x264 should automagically enable lavf input for you in the presence of FFmpeg header. This should be seen with ./configure as follows:
and after compilation should show:
filters: resize crop select_every
bit depth: 8
You can run 'make' or 'make fprofiled' now.
andrew@skamandros~/Desktop/x264$ x264 --help | head -n 14
x264 core:112 r156 22bfd31
Syntax: x264 [options] -o outfile infile
Infile can be raw (in which case resolution is required),
or YUV4MPEG (*.y4m),
or Avisynth if compiled with support (no).
or libav* formats if compiled with lavf support (yes) or ffms support (no).
Outfile type is selected by filename:
.264 -> Raw bytestream
.mkv -> Matroska
.flv -> Flash Video
.mp4 -> MP4 if compiled with GPAC support (no)
Output bit depth: 8 (configured at compile time)