gmc and qpel

[DerrickZ]

Hello, this is not a real programming question, but I'm not sure where else to post this and this seems to be the most suitable place.

I'm reading some articles about how an AVI works. I've read that every video frame starts with "00dc". This is also visible if I open a small AVI clip with notepad. Is there a way within those frames (mostly gibberish) to see if the video was encoded with gmc or qpel?

Thanks.

[unclebud]

Gspot will read an avi file and tell you if it's Qpel or GMC.
http://www.headbands.com/gspot/

[DerrickZ]

Thanks unclebud, I know that GSpot, AVICheck, MPEG4 Modifier, etc can tell whether an AVI was encoded with gmc or qpel, but I'd like to know how they find that.

I'm not talking about source code, but which part within an AVI tells you that the video was encoded with those options? I know that every frame starts with "00dc" and I assume that the gmc/qpel information is stored somewhere in a frame, but where?