": [{ "on": 1, "brightness": 20, "temperature": 315 }]}'
  fi

  # If we catch a camera stop event, turn the light off.
  if echo "$line" | grep -q "AVCaptureSessionDidStopRunningNotification"; then
    echo "Camera shut down, turn off the light."
    curl --location --request PUT 'http://[IP ADDRESS]:9123/elgato/lights' --header 'Accept: application/json' --data-raw '{"numberOfLights": 1, "lights": [{ "on": 0, "brightness": 20, "temperature": 315 }]}'
  fi
done

This doesn't work in macOS Monterey. You'll have to use a slightly different predicate:

$ log stream --predicate 'subsystem == "com.apple.UVCExtension" and composedMessage contains "Post PowerLog"'
Filtering the log data using "subsystem == "com.apple.UVCExtension" AND composedMessage CONTAINS "Post PowerLog""
Timestamp                       Thread     Type        Activity             PID    TTL  
2021-10-27 12:21:13.366628+0200 0x147c5    Default     0x0                  353    0    UVCAssistant: (UVCExtension) [com.apple.UVCExtension:device] UVCExtensionDevice:0x1234005d7 [0x7fe3ce008ca0] Post PowerLog {
    "VDCAssistant_Device_GUID" = "00000000-1432-0000-1234-000022470000";
    "VDCAssistant_Power_State" = On;
}
2021-10-27 12:21:16.946379+0200 0x13dac    Default     0x0                  353    0    UVCAssistant: (UVCExtension) [com.apple.UVCExtension:device] UVCExtensionDevice:0x1234005d7 [0x7fe3ce008ca0] Post PowerLog {
    "VDCAssistant_Device_GUID" = "00000000-1432-0000-1234-000022470000";
    "VDCAssistant_Power_State" = Off;
}

Is there a way to read the output for macOS Monterey - I tried to merge these 2 together but get nothing but the out put text - it doesnt appear to read the state of on or off - any help appreciated.

If you add --style ndjson to the command, every message is on one line. Then you can grep for e.g.'"VDCAssistant_Power_State" = On'.

henrik242 thanks fella got there in the end 👌

Thanks for the comments! I hadn't even tried this on Monterey yet but good to know it works with some predicate changes.