/ 32768                                , if i < 0
              |
              | MAX(7, 128*r_{i,q})                  , if i = 0
    icdf(i) = <
              | MAX(7-i, (icdf[i-1]*r_{i,q})//32768) , if 0 < i < 7
              |
              \ 0                                    , i >= 7