I only choose to beat this dead horse because the difficulty I'm having in this area stands in such stark contrast to the rapid and amazing development work going on everywhere else around this platform, from the server feature set and add-ons to the mobile apps. MediaBrowser is a stunning achievement and plays a central role in my house.
In short, the Xbox 360 cannot "see" the MB3 DLNA server on the network when I access the "System Video Player" app. What it's really looking for, as far as I can tell, is a Windows Media Player Sharing or equivalent service, since Windows PCs and other third-party DLNA servers on my network appear in this list.
In lieu of directly accessing the DLNA server using System Video Player, as I do via the "equivalent" Media Player app on the Xbox One with great success, I often use my mobile app or the web interface to "Play To" the console. However, this only works for certain files and file types. For example, Play To seems to attempt to play MP4s directly to the console, even if the files in question meet the criteria for transcoding under the Xbox 360 profile, resulting in consistent failure (the biggest problem with the playback of my MP4s on my 360 is the number of large files in my library encoded with 64-bit offsets).
I have attempted to make use of MBC and the Xbox 360 MCE for media playback, as the interface is beautiful, fun, and intuitive. However, it is an inelegant and impermanent solution for a number of reasons and MBC seems to be nearly deprecated anyway. There are other things I need my Windows client PC doing besides hosting a RD connection from my 360 and transcoding video files off a network share.
I have attempted to run alternative, third-party DLNA servers that the 360 will recognize (such as Serviio), alongside MB3, but I hate them. For one thing, MB3 is the only DLNA server I know of that discerns the difference between a 32-bit MP4 (which I would want the 360 to play directly) and a 64-bit MP4 (which I would want/need transcoded), which means any other solution will necessarily transcode absolutely everything at great cost to my server's performance. But most of all, by not using MB3 as my DLNA server, I lose access to the amazing plugins/add-ons and content management solutions employed by MB3, including and especially Collections and Playlists.
Short of buying an Xbox 360 for the development team or replacing my own Xbox with a Roku, options that have been categorically denied to me by my wife, what can be done?
P.S. I'm obsessed with MediaBrowser. As I mentioned on Twitter a few months ago, it's revolutionized entertainment in my home. The first thing I do every morning is log into the web interface to see if there's a new beta release of the server. I'm tech savvy, but not a dev, so if I can be of any help here, please let me know!