Unfortunately my webcam has no MPEG stream, only a live snapshot url. With this plugin the path to the live snapshot can be entered as webcam. The plugin reloads the live snapshot every 500ms to create a moving image. Technically, a new timestamp is appended to the image source every 500ms. Feel free to use this plugin for yourself and develop it further.
Install via the bundled Plugin Manager or manually using this URL:
https://github.com/eckonator/OctoPrint-Webcamimagereloader/archive/master.zip
Just install the Plugin and add a live image url path to the OctoPrint Stream-URL in webcam settings like this: "http://username:password@192.168.178.XX/tmpfs/auto.jpg"
