Abstract: An error concealment system for a digital video signal uses different methods of concealment in accordance with the severity of the error. An adaptive estimate (horizontal or vertical average) is used if all pixels need for such an estimate are valid. If not, a four pixel average is used. If that is not possible a vertical average is used, and finally a horizontal average is used. If the error is very severe, then a line store provides the last valid line.

Abstract: A phase detector for digital signals, such as television sync signals, provides a signed short path output of the phase difference between the signals. It features a means for determining which of the signals is leading and lagging, which means also provides the sign signal. A window signal is generated and clock pulses are counted during the duration of this signal. A register can provide an exact phase difference measurement or a coarse/fine output signal can be provided.

Abstract: A system is provided for filtering and demodulating digital color mixture signals, wherein the signals are filtered to remove out-of-band noise prior to completion of the demodulation process. Interleaved digital chrominance signal samples are first demodulated by a signal related in frequency to the video subcarrier to obtain interleaved color mixture signal samples of different sampling phases at baseband frequencies. The interleaved color mixture signal samples are applied to a digital filter at a rate which is a multiple of the color subcarrier frequency. The weighting coefficients of the filter are selected to obtain a bandwidth which passes the color mixture signal while removing out of band noise. Since the input signal sequence to the digital filter contains interleaved color mixture signal samples, alternate stages of the filter shift register are tapped, so that the output sequence will comprise filtered and interleaved color mixture signal samples.

Abstract: A television standards converter uses a VTR. The capstan speed is that of the video signal recorded on the tape, however, the drum speed is that of the standard to which it is desired to convert. Thus the reproduced signal has the original line rate but the new field rate. A line rate converter converts the reproduced signal to the new line rate, the signal is now totally in the new standard.

Abstract: An adaptive error concealment system uses either a horizontal or vertical average as a replacement pixel for an erroneous pixel. The choice is dependent upon the amount of horizontal information in at least one adjacent horizontal line. This avoids errors if certain horizontal or vertical stripe patterns are present in the video signal.

Abstract: A dropout compensator for time spread digital television signals uses either horizontal or vertical averaging to replace a dropped out sample. The choice of direction is made in accordance with whichever direction has the least amount of change around the missing sample or pixel. The circuitry can also be used for chroma inversion when stop or slow motion is to be transmitted or recorded.

Abstract: The storage locations of a memory system map a field of sample points. Apparatus affording parallel access to a plurality of storage locations describing an array of the sample points in an access window, which window can be shifted to any selected region of field of sample points responsive to orthogonal address coordinates of one of the sample points in the array, is described.

Abstract: Phantom raster scanning of an image memory, in which the image is stored in compacted form, is made possible by introducing offsets in strictly spatial coordinates, rather than in time coordinates parallelling a particular spatial coordinate system.

Abstract: Orthogonal Cartesian coordinates descriptive of the raster scanning of a television display screen are generated at a programmable skew angle to the Cartesian coordinates of an image stored in memory. Each of these generated coordinates has a number of more significant bits used to generate the column and row addresses for that memory, four spatially adjacent storage location of which are read from for developing each sample of video signal describing a rotated television image. Each of these generated coordinates has a number of less significant bits affording resolution higher than that with which the memory can be addressed, which are used for calculation of each video sample by two-dimensional interpolation between the read-outs from the four locations in memory. To avoid aliasing as the image is rotated, the digital video to be stored in memory is processed using two-dimensional spatial-frequency low-pass filters to reduce resolution in directions other than horizontal and vertical.

Abstract: The calculation of r.sup.2 =x.sup.2 +y.sup.2, where x and y are the Cartesian coordinates of a raster-scanned space, is carried forward by accumulation of 2x+1 and 2y+1 terms. A read-only memory can then be used for table look-up of r, the radial coordinate of raster scan in polar coordinates.

Abstract: A multichannel sampled system uses a single set of steering bits to reconstruct deleted samples from all channels. The steering bits can be derived from the channel having the greatest bandwidth or amplitude, or by majority voting logic operating on steering bits from all channels.

Abstract: A recording format is provided for video record and/or replay systems, which improves the operating performance and facilitates the implementation of many replay features. In this format, each raster of information is divided into at least two interleaved checkerboard pixel patterns and the pixels for each checkerboard pattern are recorded together and segregated from the pixels for the other checkerboard patterns.

Abstract: In a standard NTSC composite video signal, the peak excursion of the luminance plus chrominance signal for certain saturated colors exceeds the peak excursion of the white-representative luminance alone. When digitized, the signal is subject to quantizing noise. The effective spectial distribution of the quantizing noise is improved by reducing the amplitude of the chrominance signal so that the peak excursion of luminance plus chrominance for saturated colors does not substantially exceed the peak amplitude of white-representative luminance.

Abstract: In a transmission channel, such as a tape recorder, errors in code words usually occur in bursts. Further, it is usually possible to detect only some of the erroneous code words. To conceal undetected erroneous code words, concealment starts before, and continues after, a detected erroneous code word. Thus the undetected erroneous code words in an error burst have a high probability of being concealed.

Abstract: Method and apparatus for replacing defective video information in a video signal line comprises sampling the video signal. Video information from the preceding in-phase pixel and the subsequent in-phase pixel are averaged to form a replacement pixel. Weighting coefficients are generated based upon the amplitude difference between the next adjacent and semi-adjacent pixels having the same subcarrier phase. These weighting coefficients are used to determine the amount of information contribution of the previous and subsequent pixels to arrive at the closest video approximation of the defective pixel. Three times color subcarrier frequency sampling is preferred.

Abstract: A dropout compensator for time spread digital television signals uses either horizontal or vertical averaging to replace a dropped out sample. The choice of direction is made in accordance with whichever direction has the least amount of change around the missing sample or pixel. The circuitry can also be used for chroma invertion when stop or slow motion is to be transmitted or recorded.

Abstract: A TDM scheme has a Y signal that is sampled at 14.32 MHz and every other sample is discarded. The discarded samples are 180.degree. out-of-phase from line-to-line. I and Q signals are sampled at one half this frequency and every other sample is discarded also 180.degree. out-of-phase from line-to-line on a given line. The discarded samples of Q and I are 180.degree. out-of-phase with respect to each other. This allows insertion of the retained I and Q samples into the retained Y samples to allow multiplexing.

Abstract: A dropout compensator includes an estimator for forming continuous estimates of the value of a video signal subject to dropouts. In order to determine the presence of a dropout, the estimated signal is compared with the actual signal to form a difference. When the difference exceeds a predetermined amount, the estimated value is substituted for the actual value.

Abstract: Moviola color picture quality is improved for a record and replay system wherein video sampled at a predetermined multiple of the color subcarrier frequency is recorded with each frame or field being disposed on a set of multiple tracks and with only a portion of the recorded information being intended for replay to reconstruct the color Moviola signal. Only pixel groups relating to entire color subcarrier cycles are recorded on the tracks so that a video signal having proper color information can be readily reconstructed therefrom during the Moviola mode. In one preferred embodiment, sequential color subcarrier cycle pixel groups are recorded on separate tracks with those to be replayed during the Moviola mode on a single track so that Moviola pixel groups on the single track can be repeated in sequence when reconstructing the Moviola picture and thereby supply instantaneously coherent information.

Abstract: An apparatus for providing component-to-composite and vice versa transcodings of a sampled video signal features generating steering bits that indicate which of combinations of surrounding samples of a composite signal has a component that provides the closest match to the corresponding component of an original component video signal. This allows successive transcodings with a minimum of crosstalk between components, e.g., luminance and chrominance.