[benwaggoner]

And unless there are specific HDR presets, you'll also want to change some parameters. --hdr10-opt tunes chroma QPs to be better for HDR-10, for example. Maybe share your whole command line?

An essentially free minor speedup can be gained from using --selective-sao 2. x265 has gained a lot of new parameters since the presets were last refactored, which should be used in presets but aren't yet.

If you have lots of unused cores, which seems likely, --pmode can improve fps some at the cost of way more compute/heat/watts.

And don't use --tune film with x265 unless it's particularly grainy content. The default tune is better for most content, and I think would be somewhat faster as well due to rskip being used, and having lower bitrates overall.

But no way around 4K being slow. I've got dual Xeon Gold 6240 CPU @ 2.60GHz, 18/36 cores, and high-quality encodes can still run below 1 fps for 4K HDR. Even a more balanced speed/quality tradeoff is maybe 3 fps.