[any1]

VNC, the protocol, isn't at all inefficient. There are some encoding methods which are inefficient, but I'd say that more "modern" encoding methods such as "tight" aren't all that bad, depending on how they're implemented. There has also been a recent addition of h264 to some implementations.

An example of a truly inefficient encoding method is ZRLE. It is a tiled zlib and run-length encoded format that can't be split up into multiple jobs because future computation depends on past computation.

They got things right with the tight encoding method of which there are two variants: zlib (lossless) and jpeg. With zlib, you can have up to 4 separate zlib streams, which means that you can utilise 4 CPU cores for encoding in parallel. The jpeg method has no such limitations.