[MPlayer-users] Transcoding from one aspect ratio to another

[Alexander Roalter]

Am 03.11.2010 17:06, schrieb JD:
> I have a video file that has an aspect ratio of
> 2.353 : 1
> I would like to transcode it to an aspect ratio
> of 1.6 : 1 (like 1280x800).
> Is this even possible?
>
If you don't mind squeezed heads etc, simply use -vf scale=1280:800

If you like to presever the aspect ratio, use -vf expand to add black 
bars above and below, or -vf crop to cut of parts of the image you don't 
want to see.

in your example, making a letterboxed version of you original video
you'd use -vf expand=1280:800:0:100
,assuming the original video is in 1280x600 (therefore, you need to 
place the video 800-600 = 200  / 2 = 100 lines below the top line.

to make a 1.6:1 video, but full screen, you need to crop off the left 
and right border, use
-vf crop=1280:800:100:0
,assuming the original video is 1480x800 (and here you need to crop off 
100 pixels left and right).

In reality, you probably need to scale the video before that. Filters 
are applied in reverse order, so first scale it accordingly.

To expand, make sure the video is 1280px wide:

-vf scale=1280:-2

to crop, make sure the video is 800px high:

-vf scale=-2:800

-- 
cheers,
Alex