The DNS-321/323 UPnP AV server does not seem to support all video formats currently supported by the PS3. I have many HD video files in .m2ts format, which stream just fine from my Windows XP WMP 11 box to the PS3. But they cannot be seen on the UPnP AV connection from the the DNS-321. The DNS-321 only shows my converted lower resolution .mpg files. The DNS-321 should not claim to support PS3 DLNA UPnP AV streaming unless it can handle all PS3 DLNA video formats. I do not consider conversion of HD videos from .m2ts to another format, such as .mpg, to be a reasonable option for most folks. Hopefully the firmware engineers will be able to fix this issue very soon, before many potential customers are lost
due to lack of compatability with PS3, XBOX, or other DLNA UPnP media players.
I have also observed that if file of an "unsupported format" exist in the DNS UPnP folder tree, the UPnP AV server refresh often seems to stop scanning, so all files do not show up on the PS3 or other DLNA media player.