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

[Nico Sabbi]

Jorge Fábregas wrote:

>Hello guys,
>
>I would like to downscale some NTSC clip from a DVD to 640x480. I like this 
>resolution since it's 4:3 and multiples of 16.  However, I need to crop 16 
>pixels on each side.  I plan to:
>
>1- downscale to 640x480.  At this point the video is 4:3 and already 
>vertically compensated (ready for square pixels).
>
>2- now I'll crop 32 pixels horizontally (16 in each side) and I end up with 
>608x480. It's not really 4:3 but it doesn't matter as the video was already 
>vertically compensated in previous step.
>  
>

why don't you crop before rescaling?

>Now, my problem is... How do I go from step #1 to step #2 in just one 
>encoding?  It's not the same thing to crop in full size than to crop on the 
>downscaled version. How can I know beforehand that what I want actually is 
>608x480?
>
>I'm assuming that we should downscale to 4:3 considering the WHOLE frame (in 
>this case 720x480) including the black bars. If I crop in original size, and 
>I just leave THE ACTUAL CONTENT, the aspect ratio of that content may not be 
>4:3 right?  The quesition is: Should you do the 4:3 conversion considering 
>the whole frame or JUST the actual content (geting it by cropping)?
>  
>

something like
crop=704:480:8:0,scale=608:-10,expand=640:480


 
 
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