> I've always read that as: > > For every 2x2 set of Y samples, there's a 1x1 set of Cr and Cb sample(s). > In other words, just what you'd expected - Cb and Cr are sampled at a rate > 1/4 (in 2d) of the Y samples.
Having tested various settings of the command line option "-sampling-factor", I've found this explanation to be correct: "2x2, 1x1, 1x1" is IM's standard subsampling method and corresponds to 4:2:0, see http://en.wikipedia.org/wiki/Chroma_subsampling BTW: The option -sampling-factor 4:2:0 does not work correctly in IM; it produces the same output as 4:2:2. This seems to be a bug in IM. Wolfgang Hugemann _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
