S3 Graphics Chrome4xx_5xx Linux driver package includes a patch to MPlayer to enable
GPU accelerated H.264/VC-1/WMV9/MPEG-2 video decoding through VA-API.
So even S3 has hardware accelerated video decoding for Linux users, that only leaves out AMD...
S3G linux driver also implemented a new video API called VDPAU. This API is used by the latest
SVN version MPlayer for video acceleration.
AMD is making a complete fool out of itself by not letting Linux users make use of the hardware accelerated video decoding features of their GPUs.