Filter and system incorporating the filter for processing discrete samples of composite signals

A system for compensation of dropouts in a digitally encoded composite color television signal comprising a luminance component and a chrominance component, said chrominance component including a color subcarrier signal of a known frequency, the encoded color televsion signal comprising consecutive data corresponding to distinct amplitude values thereof, said distinct amplitude values being provided at a clock signal frequency equal to a rational number multiple of said subcarrier signal frequency, said rational number multiple frequency being greater than twice the frequency of the highest frequency component of the composite signal, and said clock signal being frequency and phase-locked to said subcarrier signal, comprising in combination:

• a signal averaging means coupled to receive said consecutive data at said clock signal frequency, to store said data for a predetermined number of clock signal cycles, and to successively provide an average value output signal by arithmetically combining a given number of consecutive data defining a zero average value of said subcarrier signal component, said average value output signal being representative of a separated luminance component;
• a signal differencing means having a first input coupled to receive said consecutive data and a second input coupled to receive said output signal of said signal averaging means for providing a difference signal representative of a separated chrominance component;
• a first delay means coupled to receive said difference signal provided by said differencing means for providing a delay substantially equal to one horizontal line period of the color television signal.
• a signal recombining means having a first input coupled to receive an output signal of said first delay means and a second input coupled to receive an output signal of said signal averaging means, for combining said respectively received signals into a composite color television signal;
• a second delay means for providing a substantially one horizontal line delay of both said luminance and chrominance signal components of the color television signal;
• and
• a switching means having a first input coupled to receive said color television signal and a second input coupled to receive said recombined and delayed color television signal, said switching means responsive to a control signal to selectively provide an output color television signal from one of the signals coupled to its first and second inputs, respectively.

In a system for providing dropout compensation for a digitally encoded composite color television signal comprising a luminance component and a chrominance component, said chrominance component including a color subcarrier signal of a frequency equal to a non-integral rational number multiple of the horizontal line frequency, said subcarrier signal having a known predetermined phase during each consecutive horizontal line interval of said color television signal, said color television signal being encoded into consecutive digital data by sampling at a frequency equal to an even integral multiple of the subcarrier component frequency, said even integral multiple frequency being greater than twice the frequency of the highest frequency component of the composite signal, the combination comprising:

• a signal averaging means coupled to receive said consecutive digital data and to store said date for a predetermined number of clock cycles to successively provide an average value output signal by arithmetically combining a given number selected ones of consecutive data defining a zero average value of said subcarrier component, said average value output signal being representative of a separated luminance component;
• a signal differencing means having a first input coupled to receive said consecutive data and a second input coupled to receive said output signal of said signal averaging means for providing a difference signal representative of a separated chrominance component;
• a phase adjusting means coupled to receive said difference signal to adjust its phase to correspond to said known predetermined subcarrier signal phase during the consecutive horizontal line intervals during which the dropout compensation is provided;
• a signal recombining means having a first input coupled to receive said phase-adjusted difference signal and a second input coupled to receive the output signal of said signal averaging means for recombining said respectively received signals into a composite color television signal;
• a delay means coupled to provide a substantially one horizontal line delay of both said luminance and chrominance signal components of said color television signal;
• and
• a switching means having a first input coupled to receive said color television signal and a second input coupled to receive said recombined and delayed color television signal, said switching means responsive to a control signal to selectively provide an output signal corresponding to one of the signals coupled to its first and second inputs, respectively.

A digital color television signal dropout compensator suitable for use in NTSC, PAL or PAL-M systems, said signal represented by consecutive data obtained by sampling at a clock signal frequency equal to an integral multiple of the color subcarrier signal frequency, said integral multiple frequency being greater than twice the frequency of the highest frequency component of the color television signal comprising in combination:

• a register means for receiving and storing said consecutive data in synchronism with said clock signal frequency;
• a signal averaging means coupled to said register means for successively providing an average data value by arithmetically combining an integral number of consecutive data defining an integral number of subcarrier cycles to obtain an output signal representative of a separated luminance component, said averaging means providing a circuit delay equal to a known number of clock cycles;
• a signal differencing means having a first input coupled to receive said consecutive data and a second input coupled to receive the output signal of said averaging means to provide a difference signal representative of a separated chrominance component, said differencing means providing a circuit delay equal to a known number of clock cycles;
• a first delay means coupled between an input of said signal averaging means and said first input of the differencing means to provide a delay equal to that provided by the signal averaging means;
• a second delay means coupled to receive said difference signal for providing a delay equal to a number of clock cycles defining one horizontal line period of the color television signal less the circuit delay provided by said differencing means;
• a signal combining means having a first input coupled to receive an output signal of said second delay means and a second input coupled to receive an output signal of said signal averaging means, for recombining said respectively received signals into a composite color television signal, said combining means providing a circuit delay equal to a known number of clock cycles;
• a third delay means coupled to provide a delay of both said luminance and chrominance component of said color television signal, said delay corresponding to a number of clock cycles defining one horizontal line period less combined circuit delays provided by said averaging and combining means, respectively;
• and
• a switching means having a first input coupled to receive said color television signal and a second input coupled to receive said recombined and delayed color television signal, said switching means responsive to a control signal to selectively provide an output color television signal from one of the signals coupled to its first and second inputs, respectively.

A digital color television signal dropout compensator circuit suitable for use in NTSC, PAL, or PAL-M, systems, where the television signal is encoded into consecutive digital data by sampling at a frequency equal to three times the color subcarrier signal frequency, comprising:

• means coupled to receive said consecutive data and to provide an average value output signal by continuously combining three consecutive data defining one subcarrier signal cycle, said average output signal corresponding to a separated luminance component;
• means coupled to provide a difference signal of said color television signal and said average value output signal, said difference signal corresponding to a separated chrominance component;
• means coupled to delay said difference signal by substantially one horizontal line period of the color television signal to provide a one line delayed chrominance component;
• means coupled to combine said average value output signal and said delayed difference signal into a composite color television signal form;
• means coupled to delay both the chrominance and luminance component of the color television signal processed by said circuit by substantially one horizontal line period to provide a dropout compensation signal having its luminance component delayed by one horizontal line period and its chrominance component by two horizontal line periods;
• and
• means having separate respective inputs coupled to receive said color television signal and said dropout compensation signal respectively, said means being responsive to a control signal to selectively provide an output signal corresponding to one of its input signals.

A digital color television dropout compensation circuit suitable for use in NTSC, PAL or PAL-M systems, wherein the television signal comprises a color subcarrier component having a known predetermined phase with respect to the beginning of each consecutive horizontal line interval and wherein the television signal is encoded into consecutive digital data by sampling at a frequency equal to four times the color subcarrier signal frequency, comprising:

• means coupled to receive said consecutive data and to provide a weighted average value output signal by continuously combining three alternate ones of five consecutive data with the first and fifth data weighted by a factor of one-half and the third data unweighted, respectively, said weighted average value output signal corresponding to a separated luminance component;
• means coupled to provide a difference signal of said color television signal and said weighted average value output signal, said difference signal corresponding to a separated chrominance component;
• means coupled to adjust said difference signal to have it phase corresponding to said known predetermined subcarrier signal phase with respect to the beginning of that horizontal line interval for which the dropout compensation is provided, to provide a phase-adjusted chrominance component;
• means coupled to combine said phase-adjusted difference signal and said weighted average value output signal into a composite color television signal form;
• means coupled to delay both the chrominance and luminance component of the color television signal processed by said circuit by substantially one horizontal line period to provide a dropout compensation signal;
• and
• means having separated respective inputs coupled to receive said color television signal and said dropout compensation signal, respectively, said means being responsive to a control signal to selectively provide an output signal corresponding to one of it input signals.

A digital comb filter circuit for eliminating selected periodic signal components from a digitally encoded composite signal, said selected components representing a basic periodic signal of a known frequency and higher and lower order frequency components thereof, said selected signal components being symmetrical with respect to a signal crossing axis, said encoded composite signal comprising consecutive digital representations corresponding to discrete amplitude values thereof provided at a frequency equal to a rational number multiple of said basic periodic signal frequency and in a frequency and phase-locked relationship to said basic period signal, said rational number multiple frequency being greater than twice the frequency of the highest frequency component of the composite signal, comprising in combination:

• a first means couppled to receive and store said consecutive digital representations of the composite signal;
• and
• a second means coupled to said first means to successively provide an average value output signal by arithmetically combining a given integral number of consecutive digital representations defining a zero average value of said basic periodic signal component in a time interval equal to an integral number of cycles of said basic periodic signal, a lowest order periodic signal component being eliminated by said comb filter having a frequency equal to the frequency of said discrete amplitude values divided by the number of consecutive digital representations taken for averaging .

In a system for processing a digitally encoded composite signal having a periodic signal component of a known frequency and symmetrical with respect to a signal crossing axis, said composite signal comprising consecutive digital representations corresponding to discrete amplitude values thereof provided at a frequency equal to a rational number multiple of said periodic signal frequency and in a frequency and phase-locked relationship thereto, said rational number multiple frequency being greater than twice the frequency of the highest frequency component of the composite signal, a combination comprising:

• a first means coupled to receive and store consecutive digital representations of said composite signal;
• a second means coupled to said first means to successively provide an average value output signal by arithmetically combining a given number of consecutive digital representations defining a zero average value of said periodic signal component, said average value output signal of said second means representing said digitally encoded composite signal from which said periodic signal component is eliminated;
• and
• a third means having a first input coupled to receive said output signal of said second means and a second input coupled to receive said consecutive digital representations of said composite signal to provide a difference signal representative of said periodic signal component.

A method of digitally separating the chrominance and luminance component of a digital composite color television signal represented by consecutive data obtained by sampling at a frequency equal to a rational multiple frequency of the color subcarrier component, utilizing a sampling signal frequency and phase-locked to the subcarrier signal, said rational number multiple frequency being greater than twice the frequency of the highest frequency component of the composite signal, comprising the steps of:

• receiving and storing the consecutive data in preparation for subsequent arithmetical combination thereof;
• arithmetically combining successively a given number of consecutive data which define a zero average value of the color subcarrier component to provide an average data value output signal representing the separated luminance component;
• and
• subtracting the obtained average data value output signal from said digital composite color television signal to obtain a difference signal representing the separated chrominance component.

A system for processing a digital signal representing a composite signal having recurrent intervals of similar information to replace deficient portions of the composite signal with similar information from different recurrent intervals, said composite signal including a signal component of a known frequency equal to a non-integral rational number multiple of the frequency of said recurrent intervals and having a known nominal phase during each recurrent interval, the digital signal comprising consecutive digital value representations at a frequency equal to a rational number multiple of said known frequency and in a frequency and phase locked relationship to said signal component, said rational number multiple frequency being greater than two times said known frequency, comprising:

• first means responsive to a clock signal in synchronism with said rational number multiple frequency for receiving at an input each of said consecutive digital value representations and arithmetically combining said each digital value representation with a selected number of other selected ones of said received digital value representations to generate in place of said each received digital value representation a further digital value representation of the average of the values of said arithmetically combined digital value representations that is productive of a zero average of a portion of said arithmetically combined digital value representation corresponding to said signal component of a known frequency;
• second means coupled to receive said consecutive digital value representations of said composite signal and said further digital value representation generated by said first means to provide a digital difference value representation of the difference between each received digital value representation of the difference between each received digital value representation and each further digital value representation generated in place of said each received digital value representation;
• third means coupled to receive said digital difference value representation for adjusting its phase to correspond to the nominal phase of the signal component during the recurrent interval to be replaced by a dropout compensation composite signal including said digital difference value representation;
• fourth means coupled to receive each phase-adjusted digital difference value representation and each further digital value representation to combine the received representations to form the dropout compensation composite signal at an output;
• fifth means coupled in circuit with said first, second, third and fourth means between said input and output for delaying the representations forming said dropout compensation composite signal for an interval substantially equal to the recurrent interval of said composite signal;
• and
• sixth means coupled to receive said digital signal and the delayed dropout compensation composite signal and responsive to a control signal indicative of the occurrence of deficient portions in the composite signal to selectively provide at an output one of said received signals, said sixth means responsive to said control signal to provide the delayed dropout compensation composite signal at said output when said control signal is indicative of the occurrence of a deficient portion and to provide said digital signal at said output in the absence of said control signal being indicative of the occurrence of a deficient portion.

A method of processing a digital signal representing a composite signal having a plurality of signal components one of which is of a known frequency, the digital signal comprising consecutive digital value representations at a frequency equal to a rational number multiple of said known frequency and in a frequency and phase locked relationship to said one signal component of a known frequency, said rational number multiple frequency being greater than two times said known frequency, the steps comprising:

• transmitting consecutive digital value representations through a digital signal transmission path at a rate corresponding to and synchronous with said rational number multiple frequency, said transmission path of a length equal to an interval defined by at least three consecutive digital value representations;
• combining each digital value representation transmitted through the digital value representation transmitted through the digital signal transmission path with a selected number of other selected ones of said digital value representations being transmitted through said digital signal transmission path to generate in place of said each digital value representation a further digital value representation of the summation of the values of said combined digital value representations that is productive of a zero summed value of a portion of said combined digital value representations corresponding to said signal component of a known frequency;
• and
• weighting each further digital value representation to obtain an output digital value representation of the average of the values represented by the combined digital value representations.