Abstract: Digital signal receivers for detecting BPSK modulation of a suppressed carrier transmitted through the same channel as an analog television signal are described, in which the detected BPSK is digitized with an oversampling analog-to-digital converter prior to digital comb filtering for separating the BPSK from interfering analog television signal remnants. This is done to get an increased number of bits resolution from a relatively inexpensive flash converter so that the BPSK, which is of relatively low amplitude compared to maximally interfering analog television signal remnants, is not overwhelmed by quantizing noise. The oversampling analog-to-digital converter can be of sigma-delta type.

Abstract: A video display apparatus convergence and correction arrangement includes a digital signal delay circuit which uses a sample interpolation technique to provide apparent signal delays corresponding to fractional parts of whole sample periods. Adjacent digital samples are combined using fractional coefficients that sum to unity. The selection of the fractional coefficients determines the size of the smallest delay increment. The number of whole sample delay periods as well as the initial fractional coefficients for a given horizontal scan line are provided by information that is stored in a memory device during assembly or alignment of the video display apparatus.

Abstract: A progressive scan video display apparatus incorporates beam landing error correction circuitry. Beam landing error correction may be accomplished prior or subsequent to video information interpolation and prior or subsequent to video information speedup. The correction circuits utilize sample interpolation techniques to provide accurate beam landing error correction for each of the red, green and blue video information signals.

Abstract: A chroma overload system includes an up/down counter to develop a chroma gain/attenuation signal. Overload conditions are detected and responsive thereto pulses are generated to cause the counter to decrease chroma gain. In the absence of overload conditions, a pulse generator conditions the up/down counter to increase chroma gain to a predetermined limit. ACC is incorporated by monitoring burst and establishing the counting range and thereby the range of gain developed by the up/down counter.

Abstract: A digital TV receiver is disclosed which displays the image for an auxiliary channel as an inset in the image for a main channel. The asynchronous composite video signals of the main and auxiliary channels are time division multiplexed, one line of auxiliary signal for every three lines of main signal. The chrominance and luminance components of the main channel signal are separated by an adaptive comb filter. A low-pass filter removes the luminance vertical detail components from the combed main channel chrominance and also separates the luminance components from the chrominance components for the auxiliary signal. These asynchronous time division mutliplexed chrominance signals are processed by circuitry which corrects the chrominance phase of each of the signals to be relative to a single reference phase and then separates the two quadrature modulated color difference signals. The auxiliary channel luminance and color difference signals are subsampled and stored in a memory for display as an inset.

Abstract: Circuitry corrects vertical beam landing errors for color cathode ray tubes. A digital delay circuit provides horizontal scan line video pixel information at its proper location to produce a distortion corrected raster. Accurate correction is provided by a combination of scan line offset between the input and output video signals and by sample interpolation techniques that effectively form derived pixels that have an apparent location of the derived pixel relative to the sample video pixels is determined by the selection of the interpolating coefficients.

Abstract: In a color television receiver in which video signals are processed in digital form, the rate at which the digital video samples are supplied to a digital-to-analog converter arrangement is varied in a predetermined manner to produce a display that is substantially free of raster distortion. The digital video samples are first entered into a digital store such as a FIFO and then read out of the FIFO by a selected one of four read clocks. The read clocks are of the same frequency but of different phase. By selecting different read clocks to apply to the digital store, the rate at which the store reads out the digital samples is varied.

Abstract: A digital signal processing apparatus includes a digital coring circuit removing samples of digital input signals in a range determined by a digital threshold level signal. The threshold level signal developed by a coring control device is controllable according to the results of comparing at least a portion of the digital input signals to a digital reference level. In a television receiver having digital signal processing circuitry, for example, the coring range is decreased as the luminance signal level increases towards a brighter picture level and is increased as the luminance signal level decreases towards a darker picture level.

Abstract: In a digital signal processing system, an analog-to-digital converter producing digital representations of an analog signal is dithered to increase its apparent quantizing resolution. Certain processing of the digital signals, however, can result in the loss of the dither information, because of either the form of digital filtering employed or the number of bits of the digital signals processed. To avoid the effects of such loss, the least significant bit of the digital signals is delayed and is applied to an analog output device to reintroduce a dither signal thereat having a magnitude substantially equivalent to that of the lost bit. The present invention is useful in processing digital television signals in a television receiver having a digital signal processing section.

Abstract: The quantizing resolution of an analog-to-digital converter is effectively enhanced for sinusoidal input signals by (a) sampling the signal at 90 degree intervals of the sinusoid; (b) establishing the input range of the converter to be less than the dynamic range of the signal but arranged so that at least three of four successive samples are true or correct values; (c) detecting the occurrence of saturated fourth sample values; (d) calculating correct values for saturated sample values from preceding samples; and (e) substituting calculated values for saturated incorrect values.

Abstract: A digital TV receiver having an analog-to-digital converter which generates digital representations of the analog signal asynchronously relative to the color burst reference, includes open loop circuitry for correcting the values of the chrominance component to comport with chrominance samples having a fixed phase relationship with burst. During the burst interval the angle of the chrominance phasor relative to the asynchronous sampling instants is compared with a fixed angular reference value to generate a correction factor for the respective line of video signal. The correction factor is thereafter combined with the chrominance samples to generate new chrominance samples having a desired phase relationship with the phase of the burst reference signal.

Abstract: A phase measuring arrangement for sampled signals changes the phase of the sampling signal in fine phase increments while comparing the magnitudes of the signal samples so produced to determine whether they have magnitudes within a given range of values. The range of values is indicative of a known phase angle. The number of magnitudes falling within the given range is indicative of the phase of the sampled signal relative to the known phase angle. Embodiments are disclosed in which such phase measuring arrangement is employed in a phase-locked loop useful for processing chrominance signals in a television receiver.

Abstract: A digital signal peaking apparatus combines input digital signals with filtered and scaled representations thereof to produce controllably peaked digital signals. A digital filter produces the relatively higher frequency components of the input digital signals which are controllably scaled by a digital multiplier in accordance with a multiplier coefficient. A control arrangement develops the multiplier coefficient having a value determined in accordance with the peak magnitude of the higher frequency components of the input digital signals relative to the value of a peaking control level signal.

Abstract: Apparatus providing a magnified picture display for a television receiver employs a reduced-size digital memory which stores only the digitized video signal components necessary to generate video signals to produce the magnified picture display. A simplified user-controlled picture positioning arrangement generates write and read addressing signals for the digital memory representative of both the picture area of the magnified picture display and of the normal picture display therein which is to be magnified. Writing of the digitized video signal components of the normal picture display into the digital memory is accomplished in "real time" whereas reading of the stored data from the memory and signal processing to develop interpolated digitized video signal components of the magnified picture is accomplished at a reduced processing rate on a line-by-line basis in between memory write cycles.

Abstract: A color TV receiver designed to digitally process I and Q color mixture signals incorporates chroma gain control, static tint control and autoflesh in the circuitry for converting the I and Q signals to (R-Y), (B-Y) and (G-Y) for R,G,B matrixing. The magnitude and angle of the vector sum of I and Q are first determined. The angles are then adjusted for static tint control and then applied to a ROM which is programmed to output angles adjusted for fleshtones. Angles from the autoflesh ROM are applied to a summing circuit which algebraically adds to the flesh corrected angle, angle values corresponding to the angular displacement between the I axes and the (R-Y), (B-Y) and (G-Y) axes. The angles produced by the summing circuit are applied to a look-up ROM which produces the cosine values of the applied angles.The magnitude signal is amplified by coefficients which relate the I and Q signals to (R-Y), (B-Y) and (G-Y) components and which coefficients may be amplified by a chroma gain signal.

Abstract: A sampled data filter for separating chrominance signal from digitized composite video sampled at a 4f.sub.sc rate produces filtered sampled data chrominance signal at one half the input sample rate. The input video signal occurring as a 4f.sub.sc +I, +Q, -I, -Q sample sequence is decimated in the filter so that only the filtered replicas of the +I and +Q samples are computed. This effectively doubles the computational time permitted the filter circuitry without substantially compromising signal content.

Abstract: Circuitry included in a TV receiver for enhancing the signal-to-noise ratio of the chrominance signal includes an adaptive linear phase, low pass filter which has its bandwidth controlled responsive to the upper frequency components of the current chrominance signal. A frequency analyzer coupled to the chrominance channel counts the number of chrominance signal excursions during predetermined periods to generate a number related to the maximum signal frequency during such periods. The number is applied to a decoder which generates address codes for application to a look up table which provides filter coefficients for altering the filter bandwidth in accordance with the current maximum signal frequency components.

Abstract: A comb filter arrangement operating at a reduced data rate is provided, which requires comparably fewer storage locations than previous arrangements. A digitized composite video signal of a given codeword rate is applied to a bandpass filter, which produces a filtered signal restricted to a portion of the passband of the composite video signal. The filtered signal is then subsampled at a rate which satisfies the Nyquist criterion for information of the restricted passband. Codewords, now at a reduced data rate, are applied to a one-H delay line, and delayed and undelayed signals are combined to produce a first comb-filtered signal. The first comb-filtered signal is then applied to an interpolator, which provides a sequence of codewords at the codeword rate of the original digitized composite video signal. This sequence of codewords is then combined with the codewords of the composite video signal to produce a second comb-filtered signal.

Abstract: A video disc player has two fields of buffer storage for implementing special effects. Video signal recovered from a disc record is directed into respective ones of the buffer stores for subsequent replay in particular sequences. A fixed memory device, containing a plurality of sequences of preprogrammed data words, each sequence defining a particular player function, controls the operable mode of the respective buffer storage devices. The preprogrammed sequences are addressed by a binary counter responsive to the vertical synchronization components of signal recovered from the disc record. Particular variable speed display options are effectuated by the repeated playback of selected TV fields and the omission of intervening fields.

Abstract: A desired output frequency can be generated by applying a corresponding digital phase step number to an accumulator to generate multiples of the number for application to a sine wave look-up table from which digital samples of the sine wave amplitude are obtained. The digital samples can be applied through a digital-to-analog converter to produce the desired output frequency in analog form. A time division multiplex system is disclosed in which a plurality of digital phase step numbers are used to generate an equal plurality of output frequencies. Each digital phase shift number may be altered in accordance with modulating signals so that each output frequency is frequency-shift keyed, and/or phase shift keyed, and/or on-off keyed.