'You now have an option to download all your YouTube videos in their original resolution – whether its SD or HD. Here’s how:
Go to https://google.com/takeout and click the Create Archive button. Google will now create a zipped archived with all the videos that you have ever uploaded to YouTube. Once the archive says 100%, proceed to the Downloads tab to grab the actual files. If the archive is large, Google Takeout will split them into individual files of 2 GB each.'___
from http://www.labnol.org/internet/download-youtube-videos/9139/