Synchronized demodulation of the chrominance signal with switched carrier phase angles

Claim 2

In a color video system of the type in which the chrominance component of a composite video signal is transmitted or recorded as a trisequential sequence containing the substitute color signals R', G', B' and in which at the receiving or playback end there is derived from the trisequential substitute color signals a luminance signal Y M = 0.33(R'+G'+B') where R', G', B' are chosen so as to substantially satisfy the relationship, Y M = +0.30R + 0.11B, required for black and white compatibility, the improvement that for producing said sequence of substitute color signals there are provided: three-phase demodulating means having a chrominance component and also an input from a trisequential switch means, said trisequential switch means being connected to phase-splitting means driven by a synchronized oscillator of color subcarrier frequency and supplying said trisequential switch means with three color subcarrier phases φ1, φ2 and φ3 of such angles as to cause said demodulating means to trisequentially demodulate said chrominance component directly along axes related to said substitute colors R', G', B', and gain control means interposed in series relationship with said demodulating means for automatically and trisequentially varying the chrominance component gain so as to bring about corresponding corrections of the magnitudes of the individual demodulated signals, whereby the need for means first producing the original colors R, G, B, and then processing the last mentioned colors to derive therefrom the substitute colors R', G', B' is obviated.

Claim 3

The improvement in a color video system as claimed in claim 1, wherein said demodulating means are designed to trisequentially demodulate said chrominance component along the color difference axes R'--Y, G'--Y, B'--Y.

Claim 4

The improvement in a color video system as claimed in claim 1, wherein said axes have the angles +120°, +219° and -7°, respectively, and wherein said gain control means is designed to provide the amplification factor 1.11 for the individual chrominance information of each first line, the factor 1.21 for the individual chrominance information of each second line and the factor 1.5 for the individual chrominance information of each third line.

Claim 5

The improvement in a color video system as claimed in claim 1 wherein there are provided means for adding to the signals supplied by said demodulating means the luminance component of the composite video signal.

Claim 6

In a color video system of the type in which the chrominance component of a composite video signal is transmitted or recorded as a trisequential sequence containing the substitute color signals R', G', B' and in which at the receiving or playback end there is derived from the trisequential substitute color signals a luminance signal Y M = 0.33(R'+G'+B') where R', G', B' are chosen so as to substantially satisfy the relationship, Y M = +0.30R + 0.59G + 0.11B, required for black and white compatibility, the improvement that for producing said sequence of color signals there are provided: three phase demodulating means having a chrominance component input and also an input from a trisequential switch means said trisequential switch means being connected to phase-splitting means driven by a synchronized oscillator of color subcarrier frequency and supplying said trisequential switch with three color subcarrier phases φ1, φ2 and φ3 of such angles as to cause said demodulating means to trisequentially demodulate said chrominance component directly along the color difference axes R'--Y, G'--Y, B'--Y, gain control means interposed in series relationship with said demodulating means for automatically and trisequentially varying the chrominance component gain to bring about corresponding corrections of the magnitudes of the three individual color difference signals R'--Y L , G'--Y L , and B'--Y L , respectively, and a trisequential clock pulse generator connected to said trisequential means for synchronously driving said switch means and connected to said gain control means for synchronously correcting said magnitudes, whereby the need for means first producing the original colors R,G,B, and then processing the last mentioned colors to derive therefrom the substitute colors R',G',B', is obviated.

Claim 7

In a color video system of the type in which the chrominance component of a composite video signal is transmitted or recorded as a trisequential sequence containing the substitute color signals R', G', B' and in which at the receiving or playback end there is derived from the trisequential substitute color signals a luminance signal Y M = 0.33(R'+G'+B') where R', G', B' are chosen so as to substantially satisfy the relationship, Y M = +0.30R + 0.59G + 0.11B, required for black and white compatibility, the improvement that for producing said sequence of color signals there are provided: three phase demodulating means having a chrominance component input and also an input from a trisequential switch means said trisequential switch means being connected to phase-splitting means driven by a synchronized oscillator of color subcarrier frequency and supplying said trisequential switch with three color subcarrier phases φ1, φ2 and φ3 of such angles as to cause said demodulating means to trisequentially demodulate said chrominance component directly along the color difference axes R'--Y, G'--Y, B'--Y, gain control means interposed in series relationship with said demodulating means for automatically and trisequentially varying the chrominance component gain to bring about corresponding corrections of the magnitudes of the three individual color difference signals R'--Y L , G'--Y L , and B'--Y L , respectively, and a trisequential clock pulse generator connected to said trisequential means for synchronously driving said switch means and connected to said gain control means for synchronously correcting said magnitudes, whereby the need for means first producing the original colors R,G,B, and then processing the last mentioned colors to derive therefrom the substitute colors R',G',B', is obviated.

Claim 8

In a color video system of the type in which the chrominance component of a composite video signal is transmitted or recorded as a trisequential sequence containing the substitute color signals R', G', B' and in which at the receiving or playback end there is derived from the trisequential substitute color signals a luminance signal Y M = 0.33(R'+G'+B') where R', G', B' are chosen so as to substantially satisfy the relationship, Y M = +0.30R + 0.59G + 0.11B, required for black and white compatibility, the method of producing said sequence of substitute color signals, comprising the steps of: deriving from a synchronized unmodulated subcarrier three subcarrier phases along the axes R'--Y, G'--Y, B'--Y, respectively; synchronously demodulating the chrominance component of said composite video signal trisequentially along the associated axes with the aid of said subcarrier phases to generate the signals R'--Y L , G'--Y L , B'--Y L ; and adding thereto the luminance component Y=Y L +Y H of the composite video signal where Y L is the low-frequency portion and Y H the high-frequency portion of the luminance component, thereby to produce the trisequential signal (R', G', B') + Y H for transmission or recording.

Claim 9

In a color video system of the type in which the chrominance component of a composite video signal is transmitted or recorded as a trisequential sequence containing the substitute color signals R', G', B' and in which at the receiving or playback end there is derived from the trisequential substitute color signals a luminance signal Y M = 0.33(R'+G'+B') where R', G', B' are chosen so as to substantially satisfy the relationship, Y M = +0.30R + 0.59G + 0.11B, required for black and white compatibility, the method of producing said sequence of substitute color signals, comprising the steps of: deriving from a synchronized unmodulated subcarrier three subcarrier phases along the axes R'--Y, G'--Y, B'--Y, respectively; synchronously demodulating the chrominance component of said composite video signal trisequentially along the associated axes with the aid of said subcarrier phases to generate the signals R'--Y L , G'--Y L , B'--Y L ; and adding thereto the luminance component Y=Y L +Y H of the composite video signal where Y L is the low-frequency portion and Y H the high-frequency portion of the luminance component, thereby to produce the trisequential signal (R', G', B') + Y H for transmission or recording.