View Single Post
Old 14th April 2009, 08:07   #262  |  Link
FoLLgoTT
And so it begins...
 
FoLLgoTT's Avatar
 
Join Date: Nov 2005
Location: Hannover, Germany
Posts: 64
Quote:
Since you mentioned the Germany My Fair Lady DVD, here's that DVD, enlarged to my PC display's native resolution of 1680x1050:



Left side is "SoftCubic50", right size "Lanczos8". The ringing you can see in the right side is not in the source at all. It's added by the Lanczos resampling algorithm. As you can see, I didn't have to search very long to find ringing. After all this is still the movie intro... Here are the full screenshots:
I admit in this example the additional ringing inside the fonts is clearly visible and annoying. Thank you for the example!
But is it really visible inside of text lacking movie scenes? I never saw it.

On the other hand if you look at these shots from the same movie you can see much less aliasing on the inner side of the mirror (very annoying in moving scenes), but no additional ringing.

Lanczos2:


Lanczos10:



And if we analyze the picture a bit closer with the h-sweep pattern and a waveform analyzer:



Lanczos2:


Lanczos10:


It is obvious that the higher frequencies are transported better with Lanczos10 and that this algorithm acts as a better low pass, because beats (aliasing) gets less. The h-sweep looks cleaner and very slightly more detail is visible.
Of course if you look at the sides of the h-sweep (hard edges, square wave) there is additional ringing introduced by the scaling algorithm. But these areas content high spatial frequencies which movies *usually* don't (or as I learned only rarely), because of the necessary low pass filtering.

Anyway, you are right. Because everything is just a big compromise it is just a matter of preference. Less aliasing and more detail (Lanczos8) or less ringing (e.g. Catmull-Rom).

Last edited by FoLLgoTT; 14th April 2009 at 08:21.
FoLLgoTT is offline   Reply With Quote