Up-Rezzing at DVinfo.net

Jason Chang · October 21st, 2003, 08:15 PM

Can someone tell me in simple terms what Up-rezzing is all about? How does it work? Thanks!

Robert Knecht Schmidt · October 21st, 2003, 08:48 PM

Here's a good link for you.

Resampling and Interpolation Demystified

Gints Klimanis · October 21st, 2003, 08:59 PM

Thanks for the link. The sample pictures were quite useful.

What I don't understand is why in this day and age popular
image processing programs don't offer full 2D sinc function
interpolation for image resizing. It's a computer. Sure,
the image will shift in both dimensions by the group delay,
but just crop the image by that amount automatically. Or,
just keep these new pixels produced by the resampling process
and include them in the resize automatically. There really
should no aliasing going on. I think the problem is that
coder just do connect the dots and haven't looked at the
frequency responses of these spline and low order polynomial filters. If users are worried about 8 vs. 16 bit word depth for
images, they should definitely be worrying about noise levels
that are much higher than the 8 bit level. Generally, better
interpolation filters reduce contrast at image feature edges,
but after resampling, this contrast is noise. For static images,
it may be less of a deal, but for video, this noise will appear
to swim. The horror !

As for the comment on the sharpening filter, this just amplifies
high frequencies, and of course, noise.

October 21st, 2003, 08:15 PM	#1
Jason Chang Regular Crew Join Date: Oct 2003 Location: San Diego, CA USA Posts: 163	Up-Rezzing Can someone tell me in simple terms what Up-rezzing is all about? How does it work? Thanks!

October 21st, 2003, 08:48 PM	#2
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	Here's a good link for you. Resampling and Interpolation Demystified __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

October 21st, 2003, 08:59 PM	#3
Gints Klimanis Inner Circle Join Date: Jun 2003 Location: San Jose, CA Posts: 2,222	Thanks for the link. The sample pictures were quite useful. What I don't understand is why in this day and age popular image processing programs don't offer full 2D sinc function interpolation for image resizing. It's a computer. Sure, the image will shift in both dimensions by the group delay, but just crop the image by that amount automatically. Or, just keep these new pixels produced by the resampling process and include them in the resize automatically. There really should no aliasing going on. I think the problem is that coder just do connect the dots and haven't looked at the frequency responses of these spline and low order polynomial filters. If users are worried about 8 vs. 16 bit word depth for images, they should definitely be worrying about noise levels that are much higher than the 8 bit level. Generally, better interpolation filters reduce contrast at image feature edges, but after resampling, this contrast is noise. For static images, it may be less of a deal, but for video, this noise will appear to swim. The horror ! As for the comment on the sharpening filter, this just amplifies high frequencies, and of course, noise.