cpt_paranoia: Great thread about Twonky!
There are two things missing about dlna and the way it works, maybe useful if content is not available within media players:
dlna streaming is based on so called profiles; during the first connection of a media client with the media server, the client sends a profile to the server: Content of this profile is what the client does support, e. g. file types and codecs.
Other way round: if there is content available for the media server which is not listed in this profile, then this content will not be shown in the client’s UI or cannot be accessible to be played. Problems may occur for example with MKV files. MKV is a container icluding video codec and audi codec(s). Some Smart TV state within their profile, that MKV is supported - but having not the support of the codecs within this MKV. This leads to “video codec not supported” message.
Another notice worth to be take a look is the correct identification. Within the Twonky config pages on port 9000, there is “sharing” and within sharing there is the list of all media clients. Normally, media clients with a good profile cause no problem. But sometimes, client profiles are faulty - like my private older receiver and Blu-Ray player; both are not listed as “xyz DMC” but one as o2juggler and the other as “generic”. After setting them to what they really are by using the massive drop down list, everything works fine.
Both issues described here are related to the dlna client profile, not to the Twonky Media Server. Topic 1 cannot be solved easily as this is bound to the client, Topic 2 can be solved with the help of the correct selection.
Hope this helps