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NTSC Luminance/Chrominance Equation Definition for Digital Systems

IP.com Disclosure Number: IPCOM000100001D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Cole, SR: AUTHOR

Abstract

This disclosure presents a method for redefining the classical National Television Systems Committee (NTSC) video signal luminance and chrominance equations to facilitate digital processing of these signals. The NTSC video standard is used for broadcast television in North America, most of South America and Japan.

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NTSC Luminance/Chrominance Equation Definition for Digital Systems

       This disclosure presents a method for redefining the
classical National Television Systems Committee (NTSC) video signal
luminance and chrominance equations to facilitate digital processing
of these signals.  The NTSC video standard is used for broadcast
television in North America, most of South America and Japan.

      Within the NTSC video signal standard, the luminance
(brightness) and chrominance (color) of the signal can be expressed
in terms of the red, green and blue (RGB) components of the picture.
The luminance equation is: Y = 0.30R + 0.59G + 0.11B
          (1) where Y is the luminance.  The chrominance can be
expressed by the color-difference signals:
      U = R-Y                                           (2)
      V = B-Y                                           (3)

      The coefficients of the RGB components in the luminance
equation were chosen so that, when a color picture is reproduced on a
monochrome (black and white) monitor, the grey shading is accurate.
Characteristic of the NTSC signal is that the luminance requires the
full 4 MHz bandwidth of the signal, while the color-difference
signals have a bandwidth of only about 0.5 MHz.  In applications
where the video signal is stored in digital memory, YUV format
requires less memory than RGB storage (which needs the full bandwidth
for all three of the RGB color component signals). If YUV format is
used, a conversion from YUV to RGB is needed before the image can be
displayed (monitors typically use RGB inputs).  And depending on the
type of video decoder used, a conversion from RGB to YUV is needed
before the image is stored in memory.  Use of the classical
definition of the luminance and chrominance signals would dictate
that the RGB to YUV and YUV to RGB conversions be done by non-trivial
analog circuits.

      What is suggested here is that the luminance equation be
redefined to make digital processing of YUV format data an easier
task.  The new definition of the luminance equation is: Y = 0...