Tektronix, Inc.

Triquint Semiconductor Corporation

Bruce J Penney

John C Reynolds

Dennis L Holmbo

Timothy W Slate

Stewart S Taylor

Daniel G Baker

Philip S Crosby

Michael S Overton

Douglas C Stevens

Michael D Nakamura

Robert W Parish

John D Polonio

Warren G Kafer

John Lewis

Patten A Emmons

William J Cooper

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. For sources that provide inter-frame compressed data, the conventional switcher provides a preview output and a preview tally output so that the necessary time delay for decompressing such data is anticipated to minimize delay in switching the preview output to the program output. A resource management module keeps track of which processors are committed to which sources.

Switcher using shared decompression processors for processing both

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. From these signals the luminance predictor circuit produces an ideal and an actual luminance component signal for comparison. A luminance correction signal, representing the lost brightness information, is produced from the difference between the ideal and actual luminance component signals. The luminance correction signal is input to the luminance channel of the encoder for combination with the gamma-corrected luminance signal to restore the brightness lost in the chrominance channels to the luminance channel.

Constant luminance corrector

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.

Decoder using adaptive non-separable digital filter

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.

Chrominance transition corrector

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.

Cable television test and measurement system

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. The auxiliary selector provides an HDTV format output video signal, selected from the HDTV inputs, and a corresponding standard format output video signal, selected from the standard format inputs, according to the video signal source selected by an operator at the master control switcher. A down-converter converts the HDTV format output video signal to a standard format video signal that is applied to other standard format inputs of the auxiliary selector. When the operator selects the video signal source, it is either up-converted or down-converted as necessary and output in both formats by the auxiliary selector.

Multiformat television switcher

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. A spectral display of the output of the video codec using a zone plate signal as the background component may also be used to characterize the video codec performance.

Three-dimensional testing of video codes

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.

Moire measurement system using spectral analysis

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.

Television signal generator

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.

Nonvolatile memory protection

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.

Analog to digital converter with second order error correction

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.

Component color bar alignment test signal

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.

Autocalibrated multistage A/D converter

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. The fitler serves to add the vertically correlated part of the signal corresponding to the video test signal while averaging out the noise, thus improving the overall signal to noise ratio without degrading the signal spectrum and, hence, enhancing differential gain and phase measurements.

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Portland, OR, United States of America

Bruce J Penney