The Raspberry Pi (which miniMAD is based upon) supports H264 hardware decoding with a very specific pixel format (420p) so most of the time transcoding (compressing) is required when exporting to the miniMAD.
Then, depending on the resolution and framerate of the original video-file, the part of it that will actually be mapped, and the selected projector resolution, MadMapper will crop and downscale the original file while transcoding to guaranty a smooth playback on the minMAD that has limited computing power, especially when using the graphics adapter for live video-mapping and color management as we do.
There are a few advanced options that are available for tweaking the transcoding and get better results for a specific content.
But if you feel like so, you can transcode your files with your favorite video-file-encoder and place the results in the mapping/ folder of the miniMAD. Just keep in mind the file has to be H264 / 420p encoded to be played by the miniMAD.