*cough*. We're still on the same forum page.
LAVF input is only supported through patches. MCW more or less put the kibosh on the idea of it being in the upstream source a few years ago, IIRC. Something about not wanting to deal with the maintenance burden of input modules other than raw and y4m, as I recall.
I mean, I use the LAVF support patches for my personal builds of x265 CLI, but more often than not, I just use libx265 through FFmpeg, which is probably more what MCW expects people to do if they want all the exotic input file support.