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There is an Update Now button which allows for manually forcing an update of the logos into the database. However, there is a system file watch which monitors for changes made in the logos directory and will eventually update based on those changes. There’s a delay of 2 minute for these updates mainly to protect against the case where there are several changes being made to the logos directory. That is, updates only happen 2 minutes after the final update to the directory.
If you’re using avis encoded by XPression and perhaps other codecs, you will need to install AviSynthPlus. An installer is available here.