On Wed, 13 Sep 2006 22:51:16 +0100 josephhenryblack <[EMAIL PROTECTED]> wrote:
> I have added croma subsampling and YUV to the glossary, but you may wish > to review it http://wiki.duskglow.com/tiki-index.php?page=Glossary Some comments: 4:2:2: Upsampling should be always done by interpolation and not how it is mentioned by nearest neighbor (aka copying the chroma value from the left). The YUYV format outlined there is just a packed representation that somehow fits, because U and V together are as large as Y. 4:2:1 does that even exist? I've never seen it nor heard of it 4:2:0, the most important subsampling format is missing 4:1:1 and 4:1:0 are similar to 4:2:2 resp 4:2:0 but use a smaller sample size in horizontal direction. But those are only relevant for a handfull of specific codecs. Also it's easily possible to upsample these in software to 4:2:2 and 4:2:0 respectively (though i doubt that the hardware required for this would need much area, but if we need a few gatters more for something else, it would be the first function i'd drop) Important to note here is that the chroma samples are often half a pixel off the luma pixel positions. Thus every sample needs to be interpolated and noone can be just copied. But there are different standards even for that, depending on the codec. Maybe a link to http://vektor.theorem.ca/graphics/ycbcr/Chroma_subsampling_notation.pdf Would be something. It explains a few of the things we need (though not all of it). Attila Kinali -- egp ist vergleichbar mit einem ikea bausatz fuer flugzeugtraeger -- reeler in +kaosu _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
