Dependency problems with libavcodec53 and libavcodec-extra-53

I have libavcodec53 installed but I want to install libavcodec-extra-53 instead. From what I understand the latter should include everything from the former plus some other codecs (like libx264 which is what I need installed).

However, when I try to install libavcodec-extra-53 in aptitude I get a broken dependency violation and no matter how hard I've tried, I can't seem to figure out what exactly is causing it. Part of it is that libavcodec53 conflicts with it but other packages should declare a dependancy on "libavcodec53 | libavcodec-extra-53" that is, either one of these two.

It seems that either, some package can't handle using libavcodec-extra-53 instead of libavcodec53 (I haven't been able to find what package that could be) or the package management system can't handle the transition from libavcodec53 to libavcodec-extra-53 because it seems to have implications with other packages.

Can anyone tell me what the best way to move from libavcodec53 to libavcodec-extra-53 is?