Wikipedia
CoreAVC
CoreAVC is a proprietary codec for decoding the H.264/MPEG-4 AVC (Advanced Video Coding) video format.
, the decoder is one of the fastest software decoders, but is slower than hardware-based ones. CoreAVC supports all H.264 Profiles except for 4:2:2 and 4:4:4.
CoreAVC now supports two forms of GPU hardware acceleration for H.264 decoding on Windows: Nvidia with CUDA and DXVA for both ATI and Nvidia hardware.
CoreAVC is included as a part of the CorePlayer Multimedia Framework and was being used in the now defunct desktop client by Joost a system that was distributing videos over the Internet using peer-to-peer TV technology.