Hi, [...]
> > Something like that, the filter uses 0.75x nearest chrominance sample > > and 0.25x second nearest chrominance sample. This is more accurate as > > it doesn't shift the chrominance signal by 1 pixel. > > Please, please correct me if I'm wrong here. In MPEG sampling, the > chrominance sample is halfway between the two luminance samples on the > same vertical scanline (by is138182): I think you're right, my interpolation looks like this : o o (c=.75*c1 + .25*c0) c1 o o (c=.75*c1 + .25*c2) o o (c=.75*c2 + .25*c1) c2 o o (c=.75*c2 + .25*c3) [...] > So, are not the chroma samples above and below the same distance away? > I thought this was the purpose of MPEG sampling, that is, it's > reasonable to convert to 4:2:2 sampling by doubling the scanlines. It's reasonable, but doubling the scanlines will make the image look a little blocky as both scanlines use the same chrominance values. That's why you should use filtering. > Are you sure that maybe the images where you see that nasty chroma > artifact aren't from when the DVD is using interlaced encoding? In this > case, each second chroma sample is from a different field, and you can > get blocky errors because you don't correllate samples correctly. The source was a non-interlaced MPEG-1 video file. The red blocks are very small for (high resolution) DVD movies, but they are still visible. > What do you mean by shifting the chroma by one pixel? It's actually 0.5 pixel (my mistake :)) using the following filter : o o (c=c1) c1 o o (c=.5*c1 + .5*c2) o o (c=c2) c2 o o (c=.5*c2 + .5*c3) bye, ewald _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert
