Support for acceleration MPEG-4 ASP was introduced in NVIDIA's most recent revision to their PureVideo technology and now the software support is properly in place. The current NVIDIA graphics cards that support MPEG-4 ASP decoding are the GeForce G210, G210M, GT 220 (we previously provided a NVIDIA GeForce GT 220 review under Linux), GT 230M, GT 240M, GT 240, GTS 250M, and GTS 260M. These NVIDIA GeForce GPUs support PureVideo VP4 and the said support will likely be found in NVIDIA's forthcoming GeForce 300 "Fermi" series too, unless it ends up being VP5. Earlier revisions of PureVideo and VDPAU support acceleration for MPEG-1, MPEG-2, VC-1/WMV9, and H.264, but there are some limitations depending upon the hardware and video sizes.
This MPEG-4 ASP patch was originally written by NVIDIA engineers and since has been revised by FFmpeg / MPlayer developers. A commit showing what this new patch looks like can be found here. Popular implementations of MPEG-4 Part 2 Advanced Simple Profiles (ASP) are Xvid and DivX.
It was back in January that FFmpeg gained mainline VDPAU support for its original implementation after NVIDIA introduced VDPAU in Q4'2008. VDPAU support can also be found in MythTV, XBMC, VLC, and other popular Linux media applications.