Talk:Raptor code
Rateless?
Hi,
In this edit, the edit summary says "Raptor codes are rateless". Now, I admit I've only skimmed the journal paper, but how can a code be rateless? There are a number of symbols in, and a larger number out. The processing time must be proportional (at least) to the number of input symbols; surely the standard way of stating this is "encoding takes O(k) time"! Much in the same way that we don't state that the FFT runs in O(log n) time per input sample, but that it runs in O(n log n) time... Oli Filth(talk|contribs) 10:00, 13 May 2009 (UTC)
Hi, raptor codes takes an number of symbols in, let say k, and can produce a "infinite" number of encoding symbols. "Raptor codes in this class produce a potentially infinite stream of symbols" from the article [1] Since each encoding symbols is the combination of the k input symbols, there is a maximum of k! different encoding symbols that can be produced. I agree that even if this is very large, it is not "infinite", but that is how the authors of the article and many people in the community are referring to this class of codes. I think we should clarify this in the article and write a sentence or two about the finite size of this "infinite" set ;). Cunchem 10:44, 13 May 2009 (UTC)