Apparently you can’t, but have to run $ x264 –fullhelp

or some odd.

They fixed it for me!

$ ffmpeg -i something -vcodec libx264 -preset help -tune help -profile:v help yo.avi

…

[libx264 @ 02142b80] Possible presets: ultrafast superfast veryfast faster fast medium slow slower veryslow placebo
[libx264 @ 02142b80] Possible tunes: film animation grain stillimage psnr ssim fastdecode zerolatency

But not for profile, FWIW.

NB that this isn’t all the possible presets, because there are “some” that are file-based, external still, as well:

https://github.com/FFmpeg/FFmpeg/tree/master/presets

like ipod ones.

This cheat sheet might help:

http://rodrigopolo.com/ffmpeg/cheats.html#X264_Presets