camera-notif

Receive motion/person/sound notifications from Google Nest cameras and watch live video in a small always-on-top desktop window on KDE Plasma.

Technical Hurdles Project Demonstrates:

• Software rendering video to plasma compositor overlay layer in real time. Perfect high frames even while gaming.
• WebRTC + SDP video signaling. Signal upgrade and downgrade on the fly.
• WebRTC -> v4l2loopback

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What it does

• Opens a live video stream from Google Home in a floating overlay window. The window draws on top of everything — including full-screen games and videos — and doesn't appear in the taskbar or Alt+Tab. It can be pinned to any screen corner.
• A tray icon lets you show or hide the window with a single click.
• The stream reconnects automatically if it drops.
• Can also stream to a virtual webcam you can use in any program that consumes video streams like OBS.

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Requirements

You'll need a few libraries installed before building. On Debian/Ubuntu:

sudo apt install build-essential pkg-config \
    libcurl4-openssl-dev libssl-dev \
    libdatachannel-dev \
    libwayland-dev \
    libavcodec-dev libavutil-dev libswscale-dev \
    libayatana-appindicator3-dev

On Arch Linux:

pacman -S base-devel pkgconf curl openssl \
    libdatachannel wayland ffmpeg libayatana-appindicator

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Build

make

The binary is written to build/camera-notif.

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Setup

Before running, you need to register with Google's device API. This is a one-time process.

1. Register a Device Access project

Go to the Device Access Console, create a project (one-time $5 fee), and note the Project ID.

2. Create Google Cloud credentials

1. In the Google Cloud Console, enable the Smart Device Management API and the Cloud Pub/Sub API.
2. Go to APIs & Services → Credentials, create an OAuth 2.0 client ID (Desktop app type), and note the client ID and secret.
3. On the OAuth consent screen, add yourself as a test user with these scopes:
   • https://www.googleapis.com/auth/sdm.service
   • https://www.googleapis.com/auth/pubsub
4. Create a Pub/Sub topic and subscription for receiving events:

   gcloud pubsub topics create camera-events --project YOUR_GCP_PROJECT
   gcloud pubsub subscriptions create camera-sub \
       --topic camera-events --project YOUR_GCP_PROJECT

5. Back in the Device Access Console, link the topic (projects/YOUR_GCP_PROJECT/topics/camera-events) to your project.

3. Configure

cp .env.example .env

Edit .env and fill in your credentials:

CLIENT_ID=...
CLIENT_SECRET=...
SDM_PROJECT_ID=...
PUBSUB_SUBSCRIPTION=projects/YOUR_GCP_PROJECT/subscriptions/camera-sub

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Running

First run

The first time you run, it will ask you to open a URL in your browser and paste back an authorization code. After that, it handles token refresh automatically.

Watch for events (default mode)

./build/camera-notif

Logs camera events as they arrive and saves clip images to clips/.

Live video overlay

./build/camera-notif --widget

Opens a small video window in the corner of your screen. The window starts hidden — click the tray icon to show it. Right-click the tray icon to choose which corner to pin it to, or to exit.

If you have multiple cameras, pass the device number shown at startup:

./build/camera-notif --widget 1

Other options

--stream-play       Open the stream in an ffplay window
--stream-v4l2 DEV   Feed the stream into a v4l2loopback device
--force-reauth      Re-run the Google sign-in flow
--help              Show all options

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Troubleshooting

Problem	Fix
CLIENT_ID not set	Make sure .env exists and is filled in
Sign-in fails with invalid_client	Double-check the client ID and secret in .env
Sign-in fails with invalid_grant	The code expires quickly — paste it immediately after copying
HTTP 403 on startup	Make sure both APIs are enabled in Google Cloud and your project IDs match
No events arriving	Check that the Pub/Sub topic is linked in the Device Access Console
No video overlay	Your build is missing the wayland or ffmpeg libraries — check the make output
No tray icon	The appindicator library is missing — install libayatana-appindicator3-dev
Stream disconnects	Normal — it reconnects automatically