[vorbis-dev] audio/vorbis media type registration

Mon May 14 16:29:09 PDT 2001

Linus Walleij wrote:
> 
> This is the first draft of the audio/vorbis media registration form to be
> handled to the IANA. PLEASE comment extensively, even minor spelling
> mistakes etc are to be stamped out of this I hope.
> 
> A media type for application/ogg (or should it be
> application/oggsquish?) will be created separately.
> 
> I would be very happy if someone could supply the 4-letter filetype code
> used by MacIntosh .ogg files.

'OggS'

Note that this is used for _any_ Ogg file, not just vorbis.  And note that
there doesn't exist a complete Quicktime Vorbis codec yet.

As a media type I used 'Vrbs' for Vorbis content; this is only seen by
Quicktime itself, and is not on the filesystem.

Maybe Nicolai wants to comment as well?  I hope he takes over the QT Vorbis
effort, as I have neither time or enough QT experience right now :-)

> 
> Linus Walleij
> 
> --------
> MIME media type name:   audio
> 
> MIME subtype name:      vorbis
> 
> Required parameters:    none
> 
> Optional parameters:    none
> 
> Encoding Considerations:
> 
>         The vorbis audio data is usually wrapped inside an OggSQUISH
>         bitstream, see [OGG].

Not usually, but always.

> 
>         The vorbis audio data is binary data, and must be encoded for
>         non-binary transport; the Base64 encoding is suitable for Email,
>         Binary encoding could also be used. Further lossless compression
>         may be problematic as the vorbis data is already efficiently
>         compressed using psychoacoustic algorithms with highly optimized
>         bit-allocation.
> 
> Security Considerations:
> 
>         Ideally, the vorbis file can not contain security-violating code
>         as the format is highly specified, see [VORBIS] and/or [COLEMAN].
>         However, fields can be abused if the recieving decoder
>         implementation has errors or extensions that make it possible
>         to embed interpretative or object code. The recieveing decoder
>         must therefore take these issues into account, and under no
>         circumstances allow untrusted code to be executed.
> 
>         Vorbis files are not signed or encrypted using any applicable
>         encryption schemes. External security mechanisms must be added
>         if content confidentiality and autencity is to be achieved.

It is possible (and easy) to sign Ogg streams using the generic file comment
headers; as far as I know, there's no standard way to do this yet, but GPG
signing is one likely candidate.

> 
> Interoperability considerations:
> 
>         The vorbis format has proved to be widely implementable across
>         different computing platforms. An example implementation exists
>         that has been compiled on numerous platforms.
> 
>         The technology involved in vorbis encoding and decoding is not
>         patented and may be used by third parties without patent
>         licenses or similar licensing issues.
> 
> Published specification:
> 
>         See [VORBIS] and/or [COLEMAN].
> 
> Applications which use this media type:
> 
>         Any application that implements the specification will be able
>         to encode or decode vorbis files.
> 
> Additional information:
> 
>         Magic number(s): For vorbis files wrapped inside OggSQUISH
>                          files, the first four bytes are 0x4f 0x67
>                          0x67 0x53 corresponding to the string "OggS".
>                          The vorbis header will then additionally
>                          contain the lowercase string "vorbis"
>                          (comprising the bytes 0x76 0x6f 0x72 0x62
>                          0x69 0x73) at offset 0x1d, where offset 0x00
>                          is the first byte of the file.

I'm not sure if the "vorbis" header will always be at that location, although
it seems right, yes.  Monty?

> 
>                          If vorbis files were to be delivered without
>                          the OggSQUISH header the "vorbis" string would
>                          appear at offset 0x01. This should never occur.
> 
>         File extension:  .ogg
> 
>         Macintosh File Type Code(s):    none

'OggS'

> 
>         Object Identifier(s) or OID(s): none
> 
> Person & email address to contact for further information:
> 
>         Questions about this proposal should be directed to Linus
>         Walleij <triad at df.lth.se>. Technical questions about the
>         ogg and vorbis standards may be asked on the mailing lists
>         for respective developer community, see
>         <http://www.xiph.org/archives/>
> 
> Intended usage:         COMMON

TOTAL_WORLD_DOMINATION

> 
> Author/Change controller:
> 
>         This document was written by Linus Walleij <triad at df.lth.se>,
>         changes of this document will be handled by him or a
>         representative of the Xiphophorus company or the Vorbis
>         development community.

There's a non-profit Xiph.org now (or will be there shortly; Jack?)

> 
>         The Vorbis format, and its superformat OggSQUISH are controlled
>         by the Xiphophorus company and the respective development
>         communities.
> 
> References:
> 
>  [OGG]
>      Xiphophorus company, "OggSquish logical and physical bitstream
>      overview".
>      <url:http://xiph.org/ogg/vorbis/doc/oggstream.html>

Why do you spell it OggSQUISH (different capitalization) in the doc?

> 
>  [VORBIS]
>      Xiphophorus company, "Ogg Vorbis Audio Bitstream".
>      <url:http://xiph.org/ogg/vorbis/doc/vorbis-stream.html>
> 
>  [COLEMAN]
>      Coleman, Mike, "Vorbis Illuminated".
>      <url:http://www.mathdogs.com/vorbis-illuminated/>
> 
> --- >8 ----
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Cheers,

Segher

--- >8 ----
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