[MPlayer-users] seeking explanation of -1 and -2 in -vop scale

[Chris Phillips]

hi,

> Nevertheless there is a wonderful tool for mencoder that is not so
> known. Many people ask about automatic crop-detection, but I prefer to
> use the instruction:    -vop rectangle=x:y:x':y'

it's a useful tool, but right now i'm writing a perl script that will 
automatically find and encode the main title on a dvd, without additional 
user information whatsoever. as and whan and if I get round to converting 
my console script to a GUI rectangle would definitely get a look in...

> Another point -just referring to your question- is related with the way
> the image is cropped. Your instruction: crop=720:436:4:740 is just
> impossible, as the two first numbers are the size of the image once
> cropped, and the two seconds the point origin where the rectangle just
> defined by the two first will place its upper-left corner. The
> coordinates begin from the left -for X- and from top -for Y. Your last
> "740" is outside any known height of a film.

typo, meant 74. 

> For the scale, my advice is to forget about this "-1" or "-2" story.
> Just write the size that you want for the final screen, but don't forget
> that, according to Arpi -as long as I remember- the quality is worst if
> you scale inside the encoder process, and will be better if you scale
> with "xv" at seeing time.

well again as any disc could be put in, it could be 4:3, 16:9 or something 
entirely different again from cropping, or just a plain weird vid stream. 
I need to the video to be scaled to aspect proportions (well... at least 
as a *default* option for my script.) It still seems straneg to me that a 
vob stream is not forced to aspect on mencoder, only mplayer. but then if 
what you say IS true then i guess that makes sense. it certainly needs to 
be an option at least!.. hence -1 and or -2 (which appear to be 
undocumented)

thanks

chris
xxxx