There's actually more information that's arisen in regards to the issue. My
apologies for not adding it here earlier- I've mixed up what's been written
in e-mails and what's on the forum, it seems.
The issue, which forces YouTube-DL to execute Javascript in order to capture
full functionality, is 'signature encryption'. A very good summary can be
found at
https://superuser.com/questions/773719/how-do-all-of-these-save-video-from-youtube-services-work
(read the answer starting with "YouTube Bookmarklet). Essentially, for some
videos (such as music videos...), the URL of the video itself depends on a
'signature', which is obtained from the video ID through 'encryption'. This
isn't really encryption, though, and that's the problem: it's some random set
of mix-and-match functions contained in some off-site JS, which can be
changes at YouTube's whim. At the bare minimum, then, this will require some
low-level-but-above-me-for-now reverse engineering. At worst, this could
require a daily effort from a group of 3-4 skilled hackers just to avoid
falling too far behind.
In summary, this is DRM on YouTube which YouTube-DL carries out. I refrain
from calling it that since it's so petty (all DRM is, but what does YouTube
think this accomplishes?), but it in many ways is none other than a digital
lock.
