Link errors when trying to link against AMDXvBA

[RealNC]

I'm trying to link (mplayer) against AMDXvBA but the linker barks with:

libAMDXvBA.so: undefined reference to `XF86DRICreateDrawable'
libAMDXvBA.so: undefined reference to `XF86DRIAuthConnection'
libAMDXvBA.so: undefined reference to `XF86DRICloseConnection'
libAMDXvBA.so: undefined reference to `XF86DRICreateContext'
libAMDXvBA.so: undefined reference to `XF86DRIGetDeviceInfo'
libAMDXvBA.so: undefined reference to `XF86DRIOpenConnection'

Any hints on what's wrong? I'm on Gentoo AMD64, xorg-server 1.5.3. In case it's important, driproto is 2.0.4.