What kinds of file format?
SAMSUNG SMART TV supports standard DLNA protocol?
Maybe it is a DLNA compatibility issue.

The BBC IPLAYER download format is MP4. I am using the SAMSUNG SmartTV app ALLSHARE and it supports the DLNA standard I can successfully browse through the folders and files on the NAS but get the invalid codec when I attempt to play something, the same happens if I attempt to look at a Photo. I found a thread on the web talking about which end does the codec and there is a mention from some person who has a Netgear and and can stream straight from NAS to SAMSUNG ALLSHARE. I noticed an older thread on the TP-LINK forum mentioning TP-LINK DLNA MP4 issues that have raged on for several years without resolution. It would be nice to get a statement from TP-LINK as I am sure they are aware of the issue?