First, get the latest source from http://www.ffmpeg.org/download.html and extract it in a convenient place, then configure it:

$ LDFLAGS=-L/c/met.no/lib CPPFLAGS=-I/c/met.no/include \
  ./configure --prefix=/c/met.no \
  --disable-ffmpeg --disable-ffplay --disable-ffserver \
  --enable-memalign-hack

Note that we've tried to trim it down a bit by disabling bits we don't need.

You can safely ignore the pr: command not found messages. If they really bother you, just create a do-nothing shell script:

$ echo "#!/bin/sh" >/bin/pr
$ chmod a+rx /bin/pr

Build and install the libraries:

$ make all install-libs

Now we need to fix up the headers so they look like they do on Hardy:

$ make INCINSTDIR=/c/met.no/include/ffmpeg install-headers
$ cd /c/met.no/include
$ for hdr in ffmpeg/*.h ; do \
    echo $hdr ; \
    sed -e '/^#include/s@"libav[a-z]*/@"@' <$hdr >$hdr- && mv $hdr- $hdr ; \
  done

The INCINSTDIR bit forces ffmpeg to install its headers in /c/met.no/include/ffmpeg instead of separate directories for each library (/c/met.no/include/libavformat, /c/met.no/include/libavutil etc.), and the sed command edits them so they can still find each other when installed in a non-standard location.

Finally, the copyright and license information:

$ cp README /c/met.no/copyright/ffmpeg.txt
$ cat COPYING.LGPL >>/c/met.no/copyright/ffmpeg.txt