- From: Michael Dolan <mdolan@newtbt.com>
- Date: Fri, 17 Jun 2016 16:59:59 -0700
- To: "'Timed Text Working Group'" <public-tt@w3.org>
Resending to TTWG.
-----Original Message-----
From: Michael Dolan
Sent: Friday, June 17, 2016 4:57 PM
To: 'Eric Prud'hommeaux' <eric@w3.org>
Cc: media-types@iana.org; Timed Text Working Group <public-tt@w3.org>;
Philippe Le Hegaret <plh@w3.org>
Subject: RE: [media-types] Update to media type "application/ttml+xml"
Hi Eric-
Thanks. I think I agree with your comment about "first order". It's either
right or it isn't. And what a robust decoder may wish to do if it detects
that it is wrong (and also figures out what it really is) should be out of
scope.
I'm not sure I follow your comment about the URL. TTML2 Table 6-3 needs the
text that precedes it to understand it. Maybe I don't understand your
comment.
Thanks,
Mike
-----Original Message-----
From: Eric Prud'hommeaux [mailto:eric@w3.org]
Sent: Thursday, June 16, 2016 1:07 PM
To: Michael Dolan <mike@dolan.tv>
Cc: media-types@iana.org; Timed Text Working Group <public-tt@w3.org>;
Philippe Le Hegaret <plh@w3.org>
Subject: Re: [media-types] Update to media type "application/ttml+xml"
* Philippe Le Hegaret <plh@w3.org> [2016-06-16 10:16-0400]
> The W3C Timed Text Working Group would like to update the media type
> "application/ttml+xml" as follows. Comments are welcome.
>
> It updates the media type, "application/ttml+xml" to add a new
> parameter, codecs. All other provisions of the media type
> specification remain the same. This supercedes the initial
> registration information in TTML 1.0 Second Edition.
>
> Text copied below but see also the original text at:
>
> https://www.w3.org/TR/2016/NOTE-ttml-profile-registry-20160510/#mediat
> ype
>
> [[
>
> Type name:
>
> application
> Subtype name:
>
> ttml+xml
> Required parameters:
>
> None.
> Optional parameters:
>
> charset
>
> If specified, the charset parameter must match the XML
> encoding declaration, or if absent, the actual encoding. See also
> Encoding Considerations below.
> profile
>
> The document profile of a TTMLDocument Instance may be
> specified using an optional profile parameter, which, if specified,
> the value of which must adhere to the syntax and semantics of
> ttp:profile parameter defined by TTML 1.0 Second Edition, Section
> 6.2.8 ttp:profile of the published specification.
>
> codecs
>
> The optional codecs parameter provides a short form version of
> the profile parameter with multiple-profile combinatorial capability.
> If a short
> (4-character) form of a profile is registered in the TTML Profile
> Registry, it is recommended that this codecs parameter be used and not
> the profile parameter. The nominal value of this parameter is a single
> 4 character code from the registry.
>
> Additionally, applications using the entries in the registry
> are encouraged to adopt the following combination syntax:
>
> Employ two combination operators, '+' (AND) and '|' (OR),
> which may be used to specify, respectively, that multiple processor
> profiles apply
> (simultaneously) or that any processor profile of a list of profiles
> may apply individually. If both operators are used in a codecs value,
> then the '+' operator has precedence.
>
> The example: "A+B|C+D|E" states that a TTML processor that
> implements any one of A+B or C+D or E processor profiles satisfies, at
> first order, the requirements to fetch and begin decode/processing of
> a TTML
PLH indicated that "at first order" is something like an initial claim about
the embedded codecs. Is it the intention that there be some sort of recovery
if that initial claim is incorrect? What should the processor do if the
advertised codec is ogg and the actual codec is xvid? If you strike "at
first order", I think you could avoid having to define the behavior in the
event of invalid parameters.
> document, where X+Y means that both X and Y processor profiles must be
> supported, and X|Y means that either X or Y processor profile must be
> supported.
>
> For more information about processor profile combination, see
> TTML2 Profile Combination.
"TTML2 Profile Comination" has no URL in the reg. The hyptertext version
links to
https://www.w3.org/TR/ttml2/#profile-attribute-processorProfileCombination
propose instead link to
https://www.w3.org/TR/ttml2/#processor-profile-combination-table
and embedding that link in ()s in the text.
> Encoding considerations:
>
> Same for application/xml, except constrained to either UTF-8 or
UTF-16.
> See IETF RFC 3023, XML Media Types, Section 3.2. For the purpose of
> filling out the IANA Application for Media Type
> (http://www.iana.org/cgi-bin/mediatypes.pl), the value binary applies.
> Security considerations:
>
> As with other XML types and as noted in IETF RFC 3023, XML Media
> Types, Section 10, repeated expansion of maliciously constructed XML
> entities can be used to consume large amounts of memory, which may
> cause XML processors in constrained environments to fail.
>
> In addition, because of the extensibility features for TTML and of
> XML in general, it is possible that "application/ttml+xml" may
> describe content that has security implications beyond those described
> here. However, TTML does not provide for any sort of active or
> executable content, and if the processor follows only the normative
> semantics of the published specification, this content will be outside
> TTML namespaces and may be ignored. Only in the case where the
> processor recognizes and processes the additional content, or where
> further processing of that content is dispatched to other processors,
> would security issues potentially arise. And in that case, they would
> fall outside the domain of this registration document.
>
> Although not prohibited, there are no expectations that XML
> signatures or encryption would normally be employed.
> Interoperability considerations:
>
> The published specification describes processing semantics that
> dictate behavior that must be followed when dealing with, among other
> things, unrecognized elements and attributes, both in TTML namespaces
> and in other namespaces.
>
> Because TTML is extensible, conformant "application/ttml+xml"
> processors may expect (and enforce) that content received is
> well-formed XML, but it cannot be guaranteed that the content is valid
> to a particular DTD or Schema or that the processor will recognize all
> of the elements and attributes in the document.
> Published specification:
>
> This media type registration is extracted from the TTML Profile
> Registry.
> Applications that use this media type:
>
> TTML is used in the television industry for the purpose of
> authoring, transcoding and exchanging timed text information and for
> delivering captions, subtitles, and other metadata for television
> material repurposed for the Web or, more generally, the Internet.
>
> There is partial and full support of TTML in components used by
> several Web browsers plugins, and in a number of caption authoring tools.
> Additional information:
>
> Magic number(s):
> File extension(s):
>
> .ttml
> Macintosh file type code(s):
>
> "TTML"
> Fragment identifiers:
>
> For documents labeled as application/ttml+xml, the fragment
> identifier notation is intended to be used with xml:id attributes, as
> described in section 7.2.1 of the Timed Text Markup Language 1 (TTML1)
> specification.
>
> Person & email address to contact for further information:
>
> Timed Text Working Group (public-tt@w3.org) Intended usage:
>
> COMMON
> Restrictions on usage:
>
> None
> Author:
>
> The published specification is a work product of the World Wide
> Web Consortium's Timed Text (TT) Working Group.
> Change controller:
>
> The W3C has change control over this specification.
> ]]
> https://www.w3.org/TR/2016/NOTE-ttml-profile-registry-20160510/#mediat
> ype
>
> Thank you,
>
> Philippe
>
> _______________________________________________
> media-types mailing list
> media-types@ietf.org
> https://www.ietf.org/mailman/listinfo/media-types
--
-ericP
office: +1.617.599.3509
mobile: +33.6.80.80.35.59
(eric@w3.org)
Feel free to forward this message to any list for any purpose other than
email address distribution.
There are subtle nuances encoded in font variation and clever layout which
can only be seen by printing this message on high-clay paper.
Received on Saturday, 18 June 2016 00:00:34 UTC