[vorbis-dev] Re: [theora-dev] Re: Ogg Internet Drafts - create application/ogg-vorbis, application/ogg-tarkin, etc.

Fri Jan 3 05:00:36 PST 2003

[sorry for the previously wrong speex-dev address]

Hi all,

let me summarise what I've learnt from the discussion and hope to
progress us towards a comprehensive MIME typing scheme that makes
everybody happy.

1) "application/ogg":
On the one hand, we should have the generic MIME type "application/ogg"
and the generic file extension ".ogg" for anything that uses the Ogg
container format. I guess for the moment there is no generic application
that can handle all existing defined ogg media mappings (such as
ogg-speex, ogg-vorbis, ogg-theora). But that can of course be built and
then we are on a line with Quicktime, Microsoft media player and
RealPlayer. 

Those three by the way can understand several MIME types, e.g. Quicktime
understands "video/quicktime" but also things like "audio/aiff",
"audio/wav", "audio/midi", "video/avi", "audio/mpeg", and "video/mpeg".
One word of caution here, though: while those three each try to dominate
the market with their application and do not want others to use their
container format, Ogg is open and many people have started picking up
the Ogg container format for their encoding format by only having to
define a media mapping. Therefore, it will be difficult to maintain a
generic application that will be able to interprete any random Ogg file,
because the Ogg container by itself does not know what kind of data it
carries.

2) encoded bitstreams:
On the other hand, we have several different types of encoder formats
that may need to be generically identified:
"video/vp3"
"audio/vorbis"
"audio/speex"
would identify just the encoded bitstream independent of the container.
I am not sure if these are necessary, but maybe somebody has an idea for
a use of it.

3) Ogg as container:
As a level in between, we should identify a valid Ogg bitstream
containing one or more encoded bitstreams together with their defined
media mapping:
"video/ogg-theora"
"audio/ogg-vorbis"
"audio/ogg-speex"

4) Other containers:
In a similar manner, encoded bitstreams in different container formats
would need a different MIME type again, e.g. using RTP as a container
format:
"video/rtp-theora"
"audio/rtp-vorbis"
"audio/rtp-speex"

COMMENT:
I read that there are efforts under way with the IETF to register
"audio/speex" for speex over RTP
(http://www.speex.org/drafts/draft-herlein-speex-rtp-profile-05.txt)
which is not conform to this proposal. How far is that progressed?

<p>Now, leading on from here to file extensions is a different issue. I
would recommend to have different file extensions for each of the
defined Ogg media mappings ogg-theora, ogg-vorbis and ogg-speex. My
reasoning is that it makes it easier for programs to map from the file
extension to the MIME type and from there to the application to use
without having to look inside the file. My check of MIME types also
found that mostly a MIME type maps to many file extensions, but one file
extension belongs mostly to one MIME type only. I believe that for speex
a distinct extension ".spx" is already in use. Any takes?

<p>Sorry for the lengthy email. And also sorry for mixing up theora and
tarkin before. They are of course distinct and once tarkin works it can
follow the same proposed scheme above.

Cheers,

Silvia.

<p><p>Silvia.Pfeiffer at csiro.au wrote:
> 
> Dear David,
> 
> I hope it's ok to forward your email to the developer lists. I have not
> seen a comprehensive scheme for MIME type naming and file extensions for
> ogg files yet - please anybody put me in the picture if there is.
> 
> However, I have seen application/x-ogg used for ogg-vorbis files, which
> is according to MIME type registration rules an unregistered and
> experimental MIME type (see RFC2048) and seems to have worked so far for
> ogg-based files. I understand your issues on having application/ogg as
> an all-encompassing MIME type, as ogg by itself cannot determine the
> further type of content included. Therefore your idea about having more
> specific MIME types makes sense.
> 
> Yet, I don't believe that application/ogg-tarkin or
> application/ogg-vorbis should be chosen, as "application/" to me flags
> that the content of the file can only be determined by an application
> that can read this specific type of file. In my opinion, vorbis should
> be audio/ogg-vorbis because vorbis itself is an encoding format that
> makes sense in containers only, such as ogg or rtp. Tarkin on the other
> hand is a combination of vorbis and VP3 plus a media mapping onto ogg
> such that video/tarkin might make sense, though would not be logical to
> the outside world.
> 
> As for file extensions - I've seen theora files also end in .ogg .
> 
> Cheers,
> 
> Silvia.
> 
> David Wheeler wrote:
> >
> > Thanks SO MUCH for creating Internet Drafts;
> > I cannot begin to tell you how important
> > it would be to create IETF RFCs for Ogg and Vorbis (and Tarkin, etc.).
> >
> > However, I believe there should NOT be a _single_ MIME type for ogg.
> > After all, it may contain different codecs, and different application
> > programs may only handle certain codecs.  I believe the MIME type
> > should identify the codec as well as the fact that it's ogg.
> >
> > For example, many people have _separate_ applications for audio-only
> > instead of audio+video.  It would be better if they could start the
> > "right" application using just the MIME type information (instead of
> > awkward two-stage start-ups that are different than anything else).
> > At the least, I suspect there is a need to have different MIME types
> > for audio-only vs. video.
> >
> > Also, not all applications can handle all codecs, even if they handle
> > that kind of media; that would be ESPECIALLY true if Ogg supports multiple
> > codecs... which it does.
> >
> > Thus, I believe the MIME type should identify both Ogg & the codec.
> > Perhaps an application/ogg-vorbis, application/ogg-tarkin, etc.
> > You could also register application/ogg (to be used when a more specific
> > MIME type isn't available).  Ideally the standard filename extensions
> > should be different too; Ogg Vorbis could be ".ogg" since that's become
> > so common, Ogg Tarkin could be ".ogt", etc.
> >
> > Thanks.
> >
> > --- David A. Wheeler
> >      dwheeler at ida.org
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