Update 2:15 p.m. PT, February 28:The channel in question has been removed from YouTube "due to multiple or severe violations of YouTube's policy against spam, gaming, misleading content, or other Terms of Service violations." The policy reads "It's not okay to post large amounts of untargeted, unwanted, or repetitive content in videos, comments, private messages, or other places on the site." Since the channel was posting a video every few seconds, this was likely the reason for the removal.
Got some time to kill? See if you can make heads or tails of a YouTube channel that's driving people mad.
The videos are the sort of thing, in isolation, that no one would look at twice. They seem like test videos of some sort. They show abstract, pixelated images, some not unlike a TV test screen. Others are just a single dot in a field of brown. Some are completely silent. Others feature distorted sounds.
Most of them have numbered names, but not all. There are ♐LOCK and ♐DELOCK. (Some Internet sleuths believe these videos are the key to decoding the videos.) Most of the videos are without description, but a rare few are described with numbers. The description on the simply named ♐ reads "10 x 10" vertically, and a distorted voice says "one zero one zero." The description on the completely silent ♐BRILLB reads "1000."
Some videos are seconds long. Some are several minutes. One completely silent video runs for 11 hours.
We all love a good conspiracy, and Unfavorable Semicircle offers plenty of fodder.
More-interesting theories suggest it is an espionage-related numbers station or has something to do with astronomy or aliens because the symbol that precedes most of the video titles represents Sagittarius. Other images could be constellations. This background, for example, resembles Orion.
There's also the possibility that, like other Internet mysteries such as Cicada 3301 and the Pronunciation Book YouTube channel, Unfavorable Semicircle is an alternate reality game waiting for someone to solve it. Perhaps one needs to shuffle the YouTube thumbnails into the right pattern or perform spectrographic analysis of the audio to construct an image.
The number and frequency of the videos could suggest that they're simply small parts of a much larger file, requiring someone to put the pieces together.
If you want to get involved, the Unfavorable Semicircle subreddit is on the case, a member of which has created a searchable database of all the videos. Another good place to get started is Basic Observations from Redditor KnotNotNaught and this comment from Redditor save_the_pigs.
Let us know if you figure anything out, even if it's as disappointing as Pronunciation Book turned out to be.