RE: RE: RE: Re: Re: TTML and aspect ratio

Yes please explain. Since the root container is an invisible rectangle; you can tell what tis width and height is.
The drawn regions by contrast you can tell. If the drawn region is centered and drawn 32 characters wide, then this solves the problem in 16:9, 4:3, 22:10 or anything else.

From: David Ronca [mailto:dronca@netflix.com]
Sent: 03 February 2013 23:57
To: public-tt@w3.org
Subject: RE: RE: Re: Re: TTML and aspect ratio

>Now in so much as the root container defines the coordinate system, then I believe the most
>general system is one that aligns top left 0,0 with 0,0 of the underlying media, and X,Y
>with the bottom right of the media. Since X and Y can be any real value, it doesn't really
> matter what value we use so 100%,100% seems adequate. If we then allow negative values and
>values beyond 100, we can address any relative position.

Following this model, if the media is 16:9 but the captions were done using CEA-608 (or another format that uses/assumed a 4:3 presentation), then the captions will not be positioned or spaced properly, as required.  There must be a way for the root container to occupy the full height of the underlying media, but only h*4/3 of the width, and the root container must be horizontally centered.  Further, this must be possible with any well-behaved generic W3C-TT implementation, and thus cannot use absolute coordinates.  I can see no workable way other than being able to specify the presentation Aspect Ratio of the root container.

Forgive my frustration, but I feel that we have made no progress.  If I have not explained our problem sufficiently, then please let me know where/how I can better explain.