You are correct that x264 does benefit from hyperthreading. According to the devs, the speed increase is about 20% until you are on the veryfast or ultrafast pr

You are correct that x264 does benefit from hyperthreading. According to the devs, the speed increase is about 20% until you are on the veryfast or ultrafast presets, which at this point is usually bottlenecked by decode speed, and not the speed of the encode. In making my previous claim, I was limiting the concept of 'encoding' to the more old-school definition: lossless compression of media bytestreams. This would include things like HuffYUV, ProRes, etc. But to be fair, these days it is quite likely that even a few of the newer intermediate/mezzanine codecs benefit from hyperthreading. I'd edit my post to clarify but the edit window has passed.