with buildroot version 2015.05 and the following defconfig:

BR2_arm=y
BR2_cortex_a5=y
BR2_ARM_FPU_VFPV4D16=y
BR2_DL_DIR="$(TOPDIR)/buildroot_download_cache/"
BR2_BACKUP_SITE="http://sources.buildroot.net/"
BR2_KERNEL_MIRROR="http://www.kernel.org/pub/"
BR2_CCACHE=y
BR2_CCACHE_DIR="$(TOPDIR)/buildroot_ccache"
BR2_OPTIMIZE_3=y
BR2_PACKAGE_OVERRIDE_FILE="$(TOPDIR)/local.mk"
BR2_KERNEL_HEADERS_3_12=y
BR2_TOOLCHAIN_BUILDROOT_INET_RPC=y
BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
BR2_PTHREAD_DEBUG=y
BR2_GCC_VERSION_4_7_X=y
BR2_EXTRA_GCC_CONFIG_OPTIONS="--with-float=hard --with-fpu=vfpv4-d16"
BR2_TOOLCHAIN_BUILDROOT_CXX=y
BR2_PACKAGE_HOST_GDB=y
BR2_TARGET_OPTIMIZATION=" -pipe -mfpu=vfpv4-d16 -mfloat-abi=hard"
BR2_TARGET_GENERIC_HOSTNAME=""
BR2_TARGET_GENERIC_ISSUE=""
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y
BR2_TARGET_GENERIC_ROOT_PASSWD="devkit"
BR2_TARGET_GENERIC_GETTY_PORT="ttyS0"
BR2_TARGET_GENERIC_GETTY_BAUDRATE_115200=y
BR2_ROOTFS_OVERLAY="board/mcs/ptu4/overlay"
BR2_ROOTFS_POST_BUILD_SCRIPT="board/mcs/ptu4/post-build.sh"
BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-sama5d3ekdemo.config"
BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
BR2_PACKAGE_ALSA_UTILS=y
BR2_PACKAGE_ALSA_UTILS_AMIXER=y
BR2_PACKAGE_ALSA_UTILS_APLAY=y  
BR2_PACKAGE_MPG123=y   
BR2_PACKAGE_MPLAYER=y  
BR2_PACKAGE_GDB=y  
BR2_PACKAGE_LSOF=y 
BR2_PACKAGE_MEMSTAT=y
BR2_PACKAGE_STRACE=y 
BR2_PACKAGE_GREP=y 
BR2_PACKAGE_SED=y  
BR2_PACKAGE_TAR=y  
BR2_PACKAGE_CIFS_UTILS=y
BR2_PACKAGE_DOSFSTOOLS=y 
BR2_PACKAGE_MTD=y    
# BR2_PACKAGE_MTD_FLASH_LOCK is not set                                                             
# BR2_PACKAGE_MTD_FLASH_UNLOCK is not set                                                           
BR2_PACKAGE_SSHFS=y 
BR2_PACKAGE_BITSTREAM_VERA=y  
BR2_PACKAGE_DEJAVU=y  
BR2_PACKAGE_LIBERATION=y  
BR2_PACKAGE_DIRECTFB=y 
BR2_PACKAGE_DIRECTFB_EXAMPLES=y  
BR2_PACKAGE_DIRECTFB_EXAMPLES_ANDI=y  
BR2_PACKAGE_DIRECTFB_EXAMPLES_BLTLOAD=y  
BR2_PACKAGE_DIRECTFB_EXAMPLES_CPULOAD=y  
BR2_PACKAGE_DIRECTFB_EXAMPLES_DATABUFFER=y  
BR2_PACKAGE_DIRECTFB_EXAMPLES_DIOLOAD=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_DOK=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_DRIVERTEST=y                    
BR2_PACKAGE_DIRECTFB_EXAMPLES_FIRE=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_FLIP=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_FONTS=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_INPUT=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_JOYSTICK=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_KNUCKLES=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_LAYER=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_MATRIX=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_MATRIX_WATER=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_NEO=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_NETLOAD=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_PALETTE=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_PARTICLE=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_PORTER=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_STRESS=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_TEXTURE=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_VIDEO=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_VIDEO_PARTICLE=y
BR2_PACKAGE_DIRECTFB_EXAMPLES_WINDOW=y
BR2_PACKAGE_FBSET=y
BR2_PACKAGE_QT=y
BR2_PACKAGE_QT_LICENSE_APPROVED=y
BR2_PACKAGE_QT_PIXEL_DEPTH_18=y
BR2_PACKAGE_QT_PIXEL_DEPTH_24=y
# BR2_PACKAGE_QT_FONT_MICRO is not set
# BR2_PACKAGE_QT_FONT_FIXED is not set
# BR2_PACKAGE_QT_FONT_HELVETICA is not set
BR2_PACKAGE_QT_SYSTEMFREETYPE=y
BR2_PACKAGE_QT_GIF=y
BR2_PACKAGE_QT_LIBMNG=y
BR2_PACKAGE_QT_SYSTEMJPEG=y
BR2_PACKAGE_QT_SYSTEMPNG=y
BR2_PACKAGE_QT_SYSTEMTIFF=y
BR2_PACKAGE_QT_SQL_MODULE=y
BR2_PACKAGE_QT_SQLITE_SYSTEM=y
BR2_PACKAGE_QT_GFX_DIRECTFB=y
BR2_PACKAGE_QT_MOUSE_LINUXINPUT=y
BR2_PACKAGE_QT_MOUSE_TSLIB=y
BR2_PACKAGE_QT_MOUSE_NO_QWS_CURSOR=y
BR2_PACKAGE_QT_KEYBOARD_LINUXINPUT=y
BR2_PACKAGE_QT_DBUS=y
BR2_PACKAGE_QT_XMLPATTERNS=y
BR2_PACKAGE_QT_MULTIMEDIA=y
BR2_PACKAGE_QT_AUDIO_BACKEND=y
BR2_PACKAGE_QT_WEBKIT=y
BR2_PACKAGE_QT_STL=y
BR2_PACKAGE_QT_OPENSSL=y
BR2_PACKAGE_QT_SCRIPTTOOLS=y
BR2_PACKAGE_QT_DECLARATIVE=y
BR2_PACKAGE_QEXTSERIALPORT=y
BR2_PACKAGE_QJSON=y
BR2_PACKAGE_CDRKIT=y
BR2_PACKAGE_EVTEST=y
BR2_PACKAGE_I2C_TOOLS=y
BR2_PACKAGE_PYTHON3=y
BR2_PACKAGE_PYTHON3_PY_PYC=y
BR2_PACKAGE_PYTHON_SERIAL=y
BR2_PACKAGE_LIBGCRYPT=y
BR2_PACKAGE_LIBGPGME=y
BR2_PACKAGE_SQLITE_READLINE=y
BR2_PACKAGE_SQLITE_STAT3=y
BR2_PACKAGE_SQLITE_ENABLE_FTS3=y
BR2_PACKAGE_SQLITE_ENABLE_UNLOCK_NOTIFY=y
BR2_PACKAGE_LIBUSB=y
BR2_PACKAGE_CPPZMQ=y
BR2_PACKAGE_CZMQ=y
BR2_PACKAGE_LIBCURL=y
BR2_PACKAGE_CURL=y
BR2_PACKAGE_ZMQPP=y
BR2_PACKAGE_ARGP_STANDALONE=y
BR2_PACKAGE_BOOST=y
BR2_PACKAGE_BOOST_CHRONO=y
BR2_PACKAGE_BOOST_CONTEXT=y
BR2_PACKAGE_BOOST_DATE_TIME=y
BR2_PACKAGE_BOOST_EXCEPTION=y
BR2_PACKAGE_BOOST_FILESYSTEM=y
BR2_PACKAGE_BOOST_GRAPH=y
BR2_PACKAGE_BOOST_GRAPH_PARALLEL=y
BR2_PACKAGE_BOOST_IOSTREAMS=y
BR2_PACKAGE_BOOST_LOCALE=y
BR2_PACKAGE_BOOST_LOG=y
BR2_PACKAGE_BOOST_MATH=y
BR2_PACKAGE_BOOST_MPI=y
BR2_PACKAGE_BOOST_PROGRAM_OPTIONS=y
BR2_PACKAGE_BOOST_RANDOM=y
BR2_PACKAGE_BOOST_REGEX=y
BR2_PACKAGE_BOOST_SERIALIZATION=y
BR2_PACKAGE_BOOST_SIGNALS=y
BR2_PACKAGE_BOOST_SYSTEM=y
BR2_PACKAGE_BOOST_TEST=y
BR2_PACKAGE_BOOST_THREAD=y
BR2_PACKAGE_BOOST_TIMER=y
BR2_PACKAGE_BOOST_WAVE=y
BR2_PACKAGE_LIBESMTP=y
BR2_PACKAGE_BC=y
BR2_PACKAGE_MCRYPT=y
BR2_PACKAGE_DHCP=y
BR2_PACKAGE_DHCP_CLIENT=y
BR2_PACKAGE_ETHTOOL=y
BR2_PACKAGE_IPERF=y
BR2_PACKAGE_IPROUTE2=y
BR2_PACKAGE_NETCAT=y
BR2_PACKAGE_PORTMAP=y
BR2_PACKAGE_PPPD=y
BR2_PACKAGE_PPPD_FILTER=y
BR2_PACKAGE_RSYNC=y
BR2_PACKAGE_SOCAT=y
BR2_PACKAGE_TINYHTTPD=y
BR2_PACKAGE_BASH=y
BR2_PACKAGE_FILE=y
BR2_PACKAGE_GNUPG_RSA=y
BR2_PACKAGE_GNUPG_GPGV=y
BR2_PACKAGE_LOGROTATE=y
BR2_PACKAGE_TIME=y
BR2_PACKAGE_COREUTILS=y
BR2_PACKAGE_KMOD=y
BR2_PACKAGE_UTIL_LINUX_LIBBLKID=y
BR2_PACKAGE_NANO=y
BR2_PACKAGE_VIM=y
# BR2_PACKAGE_VIM_RUNTIME is not set
BR2_TARGET_ROOTFS_TAR_BZIP2=y
BR2_TARGET_ROOTFS_UBIFS=y
BR2_TARGET_ROOTFS_UBIFS_LEBSIZE=0x1f000
BR2_TARGET_BAREBOX=y
BR2_TARGET_BAREBOX_CUSTOM_GIT=y
BR2_TARGET_BAREBOX_CUSTOM_GIT_REPO_URL=""
BR2_TARGET_BAREBOX_CUSTOM_GIT_VERSION=""
BR2_TARGET_BAREBOX_BOARD_DEFCONFIG=""
BR2_TARGET_BAREBOX_BAREBOXENV=y
BR2_PACKAGE_HOST_MTD=y
BR2_PACKAGE_HOST_SAM_BA=y

fails to build with the following error:

In file included from libavcodec/dca.c:48:0:
libavcodec/dca.c: In function 'dca_subsubframe':
libavcodec/arm/dca.h:36:5: error: can't find a register in class 'CORE_REGS' while reloading 'asm'
libavcodec/arm/dca.h:36:5: error: 'asm' operand has impossible constraints
libavcodec/dca.c:1275: confused by earlier errors, bailing out
CC      libavformat/options.o
make[3]: *** [libavcodec/dca.o] Error 1


I use an OpenSuse 13.1 host to build a rootfs for an Atmel SAMA5 board. My defconfig is based on a working config for buildroot 2013.08

Please note, that the error occurs during building the mplayer included ffmpeg-
package. Compiling the buildroot-ffmpeg-package (ffmpeg-2.6.2, BR2_PACKAGE_FFMPEG=y) works without problems.