[MPlayer-users] cropdetect accuracy with mplayer-1.0pre6a

[D Richard Felker III]

On Fri, Feb 18, 2005 at 11:46:51AM -0800, RC wrote:
> On Fri, 18 Feb 2005 00:03:57 +0100
> Josef Wolf <jw at raven.inka.de> wrote:
> 
> > In the past, I was really impressed with the accuracy of the
> > cropdetect functionality.  But since I upgraded to 1.0pre6a, the
> > detected area is too small.  That is, about 8 pixels of real video are
> > cropped off around the detected area.
> > 
> > Any idea why this change comes?
> 
> Because cropdetect is usually used for finding encoding parameters, and
> most codecs need the video dimentions to be a multiple of 16.

quite often you'll scale after cropping though, in which case it's
useless to round crop values.

> You can turn it (almost completely) off by using "2" as the "round"
> parameter eg"cropdetect=24:2".  Most codecs need the crop parameters to
> be divisible by 2, so that is the minimum.  My patch originally allowed

not the codec matter, rather image formats. basically all the image
formats used in movies are 4:2:0, meaning that non-even crop offsets
or sizes are _complete nonsense_, i.e. not possible without first
resampling.

rich