Prompted when copying a video: "do you want to convert" message

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http://forums.androidcentral.com – Tab 2 7.0 running 4.1.1. I think this is a Kies message, but if it's a general Android message I will repost in another forum. When I copy a video to my tablet I occasionally get a popup message asking if I want to convert the video. I am experimenting with the best combinations of bit rate, codec, file format, etc. for my new tablet, and I am wondering if anyone happens to know exactly what this converter does when I say yes. I compared a file it had converted to the file before the conversion took place and the frame rate, bit rate, frame size, and codec are exactly the same. Only yhr (HowTos)