[Mp4-tech] MP4 file format?

[William Tsang{RPI Alum}]

Hi all
I would like to ask if there are any sites that explain the .mp4 file 
format?  Not just the structure of a .mp4 file, but like telling you 
from what bytes represent what kind of information...etc.
I know .mp4 is not a simpel video file but instead a file container that 
have both video and audio files inside it.
I am trying to write a function that will parse the .mp4 file and locate 
  the video & audio data.  But i can't find the .mp4 file header 
anywhere.....:(  Thanks in advance guys !!!!!!
Will