[ogg-dev] How Ogg mappings translate into the codecs parameter in Ogg media types

Ivo Emanuel Gonçalves justivo at gmail.com
Sat May 24 09:26:52 PDT 2008

On 5/24/08, Conrad Parker <conrad at metadecks.org> wrote:
> The magic is not always char[8] -- it's an arbitrary number of
> characters, and as far as I know there is no official limit.

I was under the impression that 8 was the limit.  Thus the extra white
space JM adds on Speex and CELT magics.  I may be wrong, though.

> So it's 7 for Vorbis and Theora, 5 for FLAC

So char[7]: '\x01vorbis', char[7]: '\x80theora' and char[5]: '\177FLAC'?

> immediately after '\177FLAC' is a version field, which is not part of the
> codec ident string but is within the first 8 bytes.

I don't think that interferes with anything.  We are talking about the
essential part needed to be detected by applications.

> What you've listed for CMML is correct, and I'm pretty sure the
> strings are correct for Vorbis, Theora, Speex, and PCM.

Good, good.

> Also I don't know if the Dirac, MIDI, CELT or Kate mappings are yet
> finalized?

Kate is AFAIK finalized; that's the impression I get from talks with

Nobody's touched MIDI in years, so that's probably how it will stay.

Considering the similarity between the CELT and Speex strings (the
extra white space thingy) I don't think JM's changing it.

Dirac is the only one I'm not sure, since this one here's the recent
string.  The magic used to be different, and I'm not sure if whoever's
working on Dirac may have a change of ideas.

Anyway, the essential for the document is that no errors can be
present.  Changes and newer codecs may be added later on an update to
the document.



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