I have been trying to play h.264 mkv files, without success.
I already installed the restricted formats from Restricted Formats/11.1 - openSUSE-Community, and still no luck. I have no trouble playing DivX or XviD encoded videos. I have installed packages JM, libx264-64, libx264-67 and x264 (which are supposed to be x264 encoder/decoders) and libmatroska.
I’m using openSuSE 11.1 (x86-64) and VLC 0.9.9a to play the videos (but the same happens with xine).
Also, the bitrate in some h.264 files can be encoded such that one needs a powerful computer in order to play them (or if one has a supported video card use VDPAU and offload the video decoding to the GPU on one’s graphic card). For example, I find the h264 files on this web site are a good test for one’s capability to play h.264 files. Again, typically, because of their high resolution and high bit rate, one needs the sort of setup I mentioned above: H.264 Demo Clips « H264info.com
But I can play those videos with only a 10% CPU load on an old 32-bit athlon-2800 PC with a PCI card (nVidia 8400GS w/512MB on card RAM) via VDPAU technology implemented in the nVidia proprietary video driver and by also using an mplayer build that uses that technology.