I've been tinkering around and it looks like there is no way around it, gstreamer just doesn't support mkv properly, so I will have to quit on dragon and kaffeine. As I said, VLC has no problems and neither does mplayer. I would prefer mplayer2 since that's what I usually use on any distro. I tried compiling it, but it looks like vdpau acceleration doesn't work and that's the very reason I use mplayer. I suspect it's because the libvdpau version is too old. Maybe it will work once it gets upgraded in pclos. I know mplayer works, but mplayer2 is better in many ways, so I think including mplayer2 in the repos would be a good idea. Can we suggest new packages for inclusion somewhere?