The latest version of VLC supports network streaming which means you can download youtube directly into VLC media player and watch it or record it. Sometimes this also helps if youtube is blocked in your network but you have the link to the video.
Now you can watch the video inside VLC itself
Here is a video guide to the process I found on youtube.
There is only one advantage of this method and ie, to download or save the streaming video in any format of our choice.
1. In the Open Network Stream page Click on the down arrow of the Play Button.
2. Select Convert. (see pic. right)
3. Add your desired Settings in the window as below.
After the streaming is complete you will get the full video saved in format you set.
This way, you don’t have to use any online youtube downloader, or install any app. to convert youtube videos to your required output. Enjoy !