[Ffmpeg-devel] cropping + rescaling broken?

Luca Abeni lucabe72
Tue Mar 7 12:54:11 CET 2006

Hi Erik,

On Tue, 2006-03-07 at 12:35 +0100, Erik Slagter wrote:
> On Tue, 2006-03-07 at 12:33 +0100, Luca Abeni wrote:
> > ./ffmpeg -i /tmp/test.y4m -s 352x576 -croptop 10 -cropbottom 10 out.y4m
> > the output size is 352x556... This looks wrong, no?
> No? ;-)
> You are removing 10 pixels from the top and 10 pixels from the bottom,
> so you're removing 20 pixels in total, the frame is 20 pixels smaller in
> the y direction; 576 - 20 = 556. Looks ok to me?
Even more confused... If scaling is done after cropping, I do not
understand why 556 is correct :(

This is what I expect:
1) I remove 10 pixel from the top and 10 pixel from the bottom of the
input picture... So, if the input size is 352x288 it becomes 352x268
2) Then, I rescale it to 352x576. So, I'd expect the output size to be
352x576... 352x556 would be correct if ffmpeg resized the image first,
and removed the top and bottom bands after resizing... 

Anyway, if 352x556 is correct then the current code is ok and no fix is
needed. I apologize for the noise.

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