The run-time rendering switching allows changing between Cairo, OpenGL, and AGG renderers at run-time. Of course, Cairo also supports many different rendering back-ends too within this library from an experimental DRM back-end to supporting OpenGL ES. The media handler switching is for changing between FFmpeg and GStreamer for handling any media decoding.
It was nearly a year ago that we reported on VA-API capabilities for Gnash after Gwenolé Beauchesne of Splitted Desktop Systems wrote the Gnash patches. This is following his company's work on writing a NVIDIA VDPAU back-end for VA-API and the infamous AMD XvBA back-end to VA-API. With the Video Acceleration API patches now integrated into a stable Gnash release, users of Intel Clarkdale/Arrandale graphics (the Intel Core i3/i5 CPUs bearing an integrated graphics core) with recent DRM supporting VA-API, NVIDIA proprietary driver users with the VA-API front-end, AMD/ATI Catalyst driver users with the VA-API front-end, or users of other obscure drivers (i.e. the bloody Poulsbo and S3 Graphics) with VA-API support can now playback videos in Gnash with some of the the VLD, iDCT, Motion Compensation, and Deblocking for MPEG-2/MPEG-4 ASP/H.263/H.264/VC-1/WMV3 formats being offloaded to the GPU rather than being processed on the CPU.
While Adobe supports GPU-assisted video decoding in their official Flash Player for Windows and Mac OS X platforms, the Gnash project has beat Adobe into supporting GPU video decoding under Linux. Adobe hasn't implemented VA-API support nor VDPAU but rather they have just ranted about the Linux video situation at length. Nice job to Splitted Desktop Systems and the Gnash project in supporting GPU video acceleration prior to Adobe's official Flash Player for Linux. Gnash also builds fine on 64-bit Linux platforms, which as of late has been shafted by Adobe with their proprietary Flash Player.
Gnash 0.8.8 can be downloaded at GnashDev.org.