[mythtv-users] Calculating aspect ratios for DVDs

jedi jedi at mishnet.org
Thu Jan 7 17:45:01 UTC 2010


On Thu, Jan 07, 2010 at 09:24:06AM -0800, Yan Seiner wrote:
> 
> This is slightly OT, but I'm hoping someone can enlighten me.  I'm trying
> to work out a script that automatically detects the aspect ratio of a
> cropped DVD.
> 
> It seems that DVDs report either 1.33:1 aspect or 1.78:1 aspect.  If the
> movie is 2.33:1, black bars are added top and bottom.  (leaving aside the
> odd-ball ones for the moment.)
> 
> So to get the proper aspect, one would have to:
> 
> Take the DVD size, either 720x480 or 720x576, and figure out the crop box.
> 
> Take the reported DVD aspect ratio, divide by 1.33, multiply the width of
> the crop box and divide the result by the height of the crop box.
> 
> This seems weirdly byzantine and possibly inaccurate.  Is there some
> simple way to use mplayer, lsdvd, or dvdscan to get this information?

...it's perfectly reasonable given how the stuff was intended to be used.

You seem to want something that can pull the aspect ratio direct from the
video itself even accounting for embedded letterboxes. I am not aware of
anything that does that. It would be somewhat cool if there were such a 
tool. I do this manually for 4:3 content that is letterboxed.

[deletia]


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