Quantel Limited

John Albert Coffey

Anthony Donald Stalley

A method of storing digital information comprising applying the information in the form of coded pulses to an input of at least one register by means of clock pulses and shifting the information within the register by additional clock pulses between writing in and reading out the information. The number of additional pulses applied is equal to the difference between the total register length and the number of clock pulses used to enter the coded pulses, whereby the information within the register is available to be read out on application of read out pulses to the register.

Digital shift registers for video storage

A time base corrector for retiming the chrominance and luminance components of a non-phased television picture signal from a video tape recorder to local reference syncs. The time base corrector comprises digital storage means and an analogue-to-digital converter connected to an input of the storage means. A digital-to-analogue converter is connected to the output of the storage means. 'Read' clock pulse generating means are connected with the digital-to-analogue converter and the storage means to trigger the same. A first phase comparator means is operative to compare local horizontal reference signals with horizontal pulses from a divider connected to the 'Read' clock pulse means for controlling the output frequency of the same. Horizontal synchronizing pulse addition means are connected with the output of the digital-to-analogue converter for receiving the analogue signal from the digital-to-analogue converter and imparting thereto a horizontal synchronizing pulse in exact time relationship with the line frequency. Heterodyning means are connected between the input to the corrector and the analogue-to-digital converter. A second phase comparator means is operative to compare the color burst output of the digital-to-analogue converter with a local sub carrier reference signal and to control the heterodyning means. The heterodyning means imparts to said analogue-to-digital converter a chrominace component signal having a frequency controlled with reference both to the off tape horizontal synchronizing pulses and to the required sub carrier reference frequency.

Time base corrector

An input oscillator for use in a digital time base corrector comprising a triggered oscillator circuit and a variable period delay device having a first input for receiving the synchronizing pulse and for producing an output pulse whose back edge coincides approximately in time with the center of the filtered colour burst. A select burst transition device has an input connected to the delay device and an output for triggering the oscillator circuit. A window circuit has an output connected to a second input of the delay device. A pulse former is provided controlled from the trailing edge of the output of the delay device. The bistable window circuit effects change of the delay period of the delay device when the output of the pulse former coincides in the window circuit with a burst transition whereby the trailing edge of the output of the delay device is made to occur between burst transitions.

Input oscillators for time base correctors

The television digital time base corrector comprises an analogue to digital converter for receiving a video analogue signal, a store for receiving the successive line information in digital form from the output of the analogue to digital converter, a digital to analogue converter for receiving the stored signal, a read/write control circuit for writing the digital information into said store, an input oscillator for determining the rate of conversion of the analogue signal and the rate of writing the store, and an output oscillator for controlling the rate of reading out of the digital information from the store and the rate of conversion of the digital information in the store. The input oscillator is in the form of a triggered oscillator which is switched on and off in timed relationship with the video sync pulse and/or sub-carrier color burst. The oscillator thus commences its pulse generation at a time which is directly related to the timing of the sync pulse. The oscillator is of a fixed frequency and produces a series of pulses sufficient to allow all the incoming video information in one line to be converted and then stops oscillating. The oscillator is retriggered by the next start pulse derived from the incoming sync pulse information.

Digital time base correctors for television equipment

The apparatus for comparing clock phase identification signals in a time base corrector so as to control the Writing and Reading of information into and out of storage means therein, the storage means including a plurality of stores for storing sequential line information. The apparatus includes means for deriving in-phase and anti-phase 'Write' clock phase identification signals from line frequency sync signals. Selector means select one of the in-phase or anti-phase signals and first latch means receive the selected one of the signals. Means are provided for simultaneously deriving a 'Read' clock phase identification signal at a frequency which is half the line frequency from a sub-carrier reference signal. Second latch means receive the Read clock phase identification signal and comparator means compare the output signals from the first and second latch means to produce a Write clock phase identification control pulse so as to select the other of the in-phase and anti-phase Write clock phase identification signals in the selector means when the states of the signals applied to the comparator means are dissimilar.

Sampling phase identification apparatus

The drop out compensation system comprising input means for accepting a colour or monochrome picture information signal, output means, a drop out compensating signal generator, switch means for effecting connection of said input means to said compensating signal generator and for effecting connection between said compensating signal generator and said output means, and a drop out detector for effecting switching of said switch means, said compensating signal generator including delay means for providing a delayed output signal of the information signal entering the delay means, adder means for summing the information arriving simultaneously at the delay means and said delayed output, means for reducing the level of the signal from the compensating signal generator so that the low frequency luminance level of said resulting compensating signal at said output means has a value the same as that in the colour picture information signal at the input means, and storage means for effecting a delay within the compensating signal generator equal to at least one scanning line time. The resulting compensating signal at said output means has the correct luminance and hue values, but with a reduced saturation value. The compensating signal on the occurrence of a drop out is fed into the picture line being scanned at the correct time and in the correct phase relationship.

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Newbury, United Kingdom

John Albert Coffey