Could you create a version of Base91 that exactly map to 13bits?

[DonaldTsang]

I would like to have a B91 system where each 52bits maps to exactly 4 characters. Is it possible to do that?

[aberaud]

That's very close to what base91 does.
What would you do if the message length is not a multiple of 4 bytes ?

[DonaldTsang]

I though Base91 will sometimes put 14bits into 2 characters due to "higher compression", and i wanted a version of base91 that WILL NOT switch between 13bit and 14bit blocks.

P.S. 2^13 in base91 is 90:2, that means everything from C" (90:2) to "" (90:90) should be invalid pairs.

[DonaldTsang]

r-lyeh-archived/base#1 Found someone who i asked a similar question.