Re: [imsc] image based subtitle positioning ( LC-2968)

All,

I've clarified further with Simon and he has agreed that this response
constitutes both:
 a) approval of the resolution to comment LC-2968 and
 b) a new comment about the interpretation of region origin and extent
values when relating image size to video size

I've therefore marked LC-2968 as approved by commenter on the comments
tracker. When we have published the CR we can add that document to the
comments tracker and add this as a new comment against it.

Of course this is no reason to delay discussion of the substantive comment
raised, even if we only choose to implement any edits after the [first] CR.

Kind regards,

Nigel


On 21/11/2014 11:51, "Simon Hailes" <Simon.Hailes@screensystems.tv> wrote:

>Dear working group,
>
>With respect to the response to my note on image positioning in IMSC:
>
>" Working Group Resolution (LC-2968):
>An objective of IMSC 1 is to leverage as much as possible existing TTML 1
>implementations, and IMSC 1 is as such based on TTML 1. Allowing
>tts:extent and tts:origin to have a meaning on elements other than
><region> would be a significant departure from this objective. Moreover
>it is straightforward to create as many <region>s as there are unique
>combinations of origin and extent across subtitles/captions.
>
>The intent is to include such a feature in TTML 2 (see issue 176)
>
>We have added an informative note at Section 8.3 of
>https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles

>.html
>describing the use of multiple <region> elements to achieve positioning
>of individual subtitle/caption."
>
>
>I understand and agree with the philosophy behind the objective.
>Roll on TTML 2, because the splitting of position and image is ugly and
>ensures that the file cannot be progressively downloadable.
>
>
>I think it may be useful to extend the note to clarify image use, since
>the use of images produces several implied (in my mind) constraints not
>explicitly highlighted:
>The wording "the width and height of the region extent associated with
>the div element shall be specified and shall be equal to the width and
>height of the image source referenced by the smpte:backgroundImage;" to
>me implies an EXACT match of width and height.  To me, this further
>implies that these must be pixel based (otherwise how could they be
>exact), which in turn requires that the tt element have a tts:extent.
>I think the note should mention that as the tts:extent will be a
>particular value, but the file will likely be used against multiple
>bitrates/sizes of video, this implies correct and quality scaling of the
>images such that they appear the same regardless of video resolution.
>The implication from CFF-TT of the tts:extent matching other external
>metadata or matching the video size must be explicitly NOT be carried
>into this document, as could be construed as forcing production of
>multiple TTML and images, one for every video size (and it's the lack of
>simple clarity on this point which leads me to suggest simple
>clarification in IMSC).
>
>
>Possible suggested wording:
>NOTE
>In [ttaf1-dfxp], tts:extent and tts:origin do not apply to div elements.
>In order to individually position multiple div elements, each div can be
>associated with a distinct region with the desired tts:extent and
>tts:origin.
>As the tts:extent for the region referenced by the div SHALL be equal to
>the image size, the implication is that the tts:extent will be in pixels.
> Using pixels requires a tts:extent in pixels [6.10 Features] on the tt
>element, meaning in turn that the overall canvas fills the video area
>(regardless of actual video pixel dimensions) [6.7.1 ittp:aspectRatio].
>A real world player will need to scale images appropriately so they
>appear at the tts:origin and sized to the tts:extent (i.e. the same
>relative size and position compared to the video area, regardless of the
>actual video pixel dimensions).
>
>
>
>
>Best regards,
>
>Simon
>
>
>
>
>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
>BVE, Excel London 24-26 February 2015 Stand No. N19
>
>P Before printing, think about the environment-----Original Message-----
>From: tmichel@w3.org [mailto:tmichel@w3.org]
>Sent: 13 November 2014 17:54
>To: Simon Hailes
>Cc: public-tt@w3.org?subject=%5Bimsc%5D
>Subject: Re: [imsc] image based subtitle positioning ( LC-2968)
>
> Dear Simon Hailes ,
>
>The Timed Text Working Group has reviewed the comments you sent [1] on
>the Last Call Working Draft [2] of the IMSC 1.0 published on 30 Sep 2014.
>Thank you for having taken the time to review the document and to send us
>comments!
>
>The Working Group's response to your comment is included below, and has
>been implemented in the new version of the document available at:
>https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles

>.html.
>
>Please review it carefully and let us know by email at
>public-tt@w3.org?subject=%5Bimsc%5D if you agree with it or not before 20
>November 2014. In case of disagreement, you are requested to provide a
>specific solution for or a path to a consensus with the Working Group. If
>such a consensus cannot be achieved, you will be given the opportunity to
>raise a formal objection which will then be reviewed by the Director
>during the transition of this document to the next stage in the W3C
>Recommendation Track.
>
>Thanks,
>
>For the Timed Text Working Group,
>Thierry Michel
>Philippe Le Hégaret
>W3C Staff Contacts
>
> 1.
>http://www.w3.org/mid/5388058990DE50438A008F31269C7983016B5AE237@SS-IP-EXM

>B-01.screensystems.tv
> 2. http://www.w3.org/TR/2014/WD-ttml-imsc1-20140930/

>
>
>=====
>
>Your comment on Image Profile:
>> 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 (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<mailto:Simon.Hailes@screensystems.tv> |
>> www.screensystems.tv<http://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
>>
>>
>> This message may contain confidential and/or privileged information.
>> If you are not the intended recipient you must not use, copy, disclose
>> or take any action based on this message or any information herein. If
>> you have received this message in error, please advise the sender
>> immediately by reply e-mail and delete this message. Thank you for
>> your cooperation. Screen Subtitling Systems Ltd. Registered in England
>>No.
>> 2596832. Registered Office: The Old Rectory, Claydon Church Lane,
>> Claydon, Ipswich, Suffolk, IP6 0EQ
>
>
>Working Group Resolution (LC-2968):
>An objective of IMSC 1 is to leverage as much as possible existing TTML 1
>implementations, and IMSC 1 is as such based on TTML 1. Allowing
>tts:extent and tts:origin to have a meaning on elements other than
><region> would be a significant departure from this objective. Moreover
>it is straightforward to create as many <region>s as there are unique
>combinations of origin and extent across subtitles/captions.
>
>The intent is to include such a feature in TTML 2 (see issue 176)
>
>We have added an informative note at Section 8.3 of
>https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles

>.html
>describing the use of multiple <region> elements to achieve positioning
>of individual subtitle/caption.
>
>----
>
>
>
>This message may contain confidential and/or privileged information. If
>you are not the intended recipient you must not use, copy, disclose or
>take any action based on this message or any information herein. If you
>have received this message in error, please advise the sender immediately
>by reply e-mail and delete this message. Thank you for your cooperation.
>Screen Subtitling Systems Ltd. Registered in England No. 2596832.
>Registered Office: The Old Rectory, Claydon Church Lane, Claydon,
>Ipswich, Suffolk, IP6 0EQ

Received on Friday, 21 November 2014 12:16:17 UTC