http://coolsoft.altervista.org/en/h264leveleditorTo make a long story short, some mediaplayers (like my Samsung C6000 LED TV and Sony PS3) search the video file being played for an header info named AVC profile level; if this level is greater than the requested (supported) one they simply refuse to play it, even if they could.
BluRay specifications requires level 4.1, which is supported by all actual HD mediaplayers. Many of the video files you'll find on internet were encoded with an unnecessary high level, like 5.1.
I haven't tried this yet but it may well be a useful tool to gets some of those difficult MKV files to play on the BW.
