Abstract: A dynamic random access memory arrangement for storing digital television signal data under control of a system clock signal CK and input address signals A0 to A17 associated with the data, has a dynamic random access memory having a data input and a data output for the data, and an address input for the input address signals, the dynamic random access memory being controlled by a write enable signal WE, a row address strobe signal RAS and a column address strobe signal CAS, and a logic circuit is provided to derive the signals WE, RAS and CAS from the system clock signal CK with respective timings each determined by a leading edge of a pulse of the system clock signal CK and delay devices.

Abstract: A television signal processing apparatus comprises a source of system television synchronizing signals, an analog-to-digital converter for converting an input television signal to digital form, a digital-to-analog converter for converting the digital signal back to analog form, a plurality of digital television signal processors arranged in series between the analog-to-digital converter and the digital-to-analog converter, at least one of the signal processors being capable of frame synchronizing the digital television signal in dependence on a frame pulse supplied to the signal processor, and means associated with the digital-to-analog converter for producing a frame pulse and for feeding the frame pulse back to each of the signal processors, or at least to a signal processor capable of frame synchronizing the digital television signal and for synchronizing the produced frame pulse relative to the system television synchronizing signals.

Abstract: Digital televison signal processing apparatus comprise a field store arrangement comprising first, second and third field stores each capable of storing digital signals relating to one field of a televison signal, means to supply a digital television signal at a variable rate to the field store arrangement, a write control device to supply the digital television signal to at least one of the field stores for writing therein, depending on the rate of supply of the digital television signal, and a read control device to read the stored digital television signal from at least one of the field stores depending on the rate of supply of the television signal, no field store being written into at the same time that it is read from, and the write control device rotating the writing and reading around the field stores cyclically.

Abstract: A method of concealing errors in a digital television signal formed by a plurality of sample signals corresponding respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of such lines, the method comprising, in respect of each sample signal which is in error, selecting from a plurality of algorithms a preferred algorithm for correcting the error sample signal, calculating a corrected value of the error sample signal using the preferred algorithm, and substituting the corrected sample signal for the error sample signal so as to conceal the error. Where any algorithm involves the use of an error sample, that algorithm is not used. The algorithms may be twelve in number and use sample values located along four directions of the television picture to predict the known sample values at sample positions adjacent to the position of the error sample signal, the direction corresponding to the algorithm giving the best result being selected.

Abstract: A television standards converter comprises three field stores and four 4-line stores for receiving an input digital television signal of one standard and deriving therefrom arrays of sixteen lines, each array consisting of four successive lines from each of four successive fields of the input television signal, a weighting coefficient store for storing sets of sixteen weighting coefficients, respective sets corresponding to positions both spatial and temporal of respective lines of an output digital television signal of a different standard, relative to the sixteen lines of the input television signal, two interpolation filters for deriving line-by-line the output television signal by multiplying corresponding sample values from each of the sixteen lines of the input television signal by a respective weighting coefficient in a set of weighting coefficients and summing the resulting products to form an interpolated sample value, and four output field stores for receiving and storing the derived lines of the ou

Abstract: A method of correcting errors in a digital television signal comprises forming the data words of the television signal into correction units each of which comprises a plurality of the data words and a parity word formed therefrom, and recording and subsequently reproducing on a digital video tape recorder the correction units. On slow motion reproduction from the digital video tape recorder a syndrome generator derives a syndrome from the data words and the respective parity word of each reproduced correction unit. An error counter counts the number of valid words in each reproduced correction unit. If this count is one less than the total number of words in the correction unit, the syndrome is used to correct the data word which is in error, and if the count is equal to the total number of words in the reproduced correction unit and the syndrome is not equal to zero, each of the data words in the reproduced correction unit is flagged as being in error.

Abstract: Digital television apparatus comprises a field store arrangement comprising first, second and third field stores each capable of storing digital signals relating to one field of a television signal, circuit to supply a digital television signal at a variable rate to the field store arrangement, a write control device to supply the digital television signal to one or to two of the field stores for writing therein, depending on the rate of supply of the digital television signal, and a read control device to read the stored digital television signal from one or from two of the field stores, depending on the rate of supply of the television signal, no field store being written into at the same time that it is read from, and the write control device rotating the writing and reading around the field stores cyclically.

Abstract: A method of concealing errors in a composite PAL or NTSC digital television signal formed of sample signals corresponding respectively to sample positions along horizontal scan lines of a television picture made up of a plurality of such horizontal lines, comprises, in respect of each sample signal the steps of, using a first algorithm to calculate a first expected value of the sample signal, the first algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal, using a second algorithm to calculate a second expected value of the sample signal, the second algorithm using actual values of adjacent sample signals in the same horizontal line as the sample signal and actual values of adjacent sample signals in the horizontal lines preceding and following the horizontal line of the sample signal, continuously monitoring which of the first and second algorithms gives expected values closer to the actual values, and on occurrence of an error sample signal using the algor