Whats GMC and what is it good for?
GMC stands for Global Motion Compensation and that pretty much tells the story of what it does. If used, it will look at the whole frame and see if there is an amount of motion that all the parts of the frame have in common. It will then take this amount of motion and put it in a single value. The parts of the frame are the macroblocks, and the amount of motion is called a ‘motion vector’ which has both a direction and a value (as a sort of two-dimensional X,Y value) . All the macroblocks normally have their own motion vectors, but with GMC the one motion vector that they all have in common (that’s why it’s called ‘Global’) will be compensated and put into a single motion vector. Some macroblocks’ movement will be completely compensated for by the GMC vector, getting completely nullified by the compensation process. These macroblocks’ motion vector will then be removed, as it is the same and is only extra information. The possible benefit is that you can remove many or all the motion v
