Within the next few hours AMD will be publishing open-source driver code that exposes their Unified Video Decoder (UVD) engine on modern Radeon HD graphics cards. This will finally allow open-source graphics drivers to take advantage of hardware-accelerated video decoding.
Alex Deucher of AMD shared with Phoronix that tomorrow (3 April, or possibly in the late hours tonight), there will be a code drop of open-source UVD Linux support.
This UVD support will come for the Radeon HD 4000 "R700" graphics cards through the Radeon HD 7000 "Southern Islands" graphics cards. This is effectively UVD2 hardware and newer. There was the original UVD decoder found with the Radeon HD 2000 GPUs and UVD+ to come with the Radeon HD 3000 series, but this support is targetting UVD2 and beyond. The latest generation is UVD3 that was introduced with the Radeon HD 6000 series. UVD3 brought in DivX and Xvid along with Blu-ray 3D and 120Hz Stereo 3D.
This open-source AMD UVD support will allow for accelerated playback of H.264, VC-1, and MPEG variants on the HD 4000 through HD 7000 series GPUs. Interestingly, and to much pleasure, the UVD support is being exposed over VDPAU.
AMD using VDPAU to expose UVD with their open-source Linux graphics driver is a great win for Linux desktop users.
Update: The code just arrived! There's also the Mesa patches!