It looks like you're on a windows system so I've made a patch and applied it to a
win32 build here
it should now try and convert your unknown input colorspace source to i444 which will allow the non mod2 dimensions you require.
this should get you past your current issue and allow you to crop your source to mod2 dimensions to become i420 compliant for encoding with libx264.
If it works, I'll get it added to Dark_Shikari's local commit tree