Rca Inc.

Robert A Wargo

Leopold A Harwood

Chandrakant Bhailalbhai Patel

Dalton H Pritchard

Stuart S Perlman

Michael S Chartier

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.

Motion adaptive television signal processing system

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.

Vertical detail information restoration circuit

A hanging dot detector for a video signal processor including a comb filter is disclosed. The respective phases of the signals in the band of frequencies normally containing color representative information of both the comb filtered chrominance and luminance signals are detected. The magnitude of the changes of the respective comb filtered luminance and chrominance phase angle signals over a given time period are compared. A control signal is generated in response to the comparison of the changes over the period of time of the respective phases. A signal coupling unit couples the comb filtered luminance signal to the luminance processing channel. In response to the control signal, the signal coupling means alters the frequency composition of the comb filtered luminance signal so as to eliminate the color representative information. A further embodiment is disclosed to process a complementary-color vertical transition condition.

Magnitude independent hanging dot detector

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.

Digital pulse width detector

Clocked control signals are applied from a source to the input of delay means having a plurality of successive signal takeoff points, with the delay between successive ones of said takeoff points being the same (e.g., a period at the signal clocking frequency, f.sub.CL). An 'and' gate is provided with a plurality of inputs equal in number to the plurality of takeoff points. Each takeoff point is linked by a signal path to a respectively different one of the 'and' gate inputs. A succession of two-input 'or' gates is provided, with one input of each 'or' gate coupled to receive the output of the 'and' gate. The last of the succession of 'or' gates is coupled to a control signal output terminal. The output of each of the remainder of said succession is coupled via a respectively different one of a plurality of similar delay devices to the other input of the next succeeding one of said succession of 'or' gates. Each of the delay devices imparts a delay equal to a period at f.sub.CL. The other input of the first of said succession of 'or' gates is coupled to directly receive the control signal source output.

Duration-sensitive digital signal stretcher

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.

Digital chroma overload system

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. The embodiment of the system that is disclosed includes means for developing a control signal that is proportional to the instantaneous amplitude of the chrominance component of the composite video signal.

Signal filtering system having adaptively cascaded filter stages for

A peaking circuit for use in a digital video signal processing system includes a digital peak detector which produces a peak magnitude whenever the slope of the video signal changes polarity. The peak magnitudes, and the absences of peaks are summed in an accumulator over a field period. The accumulated peaks are applied to a gain calculating circuit which develops a peaking control signal having three regimes. For low valued accumulated peaks the gain or peaking control signal is constant and relatively large. For high valued accumulated peaks the gain is constant and negative. In between the gain is in inverse porportion to the value of the accumulated peaks.

Video signal auto peaking circuitry

An automatic color burst magnitude control (ACC) for a digital television receiver is compatible with and is unaffected by variation of the phase of the color subcarrier signal introduced in demodulating the color subcarrier to effect control of tint. ACC is effectuated by digital gain control for scaling the digital words representing the sampled magnitudes of the color subcarrier burst signal. Quadrature demodulation of the color subcarrier signal produces color signal digital words I and Q which are each sampled and latched during the color subcarrier burst. The averages of the sampled I and Q digital words are applied as respective portions of the address of a read only memory (ROM). The ROM provides error words indicating whether the chroma burst amplitude is too large or too small. A control device responds to the error word to scale the color subcarrier digital words, and therefore scale the chroma burst amplitude to a predetermined magnitude.

Automatic color burst magnitude control for a digital television receiver

A microprocessor is provided in a television receiver which is responsive to a clock signal phase locked to a recurrent signal component of a composite video signal, such as a horizontal line rate signal component. The clock signal frequency is chosen to be an integer multiple of the recurrent signal component and to enable the microprocessor to execute an integer number of uniform instruction cycles during an integer number of periods of the recurrent signal component. The execution of the instruction cycles is brought into a real time phase alignment with the recurrent signal component by causing the microprocessor to execute an instruction during a time interval which is greater than the time required to execute one of the uniform insturction cycles. The phase of subsequently executed uniform instruction cycles is shifted in this manner until signal sampling indicates that the desired phase relationship has been achieved.

Method and apparatus for operating a microprocessor in synchronism with

A method and apparatus are presented for detecting the presence of ghost signal contamination of a video signal by examining the picture information interval of the video signal. A baseband video signal is detected and examined to detect signal transitions. Transitions of the main video signal of a given polarity will be followed by corresponding transitions of a ghost signal. The time intervals between ones of the transitions are measured and stored. If a ghost signal is present, the time interval between corresponding ghost and signal transitions will occur more frequently than the relatively random time intervals between transitions of the main signal and the ghost signal considered separately. By correlating the time interval measurements, the recurring time interval between corresponding main and ghost signal transitions can be identified. This information may then be used to adjust the delay of a delay line in a ghost cancellation system.

Television ghost signal detection during the video information interval

Apparatus is provided which is responsive to a video signal for producing a position-modulated pulse train which is representative of the occurrence of transitions of the video signal. A transversal filter is responsive to the video signal and produces a differentiated replica of the video signal over a given band of frequencies. The output of the transversal filter contains transitional information of the video signal occupying a range of frequencies which is to be analyzed. Information representing transitions of positive, negative, or both polarities is then compared to a given threshold value. Signal transitions exceeding the threshold are converted to pulses, thereby producing a train of pulses representing significant transitions of a desired polarity or polarities. The times of occurrence of the pulses are then analyzed to generate a control signal for controlling a given characteristic of the video signal during processing.

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Ringoes, NJ, United States of America

Robert A Wargo