On Thu, 4 Dec 2003, Billy Biggs wrote: > Recently on the mplayer lists the topic of chroma from bttv in 4:2:0 > mode. At least in the past it has been true that since the Bt878 has no > true downsampling 4:2:0 mode that the bttv driver only gives chroma from > the top field. Is this still true? The bt848 only supports vertical chroma downsampling by dropping pixels. But different hardware uses all kinds of different methods to down sample data. Dropping pixels, a 2-tap filter, 4-tap filter, linear, cubic, sinc function, full line FFT, etc. For the bt848 you can select a number of different filters or lack of them for the scaling operations. It turns out, that for vertical downsampling of chroma, the bt848 doesn't have a very good filter. But you're saying, "it's not good enough for me and therefore no one else should be able to use it!" If you're going to use a low-quality fast hardware filter or a higher-quality slow software filter is a tradeoff that you have to decide on a case by case basis. Not something you should decide for everyone else.
