The Grass Valley Group, Inc.

Dubner Computer Systems, Inc.

Jon A Fairhurst

Jay S Baker

Stuart E Lang

Mark M Baldassari

A crosspoint matrix with integrated matte generators includes double buffered internal storage registers which may be serially loaded with mode and selection data to enable the crosspoint matrix to operate in a crosspoint mode wherein a selected input bus is directed to selected output bus. Further, the crosspoint matrix may be operated in a matte generator mode wherein the stored data is supplied to the output bus as a matte signal. The matte signal may be selectively toggled through a series of values to enable operation with both D1 and D2 signals. The data is latched in response to a vertical pulse which enables data values to be written in non-real time as a background task while the actual switch of data is accomplished only upon receipt of a vertical pulse.

Crosspoint matrix

A switcher with depth processing includes a depth processor module. External depth data, or internally generated depth data, are input to the depth processor to generate a priority signal for combining key video signals as layers between a background and a foreground video signal. Further a composite depth signal is generated for the combined key video signals for subsequent processing so that additional key video layers may be intersected and intertwined with the key video layers in the combined video signals.

Depth signal processing in a video switcher

A method of pattern generation for a screen using a wipe solid generator and a recursive memory includes generating from operator inputs a wipe solid. An extent of the generated wipe solid is measured to produce maximum and minimum values. These maximum and minimum values are extended to encompass a desired border size and softness. A lever-arm scaling function is selected based upon whether a change in operator input causes a reversal in pattern and/or causes the pattern to 'breathe.' The selected lever-arm scaling function uses prior values from the recursive memory to generate new values that are stored in the recursive memory. From the stored values clip levels are determined such that completion of lever-arm movement to a limit position coincides with completion of the pattern without distortion of the size of the pattern.

Pattern generation using wipe solid generator

An inverse hyperbolic comb filter decodes an encoded signal by subtracting a vertically filtered and horizontally filtered version of the encoded signal from a delayed version of the encoded signal whereupon the resulting output is further horizontally filtered to provide a first decoded output. A twice delayed version of the input signal then has the first output signal subtracted therefrom to provide a second output. Optional further vertical filtering may be employed to vertically filter the output of the first subtractor before the final horizontal filtering is performed. The filter may also be employed in encoding signals wherein the components to be encoded are first filtered prior to combining. The inverse hyperbolic comb filter is applicable to any system employing combining of two-dimensional signals via quadrature modulation and may also be employed in three-dimensional systems.

Inverse hyperbolic comb filter

An interpolating digital signal clipping circuit provides pre-clipping of the luminance component of a video signal. A difference circuit adjusts each sample so that a single bit indicates whether the sample value is closer to a positive or negative clipping limit. Interpolated samples are produced by phase shifting FIR filters and are applied, along with the actual current sample, to a minimum or maximum selecting circuit that selects the minimum or maximum sample depending on the state of the indicating bit. The selected sample is compared with the clipping limits to produce an excess signal that indicates how much the selected sample exceeds the relevant clipping limit. A gain control signal is generated to be a '1' when no clipping is required and less than one when clipping is required. A digital video signal clipping circuit receives this pre-clipped luminance signal and adjusts each sample as above. Multipliers square the chrominance components, and an adder adds the squares and applies the output as addresses to a memory that produces a chrominance magnitude signal. The chrominance magnitude signal is combined with the adjusted luminance signal to obtain a composite magnitude signal. Again, a gain control signal is generated that is a '1' when no clipping is required and less than one when clipping is required, and this signal is used to reduce the video components before they are combined into a clipped composite video output.

Interpolating digital signal clipping circuit and composite video

An apparatus and method for producing improved adaptive control signals for a luminance and chrominance separation circuit employing adaptive filtering of a chrominance signal includes a vertical difference detector, a horizontal difference detector, and a combiner. The vertical difference detector contains upper difference detector and lower difference detector, each of which receives a horizontally filtered next line signal (L.sub.N), a horizontally filtered present line signal (L.sub.P), and a horizontally filtered last line signal (L.sub.L), and which produce, respectively, an upper difference signal and a lower difference signal. In a preferred embodiment, the lower and upper difference detectors implement, respectively, the expressions .vertline.2L.sub.L +L.sub.P -L.sub.N .vertline. and .vertline.2L.sub.N +L.sub.P -L.sub.L .vertline.. The vertical detector also contains a larger valve selector that receives the upper and lower difference signals and produces a vertical chrominance difference signal that is based on, and preferably is the larger of the upper and lower difference signals. The horizontal difference detector receives the present line signal and determines the absolute value of the sum of the values of two pixels that are separated by an integral number of half cycles of a subcarrier frequency to produce a horizontal chrominance difference signal. The combiner contains a subtracter for subtracting the horizontal chrominance difference signal from the vertical chrominance difference signal to produce an adaptive control signal, and may further include a scaler on the subtracter input and a divide-by-two circuit and/or a limiter on the subtracter output.

Adaptive control signal generator for an adaptive luminance/chrominance

A chrominance filtering system reduces chrominance detail when sufficient luminance detail is present, but limits how much chrominance detail is reduced when insufficient luminance detail is present. The chrominance input signal is applied to a high pass filter and a suitable delay circuit. The output of the high pass filter, C.sub.hp, is a signal indicative of chrominance detail. It is applied to the input of a bipolar clipping circuit that also receives a control signal, .vertline.Y.sub.hp '.vertline..sub.clipped indicative of luminance detail. The control signal is derived by high pass filtering, rectifying and low pass filtering the luminance signal to produce a signal, .vertline.Y.sub.hp .vertline., that is absolute value of high pass filtered luminance activity. This signal is then scaled by multiplication by a first constant and then offset by addition to a second constant to produce .vertline.Y.sub.hp '.vertline.. .vertline.Y.sub.hp '.vertline. is then clipped to be between a minimum and a maximum value to produce the control signal .vertline.Y.sub.hp '.vertline..sub.clipped. The bipolar clipping circuit constrains C.sub.hp to produce C.sub.hpc according to the following relationships: If C.sub.hp is &gt; or =0, then C.sub.hpc is &gt; or = to .vertline.Y.sub.hp '.vertline..sub.clipped ; or if C.sub.hp is &lt;0, then C.sub.hpc is &lt; or = to -.vertline.Y.sub.hp '.vertline..sub.clipped. The first and second constants and the minimum and maximum values are optimized empirically.

Variable chrominance filtering for encoding television signals

In a new television signal decoder architecture, a mixer switches between two inputs, A and B, using an envelope function C, according to the relationship: Ouput=A*C+B(1-C), where A is either the composite television signal input in normal operation or a first test signal memory in test signal generation operation, and B is either a fixed blanking level in normal operation or a second test signal memory in test signal generation operation. A test signal generator and blanking sequencer provides the test signals to the two test signal memories and an envelope control signal to the envelope generator telling it when and in which direction to supply the transition envelope to the mixer. A variable electrical length front end is created by a microprocessor that recalls from its memory the timing associated with a particular composite video source and directs a timing circuit to wait an appropriate amount of time before releasing a frame of video stored in a FIFO buffer memory to the rest of the decoder. A bus is shared by sync signals and signals from diagnostic points of interest and is alternatively controlled by the sync generation circuitry during normal operation and the microprocessor during diagnostics.

Television signal decoder with improved architecture

An improved apparatus is provided for minimizing cross-color artifacts in the encoding and decoding of quadrature modulated color television signals during the encoding process, so that when the encoded video signals are decoded,s uch artifacts are minimized while a maximum amount of picture detail is preserved. A luminance signal is applied to both a delay element and an adaptive filter. The output of the delay element, a delayed luminance signal, is applied to a subtractor circuit. The output of the adaptive filter, an adaptive compensation signal, is applied to a variable limiter. Within the variable limiter, the adaptive compensation signal is applied to a rectifier/intergrator and a limiter circuit. The output of the rectifier/integrator, a cross-color activity signal, is sent to a scaler/combiner circuit top which is also optionally applied a chrominance activity signal. The scaler/combiner circuit weights these inputs with different factors before summing them. The output of the scaler/combiner circuit is a limiter control signal that is used to control how much of the adaptive compensation signal is applied to the subtractor circuit where it is substracted from the delayed luminance signal to produce a compensated luminance signal. A corresponding method is disclosed.

Video encoding using adaptive filters and variable threshold

A television signal encoder/decoder control provides for quick and easy modification of circuit parameters for a television encoder/decoder. A microprocessor interfaces with both local and remote interfaces for obtaining parameter data, sets up the encoder/decoder according to the parameter data, and then stores the resulting setup parameters as a preset. The preset may then be instantaneously recalled and the encoder/decoder set up in the stored configuration in the space of a video signal vertical interval.

Television signal encoder/decoder configuration control

A digital decoder for an encoded video signal has three stages. The first stage applies a multi-dimensional digital chrominance bandpass filter to the digitized encoded video signal to produce a chrominance signal, subtracting the chrominance signal from the digitized encoded video signal to produce a luminance signal. The second stage detects edges and peaks in the chrominance signal, and corrects the luminance signal where such edges and peaks are detected to produce a chrominance corrected luminance signal without dot crawl errors. An intermediate corrected chrominance signal may also be derived from the second stage. The third stage filters the chrominance signal, or intermediate corrected chrominance signal, to reduce peaks in the chrominance signal as well as to enhance edges to produce a corrected chrominance signal with minimized cross color errors.

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Grass Valley, CA, United States of America

Jon A Fairhurst