From http://askubuntu.com/questions/486297/how-to-select-video-quality-from-youtube-dl

youtube-dl

youtube-dl hacks 

Use: 

youtube-dl -c <link>     //To resume download of a stopped file
youtube-dl -F <link>    //Download after selecting the format of the file which you want to download

Example
-----------

youtube-dl -F http://www.youtube.com/watch?v=P9pzm5b6FFY
Here’s the output

[youtube] Setting language
[youtube] P9pzm5b6FFY: Downloading webpage
[youtube] P9pzm5b6FFY: Downloading video info webpage
[youtube] P9pzm5b6FFY: Extracting video information
[info] Available formats for P9pzm5b6FFY:
format code extension resolution  note 
140         m4a       audio only  DASH audio , audio@128k (worst)
160         mp4       144p        DASH video , video only
133         mp4       240p        DASH video , video only
134         mp4       360p        DASH video , video only
135         mp4       480p        DASH video , video only
136         mp4       720p        DASH video , video only
17          3gp       176x144     
36          3gp       320x240     
5           flv       400x240     
43          webm      640x360     
18          mp4       640x360     
22          mp4       1280x720    (best)
The best quality is 22 so use -f 22 instead of -F to download the mp4 video with 1280x720 resolution like this,

youtube-dl -f 22 http://www.youtube.com/watch?v=P9pzm5b6FFY