Abstract: In systems in which the current digitized level value of a synthesized-signal sample (e.g., a television video signal sample) is determined by summing a transmitted error-signal-sample level value and a delayed previous synthesized-signal-sample level value, the dynamic range of the transmitted error-signal samples are reduced by as much as one-half. This is accomplished by passing the error-signal samples through a first non-linear processor (NLP) before transmission thereof and then passing the summed output through a second NLP. Both NLPs exhibit the same specified transfer function taught by the present invention.

Abstract: A technique for transmitting compressed quantized image-data from a transmitter to a receiver over a limited bandwidth communication channel employs temporal differential pulse code modulation incorporating pyramid image processing spectrum analyzers and synthesizers. This technique permits the selective elimination by data-compression of only those portions of the original image information which contribute least to the perception of image quality by a viewer of a synthesized display image at the receiver.

Abstract: Encoding apparatus, situated at the transmitter and employing digital processing, transforms an NTSC format color television signal to a serial time-multiplexed IYQY format which (1) preserves the blanking level of the NTSC signal, and (2) time compresses the color information in a manner which permits low-distortion restoration of the NTSC format color signal by decoding apparatus, situated at the receiver and employing digital processing. The transformed format is particularly suitable for communication over a DBS (direct-broadcast satellite).

Abstract: A transmitter applies luminance and chroma components of a color television signal to a transmission path, such as a VTR or satellite, in amplitude compressed form. To obtain optimum improvement in S/N ratio, different compression laws for the luminance and chroma components are used. The signals can also be time compressed and sent in TDM form.

Abstract: Phase reversal of solely the chrominance component of only alternate frames of an NTSC format signal prior to pre-emphasis and again subsequent to de-emphasis permits simpler and less costly filter structure to be employed without any loss of filtering capability.

Abstract: A frame-to-frame comb filter system which reduces motion induced artifacts in the comb filtered luminance signal includes line comb filter circuitry for extracting luminance cross components from the comb filtered chrominance signal and reinserting them into the comb filtered luminance signal and a line comb filter in the luminance path following reinsertion of the luminance cross components to reject motion induced chrominance cross components occurring in the comb filtered luminance signal. The latter line comb filter is switched into the system during periods of interframe image motion.

Abstract: Low pass sampled data filters tend to produce pre- and post- over/undershoots in the output signal in response to input signal transitions. These over/undershoots or sequence of artifacts are eliminated in the present system by the following method. The input signal is monitored for transitions exceeding an amplitude which tends to generate objectionable artifacts. The values of such transitions are stored and applied to a plurality of weighting circuits to generate a plurality of signal values corresponding to respective ones of the sequence of artifacts. The weighted samples are selectively combined with the filter output samples in time correspondence with the occurrence of the output artifacts to cancel the effects of the artifacts.

Abstract: A digital finite impulse response (FIR) filter is provided in which a plurality of weighted signal taps are symmetrically located in time about a weighted center tap. Weighted signals from the symmetrically located taps are summed at a first point in the filter, which sum is then combined with signals from the center tap in one sense, that is, either additively or subtractively, to produce signals at a first output. The summed signals at the first point are also combined with signals from the center tap in an opposite sense to produce signals at a second output. The two outputs will exhibit bandpass and lowpass filter response characteristics, with the outputs at which the respective responses are produced being determined by the respective senses of signal combination. The FIR filter may be of either the input tap-weighted or output tap-weighted variety.

Abstract: Frame-to-frame comb filter for separating chrominance and luminance components of composite video signals produce distortions around the periphery of reproduced moving images. The color distortions are corrected by selectively adding the combed luminance signal to the combed chrominance signal during periods of detected motion, and bandpass filtering the combined signal to pass only the chrominance spectrum.

Abstract: An automatic color control (ACC) for a digital television receiver is compatible with and is unaffected by variation of the phase of the color subcarrier signal introduced in demodulating the color subcarrier to effect control of tint. ACC is effectuated by digital gain control for scaling the digital words representing the sampled magnitudes of the color subcarrier burst signal. Quadrature demodulation of the color subcarrier produces color signal digital words I and Q which are each sampled and latched during the color subcarrier burst. The sampled digital words are each squared and are then summed together. The summed digital word is compared to a chroma reference digital word and the difference digital word is employed to scale the color subcarrier digital words.

Abstract: A digital filter is provided which selectively employs binary arithmetic and offset two's complement arithmetic in an adder ladder to protect against signal overflows and underflows, as well as to minimize adder size. Signal overflows and underflows are prevented by performing subtraction and certain additions in offset two's complement notation, while adder sizes are minimized by performing certain other additions in binary notation. In an alternate embodiment, positively weighted values are combined by binary addition in a first adder ladder, and negatively weighted values are combined by binary addition in a second, parallel adder ladder. At the outputs of the two ladders, the two sums are converted to offset two's complement notation, and the negatively weighted sum is subtracted from the positively weighted sum.

Abstract: A digital memory is provided which contains digital data words representative of a desired symmetrical transfer characteristic of a digital signal processor. Digital signals which are to be processed are applied to the address inputs of the memory, producing output signals in conformance with the desired transfer characteristic. Advantage is taken of the symmetrical nature of the response characteristic to minimize the size of the memory. Data words corresponding to only a portion of the full dynamic range of the digital signal processor are stored in the memory, and memory locations are addressed and read out in accordance with the value of a polarity-determining bit of the input digital signal, with the output signals being translated over the required full dynamic range in accordance with the value of the polarity-determining bit.

Abstract: A method of synchronizing the transmissions of alternate video fields or frames from two earth stations over a common uplink channel to a satellite so that the fields or frames arrive in interleaved time periods. A synchronizing pulse is transmitted over a separate channel from a first station to the satellite and back, twice, and to the second station and back. The returned signals provide information for synchronizing transmissions from both stations.

Abstract: A system including an encoder for translating a standard color TV video signal to a buried subcarrier video signal for transmission, and a decoder for translating the received buried subcarrier video signal back to a standard video signal. A cross-hatch perturbation on screens of TV receivers using the decoded signal can result from the operation of comb filters, local oscillators and mixers in the system when there is an abrupt change in color information in adjacent horizontal lines. The perturbation is prevented by maintaining the respective outputs of the local oscillators in the encoder and the decoder at opposite phases.