Abstract: A method and apparatus for transmitting a digital television signal which provides audio, video and data packets alternating with training signals. In order to minimize interference to other systems which could occur due to the periodicity of the training signal, randomly selected training signals are inverted prior to combining them with the data packets.

Abstract: A method of processing a first series of values representing a row of pixels of a digitized image for differentially encoding the first series of pixel values to generate a first series of codes representing a first series of differential values; expanding each code of the first series into a group of codes to form a second series of codes, each group of codes representing a plurality of differential values whose sum is the differential value represented by the corresponding code of the first series; and decoding the second series of codes to generate a second series of pixel values for display. By transmitting or recording the first series of codes and then effectively dividing each received or reproduced differential value into two or more smaller differential values, known apparatus can be made with little modification to expand each line of a received image by a factor of two or more, depending on the number of codes in each group.

Abstract: Device for encoding interlaced-field picture signals, comprising a first variable-length encoding channel (10) and an associated first prediction channel (20), as well as a second variable-length encoding channel (30), arranged in parallel with the first channel and including at its input side a circuit (31) for de-interlacing the fields, an associated second prediction channel (40) including a circuit (45) for re-interlacing the fields and a decision sub-assembly (50) for comparing the signals supplied by coding in the respective first and second encoding channels and selection of the prediction and encoding channels as a function of the result of said comparison.

Abstract: A television receiver comprising an improved interface circuit which automatically activates a PIP display of an auxiliary input (for example a videocassette or videodisc) when such an input is detected.

Abstract: In the encoding of a frame (P3) in a digitised motion picture sequence, the frame is divided into blocks (A) of pixels and a motion vector (VA) found to predicts the contents of each block A from a block (A') in a previous frame (I0). Rather than evaluate many thousands of candidate vectors to find the best motion vector (VA), relatively few candidate vectors are evaluated, based on starting vector which is the estimated motion vector for a neighbouring block (LB(A)) in the same frame. To allow parallel processing of several pixel blocks, all the blocks of one row in the current frame are assigned to one processor (DSP), and a starting vector is obtained from a block (LB(A)) previously processed by the same processor. Further starting vectors are obtained if desired from neighbouring blocks (UR(B),DR(B)) in neighbouring frames of the sequence. The candidate vectors based on a starting vector may be very few in number, or may fill an area a few percent of the full search area.

Abstract: The invention relates to the selection of a source from a plurality of sources by means of shunt switches and series switches, which are respectively turned on and mined off, and vice versa. For access to, for example, four sources the device has two intermediate terminals B.sub.1, B.sub.2), one series switch (SE.sub.a, SE.sub.b) is arranged between the user installation and each of the two intermediate terminals, and each of the intermediate terminals is coupled to two sources (IN.sub.1, IN.sub.2 or IN.sub.3, IN.sub.4) by each time one series switch (SE.sub.1, SE.sub.2, SE.sub.3, SE.sub.4). Moreover, each source (IN.sub.1, IN.sub.2, IN.sub.3, IN.sub.4) is a.c. coupled to earth by a matching impedance in series with a shunt switch (Z.sub.1, SH.sub.1, or Z.sub.2, SH.sub.2, or Z.sub.3, SH.sub.3, or Z.sub.4, SH.sub.4). The device is used in CATV.

Abstract: A coding subassembly for images composed of at least one moving pattern against a fixed or quasi-fixed background, including circuits for constructing a base model representative of the useful zone of the said images, a coding circuit, and an associated decoding subassembly. The model constructing circuits include circuits for initial calibration and adaptation of the model and a circuit for determining the movement of characteristic points taken from the useful zone and a circuit for selecting at least one zone of particular interest inside the useful zone and determining its movement. The coding circuit includes a circuit for coding output signals from the initial calibration circuit, and a circuit for correcting any shifts in luminance or chrominance in zones alongside the borders of the said zone(s) of interest observed on either side of these borders.

Abstract: Digital signal transmission system which operates by coded modulation of a constellation, the system comprising an encoder (5) which includes a modulator (13) installed at a transmitting station, and a decoder (105) which includes a demodulator (113) installed at a receiving station. A multistage channel encoder (12) carries out a concatenation of internal and external codes to blocks and divides the coding over various partitioning levels of the constellation. The coded symbol blocks are subjected to the work of a frequency-division interleaver (37), the modulator (13) operating according to an orthogonal carrier frequency-division multiplexing technique. The decoder (105) includes circuitry to carry out reverse operations to those carried out for the coding.

Abstract: The pictures of a video signal (a1) are coded and quantized in data blocks by a hybrid coder (4). A quantizer (404) is controlled in dependence upon the filling level of a buffer memory. To improve the bit rate reduction without any loss of picture quality in a standardized hybrid coder, circuitry is provided with which in special cases the usual control of the quantizer (404) is replaced by another type of control. There is such a special case when a data block is recognized as being associated with the background of a scene. This data block is then transmitted with high accuracy (very fine quantization), whereas the data blocks of the subsequent video pictures associated with the same background are not transmitted at all (coarsest quantization).

Abstract: A motion detector, particularly for use in a television system for transmitting television pictures in a digital form, is adapted to partition each picture into pixel blocks, to subject each pixel block to a modified intraframe transform for determining a first coefficient which corresponds to the basic picture having the lowest horizontal and highest vertical frequency, and to determine a plurality of further coefficients which correspond to basic pictures also having the lowest horizontal frequency, but a vertical frequency which is lower than that for the first coefficient. The motion detector signalizes the presence of motion within a pixel block if the first coefficient has a large absolute value, but if simultaneously none of the further coefficients has a sufficiently large absolute value. If the first coefficient has a sufficiently large absolute value, absence of motion is nevertheless signalized if simultaneously one of the further coefficients also has a sufficiently large absolute value.

Abstract: A circuit architecture suitable for use in a television receiver which effectively performs a ghost or echo cancellation procedure on post echo components and pre echo components occurring within the transmission channel. The apparatus features a filter circuit architecture which can be configured under programmed control so as to partition groups of its filter sections to form IIR filters and FIR filters. The filter architecture is suitable for use in multi-circuit configurations and can be used with clustering algorithms to increase the efficiency and optimize the use of the available circuit architecture.

Abstract: Texture synthesis device and method, based on digital video signals. The synthesis device comprises a circuit (16) for computing and memorizing the structural characteristics, based on a sample referred to as reference sample, a circuit (17) for restituting an approximate synthesis picture by means of growth in a predetermined region, based on its characteristics and on the sample with a subdivision of said picture in blocks of an identical size, a circuit (18) for constituting a dictionary, based on the blocks of the sample of the same size as those of said picture and a circuit (19) for decorating said approximate synthesis picture, based on output signals of said circuit for constituting the dictionary. The invention also relates to a method of and a device for transmitting and/or storing texture signals, including the implementation of this method and this synthesis device.

Abstract: In a method for determining motion vectors for each of the plurality of image blocks (X, O) together constituting a television image, motion vectors are computed only for selected ones (X) of the image blocks, and motion vectors for the remaining ones (O) of the image blocks are interpolated at least in part from the computed motion vectors of the selected blocks.

Abstract: For obtaining motion information by using a conventional motion estimator, a composite signal obtained from both the luminance signal and the chrominance signal is applied to this motion estimator. Based on the signals (Cb, Cr) of the two chrominance components (U, V), the contour of the colored elements of the image is extracted by means of Sobel filters (9, 10), i.e. high-pass two-dimensional filters, and the output signals of these filters are added to the luminance signal (2) in an adder (14), the resultant signal (3) being applied to the motion estimator.

Abstract: Receiver (105) for signals transmitted according to an orthogonal frequency division multiplexing technique with carriers distributed symmetrically around a centre frequency f.sub.e, said receiver comprising a frequency synchronizer (116) for the local oscillator (214). The synchronizer (116) utilizes the fact that part of the side carriers are not transmitted to ensure in the lock-on mode a frequency synchronization having a wide lock-on range. It may also be used in the permanent mode with very little jitter. The receiver can be used in digital television for receiving signals transmitted according to an orthogonal frequency division multiplexing technique.

Abstract: In a method of controlling a picture signal processing mode, first and second motion vectors are determined (ME, D.sub.T) for first and second fields, and a picture signal processing mode control signal is obtained by comparing (D.sub.T, -, COMP-R) the first and second motion vectors. The control signal may be transmitted along with, for example, a HDTV signal to give an indication to a TV receiver whether the signal originated from movie-film or from non-movie-film or be generated within the receiver.

Abstract: For dynamically modifying pseudo-random sequences of a pseudo-random sequence generator which is re-initialized at each start of the packet of information components, the information component itself is derived, delayed and combined with one of the series of bits present in the pseudo-random sequence generator. After having delayed the derived information component by a given delay (20), the component is modified by passing it through an EXCLUSIVE-OR gate (23) and by delaying the output signal of said gate with a delay (21) equal to that (20) used for said derived information component, and by feeding it back to the input of the gate.

Abstract: The video signal to be coded is coded in data blocks by a hybrid coder (4) which comprises a picture memory (410A) and a motion estimator (410B) for calculating motion vectors (v). The filter circuit comprises a multiplexer (S1) having two inputs (a1, f1) which applies either the video signal to be coded (a1) or a filtered signal (f2) to the input of the hybrid coder (4) and to the input of a further picture memory (F4). The further picture memory (F4) is arranged in the feedback path of a recursive filter (F) with which the video signal to be coded (a1) is temporally filtered. The multiplexer (S1) is controlled by a control device (S), which multiplexer receives as input data the video signal to be coded (a1), the motion vectors (v) and the data (a410) from the picture memory (410A) of the hybrid coder (4).

Abstract: A system and method for automatically improving the picture quality of television or other video based images, based upon picture content, using improved rule based picture analysis and compensation techniques. The distribution of facial and non-facial tones in a television picture are determined and used to control of picture color quality using neural network techniques. A preferred embodiment of the invention adjusts the brightness, contrast and color saturation of a displayed picture based upon selected portions of the received picture signal. These controls are adjusted every 1/60th of a second (i.e. at the end of each field) to provide an improved visual display. Analysis of the video signal in one field of a frame provides the information for adjusting the picture quality of the subsequent field of that frame.

Abstract: An extended television signal comprises control data for controlling an extended television decoder. The control data comprise first information bits (NB) for conveying information which need not be very reliably decodable immediately upon switching between broadcast channels or when their contents have changed. Each first information bit (NB) is channel-encoded by means of a first DC-free channel code into first channel bits each having a first duration (2 Tc). The control data further comprise second information bits (LB) for conveying information which must be very reliably decodable immediately upon switching between broadcast channels or when their contents have changed. Each second information bit (LB) is channel-encoded by means of a second DC-free channel code into second channel bits which each have a second duration (10 Tc) exceeding the first duration (2 Tc).