[opendtv] Re: All colors of rainbow in new display concept
- From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 22 Aug 2006 23:09:39 -0400
MPEG uses additive colorimetry, which does not lend itself to digitizing
color info with a minimal number of bits. This is because the color
difference signals have to be scaled to luma. (Interestingly, IBM in
Britain used different bit resolution for R, G and B primaries.) Generally,
hue and saturation are better coded in polar coordinates. At one time HP
used a "color top" type of mapping, for example.
Multiplicative colorimetry is well suited to describing the full gamut of
colors in digital form. Luma is multiplied by relative saturation strengths
of the hues for each of the primaries, and more than three primaries can be
used. RCA's U. S. patent No. 4,719,503 to Craver and Arbeiter described this
colorimetry. The following paragraph is excerpted from this patent.
The number of just noticeable differences (JNDs) in chromaticity has been
estimated as being seventeen thousand, of which only about four thousand
have been estimated as being reproducible with commercially available color
kinescopes. (For a more complete understanding of JNDs of chromaticity see
pages 60-61 of PRINCIPLES OF COLOR TELEVISION by the Hazeltine Laboratories
Staff, John Wiley & Sons, N.Y.). Fortunately these chromaticity values
include those of interest in reproducing natural scenes or in producing
artistic effects. Normalization of chrominance information relative to
luminance can reduce to twelve the number of bits required to code
chrominance without perceptible error, then, if appropriate chrominance map
entries are made. MacAdam's book indicates that information concerning
optimal choices of color map entries for spacing chromaticity values
uniformly is available from work done by members of the Optical Society of
America. Where chrominance map memories are never to be updated, the maximum
number of read addresses required for them to reproduce all differentiable
colors is thus established to be about 2 to the 12th power.
The concept of JNDs is attributable to Jann, I believe. I don't remember
his first name.
I don't know if anyone has researched video compression using multiplicative
colorimetry.
Al Limberg
----- Original Message -----
From: <albert.e.manfredi@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Friday, August 18, 2006 3:22 PM
Subject: [opendtv] All colors of rainbow in new display concept
> This new display concept uses tunable diffraction gratings, maybe a couple
or more dedicated to each pixel of the display, to create color images from
all colors of the rainbow. The gratings are tiny, made of a rubbery
substance that flexes by applying different voltages to it.
>
> Will this make images from existing RGB-based displays look like cartoon
colors?
>
> Bert
>
>
>
http://www.digitaltvdesignline.com/shared/article/showArticle.jhtml?articleId=192201780
>
>
>
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