about psi

[Lu ZHANG]

Hi everyone,

I have some questions about the Nonlinearity part of the HDR-VDP:
1. What does the abbreviation "psi" stand for?
2. I know that this Nonlinearity step is to express the amplitude of the signal in the units of Just Noticeable Differences (JND) by using a look-up table in "csf_psi_mapping.h".
    But where can I find the explanation of the values in the look-up table?

Thanks a lot!
Have a nice day!
Lu

[Rafal]

Hi Lu,

These are precomputed values. You can find more in:

Mantiuk R, Daly S, Myszkowski K, Seidel H. Predicting visible
differences in high dynamic range images: model and its calibration.
In: Human Vision and Electronic Imaging.; 2005:204-214. Available at:
http://scholar.google.co.uk/scholar?hl=en&as_sdt=2000&q=visual+difference+predictor+high+dynamic+range+mantiuk#0.

and

Mantiuk R, Krawczyk G, Myszkowski K, Seidel H. Perception-motivated
high dynamic range video encoding. ACM Transactions on Graphics.
2004;23(3):733. Available at: http://portal.acm.org/citation.cfm?doid=1015706.1015794.

Cheers,

Rafal

[Lu ZHANG]

Hi Rafal,

Thanks a lot!
And what does the abbreviation "psi" stand for? There's no meaning?

Thank you again!

Have a nice day!
Lu

2010/8/23 Rafal <man...@googlemail.com>

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[Rafal]

On Aug 24, 8:49 am, Lu ZHANG <lu.zhang...@gmail.com> wrote:
> And what does the abbreviation "psi" stand for? There's no meaning?

This is just a greek letter. The same as the one used in the paper.

Rafal

[Lu ZHANG]

Ah, I see... I thought that it was an english abbreviation...
Thanks a lot!

2010/8/24 Rafal <man...@googlemail.com>

Rafal