- From: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Date: Fri, 21 Nov 2014 12:13:01 +0000
- To: "public-tt@w3.org" <public-tt@w3.org>
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