When trying to compile FFmpeg under FreeBSD 8.1-RELEASE I got an error:

Error: `ff_h264_cabac_tables+1024+128(%esi)' is not a valid 64 bit base/index expression

apparently the linker is broken, but as seen at Solaris ​here there is a workaround, also seen to work at FreeBSD ​here. After the ./configure phase apply:

 echo '#define BROKEN_RELOCATIONS 1' >> config.h

Trying this fix did still NOT solve my issue, next is trying a later/better compiler and linker, I will get the job done by clang/llvm for this matter:

  make -C /usr/ports/lang/clang install
  make -C /usr/ports/multimedia/x264
  ./configure --cc=clang --cxx=clang --ld=clang --prefix=$HOME/ff --enable-libx264 --enable-gpl
  gmake install

rplay% cp /usr/local/lib/libx264.* ~/ff/ bin/ etc/ include/ lib/ share/ tmp/ rplay% cp /usr/local/lib/libx264.* ~/ff/lib/