[MPlayer-users] Cropping in original-size vs reduced-size

[Jorge Fábregas]

On Saturday 24 March 2007 5:08 pm, Nico Sabbi wrote:
>  don't understand what you mean with "vertical compensation"

I'm talking about the PAR compensation from a non-square environment to a 
square-pixels environment. In NTSC (720x480) the full square resolution is 
720x540 (vertical compensation) while in PAL (720x576) the full square res is 
768x576 (horizontal compensation).

My concern is to whether crop or not before scaling. You see, if you take a 
NTSC source and try to downscale it to 512x384, the image at this point 
(this particular size) has the PAR corrected. NOW, I may crop to remove black 
bars. (this can be done BEFORE encoding).

It's not the same thing if I take the same source (no PAR correction at this 
point) and I crop...and then downscale. This is what the majority of people 
do (and most guides).  Doing this, you consider the ACTUAL content (no black 
bars or noise) when you downscale.  And I think you should consider the WHOLE 
frame when downscaling. That's what I'm struggling with...

> so -10 means -2:   Calculate w/h using the other dimension and the ...

Ok Ok.Got it. Thanks.

Regards,
Jorge