Add another example for mediamtx

docs/stream.mediamtx.md

@@ -47,3 +47,35 @@ Or you could watch it via web browser under endpoints such as
 http://rpi-address:8889/cam
 http://rpi-address:8889/endoscope
 ```
+
+## Example with single camera over USB
+
+Raspberry Pi Zero 2 + Logitech C920, thanks to [user [&] undso.io](https://forum.prusa3d.com/forum/profile/undso-io/)
+for working example.
+
+Allows to have a camera live stream and prusa camera script to use that stream
+as source of the images to send to PrusaConnect.
+
+<!-- markdownlint-disable line_length -->
+mediamtx config fragment
+
+```yaml
+paths:
+  cam:
+    runOnInit: ffmpeg -f v4l2 -i /dev/video0 -pix_fmt yuv420p -video_size 1920x1080 -framerate 30 -preset ultrafast -c:v libx264 -b:v 6000k -f rtsp rtsp://localhost:$RTSP_PORT/$MTX_PATH
+    runOnInitRestart: yes
+```
+
+env file for prusa connect script, remember to replace `[rpizero-ip]` with
+device address (or try `127.0.0.1` or `0.0.0.0` if script runs on the same host where mediamtx runs)
+
+```shell
+PRINTER_ADDRESS=...
+PRUSA_CONNECT_CAMERA_TOKEN=...
+PRUSA_CONNECT_CAMERA_FINGERPRINT=...
+CAMERA_DEVICE=/dev/null
+CAMERA_COMMAND=ffmpeg
+CAMERA_COMMAND_EXTRA_PARAMS="-loglevel error -y -rtsp_transport udp -i 'rtsp://[rpizero-ip]:8554/cam' -f image2 -vframes 1 -pix_fmt yuv420p "
+```
+
+<!-- markdownlint-enable line_length -->