So I've encountered an odd issue that cropped up after a couple updates ago. When I first purchased the BDPS3100 it was able to recognize and instantly stream any file type from my server. I use a Synology DS211j with a pair of 2tb drives configured in RAID.
After a patch (or two), I noticed that playing any file (except for AVIs) resulted in an "Unsupported format or unrecognizable file" error. I did a little fiddling with the settings on my DS2 but can't seem to find anything I changed that would explain the problem. On top of that, my Playstation 3 was still playing all the exact same files with no problem.
Upon further inspection, I noticed that the files that wouldn't play on the S3100 would display a "M2TS" file tag next to the file, while the ones that did play (only AVIs) would display the proper tag (AVI). Every other type of file (MKV/MPG etc) would display as M2TS.
My next step was to copy a type of each (AVI/MKV/MPEG) to a thumb drive and plug it into the S3100. Oddly enough, all the file tags displayed properly, and ALL THE FILES played properly as well!
Obviously this means there is something wrong with the streaming, but why is it affecting the S3100 and not my PS3? I didn't mess with any settings between patches, was there a patch that affected some type of network protocol that I wasn't aware of?
You referred to a manual page that conflicts with the marketing PDF about whether or not these formats are supported via DLNA. I am not sure this constitutes any type of resolution, just poor consistency on Sony's part.
Try this fix as a start. I had the same issue with my MP4 files. They kept showing as M2TS and they were not. Make a copy of your /volume1/@appstore/MediaServer/etc/agent.conf file just in case you make a mistake. Edit the agent.conf file and go to the "Sony Blu-ray Disc Player" profile. You will find this line: "profile@MPEG_TS_SD_EU":"ext@m2ts&ts&m2t&mts&mkv&mp4&m4v", change that line to look like this: "profile@MPEG_TS_SD_EU":"ext@m2ts&ts&m2t&mts&mkv", now add this line right after the one you changed: "profile@MPEG_PS_SD":"ext@mp4&m4v", Save the file off and restart the Media Server package. I have submitted my findings to Synology for review. I have tested this fix on the BDP-S3100, BDP-S780 and the BDP-S390 with success for me. I would be interested to know if you added mkv to the MPEG_PS_SD profile if that would fix your issue. Please post a reply if you try it.