I have a video in Matroska format (MKV, file extension .mkv), 3D half-SBS, where the 1280x720 frame shows the left-eye frame on the left and the right-eye frame on the right.

I don't have a 3DTV, but I have NVidia 3D Vision: I tried to open it with PowerDVD 10 with no result (program hangs). With the same PowerDVD, I tried to play the Avatar 3D trailer downloaded from YouTube (MP4 format), but it now shows it the two frames.

PowerDVD 10 is advertised to support 3D and 3D Vision. Why can't I play these videos?

NVidia Stereoscopic player plays the Avatar trailer fine, but it doesn't support MKV.