I'm very confused by those many product names.
I want to create a video player with hardware acceleration, which one should I use?
media sdk for client or Media Software Development Kit 2014 HEVC Software Pack?
also, I'm developing under linux and mac. but I could only find media sdk for client for windows only?
is it cross-platform at all?
Media SDK is growing quickly. There are 2 main Media SDK products now (Windows client and Windows/Linux server) and several add-ons.
If you were developing for Windows, the clear answer would be Media SDK. Linux support is available via the Media SDK for Linux Servers product. However, rendering is currently not a high priority for the Linux server version -- the main focus now is scenarios where transcode output is streamed from server to client. There is no Linux or Mac/OSX client Media SDK.