[Cin] removing letter boxing while preserving aspect

Georgy Salnikov sge at nmr.nioch.nsc.ru
Mon Mar 4 04:12:27 CET 2024

> Den 03.03.2024 14:40, skrev Rob Prowel via Cin:
> > I have 3:2 content that is saved in a 4:3 frame with black bands at
> > the top and bottom.
> >
> > I want to remove the banding such that the output is a 3:2 resolution
> >
> > I've tried playing with the crop filter but the black bands remain,
> > and the camera automation can remove the banding by zooming in, but
> > then the left and right image sides get cropped out of the output.
> >
> > Is there a tutorial for this exact scenario?
> You can possibly try a test on a file or clip copy using ffmpeg "crop
> and resize".
> If I understand the problem right, keep the original w(idth) of the
> video resolution and use h=w*2/3=w/1.5
> ffmpeg -i input.mp4 -vf "crop=w:h" output.mp4

It might be simpler with mplayer/mencoder:

Run from console:

mplayer -vf cropdetect input.mp4

Mplayer prints in the console something like:

crop area: X: 5..719  Y: 2..575  (-vf crop=704:560:12:10) 0.9% 6 0
These are actual crop parameters--^^^^^^^^^^^^^^^^^^^^^^
Use them:

mplayer -vf crop=704:560:12:10 input.mp4

To recode cropped content add the same -vf option to mencoder.

Georgy Salnikov
NMR Group
Novosibirsk Institute of Organic Chemistry
Lavrentjeva, 9, 630090 Novosibirsk, Russia
Phone   +7-383-3307864
Email   sge at nmr.nioch.nsc.ru

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