Description:
vlc's ffmpeg plugin, as well as a few others, is broken for me (x86_64). For example, ldd prints:

$ ldd /usr/lib/vlc/codec/libffmpeg_plugin.so
libpthread.so.0 => /lib/libpthread.so.0 (0x00002b849c7f8000)
libpostproc.so.51 => /usr/lib/libpostproc.so.51 (0x00002b849ca14000)
libavformat.so.51 => not found
libavcodec.so.51 => /usr/lib/libavcodec.so.51 (0x00002b849cc1f000)
libz.so.1 => /lib/libz.so.1 (0x00002b849d310000)
liba52.so.0 => /usr/lib/liba52.so.0 (0x00002b849d524000)
libmp3lame.so.0 => /usr/lib/libmp3lame.so.0 (0x00002b849d62f000)
libxvidcore.so.4 => /usr/lib/libxvidcore.so.4 (0x00002b849d7a4000)
libx264.so.55 => not found
libfaad.so.0 => /usr/lib/libfaad.so.0 (0x00002b849d985000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x00002b849dbc6000)
libXext.so.6 => /usr/lib/libXext.so.6 (0x00002b849decb000)
libavutil.so.49 => /usr/lib/libavutil.so.49 (0x00002b849dfdc000)
libogg.so.0 => /usr/lib/libogg.so.0 (0x00002b849e1e7000)
libtheora.so.0 => /usr/lib/libtheora.so.0 (0x00002b849e2ec000)
libvorbisenc.so.2 => /usr/lib/libvorbisenc.so.2 (0x00002b849e530000)
libvorbis.so.0 => /usr/lib/libvorbis.so.0 (0x00002b849e809000)
libfaac.so.0 => /usr/lib/libfaac.so.0 (0x00002b849e934000)
libm.so.6 => /lib/libm.so.6 (0x00002b849ea45000)
libc.so.6 => /lib/libc.so.6 (0x00002b849ecc5000)
/lib/ld-linux-x86-64.so.2 (0x0000555555554000)
libx264.so.57 => /usr/lib/libx264.so.57 (0x00002b849f00c000)
libxcb-xlib.so.0 => /usr/lib/libxcb-xlib.so.0 (0x00002b849f292000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00002b849f493000)
libdl.so.2 => /lib/libdl.so.2 (0x00002b849f6af000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x00002b849f8b4000)
libmp4v2.so.0 => /usr/lib/libmp4v2.so.0 (0x00002b849fab6000)
libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00002b849fc5f000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00002b849fd64000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00002b84a006c000)

libavformat.so.51 and libx264.so.55 is not found. Interestingly the plugin apparently depends on both libx264.so.55 and libx264.so.57, which doesn't sound good at all.. Some other .so's are also missing libx265.so.55. Both ffmpeg and x264 is installed (latest versions in repo), and reinstalling vlc doesn't fix the problem.

I also tried compiling vlc myself using the PKGBUILD and such from CVS, but the build failed:

(...)
Making all in ffmpeg
make[5]: Entering directory `/sand/src/ARCH/vlc/src/vlc-0.8.6d/modules/codec/ffmpeg'
make[6]: Entering directory `/sand/src/ARCH/vlc/src/vlc-0.8.6d/modules/codec/ffmpeg'
(...)
if gcc -DHAVE_CONFIG_H -I. -I. -I../../.. -DSYS_LINUX -I../../../include `top_builddir="../../.." ../../../vlc-config --cflags plugin ffmpeg` -Wsign-compare -Wall -march=x86-64 -mtune=generic -O2 -pipe -pipe -MT libffmpeg_plugin_a-mux.o -MD -MP -MF ".deps/libffmpeg_plugin_a-mux.Tpo" -c -o libffmpeg_plugin_a-mux.o `test -f 'mux.c' || echo './'`mux.c; \
then mv -f ".deps/libffmpeg_plugin_a-mux.Tpo" ".deps/libffmpeg_plugin_a-mux.Po"; else rm -f ".deps/libffmpeg_plugin_a-mux.Tpo"; exit 1; fi
mux.c: In function ‘OpenMux__0_8_6’:
mux.c:136: error: incompatible types in assignment
(...)

vlc 0.8.6d-1 at x86_64.