[vorbis-dev] Specification change requests

[Michael Smith]

>
>###############
>#2002-10-15-002
>
>In the document "Ogg logical bitstream framing", Ogg pages are described
>as beginning with a capture of the form "OggS". I've come across some
>older Ogg files, which have other data between the valid Ogg pages,
>mostly
>starting with the three letters "TAG". If it is common practice to add
>data between the pages, this should at least be mentioned in the framing
>specification, and a suggestion should be made how to find the beginning
>of the next Ogg page. Simply seeking forward until finding the OggS 
>pattern
>seems obvious, but this could lead to some trial and errors if the 
>pattern
>occurs in the extra data.

I'll handle this one since it's not a spec bug and is fairly
straightforward.

There are a number of broken tools out there which add ID3V(1,2) tags
to ogg vorbis files. This is not allowed. Other data between valid
ogg pages is always tolerated (because of how the ogg framing/sync
works), but is not common practice, and is very highly discouraged.
There are no known non-bug uses of it.

The ogg spec, as I recall, does specify how to find the next ogg page,
and a forward seek to the next occurrance of the sync pattern 'OggS'
is correct (there's no other way to do it, since we're considering
cases where there's garbage data between pages). The page checksum
should prevent us from incorrect sync if this string just happens to
occur in the garbage.

Mike

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