Build with recent libavutil (SVN 2010/04/27) doesn't work because it needs a special flag to build when included from C++ (__STDC_CONSTANT_MACROS, see C99 spec 7.18.4§1 note 230 or glibc's stdint.h).

There's a patch that adds -D__STDC_CONSTANT_MACROS to the CXXFLAGS when building with FFMPEG support.
Note that it fixes only scons, I don't know if other build systems are affected.