Abstract: A data structure, such as a digital television signal, includes (a) a video stream representing a picture and (b) auxiliary information, such as a closed caption stream. In one embodiment, the picture has special content that is not visible when a decoder correctly processes the auxiliary information. When an error occurs in the decoder processing, the special content becomes visible, thereby indicating the existence of the error to an observer of the rendered picture. In another embodiment, the video stream represents a sequence of time-varying pictures that provides a temporal reference for characterizing the relative timing of the decoder's processing of the auxiliary information.

Abstract: A data structure, such as a digital television signal, includes (a) a video stream representing a picture and (b) auxiliary information, such as a closed caption stream. In one embodiment, the picture has an inset window representative of a reduced version of the picture properly overlaid by the auxiliary information. In another embodiment, the data structure has two or more auxiliary information streams, and the picture is used to independently test the auxiliary information processing of each of the auxiliary information streams.

Abstract: A data structure, such as a digital television signal, includes (a) a video stream representing a picture and (b) auxiliary information, such as a closed caption stream. In one embodiment, the picture has special content that is not visible when a decoder correctly processes the auxiliary information. When an error occurs in the decoder processing, the special content becomes visible, thereby indicating the existence of the error to an observer of the rendered picture. In another embodiment, the video stream represents a sequence of time-varying pictures that provides a temporal reference for characterizing the relative timing of the decoder's processing of the auxiliary information.

Abstract: A data structure, such as a digital television signal, includes (a) a video stream representing a picture and (b) auxiliary information, such as a closed caption stream. In one embodiment, the picture has an inset window representative of a reduced version of the picture properly overlaid by the auxiliary information. In another embodiment, the data structure has two or more auxiliary information streams, and the picture is used to independently test the auxiliary information processing of each of the auxiliary information streams.

Abstract: A bitstream analyzer for detecting and verifying errors in the bitstream such as inconsistencies of time base and program specific information in real time is disclosed. Frequency tracking is provided with only a single time reference, by tracking the time of reception of various time-elements.

Abstract: A method and apparatus for creating a plurality of encoded bitstreams that represent selected waveforms in different ways such that when an audio decoder decodes the bitstream, an audible tone or lack thereof, will signify the failure of the audio decoder. The method employs a waveform having a set of baseline parameters but encodes the waveform in different ways by varying the parameter under test. The method monitors the audio decoder's ability to properly decode these alternating waveforms, by listening for an audible tone change or lack thereof. Since the behavior of the selected waveform is predictable, the method provides a set of simple and effective tests for evaluating black box audio decoders which may have no accessible internal nodes.

Abstract: A ghost cancelling system includes a ghost cancelling IIR filter and channel modelling circuitry for generating tap weighting coefficients for programming the ghost cancelling IIR filter. The channel modelling circuitry includes means for calculating the sum of all of the generated weighting coefficient values. If the sum exceeds a predetermined value indicative of the IIR filter becoming unstable, the weighting coefficients are conditionally scaled in a manner to reduce the sum, thus tending to reduce the possibility of filter instability.

Abstract: Apparatus for detecting the presence of a pseudorandom number (PRN) sequence used in a television receiver for reducing multipath interference such as image ghosts includes a multiplier responsive to a video signal containing the PRN sequence test signal component, and to a delayed version of such video signal. The amount of the delay is related to the duration of a PRN sequence, and one of the multiplier inputs is substantially devoid of average and DC components. A multiplier output representing correlation of the input signals indicates the presence of the test signal component, which is then passed to a network for processing to develop coefficients for a deghosting filter.

Abstract: A television signal to be equalized to compensate for transmission channel frequency and phase irregularities includes a test signal. A difference signal representing the difference between the average (DC) value of the test signal and a DC reference component of the television signal is obtained, and a predetermined portion of the test signal is FFT transformed. A ratio of a desired DC difference to the obtained DC difference as represented by the difference signal is developed. A ratio of a desired frequency response to a frequency response indicated by FFT transformed values, excluding DC, also is developed. Values associated with the two ratios are inverse FFT transformed, and the transformed values are used to control the parameters of an FIR filter for equalizing the television signal.

Abstract: In a cable television system an interferer signal is inserted into the video signal for scrambling purposes except during a vertical blanking reference interval containing a reference signal for use by a video equalizer in a television receiver to help reduce multipath distortion such as image ghosts.

Abstract: The present invention is directed to compensating the sin (x)/x response attendant the output signals from a Digital-To-Analog converter in systems consisting of the cascade connection of a digital processor having a non-uniform frequency response h(nT) and a Digital-To-Analog converter. This is accomplished by altering the processor to provide a frequency response of h(nT)*g(nT), where h(nT) is the impulse response of the processor, g(nT) is the impulse response of the reciprocal of the frequency response of the DAC, and the asterisk represents convolution. Alternatively, if the Fourier transform of the frequency response of the processor is given by F(.omega.), and the DAC exhibits a frequency response S(.omega.), which is the frequency transform of the time response of the DAC sample and hold type output, then the processor is substituted with one having a frequency response defined by the inverse Fourier transform IF(F(.omega.)/S(.omega.))) over the frequency band of interest.

Abstract: Deghosting apparatus for eliminating multipath signal components in a received transmitted television signal incorporates a training signal which is a finite duration sequence of repetitions of a 2.sup.n -1 psuedorandom sequence. The 2.sup.n -1 pseudorandom sequences are mapped into 2.sup.r sample intervals at either the transmitter or the receiver to facilitate fast Fourier transform processing. Power spectra of the received and mapped training signal and a stored version of the training signal are deconvolved with the deconvolution coefficients produced in logarithmic form. The logarithms are inverse Fourier transformed to produce delay coefficients related to the time of occurrence of the multipath signals, which coefficients are utilized to program variable delay circuitry in an adaptive filter to cancel the multipath components.

Abstract: A widescreen television system includes an auxiliary subcarrier modulated with left and right side panel luminance and chrominance components. The chrominance modulating component represents the difference between the average side panel chrominance information and the original side panel chrominance information. Average left and right side panel chrominance information is respectively conveyed during the horizontal blanking intervals of alternate lines.

Abstract: An NTSC compatible widescreen EDTV system encodes a television signal via a process including intraframe averaging of mutually exclusive successive paired groups of image pixels above a given frequency. At a decoder, intraframe averaged luminance image information is interpolated on a line-by-line basis to help reduce unwanted jagged diagonal image artifacts. Vertical peaking is associated with intraframe averaging at the encoder.

Abstract: Apparatus and method of synchronizing the component signals of a multi-component augmented television signal between its generation reception are disclosed. The disclosed apparatus includes circuitry which generates a training signal that indicates the position of the first pixel in each horizontal line interval of the video signal. This training signal is inserted into one horizontal line interval of the active video signal for transmission. The receiver includes circuitry which separates the training signal and derives a timing signal from it. The timing signal is used to define the pixel positions of various decoded components of the received video signal to facilitate their combination. The timing signal is also used to align the color subcarrier signal and to generate other carrier and subcarrier signals used in the decoding process. Two training signals are disclosed: a pseudo-random noise sequence and a time-reversed, all-pass filtered, raised-cosine 2T pulse.

Abstract: A sampled data tone control circuit is implemented using a two pole canonic recursive/non-recursive filter. The filter is programmed with predetermined sets of sample weighting coefficients to selectively cut or boost either the base or treble band of frequencies.

Abstract: Apparatus for estimating the square of a multi-bit digital sample having a value (A+B) segments the sample into a most significantf bit (MSB) portion having the value A, and a least significant bit (LSB) portion having a value B. The LSB portion is added back to the sample to produce a sample having a value of (A+2B), which sample is applied to the multiplicand input of a multiplier circuit. The MSB portion of the sample is coupled to the multiplier input of the multiplier circuit which produces the product (A.sup.2 +2AB) as an estimate of the square of the sample. Estimating the square in this manner significantly reduces the size of the multiplier circuit.

Abstract: A serial-bit digital processing system uses registers and latches to synchronize samples and justify sign-bits. Nominally each processing block in the system includes a sign extend register preceding an arithmetic element and an output register following the arithmetic element. Input registers of one arithmetic element may merge with output registers of the preceding arithmetic element. Ones of the registers include a serially coupled latch which is selectively controlled to pass serial sample bits or to replicate the sign bit. The respective registers are clocked with one of two clock signals having different numbers of pulses per sample period and the length of the respective registers are selected so that at the terminus of each sample period the bits of each sample in the processing system are appropriately justified.

Abstract: Circuitry for calculating the square root of a binary number iterates the equation E(K+1)=E(K)+(S-E(K).sup.2) where E(K+1) is the current estimate of the square root of the sample S and E(K) is the previous estimate. The value E(K).sup.2 is estimated in order to reduce the complexity of the hardware. An application is described for real time processing of digital audio signals in serial-bit format.

Abstract: Apparatus for multiplying a sampled data signal by a sinusoid having a period which is a multiple of the sample rate includes a plurality of sample scaling means to scale the sampled data signal by factors corresponding to the sine of angle .theta. over an angular range of 90 degrees in angular increments of 2.pi. divided by said multiple. A multiplexer multiplexes the scaled samples at the sample rate to produce a signal corresponding to the sampled data signal multiplied by the sinusoid. An embodiment is described for demodulating the stereo difference signal of a BTSC sound signal with serial-bit digital processing circuitry.