MP4s are compressed data, not a compression algorithm. An MP4 (or any compressed data) is not a “prediction”, it is the difference between what was predicted and what you’re trying to compress.

An LLM is (or can be used) as a compression algorithm, but it is not compressed data. It is possible to have an overfit algorithm exactly predict (or reproduce) an output, but it’s not possible for one to reproduce all the outputs due to the pigeonhole principle.

To reiterate - LLMs are not compressed data.