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RE: TTML and aspect ratio

From: Michael Dolan <mdolan@newtbt.com>
Date: Wed, 30 Jan 2013 11:37:10 -0800
To: <public-tt@w3.org>
Message-ID: <01ff01cdff21$3402ba10$9c082e30$@newtbt.com>
The definition of the root container and its registration to related video
is mostly application dependent.

-----Original Message-----
From: David Ronca [mailto:dronca@netflix.com] 
Sent: Wednesday, January 30, 2013 10:53 AM
To: public-tt@w3.org
Subject: Re: TTML and aspect ratio

> If the extent is specified, then it cannot be ignored by a compliant 
> client. A compliant client is obligated to respect that extent 
> specification.

Agreed, which means that extent is not useful for indicating the aspect
ratio of the root container if the frame size will vary.

> It is sounding to me like you want to avoid specifying root container 
> extent at all,

Definitely want to avoid specifying the root container extent.

>but have a way to automatically determine it in the client  based on an 
>a specified aspect ratio and possibly a safe area specification, is 
>that correct?

If the client knows the aspect ratio of the root container, it can scale
presentation for any frame size or display size.

> If so, would other length specifications always use non-pixel metrics 
> or percentages? e.g., to specify non-root region origin and extent, 
> use cells or percentages, but not pixels?

Percentage could work if the specified behavior for an extent that was not
full screen is to center the root container in the display area.
Received on Wednesday, 30 January 2013 19:37:42 GMT

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