@sjw @iska @p x264 encoding is fast because there are hardware primitives for it. same as common algorithms like SHA and AES.

also a lot of fiddling from frabrice if i recall.

the current gen codecs have a *lot* more decisions that have to be made. h264 and vp8 always cut an image in to fixed size blocks, while h265 and vp9/av1 can do that but can also choose to split images in to jigsaws of blocks.