Bilevel coding of color video signals
First Claim
1. Video signal processing apparatus comprising means for bilevel coding discrete picture elements of a colour video signal having a luminance component and a chrominance component, including:
- means for deriving from a plurality of picture elements including at least one picture element other than the picture element to be encoded a first signal, (φ
ij), proportional to said luminance component;
means for deriving a second signal (Cij) proportional to said chrominance component;
means for computing from said the first and second signals a threshold signal (Bij) anda comparator for comparing said picture element to be encoded with said threshold value and providing an output signal Yij having either one of two states in dependence upon whether or not said picture element exceeds said threshold value.
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Accused Products
Abstract
Bilevel coding of color video signals, for example video teleconference or NTSC broadcast television signals, is used to reduce the required storage capacity or transmission channel bandwidth. Each multi-level or continuous tone picture element in a frame is compared to a threshold and assigned one of two values depending upon whether or not it exceeds the threshold value. The threshold is produced by averaging the luminance components of neighboring picture elements and constraining the average by a signal derived from the chrominance of the original video signal. A significant feature is that the use of the chrominance signal in this way obviates the need, common to known monochrome systems, of adding noise (or dither signal) to the signal with concomitant picture degrading artifacts.
6 Citations
25 Claims
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1. Video signal processing apparatus comprising means for bilevel coding discrete picture elements of a colour video signal having a luminance component and a chrominance component, including:
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means for deriving from a plurality of picture elements including at least one picture element other than the picture element to be encoded a first signal, (φ
ij), proportional to said luminance component;means for deriving a second signal (Cij) proportional to said chrominance component; means for computing from said the first and second signals a threshold signal (Bij) and a comparator for comparing said picture element to be encoded with said threshold value and providing an output signal Yij having either one of two states in dependence upon whether or not said picture element exceeds said threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A process for bilevel coding of a colour video signal having a luminance component and a chrominance component comprising the steps of:
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(i) deriving from a plurality of picture elements including one or more picture elements other than the picture element to be encoded a first signal (φ
ij) proportional to said luminance component of the video signal;(ii) deriving a second signal (Cij) proportional to said chrominance component; (iii) computing from said first and second signals (φ
ij) and (Cij) a threshold value;(iv) comparing said picture element to be encoded with said threshold value and providing an output having either one of two states in dependence upon whether or not said picture element exceeds said threshold value. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification