[MPlayer-users] Re: mencoder/crop => image distortion

Hans Meine hans_meine at gmx.net
Thu Jul 31 12:47:19 CEST 2003

On Thursday 31 July 2003 12:27, Jonathan Rogers wrote:
> I was trying to end the discussion, but sure enough you showed
> your true colors. There's nothing worse than a know-it-all (well
> I don't exactly how much you know, but it's not everything)
> person.

Please, before anyone of you posts further mails, could you please calm down? 
I found the mails of both of you very instructive in the past.

@Rich: "know-it-all-user" was not nice - and Jonathan is answering many 
questions on -users, so we all should be thankful. (Even if you might not 
have answered the same in every case, but people are happy in general if the 
get good, maybe non-optimal answers, too.)

@Jonathan: You reacted very aggressively. It's understandable, but words like 
"asshole" do not really prevent escalation.

I hope we get nice constructive posts of you two again, soon.

And to the matter of cropping yv12: I would think the facts are clear; yv12 
has chroma (color) information for two adjacent pixels horizontically. So if 
an even number of pixels is cropped, everything is fine. Now if an odd # of 
pixels is cropped, the filters have to create new chrome entries for odd 
offsets. Those could be the old ones, shifted by one pixel to the left/right 
(which would make color shift by one pixel "behind" the graylevel image, be 
technically stupid, and would probably look wrong in _some_ situations, but 
IMHO would not be apparent on first sight in non-artificial movies) or 
interpolated entries of both old neighbor entries (meaning a strong smoothing 
in X-direction, IMHO also not apparent on first sight in non-artificial 
movies). So if you create a movie with 2-pixel wide vertical color stripes, 
that would obviously get broken with cropping 1 pixel, but with "normal" 
movies, one would maybe notice no difference. However, Rich's right that 
technically, cropping 2 pixels will be much more sane.

All right? ;-)

Ciao, /  /
    /  / ANS

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