AMD Media Codec Package is no longer developed by ATI Avivo and has been replaced with AMD Catalyst, then AMD Crimson.
In order to find out which version of AMD Crimson you need to download, we suggest to run the AMD Driver Autodetect.
From developer's page:
Whether you are a videophile, gamer, professional developer, or simply want a better experience from your AMD-based PC, there is something here for everyone to love.
AMD Crimson updates are focused on improving graphics performance, including enhancements for popular DirectX, Mantle and OpenGL game titles.
Every AMD Crimson driver release undergoes exhaustive testing but we set the bar even higher with this latest driver release.
In addition to increasing our automated testing by ~65% with this release, we also welcomed direct feedback from our most critical users on six of the largest PC communities -- all to ensure a user experience as intuitive, reliable, and enjoyable as possible.