FWIW the transitive dependencies of the nixOS ffmpeg add up to 764MB, but dynamically linking is always much larger than statically linking, and that calculation will include more than just the shared-libraries.

Also note that he app includes an ffmpeg that is 39MB uncompressed.

1: https://johnvansickle.com/ffmpeg/ (based on the arm64 build, since TFA is an arm64 app).