Re: [ttml2] embedded content, background image styling, other edits

Thanks for your review and input.

On Tue, Nov 25, 2014 at 2:43 AM, John Birch <John.Birch@screensystems.tv>
wrote:

>  Hi Glenn,
>
>
>
> I’ve been looking at your proposal for embedded content (and I like it J
> but I noticed the following:
>
>
>
> ...
>
> <data type="text/plain; charset=us-ascii" length="44">
>
>   <chunk length="19">
>
>     VGhlIHF1aWNrIGJyb3duIGZveA==
>
>   </chunk>
>
>   <chunk length="25">
>
>     IGp1bXBzIG92ZXIgdGhlIGxhenkgZG9nLg==
>
>   </chunk>
>
> </data>
>
> ...
>
>
>
> I don’t see ‘charset’ as an attribute of data in the later definition…
>

In the above example, charset is a parameter of the MIME type expression of
the *type* attribute. No relationship with the 'encoding' attribute.


> I thought initially this was a typo and that it should be encoding, but
> then realised that ‘encoding’ is not permitted on the parent data element
> when using chunks?
>

Correct, 'encoding' is permitted only on the data element when the content
of the data element uses simple data embedding, i.e., consists only of
#PCDATA that encodes the data bytes. If a data element uses chunked data
embedding, i.e., uses chunk element children, then all of the encoded data
bytes are in child chunk elements, so the encoding attribute applies only
to the chunk children and not the data parent.

In the above example, the encoding attribute's default value 'base64'
applies on the chunk children, and is not relevant on the data parent.



>  However, the binaryData element in EBU-TT includes an attribute that
> does not appear within your proposed scheme, which is the fileName
> attribute. This optional attribute may contain “A filename that may be used
> to identify the original filename of the tunnelled binary data”.
>

I'm not sure there is a useful use case for formalizing such a
name/identifier. It wouldn't have any relevant processing semantics in
TTML2, so it is definitely in the metadata category, which means using a
ttm:* attribute or a metadata element, e.g., one could use the following
convention with ttm:desc.

<data type='application/octet-stream'>
  <metadata>
    <ttm:desc>original_file_name=foo.bar</ttm:desc>
  </metadata>
  <chunk>
  ... encoded base64 data ...
  </chunk>
</data>

I wouldn't mind adding a new ttm:* element that generalizes the task of
defining metadata parameters, e.g.,

<ttm:parameter name='fileName'>foo.bar</ttm:parameter>

which would allow rewriting the above example to

<data type='application/octet-stream'>
  <metadata>
    <ttm:parameter name='original_file_name'>foo.bar</ttm:parameter>
  </metadata>
  <chunk>
  ... encoded base64 data ...
  </chunk>
</data>


> *There is some discussion as to the usage of this element, it could be
> viewed as metadata of ‘historic interest’ (e.g. the name of the DOS file
> that is encapsulated by the binary data) or it could be seen as a directive
> (i.e. what to name a file should a processor re-create a file from the
> binary data). My personal leanings are towards the former use…*
>
>
>
> Regardless of the use of this attribute, I would like to propose that the
> TTWG consider adding a similar attribute to the data *and chunk* elements
> in TTWG. (*As an aside the chunk element you propose would be a better
> resolution to one of the original EBU-TT requirements where multiple floppy
> disk based DOS files make up an STL document.*) Clearly the name
> ‘fileName’ would be inappropriate in a more generic specification but I
> tentatively suggest the following (below).
>

We could consider it. But it definitely would not be appropriate on chunk,
which sole purpose is to enable streaming of data fragment children of a
data element. I guess you are thinking chunk might be used to contain
multiple original files (separately named) that are concatenated to form a
single data resource. This is counter to my intention that a chunk contain
a fragment of a data resource, or, if one wished, an entire data resource
(if a data element has a single chunk child like in the above example).


>
>
> Best regards,
>
> John
>
>
>
>
>
> <chunk
>
>   encoding
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-attribute-encoding>
> = (base16|base32|base32hex|base64|base64url) : base64
>
>   length = xsd:nonNegativeInteger
> <http://www.w3.org/TR/xmlschema-2/#nonNegativeInteger>
>
>   xml:id
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#content-attribute-id>
> = ID
>
>   ident = xs:string
>
>   {*any attribute not in default or any TT namespace*}>
>
>   *Content:* #PCDATA
>
> </chunk>
>
>
>
> An ident attribute may be specified, and may contain an identifier for the
> contained data from an external context (e.g. the original filename).
>
>
>
> And
>
> <data
>
>   encoding
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-attribute-encoding>
> = (base16|base32|base32hex|base64|base64url) : *see prose below*
>
>   format
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-attribute-format>
> = <data-format>
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-value-data-format>
>
>   length = xsd:nonNegativeInteger
> <http://www.w3.org/TR/xmlschema-2/#nonNegativeInteger>
>
>   src
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-attribute-src>
> = <data>
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-value-data>
>
>   type
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-attribute-type>
> = xsd:string <http://www.w3.org/TR/xmlschema-2/#string> : * see prose
> below*
>
>   xml:id
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#content-attribute-id>
> = ID
>
>   ident = xs:string
>
>   xml:lang
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#content-attribute-lang>
> = xsd:string <http://www.w3.org/TR/xmlschema-2/#string>
>
>   xml:space
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#content-attribute-space>
> = (*default*|*preserve*)
>
>   {*any attribute not in default or any TT namespace*}>
>
>   *Content:* #PCDATA | (Metadata.class
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#element-vocab-group-metadata>*,
> chunk
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-vocabulary-chunk>+)
> | (Metadata.class
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#element-vocab-group-metadata>*,
> source
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-vocabulary-source>
> +)
>
> </data>
>
>
>
> If simple data embedding is used, i.e., the content of the data element
> is one or more text nodes, then an ident attribute may be specified, and
> may contain an identifier for the contained data from an external context
> (e.g. the original filename). If chunked or sourced data embedding is used,
> i.e., the content of the data element contains any child chunk
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-vocabulary-chunk>
> or source
> <https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#embedded-content-vocabulary-source>
> element, then an ident attribute must not be specified.
>
>
>
>
>
>
> *John Birch | Strategic Partnerships Manager | Screen *Main Line : +44
> 1473 831700 | Ext : 2208 | Direct Dial : +44 1473 834532
> Mobile : +44 7919 558380 | Fax : +44 1473 830078
> John.Birch@screensystems.tv | www.screensystems.tv |
> https://twitter.com/screensystems
>
>
> *Visit us at BVE, Excel London 24-26 February 2015 Stand No. N19*
>
> *P** Before printing, think about the environment*
>
> *From:* Glenn Adams [mailto:glenn@skynav.com]
> *Sent:* 23 November 2014 22:50
> *To:* TTWG
> *Subject:* [ttml2] embedded content, background image styling, other edits
>
>
>
> I've updated the TTML2 ED [1] a few times in the last few days to:
>
>    - add embedded content element types (new section 9)
>
>
>     - audio
>       - chunk
>       - data
>       - font
>       - image
>       - resources
>       - source
>
>
>    - add background image styling
>
>
>     - tts:backgroundImage
>       - tts:backgroundRepeat
>       - tts:backgroundPosition
>
>
>    - sub-divide former parameters section into profiles section and
>    parameters section
>
>  For detailed diffs, see change sets [2][3][4][5][6].
>
>
>
> [1] https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html
>
> [2] https://dvcs.w3.org/hg/ttml/rev/d16d284100b9
>
> [3] https://dvcs.w3.org/hg/ttml/rev/67327764d375
>
> [4] https://dvcs.w3.org/hg/ttml/rev/25035c814da5
>
> [5] https://dvcs.w3.org/hg/ttml/rev/cc2b7aad7e7a
>
> [6] https://dvcs.w3.org/hg/ttml/rev/e3fdbceb09cb
>
>
>
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