I don't think this was directed at you, but caf4926. Sorry for the confusion.
I know full well what Matroska is :)
No? Well, install it then use GraphEdit and open a file and you'll probably see how much junk filters it has added to the graph. Indeed, if you install wrong filters, it can for example make the video appear flipped. I've experienced this before and I have been keeping tabs on this like this. If you would ask in a forum concerning this kind of things, I think they too would tell you to avoid packs. Use ffdshow instead.
It can work. Sometimes it won't, and even if it does work it still probably installs a lot of junk filters that are added to the grraph.
Also, ffdshow has the advantage of a lot of options, like post processing (deblocking among them), noise reduction, volume normalization, etc.
And that's why I recommend to stay away from them :)