Wow, a whole day and no response.
What is your intended use of Shotcut? Few people concern themselves with video levels these days unless they have professional sources/destinations. My old Sony Vegas had a Broadcast Levels filter to make sure cable/studio video did not exceed the prescribed limits. A professional video editor will have these filters. If you want to deal with them on a limited budget AviSynth and VirtualDub have levels filters among many others to make a technically accurate conversion. I looked in the FFmpeg docs and they were not addressed. Shotcut makes use of FFmpeg. Also, I am not sure how you would determine whether source video exceeded broadcast levels without a suitable calibrated monitor. -=Ken=-