A multi-standard adaptive chrominance separator

Claim 2

A circuit for separating chrominance and luminance of a digital video signal and including a comb filter (26) which can be bypassed, characterised by means (44) for controlling the bypass of the comb filter in accordance with a preselected relationship between the chrominance and luminance levels of the video signal.

Claim 3

A circuit according to claim 1 and including a band-pass filter (12) having a pass-band embracing the color sub-carrier frequency, characterised in that the said means (44) provides selection of an output signal passed through the comb filter or an output signal passed through the band-pass filter and bypassing the comb filter, in accordance with the said relationship.

Claim 4

A circuit according to claim 2 in which the said means provides for the selection of an output representing an average of the said output signals.

Claim 5

A circuit according to claim 2 in which the selection between the said output signals is made according as the luminance level is greater or less than the chrominance level.

Claim 6

A circuit according to claim 3 in which the selection of the average of the said output signals is made according to the detection of substantial equality between the chrominance and luminance levels.

Claim 7

A circuit according to any foregoing claim characterised by means (20,22) for providing relatively undelayed line data, once delayed line data and twice delayed line data, means (36) for selectively weighting and adding the undelayed and twice delayed line data to provide a signal denoting the chrominance level and means for selectively weighting and adding the undelayed, once delayed and twice delayed line data to provide a signal denoting the luminance level.

Claim 8

A circuit according to any foregoing claim, and including a memory (48) for storing values indicative of the various relationships between the chrominance and luminance levels and to provide on reception from level detectors (38,42) of signals denoting the chrominance and luminance levels a control signal for controlling the bypass of the comb filter.

Claim 9

A circuit according to any foregoing claim in which the means (44) for controlling operates on a sample-by-sample basis.

Claim 10

A circuit for separating chrominance and luminance signals in a composite color television signal presented as successive lines, characterised by filter means (12,16) for providing bottom, middle and top line data from three adjacent lines and for generating therefrom a comb chrominance signal, a band-pass chrominance signal and an average chrominance signal from the comb and band-pass signals; switch means for receiving the comb, band-pass and average chrominance signals; and control means (34-44) responsive to the relative levels of the chrominance and luminance signals for selectively enabling the switch means to output the band-pass chrominance signal, the average chrominance signals, or the comb chrominance signal.

Claim 11

A circuit for separating chrominance and luminance signals in a composite color television signal presented as successive lines, characterised by filter means (12,16) for providing bottom, middle and top line data from three adjacent lines and for generating therefrom a comb chrominance signal, a band-pass chrominance signal and an average chrominance signal from the comb and band-pass signals; switch means for receiving the comb, band-pass and average chrominance signals; and control means (34-44) responsive to the relative levels of the chrominance and luminance signals for selectively enabling the switch means to output the band-pass chrominance signal, the average chrominance signals, or the comb chrominance signal.

Claim 12

A circuit according to claim 9 characterised by a chrominance detector (38) disposed to receive the middle and top line data and to generate a chrominance level indicative of the chrominance signal; a luminance detector (42) disposed to receive the bottom, middle and top line data and to generate a luminance level indicative of the luminance signal; and comparison means (40) coupled to the chrominance and luminance detectors for generating a switch control signal indicative of the said relative levels.

Claim 13

A circuit according to claim 10 wherein the comparison means includes: a PROM for storing values indicative of the various relationships between the chrominance and luminance levels and for supplying the control signal in response to a comparison of the stored values and the relative levels.

Claim 14

A circuit according to claim 11 wherein said chrominance detector includes a chrominance adder and a chrominance RMS level detector coupled to the chrominance adder; said luminance detector includes a luminance adder and a luminance RMS level detector coupled to the luminance adder, and the PROM is coupled to the chrominance and luminance RMS level detectors.

Claim 15

A circuit according to any of claims 9 to 12 wherein the composite color television signal is represented by successive digital samples of the horizontal lines and wherein said filter means provides the comb, band-pass and average chrominance signals on a sample-to-sample basis; and said control means selectively enables the switch means on a corresponding sample-by-sample basis.

Claim 18

A method according to claim 14 including comparing the magnitudes of the chrominance and luminance signals; and supplying a control signal indicative of the magnitude level relationship for adaptively switching to one of the filtering processes.

Claim 19

A method according to claim 15 including selecting sine waves of magnitudes corresponding to the respective chrominance and luminance levels; and converting the sine waves to DC levels corresponding to the respective chrominance and luminance levels.

Claim 21

A method according to claim 17, characterised by selecting the average chrominance signal as an output on the detection of substantial equality of the said relative levels.