I was wondering how you got around licensing issues, looks like you require the user to install ffmpeg and imagemagic separately which at least respects the license.

Just a question seeing as you are targeting Mac as one of the platforms. Did you concider using AVFoundation for some functionality on MacOS? Similar with Microsoft Media Foundation on windows? Although both of those would have less supported formats than ffmpeg licensing is much less of an issue.

If you ever do want wide support without the pains of having the user install ffmpeg then for video MainConcept is what I've generally seen used.