Parse MPEG4 Bit stream

[Nikki]

Hi All,
I would like to be able to parse through the mdat of an MPEG4 file and
extract information regarding the I,P,B VOPs as well as the audio
samples for some video quality analysis work. The information that I'm
most intersted in is the media time, sample number and sample size.

So my question is:
1] Rather than re-invent the wheel - has anyone done this and are they
willing to share? (Its worth a try at least ..)
2] Does anyone know where I can find info on the relevant start codes
etc. ? Im probably going to implement it in C++.
3] Are the start codes the same for H264?

Ill post the source code of whatever program I write once I get the
codes sorted.

Thanks a million,
Nikki