Timothy B. Terriberry authored Dec 17, 2010 and Jean-Marc Valin committed Dec 18, 2010

It turns out to be more convenient to store dif=low+rng-code-1
 instead of dif=low+rng-code.
This gets rid of a decrement in the normal decode path, replaces a
 decrement and an "and" in the normalization loop with a single
 add, and makes it clear that the new ec_dec_cdf() will not result
 in an infinite loop.
This does not change the bitstream.