H.265's biggest changes are probably a change from fixed macroblocks (basically a fixed grid) to a tree based structure called a coding tree (see this paper for

H.265's biggest changes are probably a change from fixed macroblocks (basically a fixed grid) to a tree based structure called a coding tree (see this paper for details: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.352.1947&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.352...). It includes 8k and HDR color support (in 10 bit in v1 via main 10 profile, and 12 and 16 bit in v2). In addition it moved from 9 prediction modes to 26.