Hello,
I'm using Mezzmo for a few months now, mainly because it was one of the few apps able to stream external SRT files to playback devices. However I have a huge complaint to file for the developers of this UPnP server: the database file that it creates and uses, Mezzmo.db, grows to unhuman proprotions uselessly.
Let me illustrate what I'm trying to say:
With a library of just 400 video files, the library is taking up 3.5 GIGAbytes. That's around 3500 megabytes of space, for just a few hundred movies. Now imagine having 3000 movies, and maybe some 20.000 songs. I would need to have a dedicated HDD just for the database file Mezzmo is using, it would easily reach 1 TB or more.

Now, being a programmer myself, I decided to take some actions about this ever since I was suspicious when it hit 1 GB in size for just 50 media files. So I did what any developer would do: started digging through the database using a SQLite database manager, so here's what I immediately detected:

- THUMBNAILS are being cloned into the thumbnails table for each playlist that contains a file for that thumbnail, and also for any other file that has the same thumbnail. So, for example, if we have movie which has a thumbnail image that takes 300 kilobytes, and that movie is the thumbnail of 30 playlists (including automatically generated playlists), then it will eat 10 MB of space, instead of just 300 kB. This takes like 95% of the DB space.
- ALL playlists are being stored in the database. This includes automatic playlists. This is stupid, since those are dynamic and should be created on-the-fly, in-memory, at runtime. Also these consume thumbnail storage since they require thumbnails...
- dead entries for a lot of stuff, including playlists. I observed this in the GUI too: when I delete a playlist, I sometimes end-up with ghost entries, or sub-items that no longer have a node parent.

So, what I did after this: wrote myself a nice PHP script to "clean" this database in the following way:

- redundant thumbnails are being completely deleted and only the unique ones are kept (since they have a hash anyway, this is a fast operation). Ofcourse, deleted items referenced by other files and playlists will get the ID of the one and only kept thumbnail's id;
- deleted thumbnails of inexistent or dead entries (as I said, this is a bug in Mezzmo, ghost entries remain many times after deleting stuff)
- removed oprhaned playlists (there were A LOT of those!). Recursively doing this until no entries with inexistent parents remain.
- vacuum - to compact the database file

Final results: after running this cleanup script, my DB file shrank from 3.5 GB to 67 MB. That's 50 times smaller in size, with absolutely the same DB content.

Unofrtunately, I have to run this script after each time Mezzmo starts or I add any new files, because on startup/adding files, it WILL re-duplicate all those thumbnails for the playlist entries again and again, ending up back to gigabytes in size.

So, my request to your DEV team is: please, please, PLEASE, figure this out for your next release. My system drive is not a black-hole storage space for the Mezzmo server. DO NOT DUPLICATE thumbnails over and over again, DO NOT keep in the DB thousands and thousands of dynamic playlists (they're called dynamic for a reason), FIX those dead entries that remain after editing the library, and you'll have happier users.

Thanks.