how to modify the relative size of i frame and p frame

I use tegra multimedia to encode vedio, but sometimes i frame is too bigger then p frame, for example, i frame is 100kB and p frame is 5kB.
I want that the diffence of i frame and p frame is not too great.

Please try to configure virtual buffer size in CBR mode.

01_video_encode$ ./video_encode -h
        -rc <rate-control>    Ratecontrol mode [Default = cbr]
        -vbs <size>           Virtual buffer size [Default = 0]