Abstract: A processor which expands a compressed video signal is disclosed. The compressed video signal applied to the processor is generated by partitioning a video image into segments and then describing how each segment is filled by using a bilinear equation, that is to say, a linear equation which is a function of a horizontal coordinate X and a vertical coordinate Y. The coefficients of the X and Y coordinates each include integer and fractional parts. The circuitry develops a table of values from the coefficient of the X coordinate by repeatedly adding the coefficient in an accumulator. As each sum is produced, the integer part of the sum is stored. The table of values is developed from the stored integer sums as the difference between alternate sums, where successive alternate pairs of sums are interleaved. For example, the table would include the difference between the first and third sums followed by the difference between the second and fourth sums, then the third and fifth sums and so on.

Abstract: A parallel-pipeline video signal processing system is disclosed which includes a statistical decoder, an arithmetic and logic unit and a pixel interpolator which operate in parallel under the control of sequencing circuitry to expand a compressed video signal. The video signal may have been developed using a variety of compression techniques including Huffman-type statistical encoding.

Abstract: An antialias filtering and subsampling system incorporates a compound accumulator including three cascade connected accumulator circuits conditioned to integrate and dump the integrated values of n input samples. The integrated values from the three integrators are scaled, delayed and combined to produce substampled values of a signal which has been filtered according to the transfer function [sin(n.pi.ft)/nsin(.pi.ft)].sup.3.

Abstract: A circuit for separating FM signals from a composite signal utilizes a comb filter having successive frequency response nulls which span the frequency spectrum of the FM signal to be separated. The comb filter response is phase linear and defines the pass-band of the desired signal. A nonideal or phase nonlinear bandpass filter can be cascaded with the comb filter to attenuate out of band signals. The cascade combination of the comb filter and nonlinear bandpass filters is a cost effective substitute for the conventional, complicated phase linear bandpass filter having a boxcar frequency response traditionally used to separate FM signals.

Abstract: In an NTSC digital television receiver, the composite video signal is digitized with a sampling frequency of 32/13 times the color subcarrier frequency, f.sub.c. The chrominance signal component of this video signal is demodulated using a pair of finite impulse responsive filters having programmable weighting factors. The weighting factors are changed in a 32 step sequence as 32 consecutive chrominance samples are applied to the filters. The circuitry which generates the weighting factors is responsive to a phase alignment signal to determine when the 32 step sequence begins.

Abstract: Computer main memory is used for storing relatively densely sampled green and detail information concerning a television display and for storing relatively sparsely sampled red information and blue information concerning the same television display. The relatively densely sampled green and detail information is read out in substantially real-time from computer main memory during line trace intervals in the television display. The relatively sparsely sampled red information and blue information are read out of computer main memory in advanced and compressed time during selected line retrace intervals in the television display.

Abstract: Computer main memory is used for storing relatively densely sampled luminance information concerning a television display and for storing relatively sparsely sampled chrominance information concerning the same television display. The relatively densely sampled luminance information is read out in substantially real-time from computer main memory during line trace intervals in the television display. The relatively sparsely sampled chrominance information is read out of computer main memory in advanced and compressed time during selected line retrace intervals in the television display.

Abstract: A digital arithmetic combiner having improved overflow signal propagation delay characteristics is disclosed. Such an arithmetic combiner includes a tristate device having a data input terminal coupled to an overflow input terminal and a data terminal coupled to an overflow output terminal. A tristate control terminal is coupled to the output of logic circuitry. The logic circuitry is responsive to operand input signals and enables the tristate device to generate a signal at its data output terminal when the operand input signals have different logic states. In addition, an overflow generator is responsive to the operand input signals, and generates a signal indicating overflow conditions at the overflow output terminal when the operand input signals have the same logic state.

Abstract: In field/frame recursive filters for providing noise reduction to composite video signal, inversion of the chrominance component of the composite video signal is obviated by selecting nearest neighbor in-phase field/frame delayed signals for recursion. The system arbitrates between two or more nearest neighbor in-phase signals or combinations thereof and feeds back the signal having an amplitude most closely matching the incoming composite video signal.

Abstract: Computer main memory is used for storing relatively densely sampled wideband video information concerning a television display and for storing relatively sparsely sampled narrowband video information concerning the same television display. The relatively densely sampled wideband video information is read out in substantially real time from computer main memory during line trace intervals in the television display. The relatively sparsely sampled narrowband video information is read out of computer main memory in advanced and compressed time during selected line retrace intervals in the television display. The wideband video information may be luminance information; and the narrowband video information chrominance information.

Abstract: A MOSFET analog signal squaring circuit is disclosed. A first MOSFET has a source electrode coupled to a bias voltage source, a gate electrode coupled to an input terminal, and a drain electrode coupled to an output terminal. A signal inverter is also coupled to the input terminal. A second MOSFET has a source electrode coupled to the bias voltage source, gate electrode coupled to the signal inverter, and a drain electrode coupled to the output terminal. A load impedance is coupled between the output terminal and a supply voltage source.

Abstract: A volume control or amplitude varying system for digital signals includes a cascade connection of a coarse multiplier/divider for changing the values of digital signals in 6 db steps and a fine multiplier/divider for changing the values of digital values logarithmically in substantially equal steps of less than 6 db per step. The coarse multiplier/divider selectively multiplies the digital signal by powers of 2. The fine multiplier/divider multiplies the digital signal by predetermined values, an ascending/descending sequence of which form a substantially logarithmic sequence. Both serial-bit and parallel-bit embodiments are described.

Abstract: A scaling circuit for scaling PCM signals by factors less than one includes a bit-shift and truncating circuit. Roundoff error compensating circuitry adds an offset value to the samples to be scaled by the bit-shift circuitry to compensate for errors produced by truncation without rounding. The offset values are dithered to increase the apparent resolution of the system.

Abstract: Apparatus for multiplying a sampled data signal by a sinusoid having a period which is a multiple of the sample rate includes a plurality of sample scaling means to scale the sampled data signal by factors corresponding to the sine of angle .theta. over an angular range of 90 degrees in angular increments of 2.pi. divided by said multiple. A multiplexer multiplexes the scaled samples at the sample rate to produce a signal corresponding to the sampled data signal multiplied by the sinusoid. An embodiment is described for demodulating the stereo difference signal of a BTSC sound signal with serial-bit digital processing circuitry.

Abstract: A sampled data filter used in a television automatic ghost cancellation system employs a single chain of cascaded delay elements and a crossbar switch matrix to implement the several different delayed sequences of samples that are used by the system to cancel several ghost signals. The rows of switch elements in the crossbar switch matrix are coupled to the individual delay elements, and the columns of the matrix are coupled to sample scaling circuitry. The scaled samples are summed to develop a psuedo-ghost signal which is combined with the input signal to cancel the ghost signal components.

Abstract: A picture-in-picture image signal generator includes a source of an auxiliary video signal and an auxiliary synchronization component separator which produces an auxiliary odd/even field signal. Auxiliary image data is stored in a memory for subsequent retrieval. A source of a main video signal and associated synchronization component separator, which produces a main odd/even field signal, is also provided. A signal combiner combines a portion of the main video signal with data retrieved from the memory to form a picture-in-picture video signal. An interlace inversion detector generates a signal indicating an interlace inversion condition in response to the main and auxiliary odd/even field signals. A correction to the interlacing is made in response to the interlace inversion signal.

Abstract: A display processor using first and second chrominance map memories for storing values of first and second color-difference signals, each normalized respective to luminance signal. An image memory supplies, at pixel scan rate, data used to provide read-addresses to said first and second chrominance map memories and data used to describe the luminance signal. The first and second chrominance map memory read-outs are each multiplied by the luminance signal of appropriate spatial bandwidth to generate descriptions of the first and second color-difference signals i non-normalized form. These first and second color-difference signals and a full-spatial-bandwidth luminance signal are supplied to color matrixing circuitry. The color matrixing circuitry responds to these signals to provide red, green and blue drive signals to display apparatus. The display apparatus may comprise video amplifiers for the drive signals and a color kinescope, by way of example.

Abstract: A digital television receiver, having a line locked clock, includes a first digital phase locked loop which regenerates quadrature phase related subcarrier signals that are used to synchronously demodulate the chrominance signal components of composite video signals into color information signals. When nonstandard video signals (e.g., from a video tape recorder) are processed by the receiver, frequency instabilities in the line locked clock signal may cause the color information signals to be distorted. To compensate for this distortion, a second phase locked loop is synchronized to a reference signal generated by an analog oscillator. The analog reference signal is linearly added to baseband analog video signals provided by a tuner. The combined signals are digitized by an analog-to-digital converter and then filtered by parallel low-pass and band-pass filters to develop digital signals representing the video signals and the reference signal, respectively.

Abstract: A television deghosting system includes an IIR filter having programmable filter coefficients which processes the input signals to remove ghost signal components. The IIR filter may be reconfigured as an FIR filter, having its coefficient and delay values changed to operate as a matched correlation filter. In this mode the filter is used to correlate a training signal to determine the relative delays of ghost signals with respect to the direct signal. The training signal used is the sum of the squared differentials of the in-phase and quadrature-phase components of the video IF signal during an interval defined by the leading edge of the vertical sync pulse and the first equalization pulse.

Abstract: A digital television receiver includes a first phase locked loop which develops a sampling clock signal that is locked to the horizontal line synchronizing signal components of a composite video signal. A second digital phase locked loop is clocked by the sampling clock signal and develops a digital signal that is phase locked to the color burst signal. This digital signal is used as a regenerated color subcarrier signal to synchronously demodulate the chrominance components of the composite video signals into I and Q color difference signals. To compensate for frequency instability in the regenerated subcarrier signal caused by frequency instabilities in the line-locked clock signal, a third digital phase locked loop develops an output signal which is phase locked to a reference signal generated by a crystal controlled oscillator.