Lossless encoding: 100% CPU for libx264, but 40-60% ffvhuff


New Member
I'm using ffmpeg to encode my recording and the two encode settings I'm using are:
libx264, qp=0 preset=ultrafast
ffvhuff, pred=median

I have already set DOOM Eternal to use the latter 12 of my logical processors and OBS to use the first 4 logical processors, so OBS shouldn't be influencing my game much, but for some reason libx264 will max out 100% cpu on all its logical cores resulting in stuttery recordings but ffvhuff does not do the same. I want to use libx264 instead of ffvhuff because (through experimentation with an ffmpeg binary) libx264 produced a more compressed video at the same 1.2x encode speed as ffvhuff. So why the max CPU usage?

Here are videos demonstrating this (they're obviously not lossless source video) and they're titled appropirately: