Hi Stefano,
I am very interested in your result. I am trying to achieve the same thing than you I think: Play full resolution (full hd) 3D files on my Lg 4k tv. And from my NAS as a bonus!
So you said that 4k isn't supported at all by DLNA? Good to know. I thought that DLNA was just "serving" the file... Because yes I have some 4k videos that play well from a USB connected HD but not from my NAS. It is sad that WebOs cannot connect to a SMB shared folder.
As for the 3D. What is your process? What software(s) are you using?
Is your source a bluray 3D?
In my research on playing full resolution 3d, I also found some discussion about "3D Frame Sequential" format (http://forum.doom9.org/showthread.php?t=170863). The sample clip posted there play perfectly on my tv. Best of all, the tv detect that it is 3D content and switch automatically!
But this forum is really really technical and I didn't understand yet how to create that kind of mp4 from a bluray. I also read somewhere else that using 3D Frame Sequential format is bad because the video encoding is trying to compress between the right and left eye images and that cause a lots of compression artifacts.
If only WebOs could be able to play MVC MKV files...
