Quantization of TV Chrominance Signals Considering the Visibility of Small Color Differences

Author

Stenger, Ludwig

Author_Institution

Technische Universität Hannover, West Germany

Volume

25

Issue

11

fYear

1977

fDate

11/1/1977 12:00:00 AM

Firstpage

1393

Lastpage

1406

Abstract

A quantizing method for chrominance signals is presented which takes into account that the visibility of small color differences and the areas of reproducible colors are a function of luminance. For the evaluation of quantizing characteristics and for an estimate of the effectiveness of such a procedure, CIE (Commission International de l\´Eclairage) formulas are used. It is proposed to subdivide the color space into several layers of constant luminance signal and to choose, switched by the luminance signal, an individual quantizer for each layer. Such quantizers are calculated for two different coding schemes: quantizing the TV chrominance signals $U_{R-Y}$ and $U_{B-Y}$ directly or quantizing chrominance signals which have been transformed into a color space derived from a neurophysiological model of vision. Because of practical reasons the quantization of $U_{R-Y}$ and $U_{B-Y}$ is preferred and elaborated in more detail. The calculated non-linear quantizing grids are approximated by two different methods, with small rectangular elements, or they are piecewise linear approximated by interpolation. To achieve a color difference of $\\Delta E_{1964 CIE} = 4.4$ as maximum distortion, a PCM quantization of 5 bits in $U_{R-Y}$ and $U_{B-Y}$ is required. First order entropies indicate an average bit rate of 3.5 for $U_{R-Y}$ and 2.7 for $U_{B-Y}$ .

Keywords

Image coding; Visual system; Bit rate; Entropy; Interpolation; Nonlinear distortion; Phase change materials; Physiology; Piecewise linear approximation; Piecewise linear techniques; Quantization; TV;

fLanguage

English

Journal_Title

Communications, IEEE Transactions on

Publisher

ieee

ISSN

0090-6778

Type

jour

DOI

10.1109/TCOM.1977.1093767

Filename

1093767