TLDR: Publish frames from a connected camera (or MJPEG/RTSP stream) to an MQTT topic, and demonstrate how this can be used to create a simple image processing pipeline that can be used in an IOT or home automation project. The camera stream can be viewed in a browser with Streamlit or Home Assistant.
Long introduction: A typical task in IOT/science is that you have a camera connected to one machine and you want to view the camera feed on a different machine, and maybe preprocess the images and save them to disk. I have always found this to be may more work than expected. In particular working with camera streams can get quite complicated, and may force you to experiment with tools like Gstreamer and ffmpeg that have a steep learning curve. In contrast, working with MQTT is very straightforward and is also probably familiar to anyone with an interest in IOT. This code uses MQTT to send frames from a camera over a netork at low FPS. Whilst MQTT is rarely used for this purpose (sending files) I have not encountered any issues doing this. Furthermore it is possible to setup an image processing pipeline by linking MQTT topics together, using an on_message(topic) to do some processing and send the processed image downstream on another topic. Note that this is not a high FPS (frames per second) solution, and in practice I achieve around 1 FPS which is practical for tasks such as preprocessing (cropping, rotating) images prior to viewing them. The code is written for simplicity and ease of use, not high performance. If you require high performance/low latency checkout Frigate instead.
On linux/OSX/Windows use a venv to isolate your environment, and install the required dependencies:
$ (base) python3 -m venv venv
$ (base) source venv/bin/activate
$ (venv) pip3 install -r requirements.txt
Do not use a venv and install openCV system wide using:
$ sudo apt install python3-opencv
$ pip3 install -r requirements.txt
I have not tested Streamlit on the Raspberry pi, but you can use the viewer on another machine (WIndows, OSX) anyways so don't worry.
Use the config.yaml file in config directory to setup the system (mqtt broker IP etc) and validate the config by running:
$ (venv) python3 scripts/validate_config.py
To publish camera frames over MQTT:
$ (venv) python3 scripts/camera.py
To view the camera frames with Streamlit:
$ (venv) streamlit run scripts/viewer.py
Note: if streamlit becomes unresponsive, ctrl-z to pause Streamlit then kill -9 %%. Also note that the viewer can be run on amy machine on your network.
To process a camera stream (the example rotates the image):
$ (venv) python3 scripts/processing.py
To save frames to disk:
$ (venv) python3 scripts/save-captures.py
The viewer.py script uses Streamlit to display the camera feed:
You can view the camera feed using Home Assistant and configuring an MQTT camera. Add to your configuration.yaml:
camera:
- platform: mqtt
topic: homie/mac_webcam/capture
name: mqtt_camera
- platform: mqtt
topic: homie/mac_webcam/capture/rotated
name: mqtt_camera_rotated
If your laptop has a built-in webcam this will generally be listed as VIDEO_SOURCE = 0. If you plug in an external USB webcam this takes precedence over the inbuilt webcam, with the external camera becoming VIDEO_SOURCE = 0 and the built-in webcam becoming VIDEO_SOURCE = 1. To check which cameras are detected run:
$ (venv) python3 scripts/check-cameras.py
Alternatively you can pass a string to an MJPEG/RTSP stream, For example "rtsp://admin:[email protected]:554/11"
Need an MQTT broker? If you have Docker installed I recommend eclipse-mosquitto. A basic broker can be run with
$ docker run --p 1883:1883 -d eclipse-mosquitto`
Note that I have stuctured the MQTT topics following the homie MQTT convention, link in the refefrences. This is not necessary but is best practice IMO.
- imageZMQ -> inspired this project, but uses ZMQ
- homie MQTT convention -> how to structure MQTT topics
- yolocam_mqtt -> another source of ideas
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