What is the difference between MPEG-4 & H.264? A rough answer is that video quality of latter is more beautiful, file size is smaller, and transmit speed is faster. It is easy to evaluate file size & transmit speed, but is it hard for amateur to distinguish video quality. In short, the smallest video block size of MPEG-4 is 8 x 8 pixel, but it of H.264 is 4 x 4 pixel. Therefore, edge is processed sharply.