Abstract: Apparatus for measuring skew in a clock signal for processing a video signal includes a cascade connection of a plurality of analog delay elements to which the clock signal is applied. The output connections of each analog delay element is coupled to a data input terminal of a respective storage element. A signal representative of the horizontal synchronizing signal is applied to the storage elements to simultaneously latch signal into the respective storage elements, thereby capturing a representative cycle of the sampling clock signal in the storage elements. Decoding circuitry is coupled to the storage elements for detecting the relative position of the e.g., leading transition of the sampling clock pulse immediately preceding the trailing transition of the horizontal pulse A ratio is calculated indicative of the skew error, which ratio corresponds to the position of the first transition, in units of delay, divided by the duration of the sampling clock period, in units of delay.

Abstract: A transition enhancing circuit includes a tapped delay line which provides successively delayed replicas of the signal to be processed. A multiplexer, responsive to a signal transition, sequentially couples delayed signal from the center tap and taps more distant from the input of the delay line to an output terminal to effectively hold the initial value of the transition for approximately half the transition period. The taps at the input end of the delay line up to and including the center tap are then sequentially coupled to the output terminal to effectively advance, in time, the end value of the signal transition. The signal transition is thereby reduced to a time equivalent to the switching interval between taps.

Abstract: A regulating circuit for controlling the speed of a rotating disc to provide a constant frequency signal from the disc includes a signal pickup device which moves radially along the disc and provides a velocity signal the frequency of which changes by a factor .DELTA.f as the position of the pickup device on the disc changes. A processor receives the velocity signal and produces a control signal in accordance with the factor .DELTA.f. A change-over switch provides a fine range voltage and a coarse range voltage which are used to control the speed of the disc in a fine range mode and a coarse range mode, respectively.

Abstract: In a method of compensating for the tolerance errors in a digital-to-analog converter (D/A) the tolerance errors of the D/A are measured and individual correction factors are provided for each of the errors. The correction factors are stored and one of them is arithmetically combined with a portion of the digital number being converted to produce a combined signal. The combined signal is input into the digital-to-analog converter to produce an analog signal accurately representative of the digital signal.

Abstract: A field synchronization system for asynchronous video signals, comprises a video display synchronized with a first video signal having a first line rate component and a first field rate component. A second video signal having a second line rate component is first stored in a field memory, having synchronous write and read ports. The second video signal is thereafter speeded up in a multiple line memory having asynchronous write and read ports and independently resettable write and read pointers. The second video signal may be subsampled, written and read into and out of the field memory respectively and written into the multiple line memory, all synchronously with the second line rate component. The second video signal is read out of the multiple line memory synchronously with the first line rate component. The write pointer is reset by a circuit which samples the first field rate component with the second line rate component.

Abstract: A digital compressed video signal transmission system includes a transport processor for segmenting compressed data into transport cells for transmission. Particular portions of the compressed data are formatted into further transport cells, which further transport cells are interspersed with normally occurring transport cells. The further transport cells include redundant video signal data which may be utilized to resynchronize a compressed video signal decoder after loss or corruption of transmitted data.

Abstract: An NTSC bandwidth-compatible HDTV system employs multiple quadrature amplitude modulation (QAM). A first suppressed QAM carrier is modulated with high priority information including predominantly low frequency information. A second suppressed QAM carrier is modulated with low priority information including predominantly high frequency information. The high priority QAM signal exhibits a larger amplitude and narrower bandwidth than the low priority QAM signal, and is disposed in the lower portion of the multiple QAM frequency spectrum normally occupied by the vestigial sideband of a standard NTSC television signal. The frequency spectrum of the multiple QAM signal exhibits signal attenuation at frequencies associated with high energy information in a standard NTSC signal, e.g., frequencies around the NTSC picture and sound carriers.

Abstract: A video signal encoding system includes a signal processor for segmenting encoded video data into transport blocks having a header section and a packed data section. The system also includes reset control apparatus for releasing resets of system components, after a global system reset, in a prescribed non-simultaneous phased sequence to enable signal processing to commence in the prescribed sequence. The phased reset release sequence begins when valid data is sensed as transiting the data lines.

Abstract: A digital transversal IIR filter, in which the sum of the magnitudes of a large number of coefficient multipliers (which may be real or complex) is greater than unity, may be stable or it may be unstable. The present invention is directed to (1) a test for stability in such a filter which is simpler and faster than solving a large number of polynomial equations, and (2) the repair of a filter found by this test to be unstable. Specifically, means responsive to the respective gradients of the magnitudes of chirp-z transforms of time-domain multiplier coefficient values within one or more selected localized regions of the complex in-phase (I), quadrature(Q) frequency-domain plane determine that a filter is unstable whenever the gradient of the magnitude values of the chirp-z transform within a selected localized region of the frequency-domain plane indicates that there is a pole in the frequency-domain plane that is located beyond the boundary of a frequency-domain unit circle.

Abstract: Apparatus for detecting the presence of a pseudorandom number (PRN) sequence used in a television receiver for reducing multipath interference such as image ghosts includes a multiplier responsive to a video signal containing the PRN sequence test signal component, and to a delayed version of such video signal. The amount of the delay is related to the duration of a PRN sequence, and one of the multiplier inputs is substantially devoid of average and DC components. A multiplier output representing correlation of the input signals indicates the presence of the test signal component, which is then passed to a network for processing to develop coefficients for a deghosting filter.

Abstract: First circuit apparatus, comprising a given number of prior-art image-pyramid stages, together with second circuit apparatus, comprising the same given number of novel motion-vector stages, perform cost-effective hierarchical motion analysis (HMA) in real time, with minimum system processing delay and/or employing minimum hardware structure. Specifically, the first and second circuit apparatus, in response to relatively high-resolution image data from an ongoing input series of successive given pixel-density image-data frames that occur at a relatively high frame rate (e.g., 30 frames per second), derives, after a certain processing-system delay, an ongoing output series of successive given pixel-density vector-data frames that occur at the same given frame rate. Each vector-data frame is indicative of image motion occurring between each pair of successive image frames.

Abstract: In a system for generating a compatible television signal with a "letterbox" display format, groups of vertically arranged picture elements (pels) are subjected to vertical DCT transformation producing eight DCT coefficients. Intermediate sixth and seventh coefficients are placed in the letterbox bar regions. The remaining six coefficients, namely the first through fifth coefficients and the highest frequency eighth coefficient, are inverse DCT transformed and processed with the main image information. A standard aspect ratio receiver displays a letterbox image using only the remaining six coefficients. A wide aspect ratio receiver uses the six remaining coefficients with the two coefficients from the bar regions, after inverse DCT, to produce a full resolution wide aspect ratio image.

Abstract: A high linearity digital-to-analog converter (D/A) provides a linear output voltage using two D/A's. One D/A provides a number of coarse steps and another D/A increments the output voltage within the coarse steps using fine steps. Discontinuities in the output voltage caused by the changing from one coarse step to another are avoided by using reference voltages which ensure that the initial voltage available at the start of a coarse step is lower than the final voltage available at the end of the preceeding step.

Abstract: In a system for coding and decoding a digital television signal, a signal representing residual image information is transformed into plural subband signals representing vertical and horizontal frequencies, and quantized. To mitigate the effects of transmission channel errors, the quantized subband signals are scrambled by line shuffling before being data compressed prior to transmission. Inverse operations including decoding, line re-shuffling, dequantization and subband synthesis occur at a receiver.

Abstract: In the process of generating a compatible 4:3 letterbox format television signal, a wide aspect ration 16:9 progressive scan television signal is vertically transcoded from 575 to 431 image lines, converted to line interlaced form and horizontally compressed. A vertically transcoded interlaced luminance component is converted back to progressive scan form via interpolation, and subtracted from a vertically transcoded original progressive scan luminance component to produce a difference (helper) signal. The difference signal is time compressed and multiplexed into upper and lower edge bar regions of the letterbox format. The compatible letterbox signal also is encoded with additional information including vertical high frequency information and horizontal high frequency information separated during the transcoding and compression processes, respectively. The encoding includes modulating the color subcarrier frequency with luminance information, and intraframe averaging.

Abstract: A high definition television receiver including analog and digital signal processing circuits receives an analog high definition television signal representative of digital television information. The received signal contains narrowband high priority information and wideband low priority information. An automatic gain control (AGC) signal is developed from the narrowband information as a function of the values of coefficients of an associated adaptive equalizer, and as a function of the number of saturated samples processed by associated input analog-to-digital converters.

Abstract: A system for activating an apparatus upon the insertion of a chip card into the apparatus by an authorized user includes a first control unit arranged on the chip card for providing an actuation signal when the chip card is initially inserted into the apparatus. A second control within the apparatus receiving the actuation signal and provides a triggering signal. A regulated voltage generator is responsive to the triggering signal and provides a regulated voltage to the first control unit.

Abstract: Apparatus for processing harmonically related plural quadrature amplitude modulated carriers includes sampling apparatus for converting the plural modulated carriers to sampled data format. The sampling apparatus is arranged to sample the signals at a frequency equal to four times the symbol rate of the highest frequency carrier such that alternate samples correspond to in-phase and quadrature-phase components of the signal. The sampled data signals are resampled to separate respective in-phase and quadrature-phase components of the respective signals. The in-phase samples of the respective signals are time division multiplexed and coupled to a Nyquist or symbol shaping filter arranged to operate in a time division multiplexed manner.

Abstract: The present invention includes apparatus for processing harmonically related plural quadrature amplitude modulated carriers. Sampling apparatus converts the plural modulated carriers signal to sampled data format. The signal is sampled at a frequency equal to four times the symbol rate of the highest frequency carrier such that alternate samples correspond to in-phase and quadrature-phase components of the signal. The sampled data signals are resampled to separate respective in-phase and quadrature-phase components of the respective signals. The in-phase samples of the respective signals are time division multiplexed, and the quadrature-phase samples are time division multiplexed. The time division multiplexed in-phase samples and quadrature-phase samples are coupled to a phase correction apparatus arranged to operate in a time division multiplexed manner.

Abstract: A receiver for receiving block coded HDTV compressed digital video signals decimates the data in each block to produce NTSC resolution images but with a significant savings in receiver hardware.