Abstract: A system for applying brightness signals to the pixels of a display device includes a transmission gate for each column of pixels. The control electrodes of the transmission gates are precharged to the threshold voltage of the gates to substantially increase the speed of the system. Comparators compare brightness voltages to a reference ramp voltage to enhance the speed and accuracy of the system.

Abstract: A motion adaptive television signal processing system is disclosed. An image change estimator estimates the image change over an image time interval. A television signal processor adaptively processes the signal in response to a control signal. A control signal generator is coupled between the image change estimator and the adaptive television signal processor. The control signal generated exhibits a function substantially described by: K=Ae.sup.-b/x where K is the value of the control signal, A is the maximum value the control signal can attain, x is the estimated image change, and b is a constant. In a second embodiment, a second estimator estimates a parameter of the television signal. The relationship of the control signal to the estimated image change is varied as a function of the estimated parameter.

Abstract: A digital television receiver, having a line locked clock, includes a first digital phase locked loop which regenerates quadrature phase related subcarrier signals that are used to synchronously demodulate the chrominance signal components of composite video signals into color information signals. When nonstandard video signals (e.g., from a video tape recorder) are processed by the receiver, frequency instabilities in the line locked clock signal may cause the color information signals to be distorted. To compensate for this distortion, a second phase locked loop is synchronized to a reference signal generated by an analog oscillator. The analog reference signal is linearly added to baseband analog video signals provided by a tuner. The combined signals are digitized by an analog-to-digital converter and then filtered by parallel low-pass and band-pass filters to develop digital signals representing the video signals and the reference signal, respectively.

Abstract: A digital television receiver which uses a line-locked clock signal employs chrominance signal demodulation circuitry which produces a digital oscillatory signal that is locked in phase to the color reference burst signal component of the incoming video signals. An analog voltage controlled oscillator generates an oscillatory signal having a frequency of approximately twice the color subcarrier frequency. This signal is combined with the composite video signals and the combined signal is digitized by an analog to digital converter. The digitized oscillatory signal is separated from the combined digital signal and is used to synchronize a digital phase locked loop. The digital phase locked loop generates two quadrature phase related signals having frequencies that are one-half the frequency of the analog oscillatory signal. These two signals are used to synchronously demodulate the chrominance signal components of the incoming video signals to obtain two quadrature phase related color difference signals.

Abstract: A digital television receiver includes a first phase locked loop which develops a sampling clock signal that is locked to the horizontal line synchronizing signal components of a composite video signal. A second digital phase locked loop is clocked by the sampling clock signal and develops a digital signal that is phase locked to the color burst signal. This digital signal is used as a regenerated color subcarrier signal to synchronously demodulate the chrominance components of the composite video signals into I and Q color difference signals. To compensate for frequency instability in the regenerated subcarrier signal caused by frequency instabilities in the line-locked clock signal, a third digital phase locked loop develops an output signal which is phase locked to a reference signal generated by a crystal controlled oscillator.

Abstract: A vertical transition processor for a comb filter detects the presence of a complementary-color vertical transition. A detector is provided for detecting if the color subcarrier on adjacent lines has the same phase angle and amplitude. This indicates the presence of a complementary-color vertical transition. If a complementary-color vertical transition is detected, then the comb filtered luminance and chrominance signals are selectively coupled to the luminance and chrominance processing channels so that the chrominance processing channel receives primarily color information and the color information is excluded from the luminance processing channel. This counteracts the adverse effects of the complementary-color vertical transition.

Abstract: In a composite color video signal, a portion of the signal spectrum is shared by high frequency vertical detail information, and high frequency modulated color difference (I) information. A circuit is described which determines whether the information in the shared frequency band is vertical detail information or color difference information without degradation in the presence of a step input signal, as, for example, in the presence of lettering in the image. A composite video signal is comb filtered to generate comb filtered chrominance and luminance signals. A baseband color difference signal is produced from the comb filtered chrominance signal and the presence of high frequency information in the baseband color difference signal is detected. The bandwidth of the low frequency portion of the comb filtered chrominance signal (i.e. the vertical detail information) which is restored to the comb filtered luminance signal is varied in response to the control signal.

Abstract: A digital television receiver, having a line-locked clock, includes a partly digital, partly analog phase locked loop. This phase locked loop regenerates two quadrature phase related subcarrier signals that are used to synchronously demodulate the chrominance signal components of the composite video signals into two color informaiton signals. The phase locked loop includes an analog voltage controlled oscillator which generates a signal that is independent of any frequency instability in the line locked clock signal. An analog-to-digital converter digitizes this signal to provide one of the subcarrier signals. This subcarrier signal is applied to a read-only memory to generate the second subcarrier signal. The two color information signals are obtained by multiplying the chrominance signals by the first and second subcarrier signals.

Abstract: Apparatus for estimating noise in an electrical signal having substantially redundant recurring intervals includes circuitry for producing difference samples corresponding to signal differences between the recurring redundant intervals. A number of difference samples are averaged, and ones of the difference samples contributing to each average are subtracted from the averages. Magnitude values are extracted from the differences between the averages and the difference samples. A predetermined number of the magnitude values are averaged to produce a noise estimate signal.

Abstract: Apparatus for passing digital pulses from a bilevel digital signal source having widths wider than a given minimum and narrower than a given maximum is described. A first duration sensitive signal gate is coupled to the signal source and passes only signals having widths wider than the given minimum duration. A second duration sensitive signal gate is also coupled to the signal source and passes only signals having widths equal to or wider than the given maximum duration. A signal selection means is coupled to the first and second duration sensitive signal gates, and passes pulses which have been passed by the first but not the second duration sensitive signal gate.

Abstract: A motion detector for determining image motion in a video signal develops an array of signals representing the difference between pixels from adjacent frames. The array of signals are grouped into subarrays, each of which include the signal corresponding to the pixel under examination for motion. Each of the subarrays are independently examined to determine if the magnitude of all of the pixel differences represented in a particular subarray exceed a predetermined threshold and/or the pixel differences have like polarity. If these conditions are met in any one of the subarrays, a motion signal is produced.

Abstract: A television receiver is arranged to selectively display either information from a broadcast television signal, or information from an auxiliary video signal. The black image reference level associated with the broadcast signal information is sampled and used to automatically establish the black image reference level of the auxiliary video signal.

Abstract: A television receiver is arranged to selectively display either information from a broadcast television signal or information from an auxiliary video signal, in accordance with the position of a switching network to which the signals are capacitively coupled via respective capacitors. Similar black reference levels are established for the television and auxiliary signals by means of respective clamping circuits, including the coupling capacitors, which operate at different times but with respect to the same clamping reference voltage.

Abstract: A digital television receiver, which uses a comb filter to separate the luminance and chrominance components of composite video signals, includes an adaptive band-pass filter for processing the comb filtered chrominance signals. Comb filtered chrominance signals may include luminance vertical detail information at the relatively high frequencies also occupied by chrominance information. The adaptive band-pass filter is controlled to have a narrow bandwidth when significant amounts of this relatively high frequency vertical detail information are present and to have a wide bandwidth otherwise. Consequently, the bandwidth of the chrominance signal provided by this filter is restricted only when it is necessary to prevent distortion, and vertical detail is added to the luminance signal only when it is not likely to be contaminated with chrominance information.

Abstract: A motion detector for detecting interimage motion represented by composite video signals analyzes both the chrominance and luminance components for image motion. Interimage motion represented by the luminance component is determined from interimage signal differences. The interimage signal differences are separated into high and low frequency spectra corresponding to fine and coarse luminance image detail. Selected signal differences from the low frequency spectrum are summed and threshold detected to determine motion in the coarse image detail. The high frequency spectrum of the sample differences are applied to parallel summing circuits which sum different combinations of sample differences in order to discriminate motion signals from non-moving chrominance transitions. The detection signals from the high and low frequency motion detectors are combined to produce a luminance motion signal.

Abstract: One-bit stream of clocked control information is applied to the input of delay means, having a succession of signal takeoff points, with the delay between successive takeoff points being the same (e.g., twice a period at the clocking frequency, f.sub.CL). Each takeoff point is linked to a respectively different input of an "and" gate. The "and" gate output is coupled to one input of a succession of two-input "or" gates, with the other input of each of said "or" gates coupled to the output of an associated one of a plurality of delay devices, each of the latter imparting the same delay (e.g., corresponding to a period of f.sub.CL). The output of the last of the succession of "or" gates is coupled to a control signal output terminal. The output of each of the remainder of the succession is coupled to the other input of the next succeeding "or" gate in the succession.

Abstract: A system for detecting overload conditions of a chrominance signal in which the chrominance signal is compared to a predetermined maximum desired amplitude value. Occurrences of the chrominance signal exceeding the predetermined amplitude are considered to be overload conditions only if the duration of the particular occurrence continues for an interval determined by the noise content of the chrominance signal. The average value of the chrominance signal over the internal is calculated to represent the overload signal.

Abstract: In a color television receiver, color reference oscillations, developed by a VCO under AFPC loop control, are supplied to a variable phase shifter. A phase detector, responsive to the phase shifter output and to the burst component of received color television signals, develops a control voltage indicative of the phase relationship therebetween at its output terminal. Application of the control voltage to a control voltage input terminal of the phase shifter completes a servo control loop for maintaining the phase of the shifter's output in a predetermined relationship with the burst phase. A manual hue control potentiometer has an adjustable tap connected to the phase detector output terminal in such manner that tap adjustment alters voltage at control voltage input terminal while concomitantly altering servo loop gain.

Abstract: An adaptive filtering system is disclosed. The system is used in a digital television receiver to extract low frequency vertical detail information from a comb filtered chrominance signal. This system provides wide bandwidth vertical detail information when the amplitude of the chrominance component of the composite video signal is low and narrower bandwidth vertical detail signals as the amplitude of the chrominance component increases. Adaptive filtering is accomplished by passing the comb filtered chrominance signal through a first low-pass filter, developing two reduced amplitude replicas of the filtered signal which are mutually supplementary. The ratio of the amplitudes of these two replicas is variable with a control signal. One replica is passed through a second low-pass filter and combined with the other replica to produce a vertical detail signal.

Abstract: In a chrominance signal demodulating system a locally regenerated chrominance subcarrier signal is phase shifted to produce R-Y, G-Y and B-Y phase subcarrier signals, which are applied to respective color difference signal demodulators together with the chrominance signal to be demodulated for producing demodulated R-Y, G-Y and B-Y color image difference signals. The subcarrier signal is at the "I" phase and is processed by an automatic flesh tone correction network responsive to chrominance signal phases in the vicinity of I phase.