where does that come from in practice it's actually your own bits so imagine you already have some bits sitting here you have some zeros ones you know maybe you've already done some compression of something else it's a random sequence it's sitting there ready to be transmitted then the first thing you have to do and the the notation here is slightly different Wyatt responds to our i M s corresponds to our X ok so keep that in mind that's the notation they use in this paper here from which we took the figure so in