[not2b]

Yes, if I take the 8 combinations aaa, aab, aba etc and assign each of them a 9 bit codeword I replace each 24 bit sequence with a 9 bit sequence. So arithmetic coders have no problem with cases like this.

[unsigner]

but LZ4 doesn't have a arithmetic coder, or any other statistical encoding - it's just matches and literals. Puzzling...