[Open-graphics] ATI and Nvidia raise the bar?

[James Richard Tyrer]

Dieter wrote:
> So ATI and Nvidia now have noise and sharpness filters.
> Perhaps I missed it, but I didn't see anything about whether this
> is done in hardware or in the driver.  I also haven't seen an
> explaination of exactly what this "twinkling" is and what causes
> it.
> 
> http://www.behardware.com/articles/635-1/ati-and-nvidia-corrects-the-twinkling-effect-of-lcds-in-movies.html

IIUC, the "twinkling" is caused by the MPEG artifacts and this is 
accentuated when using some flat panel screens.

The PSEUDO-noise reduction and ARTIFICIAL sharpening are actually the 
same function.  A small two dimension FIR filter is applied to the image.

I emphasize that this is pseudo-noise reduction because true noise 
reduction requires taking the FFT of the data, modifying the FFT by 
attenuating the high spatial frequencies or using a procedure developed 
by Bell Labs which requires multiple operations on the FFT, and then 
taking the inverse FFT.  This procedure is used to remove noise from 
images and audio but doing it in real time at 30 or (worse) 60 fps would 
require a super computer.

With artificial sharpening, only the effect of greater sharpness is 
produced by increasing local contrast without changing global contrast.

IIUC, these two operations might be somewhat in opposition to each other 
except that noise has higher spatial frequencies than the edge sharpening.

IAC, since this involves running the image data through two filters, you 
can accomplish the same thing by running it through one filter which is 
the normalized product of the two.

This is going to be quite computationally expensive since an 8x8 filter 
is going to require 64 MAC operations for each pixel in the image.  And, 
you would really need a larger filter to avoid the 8x8 block artifacts. 
  But a 5x5 (5 and 8 are mutually prime) might be sufficient -- that is 
still 25 MACs per pixel.

I have to wonder exactly how this is being done.

-- 
JRT