Media is a blessing and a curse. The pictures are nice, so are the sounds, but the space they take up can be annoying.
In general, you don't need to conserve space in your mills, 10Gi or 20 Gi is likely to be enough to keep most people happy. However, I'm not encouraging you to save space on disk. I am recommending that you should try and save space when transferring media across the network. Even with fast networking, it never hurts to trim a few Mb from the file transfers. Especially when you consider that all of your assets have to be delivered to all of your players.
There are many alternatives for image and sound formats and there can be dramatic differences in space required to store the data. Especially when you consider that significant space savings can be realised without a corresponding drop in quality.
As they should say on TV: "Don't take my word for it, read this informative article instead...".
Ok, I'm sold what should I be doing?
Well you could convert them by hand using ffmpeg.
It's boring and error prone to have to convert these things by hand. Especially if you also have to update database entries to make sure you haven't made any mistakes. Hmm, boring and error prone, sounds like an ideal task for a utility program.
We could develop a utility which minimised various media formats automagically for users on Worldmill. We would make this an opt-in feature, so that we would only minimise your assets with your consent.
At a later date we could open source the core conversion component so that all Foundry users, self-hosting or hosting elsewhere could use it.
You can discuss this in our discord #feature channel if you are interested in this or other suggestions we make on this blog.