Abstract: A switcher using shared processors has an input matrix with a plurality of inputs to which a corresponding plurality of sources may be coupled. One or more of the sources may provide compressed data. The input matrix routes selected ones of the sources to a plurality of outputs which is less in number than the number of inputs, the routing being determined by a tally output. A pool of processors, such as compression decoders, color correctors or the like, are coupled to the outputs of the input matrix as needed for processing those sources that require such processing to provide processed data. The outputs of the processors provide processed data to a conventional switcher that combines the selected processed data to provide a program output. The conventional switcher also provides the tally output.

Abstract: A constant luminance corrector for a television system determines brightness information that is discarded in the chrominance channels of an encoder, and adds it to the luminance channel of the encoder. Gamma-corrected luminance and chrominance component signals from a video source, such as a video camera, video tape recorder or the like, are input to the encoder which outputs an encoded luminance component signal and an encoded chrominance component signal that are combined to form a composite signal. The gamma-corrected component signals also are input to a luminance predictor circuit, or alternatively in lieu of the gamma-corrected chrominance component signals a coded chrominance signal and a discarded chrominance signal from the encoder may be input to the luminance predictor circuit. Likewise the encoded luminance component signal may be input to the luminance predictor circuit in lieu of the gamma-corrected luminance component signal.

Abstract: A decoder using an adaptive non-separable digital filter has a correlation control circuit that generates from a composite video signal a set of filter coefficients for the non-separable digital filter. The filter coefficients are a function of a correlation angle for the image represented by the composite video signal. The non-separable digital filter, using the set of filter coefficients determined by the correlation angle, separates the composite video signal into its luminance and chrominance components. The non-separable digital filter may be approximated by a set of discrete filters having a common input, with each output being multiplied by a correlation factor, the correlation factors being the filter coefficients. The resulting multiplicands are summed to produce the separated luminance and chrominance components.

Abstract: A chrominance transition corrector for restoring chrominance transitions after they have been degraded by a limited bandwidth channel converts input luminance and chrominance components, which represent a video image, from the time to the frequency domain. Correction coefficients are determined from a low frequency portion of the converted luminance component and the converted chrominance components. Corrected high frequency portions of the chrominance components are generated from the correction coefficients and a high frequency portion of the converted luminance component. The resulting converted and corrected high frequency portion of the chrominance components are then converted back to the time domain to produce chrominance output components, the chrominance transitions having been corrected.

Abstract: A test and measurement system for a cable television (CATV) system measures parameters of a broadband video signal at the headend of the CATV system. Characteristic data is generated from the measured parameters and combined with the broadband video signal for transmission over the distribution system of the CATV system. Also out of service video channels are detected at the headend, and a test sequence is combined with the broadband video signal for each out of service channel. In the field a receiver is coupled to a point in the distribution system to measure the parameters of the broadband video signal at that point. The parameters measured at the receiver are compared with the parameters measured at the headend, as derived from the transmitted characteristic data. The differences between the two sets of parameters are displayed to present a display of the characteristics of the CATV system, with out of service channels represented by the test sequences.

Abstract: A mulltiformat television switcher adds an up-converter, a down-converter and an auxiliary selector to an existing master control switcher to provide the ability to provide both a standard format output video signal (NTSC, PAL, SECAM, etc.) and a HDTV format output video signal corresponding to a selected input video signal from a plurality of input video sources which include both standard and HDTV formats. The master control switcher provides a selected one of the standard format input video signals to a standard format input of the auxiliary selector and to the up-converter, and provides a control signal to the auxiliary selector. The HDTV format input video signals and the HDTV format video signal output from the up-converter are applied to HDTV inputs of the auxiliary selector.

Abstract: A three-dimensional test signal for a video codec is generated by injecting a conventional foreground test signal at a predetermined location as a foreground component within a background test signal as a background component, the background component having a variable complexity. The three-dimensional test signal is input to the video codec and the output of the video codec is measured using conventional measurement instruments. The background component may be a pseudo-random noise signal, a zone plate signal or other variable complexity-type signal, with the foreground component occurring at greater intervals than the neighboring pixels used by the codec compression algorithm. The conventional measurement instruments display only the foreground component with distortions in the video codec caused by the complexity of the background component appearing in the display.

Abstract: A Moire measurement system uses spectral analysis to characterize the moire effect on a television signal introduced by a particular device. A known television signal is processed by the particular device, such as a video tape recorder, and the output is input to a spectral analyzer, such a windowed fast Fourier transform. The spectral analyzer includes input gating to select a portion of the known television signal from the particular device. The frequency of the desired component of the known television signal, together with the rms values of all the other components introduced by the Moire effect, give the X- and Y-coordinates of a point on an output display. The window is moved across the test signal, giving a family of X- and Y-coordinates that characterize the Moire effect as a function of amplitude, frequency or video pedestal. The Moire characteristics of the particular device then may be used to correct the output of the particular device.

Abstract: A television signal generator which is fully digital has digital data stored in PROMs, one PROM for each component of the desired encoded television signal corresponding to luminance data and chrominance data. A system clock allows a signal address generator to fetch data from the PROMs. The chrominance data from the PROMs is mixed with appropriate digital representations of a sinusoidal function and a phase offset and is added to the luminance data. The combined digital signal is converted to analog, filtered and output as the desired encoded television signal.

Abstract: A television signal generator which is fully digital has digital data stored in PROMs, one PROM for each component of the desired encoded television signal corresponding to luminance data and chrominance data. A system clock allows a signal address generator to fetch data from the PROMs. The chrominance data from the PROMs is mixed with appropriate digital representations of a sinusoidal function and a phase offset and is added to the luminance data. The combined digital signal is converted to analog, filtered and output as the desired encoded television signal.

Abstract: A nonvolatile memory protection system for a microprocessor system having a common address bus, to which a nonvolatile memory is connected, interposes a controller connected to the common address bus between the commands generated by the microprocessor and the nonvolatile memory. The controller generates valid commands for the nonvolatile memory upon receiving a predetermined sequence of commands from the microprocessor, disabling the nonvolatile memory in the absence of valid commands. A power protect circuit connected between the microprocessor system power supply and the nonvolatile memory provides a disable signal to the nonvolatile memory during power up and power down of the microprocessor system.

Abstract: An analog to digital converter with second order error correction provides a more accurate digital output code for a high frequency input analog signal. A slope of the input signal is determined from the digital output code of a quantizer, and the slope is used to provide a correction value that is a function of the slope. The correction value may also be a function of a level range of the quantizer. The correction value is added to the digital output code to produce a corrected digital output code.

Abstract: A component color bars alignment test signal for calibrating a component picture monitor having as inputs a luminance component and two orthogonal chrominance components has a standard set of color bars and a contiguous chroma set of color bars. The chroma set of color bars is matched to the standard set so that a color that is sensitive to the adjustment of one of the chrominance components is adjacent to a color that is relatively insensitive to the adjustment of that one chrominance component. A gun of the component picture monitor is turned off and one chrominance component is adjusted until the appropriate pair of standard set and chroma set color bars are indistinguishable.

Abstract: An autocalibrated multistage analog to digital converter precisely maintains appropriate error correction levels for each stage during operation of the converter to minimize quantization errors. An error signal is derived from the digital output of the converter based upon the slope of the input analog signal, determined either explicitly via hardware or implicitly via software, and an overflow/underflow condition. The error signal is fed back to a calibration control circuit to generate individual error correction levels for various variable correction devices within the analog to digital converter, such as a variable analog delay device. The variations from nominal established at calibration that are due to age, temperature or other environmental factors generate the error signal that varies from a nominal value and is fed back to alter the various error correction levels to minimize the error variation.

Abstract: A recursive noise reduction filter for video components reduces the noise bandwidth of a signal without degrading the signal spectrum. Demodulated chrominance or peak detected chrominance from a video signal output by a video system in reponse to a video test signal is input to the recursive noise reduction filter which acts as a comb filter to suppress noise significantly at frequencies other than harmonics of the horizontal line rate. The signal is scaled by a first attenuator having a scaling factor of (1-a), where (a) is less than one, and input to a summing circuit. Also input to the summing circuit is a delayed signal from a prior horizontal line scaled by the scaling factor (a). The output of the summing circuit is a filtered output signal. The signal is sampled only during horizontal lines that have the video test signal and is stored for subsequent accumulation with other horizontal lines also having the video test signal.

Abstract: The relative gain and/or delay of two signal transmission channels may be measured by impressing on each channel a repetitive signal comprising a burst packet. The burst packets of the signals applied to the channels are of constant, but different, frequencies, and their amplitudes are related in predetermined manner. The two burst packets are timed to have a predetermined phase relationship at a selected time during the packets. The output signals of the two channels are additively combined, and a determination is made as to at least one of (a) the amplitude of the combined signal at a turning point in the amplitude of the signal envelope and (b) the time relative to the selected time at which a turning point in the amplitude of the signal envelope occurs.

Abstract: A heterodyne color signal recognition circuit generates an error signal for each horizontal line of an input video signal for which the phase relationship of the horizontal sync pulse and color subcarrier burst exceeds a given phase relationship by a predetermined tolerance. The error signals are summed over a video field to produce a preliminary non-direct color signal for the video field. Preliminary non-direct color signals for successive video fields are digitally filtered to generate a non-direct color signal indicative of a heterodyne color signal source, the non-direct color signal being used to automatically switch in a time base corrector between the input video signal and further video processing.

Abstract: A digital phase-locked loop maintains a clock signal in a predetermined phase and frequency relationship with an input video signal having a repeating signal element, such as horizontal sync pulses and/or color burst signals. The clock signal is generated by a voltage controlled oscillator, the frequency of which depends on an input digital control signal. The input video signal is sampled by an analog-to-digital converter at the clock signal frequency to generate a succession of digital words representing the amplitudes of successive samples. A portion of the successive digital words is stored in a memory, the access to which is controlled so that the samples representing the repeating signal element are stored and then read out for processing by a microprocessor.

Abstract: Apparatus for providing an indication that a color represented by a color video signal having a luminance component Y and two color difference components R-Y, B-Y is validly reproducible on an RGB color display device. A resistive matrix converts the Y, R-Y, B-Y components of the color video signal to three primary color components R, G, B. Comparators compare the amplitude of each primary color component with predetermined minimum and maximum values, and an OR-gate produces a gamut error signal if the amplitude of one or more of the primary color components is outside the range established by the corresponding predetermined minimum and maximum values. The gamut error signal is applied to a display modifier which modifies the luminance and color difference components to produce a visually distinct effect on a waveform or display monitor. Alternatively, the gamut error signal may be applied to, for example, a color shutter incorporated in the waveform or display monitor to modify the color of the display.

Abstract: A current source utilizes N+1 transistors to produce N output currents of magnitudes proportional to a variable reference current. Each transistor emitter is resistively coupled to a common potential and each transistor base is driven by a common control voltage, offset by a separately adjustable amount for each transistor. The control voltage is produced by an amplifier having a grounded inverting input and a non-inverting input coupled to the collector of a first of the transistors and resistively coupled to a variable reference voltage source. The reference voltage source is adjusted to produce a desired reference current in the collector of the first transistor and the magnitude ratio of an output current produced in the collector of each of the N remaining transistors to the reference current is controlled by adjusting the ratio of emitter resistance of the first transistor to the emitter resistance of the remanining transistors.