W3C home > Mailing lists > Public > public-tt@w3.org > October 2014

Re: [imsc] image based subtitle positioning

From: Glenn Adams <glenn@skynav.com>
Date: Wed, 8 Oct 2014 10:22:05 -0600
Message-ID: <CACQ=j+d1WnKy0TzrcGOwA+3TDkfnCB5vzA8=48VS1W0ZNYZM2A@mail.gmail.com>
To: Simon Hailes <Simon.Hailes@screensystems.tv>
Cc: "public-tt@w3.org" <public-tt@w3.org>
To reaffirm what Nigel said, we have already added this support to TTML2 in
the form of "inline region" specifications. about which see [1]. One can
either specify a region child of a div or p, called an *explicit inline
region specification* or use a shorthand of specifying tts:{origin,extent}
directly on a div or p, called an *implied inline region specification*.

[1] file:///Users/glenn/work/w3c/ttml/ttml2/spec/ttml2.html#semantics-inline-regions

On Tue, Oct 7, 2014 at 3:28 PM, Simon Hailes <Simon.Hailes@screensystems.tv>
wrote:

>  Dear all,
>
>
>
> As the public review period nears its end, I’d 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> (i’m 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 don’t
> monitor the mailing lists….
>
>
>
>
> *Simon Hailes | Chief Technology Officer | Screen *Main Line : +44 1473
> 831700 | Ext : 2161 |Mobile : +44 7802 759311 | Fax : +44 1473 830078
> Simon.Hailes@screensystems.tv | www.screensystems.tv |
> https://twitter.com/screensystems
>
>
>
> *Visit us at SMPTE Annual Technical Conference, Loews Hollywood Hotel,
> Stand 107, October 21-23 Languages & the Media, Hotel Radission Blu,
> Berlin, November 5-7 *
>
> *P** Before printing, think about the environment*
>
>
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Received on Wednesday, 8 October 2014 16:22:52 UTC

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