t3g, 720P or higher WebM videos are no longer provided by YouTube when using
youtube-dl or ViewTube (I have no idea whether they can be accessed using
other methods). For music videos, you can usually get much better quality
versions (unfortunately in H.264 format only but you can transcode to get a
much higher quality WebM videos) from the vevo.com website (youtube-dl can
download from it - you might need to use a VPN for it) or the MTV websites
(you just need to use the id numbers of the videos and copy them to a website
such as the two below and then use rtmpdump - a VPN might also be needed to
access some videos).
Here are two sites that provides rtmp links for MTV websites:
http://www.mtv.com/player/includes/mediaGen.jhtml?vid=****
http://intl.esperanto.mtvi.com/www/xml/media/mediaGen.jhtml?uri=mgid:uma:video:mtv.co.uk:****
Just replace the stars by the video id, e.g. for this video
http://www.mtv.com.au/music/artists/florence-and-the-machine/videos/shake-it-out-698321/?playlist=florence-and-the-machine-playlist
the i.d. is 698321.
