Hallo > >While playing around I have noticed a problem that the boarder seems to > >be fine as long as I set the color to black. But If I set is for example > >to a nice red (yuv: 16,128,234). I have something like a shadow around > >the area. First I thought it would be problem in my code. After searching > ... > >For the creation I used that command: > >lav2yuv -f 1 test.eli | yuvinactive -i 10x10+4+4 -s 16,128,234 | > >y4mtoppm >test.ppm > > Actually, there is no problem... y4mtoppm uses a linear/triangle filter > to upsample from 4:2:0 to 4:4:4. This will cause smoothing of what are, > in fact, artificially sharp transitions in the image. Ok, I noticed in the manpage the upsample note. But did not think that this could cause any other effects.
> (Not to say that your code doesn't have bugs, but this isn't one of them. ;^) What do you mean, or which places in the code ? That program ist obvious my first try. Sometime I wonder that it works ;) > >The thing I don't understand is, according to the DMG "Chroma > >Subsampling Standards" Page from Matthew Marjanovic. > >The 4:2:0 samples should be aligend like JPEG/MPEG-1/MJPEG. The croma > >sample in the center of four luma pixles. The thing I don't understand > > ...That's where the chroma sample is located, but it's a common mistake Ok. > to think that it is 'defined' by the four original surrounding chroma > samples. This is only true when a (spectrally-poor) box filter is used, > which downsamples by simply averaging the four closest pixels. Better > filters will use more pixels, weighted appropriately, for both downsampling > and upsampling. OK. But if I only want to set a area to a certain color, that should not matter ? Or would it be wise to make "soft border" by filtering the pixles on the border ? BTW: If you have any locations where I can also find more information just tell me. auf hoffentlich bald, Berni the Chaos of Woodquarter Email: [EMAIL PROTECTED] www: http://www.lysator.liu.se/~gz/bernhard ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/ _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
