Tim,
You can find information about the ATF (ASAM Transport Format) at this web site:
http://www.asam.de/new/03_standards_07.php?memberlogin=
Once you are there, click on the link for "Chapter 5, ATF 1.4.1" and you will see a PDF with technical descriptions of the relevant ASAM specifications.
I have attached the PDF for your convenience, there may be more information at the address I added above.
Let me know if you have any additional questions,
Otmar
Otmar D. Foehner