A method of video coding comprising Intra prediction coding at least a predetermined constant M macroblocks within an ordinary frame. These M macroblocks include naturally selected macroblocks where the bit cost of Intra prediction coding is less than for Inter prediction coding and optional additional macroblocks. The optional additional macroblocks have the least bit cost of Inter prediction coding as adjusted by a penalty factor each time a corresponding macroblock is Intra coded in a predetermined number of frames. An end frame Intra prediction codes each macroblock having no corresponding Intra prediction coded macroblock in a predetermined number of ordinary frames.