While, miniDLNA works great with the Asus O!Play Mini/Mini Plus Media Players (http://www.asus.com/Multimedia/OPlay_Mini_Plus/), subtitles do not work. However subtitles work just fine with a program called "serviio" (http://serviio.org/). A bit of debugging of the stream data showed that Asus likes to accept the subtitles as a "res" tag just like the LG TV (DIDL XML attached).
Would it be possible to add subtitle support for this player (i would ultimately like to use miniDLNA via DDWRT on DLNA capable routers.)
Patch is attached.