He plays OTB so he would already know what an OTB rating is and he already has one, 1500 something i heard. Anyways:
You have select A. Rating
An OTB rating is a chess rating assigned to an OTB player.
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Help ppl out since 1982
Don't know if this sheds any light, but I went here...
http://www.chiariglione.org/mpeg/faq/mp4-sys/sys-faq-esm.htm#ESM-24
..and found this:
"24. I know STB from MPEG-2. Now, what is an OTB?
An object time base is the flow of time that can be reconstructed from the set of OCRs sent for this time base. As in MPEG-2, the process of time base reconstruction is not normatively specified in MPEG-4."
Think we may be getting closer.