Even mathematicians are conflicted whether mathematics is discovered or invented. My personal belief is that if something is true about the world without the presence of man, those are things to be discovered. If something is created that could not exist without man, those are invented. Of course, lots of shades of gray in between, but let's face it: Video codecs exist only because of things man created. They are definitely invented, even though the principles on which they operate may be discovered. Example: Taking the DCT of an image results in a particular pattern of numbers. That is a discovery. Exploring the repetition in that pattern to achieve compression is an invention.