Abstract: 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.

Abstract: 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..

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.