HandBrake

Just to answer the question on the effect of tile columns on quality, the impact of tile columns on compression quality is very very small. It is neglectable for all practical purposes.

multithreaded encoding is supported in libvpx vp9 encoder already: https://groups.google.com/a/webmproject ... YMn21BA5cJ

If you enable multhreaded encoding for vp9, you should see a significant speed up comparing to single threaded encoding.