[vorbis-dev] Mime Type and Ogg (More)

[Rudd-O]

Se me ocurre:

I think we should hand the Ogg stream or file to a 
program X, and let X decide which 
view/presentation/form factor it should have.

After all, the player should open the video window if 
it senses a video stream.  Right?  that way we can 
configure  our file managers and browsers to personal 
taste, and let them hand file types properly to one 
plugin/standalone app.

Quoting Ali Abdin <aliabdin at aucegypt.edu>:

> * Ralph Giles (giles at snow.ashlu.bc.ca) wrote at 16:56 
on 20/10/00:
> > On Thu, 19 Oct 2000, Ali Abdin wrote:
> >
> > > You are right. I apologize for not 
reading/browsing the archive.
> > >
> > > I have read/browsed the threads related to 'Mime-
type' and 'Header'.
> > >
> > > Monty - in one of the threads
> > > (http://www.xiph.org/archives/vorbis-
dev/0416.html) you said:
> > >
> > > 'Magic to detect Ogg (and detect Ogg/Vorbis) is 
easy'
> > >
> > > The magic to detect Ogg is 'obvious'. But what 
about the 'Magic to
> detect
> > > Ogg/Vorbis'.
> > >
> > > You also said 'Whipping out docs for this now.' - 
Where can I find
> this?
> > > (I couldn't find any details about mime magic in 
the docs that I looked
>
> > > in).
> >
> > These are both very fair points. I suspect Monty 
meant the procedures
> > we've alreay touched on. And yes, the lack of 
(promised) documentation is
> > annoying. :-/
> >
> > > Is there, (or shouldn't there be) an area in the 
Ogg header to identify
>
> > > its contents?
> >
> > There's been some discussion of this as well, and 
we do intend some sort
> > of 'stream description' substream. My favorite idea 
is to include along
> > with the other general metadata in RDF/XML, but 
some have suggested a
> > simpler binary header. Mostly to avoid the overhead 
of the parser,
> > though I would imagine that's less of an issue than 
speed for Nautilus.
> >
> > Still, there's no room for this data in Ogg except 
in a substream, so the
> > static bytesequence at a firm offset isn't going to 
happen. Doesn't
> > Nautilus provide its own extended attribute system 
to cache the results
> if
> > filetype determination is slow? Might that be 
enough? Wouldn't that also
> > be a way to implement (in general) file-specific 
app association like
> > Chris has described in MacOS?
>
> Like I said, we could build an algorithmic detection 
of Ogg Vorbis, but
> this
> would be "unweildy" if every new file format asks us 
to use an algorithm to
> determine mime-type.
>
> The mime magic is a nice simple way of determining 
mime-type with almost
> '0'
> overhead for the new file format.
>
> > > I read some other threads, but only the above two 
seems to be the most
> > > relevant ones. None of the threads really 
discussed
> mime-type/mime-magic
> > > in depth and NONE of them really reached a 
consensus or a decision
> about
> > > any particular issue.
> > >
> > > Note: this thread has _NOTHING_ to do with the 
filename extension
> >
> > It does from our point of view. In both cases 
people have written to
> > complain that Ogg doesn't make a handy distinction 
between vorbis-only
> and
> > otherwise within their favored scheme. Both file 
extensions and
> mime-magic
> > are inadequite for the way Monty designed the 
format. Why are you
> > contemptuous of one but not the other?
>
> Because filename (and/or extension) has nothing to do 
with mime-type. To
> determine the type of file you use mime-type, not 
extension.
>
> The way MIME works is that you have two methods of 
detecting mime-type: 1)
> Filename extension and 2) Contents of the file.
>
> Obviously, the contents of the file are a much more 
reliable method (since
> anybody can mv/cp the files to anything they wish). 
Now the contents of the
> file can be detected in two ways: 1) A magic number 
somewhere at the
> beginning
> of the file, or 2) Using an algorithm.
>
> If every file format used an algorithm, it would be 
slow and unweildy. To
> determine the mime-type you would have to pass the 
file through EACH
> algorithm
> until you found a match.
>
> > Of course, I'm unconvinced of the need to make the 
distinction at this
> > level, so my argument is more that yours is moot 
than that your
> suggestion
> > have no merit. If that makes sense?
>
> I could implement suggestion '0' and just wait until 
you guys develop the
> video codec. But I think the lack of mime-magic is a 
flaw. I guess we can
> only
> agree to disagree on this point
>
> > To summarize, for Nautilus (and mime-types in 
general) I'd suggest:
> >
> > 0. Just associate .ogg and 'OggS' with 
application/x-ogg. Hook that up
> >    to ogg123 or any other supporting player. This 
has been our
> >    recommended solution.
>
> Accordign to the previous Mime-type thread, Monty 
said that the "official"
> mime-types would be 'audio/x-ogg' and 'video/x-ogg'. 
I did not manage to
> find
> someone saying something to the cotnrary (until now).
>
> > 1. If in the future it becomes desireable to make 
audio/audio+visual
> >    distictions, run the file through a laucher or 
an 'ogginfo' utility
> >    or embed algorithmic detection yourself. There 
will be a metadata
> >    substream that will let you distinguish, but not 
cheaply.
> >
> > 2. Associate audio/x-ogg (or better audio/x-
oggvorbis) with vorbis at
> byte
> >    29. The bytes immediately before say the data 
begins at byte 29, so
> you
> >    can use them to reject text. This would be 
forking the mimetype; I
> >    don't know how we feel about that.
>
> yeah, i'd rather not do this.
>
> > Cheers,
> >  -ralph
>
> Regards,
> Ali
>
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----------------------------------------------------------
   Universidad Federico Santa Maria - Campus Guayaquil

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