UMC Mpeg-4 encoder question

[GrassValley_Eng]

I am using the UMC MPEG-4 Video Encoder to encode videos into Mpeg-4 P2, (simple profile, level 1) at 1Mbps. My questions is that even if I defind the GOP to be 30 frames, but from the result data streams, I saw that sometimes (very often), the gap between two I frames is less than 30 frames, I even saw 2 frames in between. is there a way, or configuration, to force that I frames only show up once in every 30 frames interval?

Thanks.

[Gennady_F_Intel]

could you please try with each frame to indicate it's type and then it will not be change.