lossless compression

Seems to me there can't really be such a thing as lossless compression of data. Any system of compression must involve some assumption or prior knowledge of the information that is important in order to discard the rest. This is supported to my mind both philosophically: there is no redundant information in the universe; and empirically: no system of audio or video capture and replay ever looks or sounds like the original and they all differ from each other. There is not even a general movement towards 'better' as more advanced technology is involved. This is because one person's background noise is another person's atmosphere.