MPEG asks for MIME review for the MPEG21 file format

Wed May 23 17:53:37 CEST 2007

Dear all,

  as the "source" of this MIME type please apologize my late reply because I
was one week w/o email access. It took some time to catch up. Regarding the
"+xml" suffix I agree that it is inappropriate since an MPEG-21 file is not
purely XML (see below for further details).

MPEG-21 Part 1 (Technical Report) is publicly available [1].

Concerning Digital Items, Digital Item Declaration, and MPEG-21 File Format,
let me try to clarify something because I think there's a misunderstanding:

.         A Digital Item can be seen as a digital container format that puts
(media) resources (e.g., audio, video, image, text (PDF), etc.) and metadata
(e.g., data describing the resources, licenses, identifiers, etc.) within a
standardized structure.

.         A Digital Item is declared by an Digital Item Declaration (DID)
which is based on the Digital Item Declaration Language (DIDL) that is a
representation of the Digital Item Declaration Model. The model and DIDL are
specified in MPEG-21 Part 2 which is publicly available [2]. The model is an
abstract model defined using EBNF whereas DIDL - the representation of the
model - is defined using XML Schema, thus, DID is XML-based. That is, it is
possible that other, non-XML-based representation may be derived from the
model (However, this should not be the discussion point)

.         A Digital Item may be distributed which means that its declaration
(i.e., DID) may be at one location whereas its (media) resources and
metadata may be located elsewhere on various locations.

.         The MPEG-21 file puts everything, i.e., (media) resources,
metadata, and structure (i.e., declaration), into one file, the MPEG-21 file
which is binary and contains the DID and (maybe) also the
referenced/included (media) resources.

Hope this information is helpful for you. 

Thank you.

Best regards,

 -Christian

[1]
http://standards.iso.org/ittf/PubliclyAvailableStandards/c040611_ISO_IEC_TR_
21000-1_2004(E).zip

[2]
http://standards.iso.org/ittf/PubliclyAvailableStandards/c041112_ISO_IEC_210
00-2_2005(E).zip

:--

:- Dipl.-Ing. Dr. Christian Timmerer

:- Department of Information Technology (ITEC)

:- Klagenfurt University, Austria

:- http://research.timmerer.com

:----------------------------------------------------------

>> Visit the IT Campus Carinthia

>> http://www.it-campus.at

From: Dave Singer [mailto:singer at apple.com] 
Sent: Monday, May 14, 2007 8:32 PM
To: Graham Klyne; Stephan Wenger; Christian Timmerer (ITEC)
Cc: ietf-liaisons at ietf.org; ietf-types at alvestrand.no
Subject: Re: MPEG asks for MIME review for the MPEG21 file format

I've added Christian here, who actually authored the document.

At 8:50  +0100 14/05/07, Graham Klyne wrote:

I have a couple of comments:

(1) the "Encoding considerations" section appears to confuse MIME
requirements
for text with encoding for transmission over non-binary channels.  A MIME
content transfer encoding of "Binary" would be sufficient to indicate
prohibition of CR/LF conversion or 7-bit stripping.

I think this text was copied from other MIME registrations.

(2) the subtype name -- if I recall correctly, MPEG-21 uses an XML
encapsulation
layer (MPEG21-DIDL) for assembling various subparts into a composite for
transmission (unfortunately, lack of a freely available online version of
the
cited document means that I can't check this).  If I am correct here, then
it

may be more appropriate to use content type name "application/mp21+xml".

Correct, the main document inside the binary archive is indeed in XML.  But
the overall file format is binary.  Doesn't the mime type "+xml" suggest
that the document is specialized XML only (i.e. a text document)?

Also, if I recall correctly, the use of BASE64 for binary components within
an
MPEG21-DIDL XML wrapper is covered by the MPEG21 specification itself, so it
may
be quite inappropriate to suggest Base64 encoding applied at the MIME level.

The file format contains the XML, and also the attached binary resources,
outside the XML but inside the file format.  They are not (necessarily or
normally) encoded at all.

It would be very much easier to give useful review if there was at least a
publicly web-accessible summary of what this content type is expected to
convey.

Sure.  There are brief intros at

<http://www.chiariglione.org/mpeg/mpeg-tech.htm>;  have a look at

ISO Base Media File Format

and specifically:

Digital Item File Format

The base file format specification contains a lot of otehr stuff as well
(stuff MPEG-21 doesn't use), but if you want to view it, it is freely
available

<http://isotc.iso.org/livelink/livelink/fetch/2000/2489/Ittf_Home/PubliclyAv
ailableStandards.htm>

and find 14496-12

Christian may well have introductory material as well.

Hope that helps.

#g
--

Stephan Wenger wrote:
> That's Dave Singer as the contact, of course.  Sorry for the typo.
> Stephan
>
> On May 14, 2007, at 6:33 AM, Stephan Wenger wrote:
>
>> Folks,
>> MPEG (ISO/IEC JTC1 SC29) sent us an liaison statement asking us to
>> review their draft for a MIME registration of the MPEG-21 file
>> format.  I know nothing about the subject matter, but hope some of you
>> could give them a hand.  Please direct any technical questions to Save
>> Singer of Apple, singer at apple.com <mailto:singer at apple.com>.  Below,
>> please find what I believe they want to register.  Their full liaison
>> statement (in a bunch of word files) can be found
>> here: https://datatracker.ietf.org/public/liaisons.cgi, look for
>> ISO/IEC JTC1 SC29, May 2007
>> Best regards,
>> Stephan
>>
>>> MIME media type name: application
>>> MIME subtype name: mp21
>>> Required parameters: none
>>> Optional parameters: none
>>> Encoding considerations: base64 IS generally preferred; files are
>>> binary and should be transmitted without CR/LF conversion, 7-bit
>>> stripping, etc.
>>> Security considerations: It is possible to inject non-compliant MPEG
>>> streams (Audio, Video, and Systems) in the MP21 file to overload the
>>> receiver/decoder's buffers. This might compromise the functionality
>>> of the receiver or even crash it.
>>> An MP21 file supports the storage of stream types, including commands
>>> that are executed on the terminal such as Digital Item Methods based
>>> on ECMASCRIPT for which also bindings to Java(TM) and C++ exists. It
>>> is possible to use one or more of the above in a manner non-compliant

>>> to MPEG to crash the receiver or temporarily make it unavailable.
>>> Authentication mechanisms can be used to validate of the sender and
>>> the data to prevent security problems due to non-compliant malignant
>>> MP21 files.
>>> Interoperability considerations: A number of interoperating
>>> implementations exist within the ISO/IEC 21000 community, and that
>>> community has reference software for reading and writing the file
format.
>>> Published specification: ISO/IEC 21000-9:2005
>>> Applications which use this media type: Multimedia
>>> Additional information:
>>>
>>> Magic number(s): none
>>>
>>> File extension(s): mp21 and mpg21 are both declared at
>>> http://pitch.nist.gov/nics/ and http://filext.com/
>>>
>>> Macintosh File Type Code(s): mp21 is registered with Apple.
>>>
>>> Person & email address to contact for further information: David
>>> Singer, singer at apple.com <mailto:singer at apple.com>
>>> Intended usage: COMMON
>>> Author/Change controller: David Singer, ISO/IEC 21000 file format chair
>

--
Graham Klyne
For email:
http://www.ninebynine.org/#Contact

-- 

David Singer
Apple Computer/QuickTime

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