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

[Jorge Fábregas]

On Friday 23 March 2007 12:52 pm, Nico Sabbi wrote:
> -vf crop=704:480:8:0,scale=640:-10
> scales to y' (closest x16) keeping A/R, even after having cropped

Thanks Nico but I think you're not getting my point. I can put this way:

My AR goal is: 512 x 384  (x16's dimensions and 4:3)
My source: NTSC DVD (720 x 480) with 4:3 AR
Problem: I need to remove 8 pixels on each side (black bands) and I know how 
to do it. I just have a dilemma right now which I can describe with the 2 
ways I could encode this footage:

Way #1:
--------------------

Before encoding:
mplayer dvd://1 -chapter 4 -vf cropdetect 

...to get where to crop exactly

Actual encoding:
... -vf  crop=704:480:8:0,scale=512:384 

Way #2:
------------------

Before encoding:
mplayer dvd://1 -chapter 4  -vf scale=512:384,cropdetect

...Notice here that in order to get the proper crop values I'm actually 
dowscaling first..thus I'll get the values for the downsized image.

Actual encoding:
... -vf  scale=512:384,crop=496:384:8:0


Could you guys please tell me which on is the best one? In Way#1 I'm scaling 
to 4:3 the ACTUAL content.  In Way #2 I'm scaling the WHOLE frame.  Obviously 
these are 2 different things. Ok, for the regular eye, there won't be much 
difference but I think Way#2 is the way to go.  In Way#2 even though I end up 
with 496x384 (which isn't 4:3) the thing is that this frame was cropped from 
a 4:3 one (which already considered square pixels).

Thanks,
Jorge