Wild media server (UPnP, DLNA, HTTP)

I have the sony nx700. Whe i watch movies with black bars, they looks stretced on the tv as if the original video format was 4:3!

I noticed that i can fix the issue by changing the screen size from 16:9 to 4:3 (on WMS), but i don't think this is the right way, even if the result is the same.

I ask that, even because if i use this "solution" i must pre-transcod movies, because a "live trascoding" is too heavy for my CPU, and it causes a non-fluent reproduction

Thanks

thank you. unfortunatly the 4:3 solution seems to be the only one.