Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal, encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. The dynamic range of the encoded signal is reduced by combining groups of adjacent samples that are smaller than a "floor" threshold to form larger samples, and by splitting samples that are larger than a "ceiling" threshold to form a plurality of smaller samples. Encoding of the combined samples is carried out in a conforming manner to minimize deleterious effects of transmission noise.

Abstract: An arrangement for a television receiver to attenuate correlated noise injected by the transmission medium. Recognizing that there is substantial line to line correlation of the transmission noise injected by interfering television stations, this arrangement enhances noise immunity by inserting in the receiver a de-emphasis stage that includes a circuit for removing the correlated noise. To account for the modifications to the desired signal that are introduced by the de-emphasis circuit, a pre-emphasis circuit is included in the transmitter. In accordance with one embodiment, the receiver's circuit comprises a feed-forward arrangement where the received signal of a scan line is subtracted from a fraction of the received signal of the previous scan line. At the transmitter, a feedback loop develop a scan line to be transmitted that corresponds to a video scan line subtracted from a fraction of the previous scan line to be transmitted.

Abstract: A motion compensated encoder where motion vectors are selected based on the prediction error generated in localized areas of the encoded image and based on an available bit budget. The motion vectors are created by dividing the image into blocks of two sizes and by considering the best mix of large and small size blocks, and their associated motion vectors, that minimize the overall prediction error, within the constraints of the bit budget. For convenience, the image division is arranged so that a given number of small sized blocks forms one large sized block (e.g. 16:1). Also, the block sizes are arranged so that employing only large sized blocks does not exceed the given bit budget, while employing only the small sized blocks does exceed the given bit budget.

Abstract: A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer.

Abstract: An HDTV receiver design includes a reconstruction section and an inner loop section. The reconstruction section comprises a receiving section for accepting the television receiver's antenna signals, for separating out the component signals from the received signals and for decoding the separated signals. The decoded signals are applied to a quantization decoder that is responsive to vector codebook and to applied quantized vector signals, and the output signals of the quantization decoder are applied to an inverse DCT circuit. The inner loop comprises an adder for adding an estimate signal to the output of the DCT circuit, a frame buffer, a motion compensation circuit that is capable of translating large blocks as well as small blocks and a leak circuit that modulates the output of the motion compensator circuit in accordance with a received leak control signal.

Abstract: In a differential PCM encoder, the problem of error perpetuation is solved by leaking a changing, rather than a fixed, fraction of the input signal to the differential PCM. The fraction leaked is sensitive to the characteristics of the signal. In one embodiment the fraction leaked is fixed for a frame in accordance with a chosen characteristic of the frame signal. In another embodiment, the fraction leaked is set in accordance with one function when a chosen characteristic of the frame signal exceeds a given level, and follows another function when the chosen characteristic does not exceed the chosen level. In a still another embodiment, the fraction leaked is set to one of two levels, based on a chosen characteristic of the frame signal.

Abstract: Deinterlacing systems and methods useful with television and other interlaced data signals derive values for pixels on missing lines using best matching values for blocks of pixels through time-recursive comparison of current pixels block values with such values for prior frames of data and also with later frames. Noise propagation is attenuated by mixing of current interpolated pixel data and memory size efficiency is achieved by comparisons based on blocks of pixels, with the block size adjustable for data accuracy. Use of chrominance signal comparisons and reduced data rate coding techniques provide added capabilities to the deinterlacing systems and methods.

Abstract: A packet transmission protocol, which operates in a full-duplex mode in a system, which includes a transmitter, a receiver, and a communications network having a channel that logically ties the transmitter and the receiver together through the network, is disclosed. The receiver regularly sends a control packet to the transmitter. The control packet includes a plurality of data fields, which are useful in describing the state of the receiver to the transmitter. The transmitter receives the receiver's control packet and analyzes the data. If it finds that a particular block of packets had been received with an error (or not received at all), then the transmitter retransmits the block. The protocol includes two windows for controlling the volume of information, e.g. number of blocks, in the network.

Abstract: Graceful degradation for digitally encoded HDTV signals is achieved by appropriately coding the image to provide a controllable degradation of chosen image characteristics, such as temporal degradation, spatial degradation, and dynamic range degradation. In the temporal degradation approach of this invention, the resolution of movement suffers when noise is introduced. In the spatial degradation approach, the spatial resolution of the image is sacrificed. In the range degradation approach, the dynamic range of the signals is sacrificed. The graceful degradation is achieved by dividing the transmitted signal into two or more parts, such as parts A, B and C. Part A is given the heaviest error-correcting code; part B is given a "medium" error correcting code; and part C the is given the least powerful error correcting code (or perhaps none at all). A receiver that is close to the transmitter most likely receives parts A, B and C.

Abstract: Apparatus for reducing interference in a first signal caused by a second signal. Before the signals are transmitted, the first signal is tested to determine how much interference can be tolerated. During portions of the first signal which can tolerate a large amount of interference, the amplitude of the second signal is increased. During portions of the first signal that can only tolerate a small amount of interference, the amplitude of the second signal is decreased. The average amplitude of the second signal is large enough to provide an acceptable bit error rate or signal to noise ratio, yet small enough not to substantially corrupt the first signal. In one embodiment, the technique is employed to allow transmission of additional data on a television channel.

Abstract: A communications protocol that communicates absolute state information, as contrasted to incremental information, on a regular basis to achieve high throughput by reducing the need for retransmissions. The protocol exchanges control messages that contain all of the relevant state information between the receiver and the transmitter on a frequent, routine and periodic basis, independent of any significant event that may have taken place in the receiver or the transmitter. The periodic rate of state exchange depends on the activity on the logical channel. The data communication from the transmitter to the receiver is in blocks of packets, with each block carrying a sequence number. Selective retransmission procedures are initiated by the transmitter whenever a control packet from the receiver identifies a failed reception. When a packet in a block fails to be received properly, the entire block, but only that block, is retransmitted.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing much of the redundancies in the signal, efficiently encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. To enhance noise immunity a number of techniques are employed. One is to encode adjacent low-amplitude signals into larger signal samples, another one is the introduction of a controllable gain feature, a third one is the introduction of both fixed and variable leak, and still another one is the incorporation of signal scrambling.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal, encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. In the encoding, groups of signals to be sent are mapped to codebook vectors and the identities of the codebook vectors are sent together with those signals of the groups of signals that correspond to the codebook vectors. To insure that the total number of signals that are sent does not exceed the available capacity, the signals are sorted by a selected importance parameter and assigned for transmission in descending order of importance until the capacity is exhausted. Signals that are not assigned for transmission are discarded.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by in a manner removing much of the redundancies in the signal, efficiently encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. Specifically, the television signal is encoded by developing motion vectors that describe the best motion estimate of the image to be transmitted, by developing motion estimation error signals, by encoding these error signals within the same bandwidth as occupied by standard NTSC signals and by transmitting the encoded error signals during periods that correspond to the active scan intervals of the NTSC TV signal. The motion vectors themselves, together with video and control signals, are transmitted during the NTSC retrace period.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal and encoding the remaining signals. In the encoding, a portion of the signals to be transmitted is created in the form of an analog signal or a concatenated plurality of pulse amplitude coded samples (A-signal), and another portion of the signals to be transmitted is created in digital form (D-signal). The D-signal is consigned to a specified portion of the transmitted signal, leaving the remainder of the transmission capacity for the A-signal. When the normally created digital signals do not fully occupy the digital portion, enhanced operation results when selected ones of the analog signals or samples are excised from the A-signal, encoded digitally, and added to the D-signal. The excising of those signals leaves room in A-signal portion to include additional analog signals. This leads to an overall better image reproduction at the receiver.

Abstract: A method for realizing, and a structure for implementing a switching network employing 2.times.2 switches. The network is dilated in that none of the 2.times.2 switches concurrently carry an active signal. The method for realizing such a network alters a given non-dilated network by replacing each 2.times.2 switch in the non-dilated network with a dual rail switch having a pair of 2.times.2 interconnected switches, and by replacing each link in the non-dilated network with a pair links. The final output of the dilated network is obtained by adding a combiner final stage which combines the pairs of signals to form output signals that parallel the output signals of the given non-dilated network.

Abstract: An arrangement for butt coupling of waveguide electrooptic plates to form a crossbar switch. The arrangement includes a stack of M splitter plates, each of which routes an injected optical signal to one of N outputs, and a stack of N combiner plates, each of which routes the signal of a selected one of M inputs to a common output. The stack of splitter plates is rotated with respect to the stack of combiner plates and the output signal ports of the splitter plates are coupled to the input signal ports of the combiner plates, so that each output of an splitter plate is connected to a different combiner plate. Within each splitter plate there is a fan-out network of waveguide electrooptic couplers and each coupler, under electric control, routes signals from one input to either one of two outputs. With j levels of such interconnected couplers 2.sup.j output are developed. The combiner plates have an identical architecture but with a signal flow in the reverse direction.

Abstract: There is disclosed a system for providing an economical telephone toll service in which a telephone subscriber selects the economical service by, for example, sending an appropriate signal, and then dials his directory assistance call or other telephone toll call. After the caller's options are determined and typically before signaling for the call is commenced, a recorded-announcement of an aural or visual nature is connected to the subscriber's line, the announcement consisting of at least one advertisement. The advertisements are selected from a databank according to some predetermined technique of selection, which may include any number of factors or features to make the service attractive to subscribers and of a nature to make the service also sufficiently rewarding to advertisers.

Abstract: A method and apparatus that employ precomputed line profiles to draw lines on a raster scan terminal with mostly horizontal or vertical "brush strokes" that develop the desired line profiles. The precomputed line profiles relate mostly to the slope of the drawn lines and to the position of the drawn lines between adjacent pixels on the raster scan terminal in the direction of the "brush strokes". A relatively small number of precomputed values is required, permitting the apparatus to operate at the low resolution of the raster scan and be driven advantageously by a look-up table. This results in a very fast operation of the system while leading to pleasing results. The method also takes into account corners and end-of-line conditions to avoid very abrupt and unnatural looking end points.

Abstract: A light pen which includes a transparent rod at its pointing end through which light is directed to a photodetector that is fixedly positioned within the light pen. The rod is spring loaded and axially slidable in response to applied pressure, resulting in different light intensities being applied to the photodetector and further resulting in an output voltage generated by the photodetector that is directly related to the applied pressure.