[btvbuddy]

You mentioned the structures are the same,

just as backgroud there are three GOP structure types that I can build

IBP
IBBP
IBBBP

In a I frame, it's a full frame.

<snagged from google - thanks Mr. John McGowan>
In a B frame, Bi-directionally encoded macroblocks contain a backward
and a forward motion vector encoded using variable length codes in the
macroblock header. Each macroblock has a header which amongst other
things identifies the macroblock as intra-coded, predictive coded, or
bidirectionally predictive coded. The bidirectional macroblocks are only
allowed and used in B frames.

In a P frame, it's a Predicted frame and decoded from the previous I or P frame.

So, when you said it's the same did you mean both have only 1 bi-directional frame in the GOP?

I think there is a net tool to analzye mpeg GOP's is that what you used?