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

[Jorge Fábregas]

On Saturday 24 March 2007 11:34 pm, RC wrote:
> If you just let -vf scale calculate the final dimentions for you (using
> -10 for either height or width), either way you will end up with almost
> exactly the same result, and both will have the proper aspect ratio.

I see. I tried it and you are right.  I never used those options for 
specifying the dimensions ( I always wrote them completely). I see that -10 
works and it gives me the same result.  I just cropped first and then scaled 
down using -10 in one of the dimensions. A couple of things I found during 
the way:

I had hardcoded ,among the lavc options the aspect ratio set to 4:3 which 
didn't make sense If I was using the -10 value. My perfect PAR-corrected 
footage should be 496x384 but it was stretched during playback to 4:3 (no 
good).

I then figured out that I needed to use "autoaspect" in lavc options.  The 
final footage then came up as 1.30:1 aspect ratio. When I play it I see that 
my 496x384 are streteched to 500x384 (because of the new calculated aspect 
ratio). No problems with me here (just 4 pixels the difference).  

However, I did just one final encoding, this time removing "autoaspect" from 
my lavc options and my final footage has an AR of 1.29:1...When I play it, it 
plays it a 496x384 exactly. I noticed there's some aspect ratio stored in 
there. I guess this is mencoder doing it because I didn't specify any 
AR in the lavc options...

RC:  Thanks for clayring. I appreciate it.

All the best,
Jorge