Abstract: In a method of transmitting a signal wherein the signal is partitioned into windows comprised of overlapping blocks with each block containing a partial signal. The partial signal in each block is converted into a digital signal and individually coded with a selected window function f(n). The overlapping areas of the window functions are weighted such that the resultant of the overlapping functions in each block equals one. The coded signals are transmitted. The received signals are reconverted into partial analog signals. The window functions are selected in accordance with frequency changes in the original signal.

Abstract: The present invention is a video drive apparatus of the two ramp type which includes facility to selectively adjust the brightness and/or the contrast of an image reproduced on a display device. In this apparatus, at least one of the ramp signals is generated digitally by for example a counter. Provision is made to change the counting rate of such counter which effects a change in display contrast. Provision is also made to selectively change the phase of the ramp signal applied to the second stage relative to the start of respective pulses of the PWM signal thereby effecting brightness changes in the reproduced image.

Abstract: A film/video detector includes circuitry for generating the differences between corresponding pixel values in successive frames of video signal. These differences are accumulated over respective frame intervals. Accumulated values for respective frames are applied to a signal averager and to a correlation circuit. Average values from the averager are subtracted from correlation values from the correlation circuit, and film mode signal is indicated if the latter differences are greater than a predetermined value.

Abstract: An encoding scheme resistant to transmission errors encodes a data bitstream for application to a quadrature amplitude modulator (QAM) in a high definition television system. The error-resistant code provides a rotationally symmetrical 32-point constellation on a plane defined by I,Q quadrature axes. The constellation is divided into first and second partitions arranged so that constellation points that are closest in distance to any constellation point of the first partition belong to the second partition, and constellation points that are closest in distance to any constellation point of the second partition belong to the first partition. The binary value of one bit of each of successive 9-bit packets in the bitstream determines that one of the two partitions to which both of a consecutive pair of first and second constellation-point transmissions belong (the first and second transmitted constellation-points of that consecutive pair being selected by the then current 9-bit packet of the stream).

Abstract: A television receiver responds to a quadrature amplitude modulated (QAM) signal containing symbols mapped into a four quadrant grid-like constellation defined by I and Q axes. Demodulated I and Q components are processed by a carrier recovery network which adjusts the parameters of a locally generated carrier reference signal so as to maintain a desired orientation of the QAM constellation. The carrier recovery network includes a time multiplexed processor, including a signal multiplier, exhibiting plural operating modes in a digital phase locked loop exhibiting a loop delay of one symbol period.

Abstract: A data processing system augments compression of non-zero values of significant coefficients by coding entries of a significance map independently of coding the values of significant non-zero coefficients. A dedicated symbol represents a zerotree structure encompassing a related association of insignificant coefficients within the tree structure, thereby compactly representing each tree of insignificant coefficients. The zerotree symbol represents that neither a root coefficient of the zerotree structure nor any descendant of the root coefficient has a magnitude greater than a given reference level. The zerotree structure is disclosed in the context of a pyramid-type image subband processor together with successive refinement quantization and entropy coding to facilitate data compression.

Abstract: In a high definition television signal encoder, high priority and standard priority digital data are each separated into quadrature I and Q components, spectrally shaped by digital filtering, and time division multiplexed to produce respective quadrature amplitude modulated signals of the 32-QAM type. The high priority QAM signal and the standard priority QAM signal exhibit different bandwidths and carrier frequencies. The high priority and standard priority QAM signals are combined in digital form to produce a prioritized dual 32-QAM digital signal before being conveyed to a single analog-to-digital converter and analog RF transmission networks.

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 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: 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: 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.