You know those Golden Records NASA sent into space in the 70s, on the Voyager spacecrafts? They contained images, music and sounds from Earth, as well as greetings in 55 languages. If any alien were to come across these disks, accessing their contents is far from straightforward.
Decoding images from the Golden Record
You might think that the images were included in some printed or digital form, such as a .jpeg or .tiff. But back in 1977, there was no technology available to put images on analog disks. Voyager’s computer systems could only hold 69 kilobytes of information, barely enough for one image, let alone 115. So NASA invented a way to include image data on the LPs.
By projecting images onto a screen, recording them with a television camera, and then turning those video signals into audio waveforms, the images could be properly pressed onto the records. The reversal process — turning that image data back into images — is what any extraterrestrial (or curious human) would have to figure out how to do.
Nevermind the contents of these records, the instructions alone will have the aliens scratching their heads. If they have heads, of course.