RE: Track "id" format?

> Id is DOMSTRING. Why not a string representation of the id as a decimal number? Could also allow hex if the representation conformed to 0xNNN.

A decimal string seems like a good representation, at least for Matroska and MPEG-TS (other formats may be similar, but I haven't researched them). I'd like to make sure that's the common format though. With MPEG-TS, it seems fairly common to just represent PIDs as hex (probably because they're just defined as "13 bits", not as an particular "type").