W3C home > Mailing lists > Public > whatwg@whatwg.org > November 2008

[whatwg] video tag: pixel aspect ratio

From: Philip Jägenstedt <philipj@opera.com>
Date: Tue, 18 Nov 2008 11:13:29 +0100
Message-ID: <1227003209.6653.54.camel@localhost>
On Mon, 2008-11-17 at 22:28 -0800, Sander van Zoest wrote:

> Depending on how you want to accomplish you can do that with an enum
> that defines how to handle the case:
> 
> 1) do nothing.
> 2) disproportionately adjust
> 3) stretch follow by letter-,pillar-,windowbox appropriately.
> 4) complete fill the screen and ignore overscan (ala pan & scan or
> zoom)

The spec says 3, but if stretch behaviour is wanted I guess one could
consider doing something like SVG:s preserveAspectRatio attribute[1]

>         Oh, and if the video also needs cropping to get the correct
>         aperture,
>         couldn't this be done with CSS perhaps?
> 
> Wow. How would you know how much to crop for each video clip? Wouldn't
> specifying the enum above do the trick? 

I don't know, is aperture encoded in the media file itself or is it
implicit in certain types of video formats that aperture cropping (or
whatever the technical term is) should be applied? If you should always
crop e.g. 8 px on left and right then a CSS container with some overflow
tricks would certainly work. If on the other hand it's given in the
media file and it's likely to be incorrectly set then perhaps we do need
an override for it (although it's likely that such cropping is performed
by the video decoder and not a subsequent crop filter so it might not be
so trivial to fix in all media frameworks).

[1] http://www.w3.org/TR/SVG/coords.html#PreserveAspectRatioAttribute

-- 
Philip J?genstedt
Opera Software
Received on Tuesday, 18 November 2008 02:13:29 UTC

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