So I am a bit confused on the motion vector calculations. As I understand for a macro-block in one frame to be considered the same as a block in another frame every pixel must have the same Y value as the corresponding pixel in the alternate frame. Does this mean that if for any reason even if a block has 1 pixel that is even the smallest amount different the block is not considered to be a match?

Also when calculating motion vectors I do not really understand what is done for blocks which have no match are they simply ignored? How does the rendering of the frame deal with these blocks which there is no motion vector for