Alexandre,
If the possible (even rare) presence of a libavcodec.so lib can causes troubles. Would it be acceptable to force static linking with a configure check such as this one?
dnl **** Check for avcodec lib **** AVCODECLIBS="" LIBS="/usr/lib/libavcodec.a -lz -lm" AC_CHECK_HEADERS(ffmpeg/avcodec.h, [AC_TRY_LINK([#include ],[avcodec_init();], [AC_DEFINE(HAVE_LIBAVCODEC, 1, [Define if you have the avcodec library (libavcodec.a)]) AVCODECLIBS="/usr/lib/libavcodec.a -lz -lm"])]) LIBS=""; AC_SUBST(AVCODECLIBS)
Bye, Christian