A file format can be notably more or less resilient to bit errors. It can be the difference between getting a slightly different output, a garbled one or an oop

A file format can be notably more or less resilient to bit errors. It can be the difference between getting a slightly different output, a garbled one or an oops, sorry. BTW compression efficiency is orthogonal not opposite of structured redundancy that you would want. As a thought experiment, imagine as a last step of coding, encrypting the data with a publicly known key. Theoretical redundancy remains the same, but good luck¹ getting your data back, if you get a bit error. ¹ Imagine a variable length single block cypher was used, multi round CBC or something.