According to the
You can now cast videos to your Google cast using mkchromecast. This feature works both with node and ffmpeg backends and from command line. In the future, they may be a graphical interface for this process. See this project.
Cast a file from your computer to your chromecast:python mkchromecast.py --video -i "/path/to/file.mp4"
However when I try this I get the following error:
mkchromecast.py: error: unrecognized arguments: --video
Is support for this not compiled in?