[theora-dev] [ogg-dev] handling multitrack Ogg

[ogg.k.ogg.k at googlemail.com]

> Right now, I can see two different systems: the order in which their
> BOS pages are given in the Ogg header part - or the order in which the
> serial numbers go, when ordered. Alternatively, we can introduce an
> explicit track ID and order by that number.

If one reencodes an Ogg stream (eg, using a video editor, etc), the
serial numbers and BOS ordering might change.

There are no tools that I know of that allow ordering BOS pages in a
specific order, so that'd have to be created, and all writing programs
would have to be made to preserve ordering.

Ordering by serial numbers, even assuming they do not change, will
give you an arbitrary ordering (as serial numbers are most often
random to avoid collisions when merging with another file), which
conflicts with an author specified ordering.

Such an ordering is a property of the whole stream, rather than its
individual constituent logical streams. Indeed, it may change if you
remove/add streams, while the constituent streams will stay unchanged.

Thus, I think such an ordering may be best done as a specific property
placed in the fishead for this particular stream, eg "Track-ID: 5".