Where in Drupal database do I store additional file properties? I have an (architectural) problem with D7 and don't know what would be a good solution to it. Here is what I'm trying to do: I have an article with a sound sample attached to it. I thought it would be great to calculate sound sample duration and bitrate and store it somewhere in the database. What would be the proper place for that? I thought of node fields first, but number of sound samples for one article is not restricted and it seems I'll need to define a field with unlimited number of values to hold durations and then somehow match samples with their respective durations. Don't think it's a proper solution here. So what's the common practice in such cases?
You might want to look into the Media project which provides bundles for files and allows to add fields to them.

Another approach would be to use a module like Field collection which allows you to group a number of fields into a group that you can add as a field to another entity. That field can then have an unlimited amount of values which allows you to attach n fiels + meta information to your node.