Distribution/Version: Gentoo

Trying to compile gst-ffmpeg leaves me with the following error: 
 
if /bin/sh ../../libtool --mode=compile gcc -DHAVE_CONFIG_H -I. -I. -I../.. 
-I../../libavcodec -DHAVE_AV_CONFIG_H=1 -fomit-frame-pointer   -msse -g -O2 -MT 
libmmxsse_la-fdct_mmx.lo -MD -MP -MF ".deps/libmmxsse_la-fdct_mmx.Tpo" -c -o 
libmmxsse_la-fdct_mmx.lo `test -f 'fdct_mmx.c' || echo './'`fdct_mmx.c; \ 
then mv -f ".deps/libmmxsse_la-fdct_mmx.Tpo" ".deps/libmmxsse_la-fdct_mmx.Plo"; 
else rm -f ".deps/libmmxsse_la-fdct_mmx.Tpo"; exit 1; fi 
 gcc -DHAVE_CONFIG_H -I. -I. -I../.. -I../../libavcodec -DHAVE_AV_CONFIG_H=1 
-fomit-frame-pointer -msse -g -O2 -MT libmmxsse_la-fdct_mmx.lo -MD -MP 
-MF .deps/libmmxsse_la-fdct_mmx.Tpo -c fdct_mmx.c  -fPIC -DPIC 
-o .libs/libmmxsse_la-fdct_mmx.o 
In file included from fdct_mmx.c:16: 
../../libavcodec/common.h:67: error: array type has incomplete element type 
../../libavcodec/common.h:71: error: array type has incomplete element type 
make[8]: *** [libmmxsse_la-fdct_mmx.lo] Fehler 1