How to install X264

I'm trying to make a program. When I run ./configure, this is what I get:

checking for X264... configure: WARNING:
Test application not built (x264 codec missing).
Either you have not installed x264, or you
have not installed i开发者_StackOverflowt with the Gtk+ interface.
If you compile it from source, add these options
to configure:
--enable-shared
--enable-gtk

I have installed various packages that are related to x264 and gtk, but I'm still getting this message. Which packages do I need to install?

I used this howto to install ffmpeg and x264 on my machine...