1. Method for data compression of a video picture, comprising: dividing a current picture into macroblocks; calculating quantizing factors for each macroblock, as a function of a set data rate; adjusting respective quantizing factors as a function of amplitudes of motion vectors associated with respective macroblocks and as a function of coding cost of the respective macroblocks, to produce adjusted quantizing factors, wherein the coding cost of a macroblock is averaged over a window centered on said macroblock; and quantizing data in each macroblock using said adjusted quantizing factors.