RE: VTT edge margins: we need to know current practice. PLEASE RESPOND If you implement a VTT UA (even in a polyfill)

By my calculation for SD that is ~7%... [50/720 * 100]
As previously for HD there are practical reasons (not just aesthetic reasons) for placing the margins closer to the centre of the wider picture.

I suspect there is no scope within your algorithm for a sensitivity to the rendering area aspect ratio - in which case a value of #7% would also work... but result in an atypical presentation (from a broadcasters perspective :)

Best regards,
John



John Birch | Strategy and Business Development 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

Visit us at
BVE, Excel London, Stand N25, 27 Feb - 1 Mar


PBefore printing, think about the environment

-----Original Message-----
From: singer@apple.com [mailto:singer@apple.com]
Sent: 14 November 2017 16:08
To: John Birch <John.Birch@screensystems.tv>
Cc: public-texttracks@w3.org; TTWG <public-tt@w3.org>
Subject: Re: VTT edge margins: we need to know current practice. PLEASE RESPOND If you implement a VTT UA (even in a polyfill)

Hi John

it really is the exact value used in the algorithm in 6.1 for this step that I am looking for:

"       • Let edge margin be a user-agent-defined horizontal length, expressed as a percentage of the width of the video’s rendering area, which will be used to define a margin at the left and right edges of the video into which this cue will not be placed. In situations with overscan, this margin should be sufficient to place the cue within the title-safe area. In the absence of overscan, this value should be picked for aesthetics (to avoid text being aligned precisely on the left or right edge of the video, which can be ugly)."

> On Nov 14, 2017, at 5:30 , John Birch <John.Birch@screensystems.tv> wrote:
>
> Hi David,
>
> As an information point... in our systems for the generation of subtitles in DVB bitmap format or for open (burnt in) insertion we use the following starting values for subtitle 'margins'.
> N.B. These are often subsequently adjusted (tweaked) on a channel by channel basis to suit local requirements.
>
> For SD resolution...
> 50 pixels left and right
>
> For HD resolution...
> 240 pixels left and right
>
> I hope this is of use...
> N.B. the HD values are intended to create a centred 4:3 style presentation. Even though the screen has a wider aspect ratio in HD, subtitles still tend to be maintained in a 4:3 presentation window in the screen centre to minimise eye movements - but this is up to the broadcasters... some choose to push the left and right margins closer to the screen edges. Our system, as is typical practise in subtitling, justifies to the set margins, rather than using absolute pixel positioning for the subtitles.
>
> Best regards,
> John Birch
>
>
>
> John Birch | Strategy and Business Development 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
>
> Visit us at
> BVE, Excel London, Stand N25, 27 Feb - 1 Mar
>
>
> PBefore printing, think about the environment
>
> -----Original Message-----
> From: David Singer [mailto:singer@mac.com]
> Sent: 13 November 2017 23:35
> To: public-texttracks@w3.org; TTWG <public-tt@w3.org>
> Subject: VTT edge margins: we need to know current practice. PLEASE
> RESPOND If you implement a VTT UA (even in a polyfill)
>
> This sentence is problematic giving each UA a free hand:
> "In the absence of overscan, this value should be picked for aesthetics (to avoid text being aligned precisely on the left or right edge of the video, which can be ugly)."
>
> Resolution at TPAC: add a default edge margin instead of the above
> sentence ? (find out what the different UAs have implemented right
> now)
>
>
> * * * *
>
> Please let us know what you actually implement. We would like to
> settle on a recommended or even mandated value for edge margin.  If we
> all actually have the same value, we can choose that and not cause
> disruption, so KNOWING what EVERYONE does kinda makes sure you’re not
> accidentally disadvantaged…
>
> PLEASE tell us….
>
> David Singer
>
> singer@mac.com
>
>
>
> 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

David Singer
Manager, Software Standards, Apple Inc.


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 Tuesday, 14 November 2017 16:27:39 UTC