Noise reduction in television signals
AssigneesThe Marconi Company Limited, Standard Telephones and Cables, PLC
InventorsJohn Oliver Drewery, Martin Weston
Life of this patent
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Abstract
Reduction of noise in a television signal is achieved by comparing signals from successive frame or field scans and noting the differences. Low amplitude differences are assumed to represent noise and are attenuated. Differences above a predetermined level are assumed to represent movement and are not so attenuated by a factor K. Where there are inherent differences between the signals compared, for example they are different fields of an interlaced scan or are color signals with different subcarrier phases, the signal from the earlier scan is modified to compensate for these differences and provide a signal for comparison which is a better estimate of the expected signal on the later scan.
Claims9
A method of reducing the effect of noise in an electrical input signal which is obtained by scanning, to provide an output signal, comprising the steps of subtracting from the input for the current scan the said output signal for a preceding scan to provide a difference signal, attenuating low-amplitude portions of the difference signal relative to high amplitude portions thereof, and adding the thus-attenuated signal to the said output signal for the preceding scan to provide an output signal for the current scan.
Apparatus for reducing the effect of noise in an electrical signal which is obtained by scanning, comprising the steps of subtracting from the input for the current scan the said output signal for a preceding scan to provide a difference signal, attenuating low-amplitude portions of the difference signal relative to high amplitude portions thereof, and adding the thus-attenuated signal to the said output signal for the preceding scan to provide an output signal for the current scan.
Dependencies are inferred from the claim text.