It's pretty clear that OGG players can identify which codec is being
used. But this document does not say which bytes of the BOS page can
be used to identify the codec. (first 4 bytes? first 16 bytes? up to
the first NUL?)
Again, based on vorbis as an example (for the spec doesn't explicitly
state this), any leading part of the data (i.e. packet contents, so these
are not the absolute leading bytes in the stream, since there is the page
header first) in this first page. Vorbis uses the first 7 bytes (0x01,
0x76, 0x6f, 0x72, 0x62, 0x69, 0x73 -- which is a leading 0x01 followed by
the ascii values for "vorbis"), but the intent is to not have a single
fixed-size identifier. We should, however, specify a _maximum_ length for
this).
followup..... the IETF's been dealing with multilevel protocols for some
years, so identifying the "protocol at the next layer" is something we're
used to... not trying to say what's the right way, just musing about the
problem....