As anticipated, the open-source Radeon DRM driver will support AMD's "VCE" block with the Linux 3.15 kernel. At the start of February AMD made the surprise move of publishing open-source AMD GPU driver support for VCE, an engine found on newer graphics processors that supports low-latency H.264 video encoding. This work is to open-source video encoding as last year's landmark open-source AMD UVD code was to video decoding on AMD graphics hardware.
The video encoding support is exposed to user-space applications via Gallium3D's OpenMAX state tracker and since last week AMD's VCE code is already in Mesa (for the Mesa 10.2 release in about three months time). The kernel side of the equation is now landing for the Linux 3.15 kernel, also in a couple of months.
Christian König is managing the Radeon drm-next tree for Linux 3.15 in place of Alex Deucher this release cycle and he's went ahead to send the pull request for the VCE bring-up code into drm-next. This VCE work includes dynamic power management support for the block to have dynamic state switching and clock gating. This first pull request of code for the Radeon GPU DRM driver in Linux 3.15 also has some clean-ups to the ring handling code. More code will likely land in the weeks ahead since the Linux 3.14 kernel still has about one month to go until its official release. Today's pull request for the initial Radeon DRM 3.15 code can be found on the dri-devel list.
Besides needing the Linux 3.15 kernel and Mesa 10.2 development code, you need a really recent GPU that has the VCE 2.0 hardware (Sea Islands, Kabini, etc). The Radeon HD 7000 "Southern Islands" hardware only supports VCE 1.0 (pre-GCN hardware doesn't have this VCE capability) and it's not known if/when there will be open-source VCE support for that generation.