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Re: [imsc] image based subtitle positioning

From: Thierry MICHEL <tmichel@w3.org>
Date: Wed, 08 Oct 2014 10:48:02 +0200
Message-ID: <5434FA42.3090109@w3.org>
To: "public-tt@w3.org" <public-tt@w3.org>, Nigel Megitt <nigel.megitt@bbc.co.uk>

Nigel,

I guess you are the one who has added this new comment into Comment 
tracker [1]

Thanks for doing so, you were faster than I !

I have added a link to [1] in the publication dashboard.


[1] 
http://www.w3.org/2006/02/lc-comments-tracker/34314/WD-ttml-imsc1-20140930/


Thierry

On 07/10/2014 23:28, Simon Hailes wrote:
> Dear all,
>
> As the public review period nears its end, Iíd like to highlight a
> positive addition to the imsc spec to facilitate image based subtitling.
>
> A basic image based subtitling script file will normally contain:
>
> Incue/Outcue
>
> Image name/url
>
> Image position
>
> Optionally, image size may be specified, and the overall size of the
> canvas may be specified.
>
> Imsc by inclusion of backgroundimage just about allows for these.  But
> the specification of image size and position is very convoluted.
>
> For image based subtitling, position and size of the image in relation
> to the video is paramount.
>
> It would be really good if tts:origin and tts:extent were enabled on div
> for image based subtitling; at the moment I cannot see how they are
> allowed.  Please correct me and include a sample in the document if I am
> wrong.
>
> It would also be good to be explicit about image scaling.  Ideally, the
> image should be scaled to match the specified image extent (with some
> notes that if this scaling is close to 1:1 after taking into account
> player size, etc., then the decoder may prefer not to scale to retain
> quality).
>
> This modification would make image based subtitling in imsc a relatively
> simple and easy to understand construct.  It makes it almost as simple
> to write as current extant image + script formats, and (I would imagine)
> make it relative easy to parse.
>
> Modified example from
> http://en.wikipedia.org/wiki/User:Cwmwenallt/SMPTE-TT
> <http://en.wikipedia..org/wiki/User:Cwmwenallt/SMPTE-TT> (iím not
> claiming this was correct to start with!).
>
> <tt xmlns:smpte="http://www.smpte-ra.org/schemas/2052-1/2010/smpte-tt"
>
>     xmlns="http://www.w3.org/ns/ttml"
>
>     xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
>
>     xmlns:tts='http://www.w3.org/ns/ttml#styling'
>
>     xml:lang="en">
>
> <head>
>
>     <layout>
>
>       <region xml:id="imageRegion" tts:color="transparent"
> tts:origin="0% 0%" tts:extent="100% 100%" >
>
>         <set begin="0.19305s" end="0.21581s" tts:origin="0px 2px"
> tts:extent="4px 8px" />
>
>         <set begin="5.89876s" end="8.09467s" tts:origin="230px 50px"
> tts:extent="243px 58px" />
>
>         <set begin="8.20106s" end="10.1922s" tts:origin="202px 50px"
> tts:extent="302px 64px" />
>
>         <set begin="10.3032s" end="12.2943s" tts:origin="180px 402px"
> tts:extent="341px 32px" />
>
>       </region>
>
>     </layout>
>
> </head>
>
> <body>
>
>     <div region="imageRegion">
>
>       <div begin="0.19305s" end="0.21581s"
> smpte:backgroundImage="Subtitles_EN/SPU0.png">
>
>         <p>[Example SMPTE-TT file]</p>
>
>       </div>
>
>       <div begin="5.89876s" end="8.09467s"
> smpte:backgroundImage="Subtitles_EN/SPU1.png">
>
>         <p>Hello Wikipedia</p>
>
>       </div>
>
>       <div begin="8.20106s" end="10.1922s"
> smpte:backgroundImage="Subtitles_EN/SPU2.png">
>
>         <p>This is a basic Example</p>
>
>       </div>
>
>       <div begin="10.3032s" end="12.2943s"
> smpte:backgroundImage="Subtitles_EN/SPU3.png" >
>
>         <p>of pop on style captioning with preformatted background
> images</p>
>
>       </div>
>
>     </div>
>
>   </body>
>
> </tt>
>
> Becomes (I did not add the required namespace):
>
> <tt xmlns:smpte="http://www.smpte-ra.org/schemas/2052-1/2010/smpte-tt"
>
>     xmlns="http://www.w3.org/ns/ttml"
>
>     xmlns:ttm="http://www.w3.org/ns/ttml#metadata"
>
>     xmlns:tts='http://www.w3.org/ns/ttml#styling'
>
>     xml:lang="en">
>
> <head>
>
>     <layout>
>
>       <region xml:id="imageRegion" tts:color="transparent"
> tts:origin="0% 0%" tts:extent="100% 100%" >
>
>       </region>
>
>     </layout>
>
> </head>
>
> <body>
>
>     <div region="imageRegion">
>
>       <div begin="0.19305s" end="0.21581s"
> smpte:backgroundImage="Subtitles_EN/SPU0.png" tts:origin="0px 2px"
> tts:extent="4px 8px" >
>
>         <ittm:altText>[Example SMPTE-TT file]</ittm:altText>
>
>       </div>
>
>       <div begin="5.89876s" end="8.09467s"
> smpte:backgroundImage="Subtitles_EN/SPU1.png" tts:origin="230px 50px"
> tts:extent="243px 58px" >
>
>         <ittm:altText>Hello Wikipedia</ittm:altText>
>
>       </div>
>
>       <div begin="8.20106s" end="10.1922s"
> smpte:backgroundImage="Subtitles_EN/SPU2.png" tts:origin="202px 50px"
> tts:extent="302px 64px" >
>
>         <ittm:altText>This is a basic Example</ittm:altText>
>
>       </div>
>
>       <div begin="10.3032s" end="12.2943s"
> smpte:backgroundImage="Subtitles_EN/SPU3.png" tts:origin="180px 402px"
> tts:extent="341px 32px" >
>
>         <ittm:altText>of pop on style captioning with preformatted
> background images</ittm:altText>
>
>       </div>
>
>     </div>
>
>   </body>
>
> </tt>
>
> Best regards,
>
> Simon Hailes.
>
> p.s. please reply direct if you have any comments/questions.  I donít
> monitor the mailing listsÖ.
>
> *Simon Hailes | Chief Technology Officer *|*Screen**
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Received on Wednesday, 8 October 2014 08:48:33 UTC

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