[MPlayer-users] probably my usual stupid question of the week

rcooley rcooley at spamcop.net
Sat Apr 17 22:43:44 CEST 2004

On Fri, 16 Apr 2004 04:04:01 -0400
D Richard Felker III <dalias at aerifal.cx> wrote:

> The code seems to be incorrect. It rounds to a larger region, leaving
> black border, which makes cropping pointless.

I've been using it for months, and I can assure you that there are no
black borders on anything I encode.  You must have simply read it wrong.
 The way I formatted it might not have helped readability any.

> But even this is nonsense, since you
> should just scale after cropping rather than overcropping or
> undercropping to meet n%16==0 requirements.

First off, I would think that any scaling the video would cause some
quality loss.  Am I wrong here?  Is there some method of losslessly
scaling video that mplayer impliments?  I can deal with loosing 4 lines
of picture, but adding more blur or other artifacts across the whole
video is something I definately want to avoid. 

Also, this code has another purpose as well.  I couldn't use
cropdetect by itself, because it usually didn't completely chop off
the black.  I tried different values to cropdetect, but it was always
either leaving a couple lines of black borders, or regularly cropping
off too much.  It was mainly a problem on videos where the picture fades
into black over 2-4 lines, like most videos recorded from a TV signal. 
Interlaced content seems to confuse cropdetect as well, even when
cropdetect is invoked after a deinterlacer, it seems that cropdect never
gets it quite right.

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