Abstract: A digital data processing system receives compressed variable length encoded digital data in the form of variable length codewords in contiguous variable speed Blocks of data. The boundary signals between adjacent codewords are determined and a demultiplexer sequentially sorts the serial digital data among a plurality of parallelly connected buffers for reducing the bit read speed of the buffers. A corresponding plurality of variable length decoders decodes the data from the buffers and outputs the data in parallel form to a multiplexer where it is reassembled into a serial expanded data stream. The incoming data includes selector information in fixed length headers that are separated, buffered and variable length decoded for controlling the demultiplexer. In one aspect of the invention, the data is sorted into substantially equal sized groups of integral codewords for equalizing the loading of the parallel buffers.

Abstract: A circuit for error correcting a received complex data signal comprises a synchronous detector for recovering an in-phase data component from the received signal and a Hilbert transform filter for estimating the related quadrature component from the recovered in-phase data component, the recovered in-phase data component including a periodically recurring reference signal. A decision feedback loop is periodically operable in response to the reference signal for initially error correcting a selected characteristic of the received signal at a first relatively rapid rate and for subsequently error correcting the selected characteristic at a rate which is less than the first rate and which is dependent upon the estimated S/N ratio of the received signal. In one embodiment, phase errors are corrected at a rate which is also directly related to the value of the estimated quadrature component. In another embodiment, amplitude errors, e.g.

Abstract: A high definition television transmitting system includes a source of high definition analog RGB video signals which are converted to corresponding digitally encoded signals and thereafter compressed by a video encoder to a six megahertz bandwidth. The compressed data is formatted by a transmitter and processed in accordance with a Reed-Solomon error control system for broadcast as an NTSC-type broadcast signal. A high definition television receiver includes a high definition signal receiver coupled to the transmitter by a transmission link. The receiver extracts the compressed video, audio and ancillary data signals and applies a Reed-Solomon error correction thereto. The compressed video data is reconstructed by a video decoder and processed for high definition display.

Abstract: A hybrid television signal of less transmission power or better signal to noise performance is made up by removing low frequency analog components from the video signal, digitizing them and sending them as data in non-active video portions of the transmitted signal. A two step hybridization process, with the first step removing the line averaged value of the video components of the video signal and the second step removing the remainder of the video components under 200 KHz, is described. Temporal filtering, signal preemphasis, compression, time dispersion and double sideband suppressed carrier modulation about a centered carrier are disclosed for reducing peak signal amplitudes and for minimizing co-channel interference to and from NTSC signals. Time dispersion is done horizontally, vertically or both to reduce the peak signal amplitudes. Time dispersion in conjunction with low frequency removal and temporal filtering is preferred.

Abstract: A hybrid television signal of less transmission power (or better signal to noise performance) is made up by removing low frequency analog components from the video signal, digitizing them and sending them as data in non-active video portions of the transmitted signal. A two step hybridization process, with the first step removing the line averaged value of the video components of the video signal and the second step removing the remainder of the video components under 200 KHz, is described. Temporal filtering, signal pre-emphasis, compression, time dispersal and double sideband suppressed carrier modulation about a centered carrier are disclosed for reducing peak signal amplitudes and for minimizing co-channel interference to and from NTSC signals. Temporal filtering is performed with a feed forward filter in the transmission and a complementary feedback recursive filter in the receiver or with a recursive filter in the transmitter and a complementary feed forward filter in the receiver.

Abstract: A hybrid television signal of less transmission power or better signal to noise performance is made up by removing low frequency analog components from the video signal, digitizing them and sending them as data in non-active video portions of the transmitted signal. A two step hybridization process, with the first step removing the line averaged value of the video components of the video signal and the second step removing the remainder of the video components under 200 KHz, is described. Temporal filtering, signal pre-emphasis, compression, time dispersion and double sideband suppressed carrier modulation about a centered carrier are disclosed for reducing peak signal amplitudes and for minimizing co-channel interference to and from NTSC signals. Time dispersion is done horizontally, vertically or both to reduce the peak signal amplitudes. Time dispersion in conjunction with low frequency removal and temporal filtering is preferred.

Abstract: A television system includes a plurality of complementary transmitter and receiver stages for processing an HDTV signal to minimize co-channel interference to and from NTSC signals, thereby facilitating the use of so-called "taboo" channels for the transmission of HDTV signals. The HDTV signals are encoded for transmission in a format exhibiting dominant periodicities equivalent to that of NTSC to further minimize such co-channel interference.

Abstract: A video signal comprising a successive series of frames is sub-band coded to derive a plurality of groups of coefficients for each frame. Each group of coefficients comprises a spectral representation of the video content of a respective portion of the frame, which portions are spatially decorrelated relative to the corresponding portions of the immediately preceding and immediately following frames to reduce block artifacts in the reproduced image.

Abstract: An adaptive filter for equalizing a received information signal is controlled by an error signal generated in response to a reference signal alternately transmitted in inverted and non-inverted form. The received reference signal transmitted in inverted form is reinverted prior to generating the error signal for negating the effects of DC offsets acquired by the reference signal during transmission and reception.

Abstract: A hybrid television signal of less transmission power or better signal to noise performance is made up by removing low frequency analog components from the video signal, digitizing them and sending them as data in non-active video portions of the transmitted signal. A two step hybridization process, with the first step removing the line averaged value of the video components of the video signal and the second step removing the remainder of the video components under 200 KHz, is described. Temporal filtering, signal pre-emphasis, compression, dispersal and double sideband suppressed carrier modulation about a centered carrier are disclosed for reducing peak signal amplitudes and for minimizing co-channel interference to and from NTSC signals. In an FM implementation, the benefits of the hybrid signal are realized as a reduction in bandwidth and consequent improved noise performance. The hybrid signal system is uniquely adapted to a high definition television signal in a limited frequency channel.

Abstract: A television system includes a plurality of complementary transmitter and receiver stages for processing an HDTV signal to minimize co-channel interference to and from NTSC signals, thereby facilitating the use of so-called "taboo" channels for the transmission of HDTV signals. The HDTV signals are encoded for transmission in a format exhibit dominant periodicities equivalent to that of NTSC to further minimize such co-channel interference.

Abstract: A hybrid television signal of less transmission power or better signal to noise performance is made up by removing low frequency analog components from the video signal, digitizing them and sending them as data in non-active video portions of the transmitted signal. A two step hybridization process, with the first step removing the line averaged value of the video components of the video signal and the second step removing the remainder of the video components under 200 KHz, is described. Temporal filtering, signal pre-emphasis, compression, time dispersion and double sideband suppressed carrier modulation about a centered carrier are disclosed for reducing peak signal amplitudes and for minimizing co-channel interference to and from NTSC signals. Time dispersion is done horizontally, vertically or both to reduce the peak signal amplitudes. Time dispersion in conjunction with low frequency removal and temporal filtering is preferred.

Abstract: A high definition television system includes an encoder for encoding a video source signal having a horizontal bandwidth of about 28-30 MHz for transmission through a 6 MHz RF channel. The video source signal is provided in the form of a plurality of horizontal video lines occurring at a vertical rate equal to the NTSC field repetition rate and at a predetermined horizontal rate greater than the NTSC horizontal scanning rate. The video lines of the source signal are encoded for transmission at NTSC vertical and horizontal rates, with the lines representing the lower frequencies of the video source signal being transmitted at a higher temporal rate than the lines representing the higher frequencies. The transmitted lines are converted to a plurality of display lines by a receiver for display at a vertical rate equal to the NTSC field repetition rate and at a horizontal rate equal to the predetermined horizontal rate.

Abstract: A CATV television system has the sync and color subcarrier reference information replaced in the horizontal blanking intervals with compressed digital audio data. The digital audio data is in the form of a modified duobinary signal having data sampling points selected to coincide with the zero crossings of a color reference subcarrier. A phase locked loop provides the master clock for the signal generator and the data sampler. A horizontal interval detector circuit recovers a 1.8 MHz CW signal of greater than one half line duration, followed by a white horizontal identification pulse of 4.7 microseconds width, that are supplied in place of the pre-equalizing, vertical sync and post equalizing pulses in the vertical interval.

Abstract: A circuit for phase locking the flyback pulse to a reference signal. A phase detector receives the flyback pulse (to be phase locked) and receives the reference signal. It outputs an error signal to a control circuit including first and second differential amplifiers having differing operational characteristics, one being linear in a narrower range than the other. The differential amplifier having the larger linearity range provides control signals to a coarse delay adjust circuit in the form of a programmable divider which also receives clock pulses at a high multiple of the horizontal frequency f.sub.H. The output of the coarse delay adjust circuit is applied to a fine delay adjust circuit responsively connected to the output of the first differential amplifier, which is linear over the narrower range. The output of the fine delay adjust circuit is coupled to the horizontal system.

Abstract: To adjust the free running frequency of a voltage controlled oscillator so that it is close enough to a target frequency for a phase locked loop to lock the frequency, a reference signal is derived from a stable external source. A derived signal is generated from the oscillator. The derived signal and the reference signal are applied to a comparison circuit which examines the relationship of a specific edge of the reference signal at times determined by the signal derived from the oscillator. If the oscillator is within its proper frequency range, the edge of the reference signal will have a certain relationship to the times determined by the derived signal. If this relationship is found to be improper, correction signals are applied to the oscillator. In the preferred embodiment, this occurs in a television receiver where the reference signal is based on a 3.58 megahertz signal. The examination which is made takes an output from a counter which divides by 455, specifically, the 160 count.

Abstract: A system for encoding or scrambling a television signal and for subsequently decoding or unscrambling the signal for presentation on the viewing screen of a television receiver. Encoding is achieved by suppressing the amplitude and changing the phase of the television signal carrier during selected horizontal blanking intervals. Decoding is achieved by synchronously detecting the horizontal blanking intervals of a received signal having a suppressed amplitude and changed carrier phase and restoring the original relative characteristics of the television signal during the detected intervals.

Abstract: A channel equalizer and ghost cancelling technique are disclosed for removing ghosts from a communications signal which includes a training signal and data. The training signal and its ghosts are processed as a finite length sequence of numbers. The equalizer includes a chain of cascaded filters, the first of which receives the training signal and its ghosts for assuming a filter condition which reduces the finite sequence by two points at the filter's output. Each successive filter in the chain receives the output of an immediately preceding filter and assumes a filter condition in which an additional two points of the finite sequence are eliminated or forced to zero. The filter conditions assumed in response to the training signal and its ghosts are maintained while the data is applied to the filter chain so that ghosts of the type experienced by the training signal are removed from the data.

Abstract: A network is described for use in enhancing the bandwidths of color signals in a color television system. The network is a feedback arrangement in which amplifiers multiply each color signal by a variable factor K to provide manifold color signals. High frequency luminance components are inserted into the modified color signals to develop high frequency color output signals. The modified color signals are weighted by selected coefficients and summed. The value of the summed signal is used to vary the factor K so that the high frequency luminance components in the color output signals are substantially equal to the high frequency components of the luminance signal.

Abstract: A color demodulation and comb filtering system is described for use in a color television receiver. The system includes a pair of charge coupled devices (CCD's) which each receive a filtered video signal and which develop outputs which are delayed, one from the other, by one horizontal line interval. Both devices are clocked at the color subcarrier frequency to develop outputs which include demodulated color and luminance components. The outputs of the two CCD's are combined in a summer, the output of which includes demodulated color components from which luminance components are eliminated.