Once you stream and played the YouTube video on VLC media player after that you can also download the same if you want, for that follow the below steps.
While playing the Tube video on VLC, click on the Tools and then on Codec information (CTRL+J).
Now from the Codec Information copy the media link or location
Paste the above-copied link location in the browser and press enter key from the keyboard. When the video starts getting played, right click on that and select the Save as video option
Have you tried the command line tool "youtube-dl" used with the option -F to see the available formats, then change the F to f, add a space and the number of the format that interests you?
I tried VLC, but I have found YouTube downloader 7.3.5 with it's companion app to be a lot simpler - works with almost every site that I've tried it with. VLC is my default playback app no matter what, but YouTubedownloader is so much easier to use!
it is a firefox plugin