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

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
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-----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



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Received on Tuesday, 14 November 2017 12:30:42 UTC