correct, it is integer DCT. Lot of techniques adopted from the integer transform of H.264. That's what I meant, not the floating point DCT proposed in 70s.
The big change is basically that we now typically specify exactly which integer approximation to the (real-valued, “ideal”) DCT to use; this means the decoder and encoder is much likely to fall out of sync. As a bonus, this means we can use a slightly worse but much faster approximation without catastrophes happening, and possibly also make it exactly invertible.
