Abstract: A branch metric computer for the Viterbi decoder of a convolutional decoder primarily intended for use in a multi-channel compressed-digital television receiver capable of receiving FEC data transmitted over satellite, terrestrial and transmission channels. The branch metric computer employs a RAM, having an effective depth of 2.sup.x storage locations and an effective storage-location width of 16 m, which is preloaded with two selectively programmed I and two selectively programmed Q lookup tables, wherein each table entry is made up of four m-bit values,. The RAM is designed to operate with either QPSK punctured-coded I and Q signal inputs or any one of a plurality of different PAM or QAM higher alphabet or an 8-PSK pragmatic trellis-coded 2.sup.x -bit I and 2.sup.x -bit Q signal inputs to the convolutional decoder that are forwarded as signal inputs to the RAM for controlling the particular I and Q lookup-table entries read out from the RAM.

Abstract: Compensation for offset errors caused by data truncation is accomplished by adding a compensation value to processed data in systems where the truncation stages are arranged in determinable configurations. More than one compensation value may be selected and applied. The selection of the appropriate value is determined by the number and type of truncation stages used in a given system configuration. The compensation value may be predetermined or measured.

Abstract: Video signal compression apparatus includes a memory for storing two fields of image data and providing fields of image data separated by one frame intervals. Image data from corresponding fields of successive frames are subtracted to generate field differences. The field differences are accumulated over respective field intervals, and the sum is compared against a predetermined value. If a sum of differences over a field is less than the predetermined value, the most recent field is considered to be redundant and may be excised. After respective fields are excised, frames of video signal are composed from the remaining fields. The field types (e.g., odd or even) of the fields in the memory are determined, and the data is accessed from the respective fields in memory such that data from odd and even fields occupy odd and even lines in the composed frames respectively.

Abstract: Apparatus for developing synchronization of an intermediate layer of signal such as the transport or multiplex layer of a multi-layered compressed video signal, includes at the encoding end of the system apparatus for including a time stamp reference, such as a count value from a modulo K counter, and provision for a differential time stamp which may be updated by the transit times of respective (e.g., multiplexing) circuits as the signal transits such circuits. At the receiving end of the system a counter is responsive to a controlled receiver clock signal and the count value of this counter is sampled at the arrival of the time stamps embedded in the transport layer. The time stamps and the differential time stamps are retrieved from the signal and combined to form a corrected time stamp. The differences of successive sampled count values of the receiver counter are compared with the differences of corresponding successive corrected time stamps to provide a signal to control the receiver clock signal.

Abstract: A process and an arrangement for identifying the type of defects in optical information from an optical information carrier includes circuitry for detecting the displaying various types of defects which can occur in the information carrier. A processing circuit is linked to a display device to enable the cause of the defect to be displayed.

Abstract: A radio broadcast receiver for receiving digitally coded sound broadcasting data (DAB) includes a bit error rate measuring device. A control device controls the reproduction of the sound broadcasting data, wherein a reception quality threshold value is defined in the control device and, upon the measured reception quality falling below the threshold value, the control device alters the reception quality and/or the reproduction signals in a perceptible manner.

Abstract: In an inverse transport processor, program component packet payloads of respective program components are directed to select areas of random access memory (RAM) (18) in accordance with a plurality of start and end pointers which are stored in a first plurality (86, 89) of registers, one for each program component. Addresses are generated, in part, by a plurality of read pointer registers (82) multiplexed with an adder (80) to successively increment the pointers for respective program components. The start pointers are associated with read pointers to from memory addresses that scroll through designated memory blocks selectively assigned to respective program components. Memory access for read and write functions are arbitrated (98) so that no incoming program data can be lost, and all component processors are serviced.

Abstract: In an inverse transport processor of the type which directs video payloads of a packet signal to buffer memory space, apparatus is included for writing a media error codes at sequential first memory address locations in the memory ahead of each packet payload. Concurrently a processor examines the current packet to determine if it occurs in proper sequence. If a packet is lost, the payload is written to memory in subsequent sequential address locations. If there is no packet loss, the sequential first memory address locations are simply overwritten by the packet payload to excise the undesired media error code. Media error codes can thus be inserted in the packet payload stream without creating timing obstacles, for a system designer.

Abstract: In an audio/video transmission system, a method of forming program guide information conducive to selective display at respective receivers includes arranging program guide information in different data blocks according to types of guide information. One such data block contains channel information (CSSM.sub.i) describing the respective channels. Respective CSSM.sub.i in this block include a channel information customer service system byte (CI.sub.-- CSS) which contains conditional access information related to a channel associated with a CSSM.sub.i. In a receiver embodiment, a subscriber specific byte (CA.sub.-- CSS) is stored and accessible to program guide processing apparatus. Prior to displaying received program guide information for a particular channel, the subscriber byte CA.sub.-- CSS is compared with the channel information byte CI.sub.-- CSS in the program guide.

Abstract: A control circuit for maintaining the mean value of the amplitudes of control pulses having a first level and data pulses having a second level includes a detector for providing the control pulses and the data pulses. A reference voltage source provides first, second and third reference voltages having three different levels. A plurality of comparators each receive both the control pulses and the data pulses. A first comparator also receives the lowest of the reference voltages and provides regulation pulses when the control pulses reach the level of the lowest reference voltage. A second comparator receives the second highest reference voltage and provides level limiting pulses to maintain the level of the regulation pulses constant. A third of the comparators receives the highest reference voltage and provides data pulses when the third reference voltage is reached.

Abstract: A compressed audio/video, A/V, receiver provides A/V component timing reference signals (PTS's) coincident with reproduction of associated decompressed component signals. Synchronization apparatus generates a function of the difference of occurring component audio and video PTS's. This function, which is indicative of relative audio and video synchronization, is compared with a predetermined threshold value, and a mute control signal is generated when the threshold is exceeded. Muting circuitry, responsive to the control signal disables audio reproduction when the reproduced audio and video component signal timing deviate from mutual synchronization.

Abstract: Apparatus for developing synchronization of an intermediate layer of signal such as the transport or multiplex layer of a multi-layered compressed video signal, includes at the encoding end of the system apparatus for including a time stamp reference, such as a count value from a modulo K counter, and provision for a differential time stamp which may be updated by the transit times of respective (e.g., multiplexing) circuits as the to signal transits such circuits. At the receiving end of the system a counter is responsive to a controlled receiver clock signal and the count value of this counter is sampled at the arrival of the time stamps embedded in the transport layer. The time stamps and the differential time stamps are retrieved from the signal and combined to form a corrected time stamp. The differences of successive sampled count values of the receiver counter are compared with the differences of corresponding successive corrected time stamps to provide a signal to control the receiver clock signal.

Abstract: Apparatus for selecting predetermined ones of packets of signal components, from a signal stream of packets includes a control device, responsive to user selection and a transmitted program guide, for determining packet identifier codes, SCID's, for respective program signal components. The respective component SCID's are stored in progrommable registers. SCID's, from respective packets in the signal stream, are successively loaded into a further register. Comparators which are associated with the programmable registers, compare the stored SCID's with the SCID's from packets in the signal stream. Output signals from the respective comparators control the utilization of the respective signal component packets in the signal stream. Programming of SCID's in the respective programmable registers is performed according to a schedule to preclude undesired data inadvertently being accepted by the system.

Abstract: In a CD system of the type which stores data in both pits and magnetic domains, crosstalk injected into the signal recovered from the magnetic domains is significantly reduced by causing the modulator used to record the magnetically stored signal, to rapidly switch the direction of polarization of the laser light used to read the magnetically recorded signal. This tends to introduce a signal component which is similar to, but opposite in phase, the crosstalk created by the edges of pits recorded under the magnetic layer. This signal is inherently combined with the crosstalk components at the signal recovery circuitry and significantly reduces or cancels the pit induced crosstalk.

Abstract: A device for retaining an electronically readable card in an electronic device includes a substantially V-shaped resilient retainer dimensioned to engage a portion of the card while the rest of the card remains exposed for electronic reading purposes. The resilient retainer is held in the electronic device by a clip having a first detent member. The retainer includes a second detent member which engages the first detent member as the retainer enters the slit during insertion of the card into the electronic device. The thicknesses of the retainer and the card and the width of the slit are selected so that the resilient retainer is firmly held in the electronic device.

Abstract: An impedance converter includes an emitter follower constructed of a first transistor with a first resistor connected between an emitter electrode of the first transistor and an output terminal. Input to the emitter follower is provided by a second transistor of complementary type, with input signal applied to the base of the second transistor and the emitter electrode of the second transistor coupled to the base of the first transistor with a second resistor. Bias current in the second transistor and second resistor is in constant proportion to bias current in the first transistor and first resistor. Output impedance can be made positive, negative or zero by appropriate proportioning of the first and second resistors.

Abstract: A digital video signal processing system includes apparatus for concealing errors which might occur in reproduced images due to image data lost during signal transmission. The system includes circuitry for detecting transmitted video data, generating error signals if errors are present in segments (transport blocks) of the received data, and excising segments having errors from the data stream. The received data is applied to a decoder/decompressor system which decodes and decompresses the transmitted video data according to a predetermined sequence and applies the decompressed video data to a memory (for subsequent display or recording, etc.). The decompressor is responsive to the error signals for altering the predetermined sequence.

Abstract: A method for generating amplitude-coupled voltages for driving a multiple-winding electric motor using tapped voltages which correspond to the values of at least one predetermined curve configuration and using amplitude-coupled output voltages having a progression determined by time-controlled switching of the tapped voltages according to at least one temporal function includes an improvement wherein the tapped voltages have a progression, and the tapped voltages are controlled in such a way that the motor receives voltages having a first curve configuration during a start-up phase and voltages having a second curve configuration during normal operation.

Abstract: A method for determining which of similar video fields may be excised to enhance video signal compression evaluates parameters of four successive fields denoted 0, 1, 2, and 3. Accumulated differences d(0, 2) and d(1,3) of corresponding pixels in successive frames are generated. In addition a determination is made whether fields 1 and 2 exhibit interlace characteristics. If they do not exhibit interlaced characteristics, a comparison is made of d(0, 2) and d(1, 3). If d(0, 2) is less than d(1, 3) by a predetermined amount, field 2 is excised from the signal stream and a code is generated to condition a receiver to display two of the remaining four fields in a three field interval. Subsequently the latter two fields of the set of 0, 1, 2 and 3 fields, and the next two occurring fields are similarly analyzed.

Abstract: An optical disc record playback apparatus includes tracking circuitry for radially translating the scanning pickup device during normal playback of the disc. Coarse and fine drive circuits are responsive to tracking error signals to provide coarse and more precise radial translations respectively. The tracking error signals are monitored for the occurrence for abnormalities such as may be produced by dust on the disc surface, and responsive to the detection of such abnormalities the coarse drive system is disabled to preclude the pickup from leaving the track.