On Fri, 2003-12-05 at 00:36, 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? If you want two-field perfect, capture, then 4:2:0 wouldn't be a good choice anyway, since it's chroma planes are vertically downsampled so you drop most field information already. Even if you do correct MPEG-downsampling, then you'll have two of the same scanlines in your upsampled 4:4:4 fields. The only good choice here is non-vertical-downsampled stuff, so 4:2:2 (or 4:1:1, 4:4:4, etc.), or a frame approach (in which cases it doesn't matter whether you interpolate or drop scanlines). Note that MPEG2 4:2:0 chroma ordering isn't the only valid 4:2:0. Scanline dropping is perfectly valid in other 4:2:0 cases. I'd say that it'd be a good thing to add a field in the v4l2 image struct that tells us on whether it was downsampled using interpolation, scanline dropping or something else. > [1] http://mplayerhq.hu/pipermail/mplayer-dev-eng/2003-December/022612.html Richard Felker is not a technical guy. Ronald -- Ronald Bultje <rbultje@xxxxxxxxxxxxxxxxxxx> Linux Video/Multimedia developer
