Abstract: Faults resulting in reception of a still, but unknown, frame are recognised by comparing each received frame of the video signal with its predecessor, incrementing a counter in the event that the difference between the frames falls below a threshold; and generating an alarm signal in the event that the count of the counter exceeds a predetermined count. Other types of fault such as loss of signal (i.e. reception of just noise) are recognised by incrementing the counter whenever the difference exceeds a threshold. Similar results may be obtained by instead the monitoring quantisation step size and/or number of transmitted bits of a digitally coded signal, and noting that it falls below, or exceeds, a threshold. A preferred option is to compute a complexity measure, being a monotonically increasing function (e.g the product) of the quantisation step size and of the number of coded bits and compare this with the threshold value.

Abstract: A system comprising a first filter having an input and an output adapted to compensate for the characteristics of a first length of twisted-pair wire is disclosed. A first bypass path has an input and an output for bypassing the first filter. A second filter has an input and an output adapted to compensate for the characteristics of a first length of twisted-pair wire. A second bypass path has an input and an output for bypassing the first filter. A third filter has an input and an output adapted to compensate for the characteristics of a first length of twisted-pair wire. A third bypass path has an input and an output for bypassing the first filter. The three filters can be configured form a signal path or one or more filters removed from the signal path by switching in bypass paths.

Abstract: A system and method are provided for performing wireless diversity processing in a data-over-cable network. A diversity controller is provided which, based on signal-to-noise ratio, chooses an optimal path for receiving and transmitting data to and from a subscriber location. A stand-mounted access point enables wireless communication with subscriber locations. Diversity processing includes selection diversity, maximal rate combining, and equal gain combining.

Abstract: A monitoring system for an RF transmission system, such as a multi-channel television broadcasting antenna feed system, gathers data about the physical and electrical condition of the RF transmission system in real time. The system can detect and localize deterioration and other time-dependent faults in the transmission system by the tendency of faults to produce reflections back to the transmitter that were not part of the original characterization of the installation. Some kinds of faults, identified early enough, can be corrected without replacing components, and especially without shutting down the transmission system during prime viewing hours in the case of television broadcasters, or during a critical period of use of the system in the case of other user types. Other faults can be detected in time to order replacement parts before the underlying problem becomes severe, and to allow servicing during periods of low demand.

Abstract: Assessment of de-interlaced video quality is determined automatically by de-interlacing interlaced video content using a reference de-interlacer and a test de-interlacer. The reference de-interlacer produces a result of known quality and the test de-interlacer is one which is being assessed. The result from each de-interlacer is compared to reference video content to derive a signal-to-noise ratio for each relative to the reference video content. The difference in the signal-to-noise ratios is compared against a predefined threshold. If the difference is within the range defined by the threshold, the test de-interlacer is determined to produce an acceptable product.

Abstract: A receive part demodulates and decodes a digital modulated signal obtained by receiving a digital broadcast to generate a transport stream, and extracts data-broadcast data transmitted over a data channel. An electronic program list generator generates, from program sequence information included in the transport stream, display data for a program list. Based thereon, a video display part displays the program list. When the user looks at this and selects a program desired for preset recording through an input operation part, a system control part determines whether or not the weather during the broadcast time period of the program will be bad based on weather forecast information obtained from the data-broadcast data. As a result, if the weather is determined as bad, the system control part causes the video display part to provide a display indicating a possibility of degradation in image quality, etc., during the broadcast time period.

Abstract: Feature quantities of a transmitted picture and a received picture are extracted from a first and second block-by-block feature quantity extraction parts which are provided on a transmitting and receiving sides, respectively. The extracted feature quantities are transmitted to a block degradation calculation part which compares the transmitted feature quantities and finds the degree of picture quality degradation for each block. Next, a median filter replaces the degree of picture quality degradation for the each block with a median of the degrees of picture quality degradation among the neighboring blocks of the each block. Then, a degraded block detection part compares the median with a predetermined threshold and detects a degraded block. Finally, a degraded region detection part removes an isolated degraded block and detects a degraded region. According to the invention, local picture quality degradation in a frame caused by transmission failure can be automatically detected with high accuracy.

Abstract: A switch router and one or more gateways incorporating a diagnostic and calibration system that performs RF characterization of an underlying cable plant. The switch router is connected at a point of insertion or point of distribution and each gateway is located downstream, such as at corresponding subscriber locations. The switch router and each gateway sends a test signal with known characteristics and power level, and the receiving device determines noise level and power loss for the corresponding downstream and upstream channel pair. The power loss information is used to calibrate the power level of the transmitters. The noise levels are used to determine if the selected modulation schemes employed for normal communications is realizable. A frequency analysis, such as FFT or the like, is performed on the upstream test signal spectrum to derive valuable frequency information for the upstream channel or the entire upstream bandwidth.

Abstract: An optical projection system has a parallel light source for producing a parallel light beam. A first color splitter splits the parallel light beam into a first color beam and a color mixing beam. The color mixing beam includes a second color beam and a third color beam. A first both-side telecentric group is disposed on a first light path of the first color beam, so as to transform into a first light beam. A second both-side telecentric group is disposed on a second light path of the color mixing beam. A second color splitter is disposed on the second light path to split the color mixing beam into a second light beam and a third light beam. A light-combining unit receives the first, second, and third light beams and combines into a mixed beam. Then the mixed beam is projected.

Abstract: A method of determining noise in a CATV channel, wherein the CATV channel comprises a predetermined frequency band, that employs digital signal processing to isolate the noise signal from an in-service television signal. The method includes an initial step of obtaining a television signal corresponding to a predetermined CATV channel, the television channel comprising a carrier signal modulated by an information signal. Thereafter, the method includes the step of sampling at least a part of the television signal to produce a digital signal segment, said digital signal segment comprising a carrier component, a noise signals component, and an information signal component, wherein said information signal component has a substantially predetermined signal pattern. The method then employs digital signal processing to separate the carrier component from the digital signal segment to produce a baseband signal substantially comprising the information signal and the noise signal.

Abstract: An antenna level display device capable of faithfully reflecting any deterioration of a picture quality in receiving a satellite broadcast. In this display device, orthogonal detection of an input signal is executed in a demodulator, and a CN ratio is calculated from a conversion table in a ROM according to the mean value of deflections of mapped points of the received signal on an IQ plane. The demodulated data is compared, in a comparator, with the demodulated data obtained after error correction by a Viterbi decoder, and a CN ratio is calculated on the basis of the bit error rate from a conversion table stored in another ROM. A decision is made to select one CN ratio, which is to be displayed as an antenna level, out of the two calculated CN ratios, and the selected CN ratio is displayed through adaptive switching.

Abstract: The present invention comprises a device which may be attached to a cable ground block (62) such that the level and type for signal emitted through the upstream flow of the signal, from a residence or business (59), may be determined along with the location of the source of ingress of any such signals. The invention, further includes a device (10) to transmit a signal of predetermined frequency towards a residence, such the source of errant signal ingress may be determined. Further, a method of causing the transmission of the signal at a predetermined time, measurement of the signal and determination of the source of the ingress of the signal is provided.

Abstract: A first characteristic value extracting unit extracts a characteristic value from a picture transmitted from a transmission side, and a second characteristic value extracting unit extracts a characteristic value from a picture received on a reception side. These extracted characteristic values are supplied to a central monitoring unit through low speed lines, respectively. In the central monitoring unit, an MSE (mean square error) is assessed from the data by an MSE assessing unit. The first and second characteristic value extracting units divide an input picture into blocks, subject the blocks to an orthogonal transformation, or subject the blocks to PN sequence multiplication before the orthogonal transformation, and extract and output orthogonal transformation coefficients.

Abstract: A linear compensation system of a digital TV relay or other apparatus preferably includes a transmitting unit configured to modulate a data to an intermediate frequency (IF) signal, up convert the IF signal to an RF signal, and amplify the RF signal to a predetermined level using a high power amplifier (HPA). The system also includes a linear compensation unit to preferably directly vary a step size of an adaptive equalizer according to whether a signal-to-noise ratio (SNR) or an error vector magnitude (EVM) for an output signal of the HPA satisfies an advanced television systems committee (ATSC) or other standard. The linear compensation unit is thus configured to output an improved linear compensation coefficient to a modulator of the transmitting unit.

Abstract: The invention, in part, provides an integrated digital television (DTV) diagnostic instrument comprising: at least one of a video display device (VDD) and an audio display device (AudDD); DTV circuitry (AV) to receive a DTV signal, to reconstruct at least one of a video stream and an audio stream from the DTV signal, and to display at least one of the video stream and the audio stream on the VDD or the AudDD, respectively; and at least one of monitoring circuitry (M), responsive to the DTV circuitry, to monitor digital properties of a live DTV signal and analysis circuitry (AN), responsive to the DTV circuitry, to analyze digital properties of a recorded DTV signal.

Abstract: A picture quality measurement technique using blockiness provides realtime analysis without the use of a reference signal. A field/frame of an image represented by a processed video signal is captured in a bit-map for analysis. The image is filtered to enhance edges and then correlated with a kernel having a size corresponding to the block size of the compression algorithm used in compressing and decompressing the video signal to produce the processed video signal. The correlation results are processed by comparing an average value with the maximum value to produce a picture quality rating for the processed video signal.

Abstract: Cable modems are provided for measuring a noise signal power level on the upstream side of the cable network. The cable modem may be configured to make the signal power measurements at a variety of frequencies and at a selected bandwidth during a specified test time period responsive to a request received from the cable network. Methods and systems are provided for identifying a noise signal source on a cable network including specifying a time window for measurements, the desired measurements and the cable modems from which measurements are desired when the need to initiate a test to identify a noise source is detected. Tests may be initiated based on noise signal measurements by individual cable modems or by the cable services provider which indicate an unacceptable noise level. In addition, the reliability of the test measurements may be improved by not allowing any transmissions on the upstream side during the concurrent test window while cable modems are making the requested measurements.

Abstract: A communication system (100) processes forward signals generated by headend equipment (105) and reverse signals generated by subscriber equipment (135). A communication medium (110, 120), such as fiber optic cable or coaxial cable, connects the headend equipment (105) and the subscriber equipment (135), and amplifiers (400) are positioned at various locations along the medium (110, 120) to amplify the forward and reverse signals. The amplifiers (400) include a dual forward/reverse test circuit (FIG. 6) having a forward test point (406) coupled to the forward signal, a reverse test point (408) coupled to the reverse signal, and a single directional coupler (404) connected to the forward test point (406), for providing the forward signal thereto, and to the reverse test point (408), for providing the reverse signal thereto.

Abstract: A method for decreasing upward-joining-noise in an upward-signal-inputting position of a center device includes the steps of: measuring a noise level of each of a plurality of upward signals supplied from a plurality of transmission lines; determining whether the measured noise level of each upward signal is low enough or not; and based on a determination result, controlling and adjusting a level of each upward signal. Therefore, the level of an upward signal, for which the noise level of the upward signal is determined to be low enough, is adjusted higher but still kept at a level low enough not to interfere with upward signals from other transmission lines.

Abstract: Detecting tampering of an incoming cable to which a network interface unit (NIU) is connected by testing for the reflected signal that is present when the signal being transmitted to the head end is not connected to a properly terminated coaxial cable. In particular, by comparing the phase of the transmitted signal from the NIU with that of the reflected signal, a distinction can be made between a signal that travels many feet before being reflected back and a signal that reflects back right or near the connector of the NIU. Only the latter is used as a stimulus to indicate tampering since the first is likely caused by cable personnel disconnecting the cable further into the network. The key difference between the two types of reflected signals is the time delay of the reflect signal with respect to the transmitted signal from the NIU.

Abstract: A device for objectively evaluating the quality of a digitally transmitted picture. This device compresses encoded pictures x1 and x2 transmitted on two links that are decoded by a first decoder and a second decoder. A variance value &sgr;2(x1) of the decoded picture decoded by the first decoder is measured by a variance measuring unit. A variance value &sgr;2(x1−x2) of a signal indicative of a difference between the decoded pictures decoded by the first and the second decoders is measured. These two variance values are used to determine image quality.

Abstract: A method of transmitting a leakage tagging signal includes inserting a tagging signal into a CATV television signal only during portions of the television signal in which control information is present. A method according to the present invention is a method of transmitting a tagging signal in a communication system, the communication system transmitting television signals comprising control information and program information. One step of the method includes generating a tagging signal that is detectable by corresponding leakage detecting equipment. The method also includes the step of identifying a portion of a television signal in which control information is present. Finally, the method of the present invention encompasses inserting the tagging signal into the television signal only during the portion of the television signal in which control information is present.

Abstract: The present invention relates to a method and system for evaluating the quality of encoded video data without gaining access to the source data or the compressed video bitstream. The system is configured to decode compressed video data using an MPEG decoder to produce decompressed video data. The decoded data is analyzed to determine whether the decompressed video data is intra-coded. If so, a discrete cosine transform (DCT) is performed to produce a set of DCT coefficients for at least one AC frequency band in the decompressed video data. At the same time, quantization matrix data of a frame of the decompressed video data as well as a quantizer scale for each block of the decompressed video data are extracted. Thereafter, the variance of the converted DCT coefficients is obtained, and then an average quantization error for each set of said DCT coefficients is determined based on the variance, the quantization matrix, and the quantizer scale.

Abstract: Apparatus, methods, and computer program products are disclosed for detecting or locating a viable data carrier in a downstream channel by a cable modem. When a cable modem is first installed by a cable operator or powered up by a user, it must first locate or tune in to the correct downstream channel in order to receive data from the headend of the cable plant. This time-consuming process can be shortened by performing two matches between the selected, potential downstream data carrier and constellation diagrams of certain modulation schemes. Through this method, potential channels for data carriers can be eliminated quickly by going through a “screening” process (the first constellation diagram match) thereby preventing those potential channels from going through a significantly more time-consuming second constellation match. The process begins with selecting a potential frequency channel from the downstream band.

Abstract: Apparatus, methods, and computer program products for utilizing a frequency channel determined to be unacceptably noisy by finding a cleaner, narrower bandwidth within the frequency channel. Initially data is received on a frequency channel at a CMTS, specifically an upstream receiver, and by a narrow bandwidth detector, connected to a processor also used by components in the CMTS. The narrow bandwidth detector performs a Fast Fourier Transform (FFT) on the frequency channel thereby creating multiple FFT points within the frequency channel. A clean bandwidth for transmitting data within the frequency channel is identified where the clean bandwidth is derived from a subset of FFT points from the full set of FFT points. The subset of FFT points are contiguous points that have a noise level below a predetermined noise threshold.

Abstract: A cable television system (400) includes a transmitter (200) for generating a digital optical signal (204) and a receiver (300) for receiving said digital optical signal and converting it to an analog signal. The transmitter (200) includes a processor (238) for processing inputs and generating a gain/loss parameter which is applied via a gain/loss amplifier (250) to an incoming analog signal (232). The modified digital signal received by the digital optical receiver (300) decodes the applied gain/loss parameter at a converter (325) and applies the information to the output analog signal via a gain/loss amplifier (330).

Abstract: An apparatus for measuring the quality of a video transmission or storage system when the input and output of the system may be spatially separated, when the apparatus might not have a priori knowledge of the input video, and when there exists an ancillary data channel that can be used by the apparatus. The apparatus makes continuous quality measurements by extracting features from sequences of processed input and output video frames, communicating the extracted features between the input and the output ends using an ancillary data channel of arbitrary and possible variable bandwidth, computing individual video quality parameters from the communicated features that are indicative of the various perceptual dimensions of video quality (e.g., spatial, temporal, color), and finally calculating a composite video quality score by combining the individual video quality parameters.

Abstract: The invention concerns a method for determining the quality of a video and/or television image signal. In diversity reception installations comprising several receivers, it is necessary to establish a criterion for assessing the reception signals, so as to select the receiver with the best reception. In order to determine the quality of a television image, the interfering impulses appearing in a line after a horizontal synchronization impulse are detected then their parameters are evaluated. The invention is applicable to television receivers, video recorders, diversity reception installations, in particular for mobile installations.

Abstract: A CATV system in which a technician in the field requests via a field client that a node of the CATV system be tested for ingress. The CATV system includes a headend facility that is coupled to a CATV distribution network. The CATV distribution network includes a plurality of nodes through which upstream signals are transmitted to the headend facility. A method of ingress testing for use in the CATV system includes one step of receiving at the headend facility a first reverse telemetry signal transmitted by a first field client that is coupled to the CATV distribution network at a first location downstream from the headend facility. Another step of the method includes selecting at the headend facility a first test node from the plurality of nodes of the CATV distribution network, wherein the selection is based upon the received first reverse telemetry signal.

Abstract: An apparatus and concomitant method for creating and applying an encoded bitstream to evaluate the performance of a black box video decoder. The encoded bitstreams are designed such that the results from the DUT can be evaluated without the need of a human observer. The method applies the encoded bitstream to both a DUT and a compliant reference decoder and compares the results from both decoders to determine compliance of the DUT. Additional embodiments address postprocessing and the selection of a subset of test frames for evaluation.

Abstract: An S/N ratio measuring method of a video signal which is suitable for the formation of an IC and can precisely detect a fluctuation of an S/N ratio of a video signal at high response speed while suppressing the total cost and a system based on this method. In operation, a composite video signal is received, a noise density in a predetermined period of the composite video signal is detected, and an S/N ratio of a video signal included in the composite video signal is recognized basis on the detected noise density. The S/N ratio measuring system has a demodulator for demodulating the composite video signal from the reception signal and a counter for counting noises which are generated in a predetermined period of time of the composite video signal and recognizes the S/N ratio of the video signal included in the composite video signal based on a count value obtained.

Abstract: A graphical video editing system that allows manipulation of images for input to the video encoding and decoding process. The debugging of video encoders and decoders is aided by user controlled editing of problem areas in test images, and the graphical video editing system is coupled directly to the video encoder or decoder being debugged so that the effects of the editing can be immediately observed. This system advantageously provides a speedup in the debugging process by simplifying the detection of problem areas and providing a fast method for narrowing the possible causes of image flaws. Broadly speaking, the present invention contemplates a graphical video editing system for regeneration of bitstreams. The system comprises an encoder module, a decoder module, a display editor module and a display. The encoder module is configured to receive an input image and to convert the input image into an encoded bitstream.

Abstract: A method of transmitting a leakage tagging signal includes inserting a tagging signal into a CATV television signal only during portions of the television signal in which control information is present. A method according to the present invention is a method of transmitting a tagging signal in a communication system, the communication system transmitting television signals comprising control information and program information. One step of the method includes generating a tagging signal that is detectable by corresponding leakage detecting equipment. The method also includes the step of identifying a portion of a television signal in which control information is present. Finally, the method of the present invention encompasses inserting the tagging signal into the television signal only during the portion of the television signal in which control information is present.

Abstract: An exemplary embodiment of the present invention is an apparatus for receiving sweep testing signals and generating frequency response values therefrom. The apparatus includes a test input, a controller, a receiver circuit and a measurement circuit. The test input has a first connection arrangement for connecting to a test output of the sweep transmitter and also has a second connection arrangement for connecting to a terminal of the communication system to be tested. The controller is operable to generate a sweep control signal responsive to a sweep plan. The receiver circuit has a control input connected to receive the sweep control signal from the controller, and is operable to tune to a plurality of frequencies responsive to the sweep control signal. The measurement circuit is coupled to the receiver circuit and is operable to generate measurement signals corresponding to the plurality of frequencies.

Abstract: An apparatus for evaluating digital picture quality, includes a SNR calculation module for calculating a SNR based upon differences between data of video picture to be evaluated and data of original video picture, a module for calculating a power of AC component of overall data of one of the video pictures in a frame, and a weighting module for weighting the calculated SNR based upon the calculated power of the AC component.

Abstract: A discrimination about a standard screen or a wide screen is performed by a discriminating circuit in accordance with the presence or absence of upper and lower black stripes of a wide screen video signal. A video signal transmitted through a low pass filter is supplied to the discriminating circuit, the presence or absence of the upper and lower black stripes of the video signal is detected and the discrimination about the standard screen or the wide screen is performed by the discriminating circuit. A noise level of the video signal is detected by an S/N ratio detecting circuit. Characteristics of the low pass filter are set in accordance with an output of the S/N ratio discriminating circuit.

Abstract: A digital receiver (e.g., an ATV or HDTV receiver) which receives digital signals (e.g., ATV or HDTV signals), and which includes an equalizer for equalizing multipath channels having known co-channel interference (e.g., co-channel NTSC interference) present therein. A co-channel interference rejection filter is inserted in the digital receiver upstream of the equalizer, and the equalizer is modified in such a manner that it will not attempt to equalize the co-channel interference. Thus, co-channel interference cancellation is done primarily by the rejection filter, while multipath equalization (correction) is the exclusive function of the equalizer. This leads to better co-channel performance than that which can be obtained by relying on the equalizer alone to perform both functions. The co-channel interference rejection filter is preferably a multi-tap filter having fixed filter coefficients which are designed to optimize cancellation of the known co-channel interference.

Abstract: In FIG. 5, a plurality of signal sources 21.sub.1 to 21.sub.N each generate a carrier with different frequencies. A pulse signal generating portion 23 generates a pulse signal with the same period and time width as those of a horizontal synchronizing signal in NTSC system color television broadcasting. Delay devices 32.sub.1 to 32.sub.N delay timing of the pulse signal for a randomly predetermined delay amount. Level adjuster 52.sub.1 to 52.sub.N generate a modulating signal by adjusting each pulse base of the delayed pulse signal for a level within a range between 12.5% and 74.375% with respect to a pulse top. Modulators 42.sub.1 to 42.sub.N output a signal obtained by modulating the carrier with the modulating signal. A multiplex portion 24 multiplexes the modulated signals to output a resultant signal as a test signal. The error rate of a QAM signal is evaluated with the test signal.

Abstract: A portable HDTV testing device inserts a deterministic test signal having a frequency close to the symbol rate of the received HDTV signal. As the received HDTV signal is randomized prior to broadcast for synchronization purposes, the addition of the deterministic test signal to the randomized data signal is essentially equivalent to the addition of a random (or white) noise signal to an information bearing signal. The use of a deterministic test signal avoids the expense associated with a random signal generator, thus making possible an inexpensive and portable HDTV test device. To test the noise margin of a received signal, which is used to determine if the installation of the antenna and HDTV receiver is optimized, the test unit inserts known levels of the noise signal incrementally and measures the bit error rate until the bit error rate exceeds a known threshold above which proper decoding is not possible.

Abstract: A system and method for locating ingress noise gaps for an upstream data carrier in a cable network utilizing cable modems is described. A system for identifying a transmission frequency that has less noise than other available frequency bands includes a packet generator, a rate controller, an echo device, a demodulator, and a packet checker. The packet generator and rate controller, contained in a cable modem termination system, send test data downstream to the echo device which then redirects the test data upstream at a selected test frequency. The echo device, which may be located within the cable modem termination system or outside the termination system, listens on the downstream path for data packets addressed to it. Once received, the echo changes the address of the test data to the address of the packet checker. The packet checker then receives and analyzes the test data packet sent from the echo device to assess the amount of noise on that particular test frequency.

Abstract: A character reader comprises an input unit for reading characters by a scanner-typed photoelectric transfer unit as an image, creating the image data formed by binary pixel of white and black lying on the plain surface and entering the same, a tangent detecting unit for detecting tangent information on tangents contacting with black pixels forming a character string within the image data, a tilt deciding unit for deciding a representative tangent which is representative for the direction of a row of character string, from the above-mentioned tangents, on the basis of the tangent information detected by the tangent detecting unit.

Abstract: An error detecting/correcting circuit 9 in a digital broadcast receiving device calculates a error rate from the error amount for the amount of input information. A controlling part 15 converts the error rate into the C/N ratio as a receiving signal quality and indicates it on a screen of a TV receiver 5 or other indicator 18. In this method, after digitally demodulating the received digital broadcasting signal, the error rate is obtained by an error detecting part 9 and the error rate is converted into the receiving signal quality for indication. Therefore, compared with the reception performance indication based on the input level such as the AGC voltage, the method is high both in precision and in stability. The receiving signal quality can be detected only while receiving a digital broadcasting signal, so with reference to the converted receiving signal quality in antenna bearing adjustment, a digital broadcasting signal can be surely received without confusing it with an analog broadcasting signal.

Abstract: A system and method for locating ingress noise gaps for an upstream data carrier in a cable network utilizing cable modems is described. A system for identifying a transmission frequency that has less noise than other available frequency bands includes a packet generator, a rate controller, an echo device, a demodulator, and a packet checker. The packet generator and rate controller, contained in a cable modem termination system, send test data downstream to the echo device which then redirects the test data upstream at a selected test frequency. The echo device, which may be located within the cable modem termination system or outside the termination system, listens on the downstream path for data packets addressed to it. Once received, the echo changes the address of the test data to the address of the packet checker. The packet checker then recieves and analyzes the test data packet sent from the echo device to assess the amount of noise on that particular test frequency.

Abstract: A transformation block optimization method provides transformation blocks of variable size for video compression processes. The method includes defining a transformation block of multiple pixels in an image frame and determining a peak signal-to-noise ratio for the transformation block. The transformation block is tentatively subdivided into subcomponents for which a signal-to-noise ratio is also obtained. The subcomponents are adopted as transformation blocks whenever the signal-to-noise ratios of the subcomponents are greater than the signal-to-noise ratio of the transformation block by more than a predetermined threshold.

Abstract: Method and apparatus for non-invasively testing performance of a digital communication system. The test system finds particular application in digital broadcast systems where interruption of regular service for test purposes is impracticable. In one embodiment oriented to digital television cable broadcast systems, unwanted reflections due to loose connectors and other causes may be localized within a subscriber's home. The test system takes advantage of information typically generated by digital receivers to correct for communication channel imperfections. Examples of such information include current filter parameters computed for use in an internal adaptive equalizer, internal loop parameters, and the difference between the signal received and a reconstruction of that signal from the symbols estimated by the receiver.

Abstract: An in-service composite triple beats (CTB) measurement system for a cable television (CATV) system isolates and measures weak composite triple beat components in the presence of a visual carrier modulated with program material for selected channels of the CATV system. Each channel is demodulated and digitized in a frequency bandwidth about the visual carrier for the channel (the CTB frequency range). The digitized video is sampled during the vertical interval, and corresponding samples from consecutive frames are differenced, squared and accumulated to produce a CTB value, which may be scaled and corrected for noise. Noise correction is achieved by performing the same measurement, but digitizing in a frequency bandwidth offset from the CTB frequency range. The difference between the two measurements provides a corrected CTB value.

Abstract: Video cameras, such as charge coupled device cameras, are used for optically making spatial measurements. For example, such cameras are used for laser beam analysis. Such cameras also have drawbacks including baseline offset error and poor signal-to-noise ratio. By adjusting the baseline so that both noise and the desired signal produce only positive digital counts, deriving a baseline offset level with only noise, and then subtracting the baseline offset level from subsequent frames Containing data representing both noise and the desired signal, the baseline offset is corrected. With the baseline offset being corrected, signal-to-noise ratio improving techniques, such as frame averaging and results averaging, can be applied to extract the desired signals which would otherwise be buried in the noise. The method and apparatus is particularly suited to laser beam performance evaluations.

Abstract: Video cameras, such as charge coupled device cameras, are used for optically making dimensional measurements of laser beams. Such cameras have drawbacks including baseline offset error, shading error, pixel-to-pixel fixed pattern offsets, and poor signal-to-noise ratio. Methods and apparatus to correct for these errors, without losing any desired signal components, wherein the baseline offset error is corrected without the loss of any signal components that may otherwise be obscured due to noise. The baseline of the signal is raised above a digitizer's zero level, an average baseline without an input signal present is determined, and then the average baseline is subtracted from the subsequently obtained signals. The subtraction process is performed such that the subsequent frames in memory retain all negative signal components, as well as positive signal components, and thus there is no loss of the desired signal.

Abstract: A method of determining the noise content of a video signal by digitizing a frame based on the video signal to provide a digitized signal which is then filtered via a high pass filter. The filtered image is then divided into a plurality of subimages and the noise signal in each of the subimages is determined from a selected number of subimages having the lowest noise signal are further processed to determine the average noise in the selected subimages and the signal-to-noise ratio determined. The carrier-to-noise ratio may also be determined if desired.