Abstract: The system includes a base station (1) which communicates with a plurality of data carriers (2.sub.1, 2.sub.2) via wireless links. In order to enable the station (1) to identify several data carriers simultaneously, the system includes a device (15) for the separation of sources and also several demodulation units (12.sub.1, 12.sub.2).Depending on the type of modulation, the type of link used, and the arrangement of the source separation device (15) with respect to the demodulation units, the signals received by the source separation device can be convolutional mixtures or instantaneous linear mixtures of the signals transmitted by the data carriers. In order to process the different types of signal received, the source separation device may have a recursive structure, a direct structure or a mixed structure.

Abstract: For an arrangement for reproducing decompressed video and/or audio data at a video and an audio reproduction clock frequency, the arrangement comprises a circuit for generating the video and/or audio reproduction clock, which the circuit derives the reproduction clocks from the externally supplied digital video signal, for the purpose of synchronizing these data and for a possibly joint representation by an external video signal.

Abstract: A method and apparatus are provided for encoding of digital video signals in the form of video clips (A,B) to enable them to be seamlessly joined without requiring reset of a decoder to a starting state. The system uses an encoder having a coding stage and an encoder buffer, and comprises successively encoding the pictures of a clip according to a predetermined coding scheme (suitably according to MPEG standards), reading the encoded pictures into the buffer, and subsequently reading the encoded clip out of the buffer at a substantially constant bit rate. To enable simple joining of the clips, a predetermined encoder buffer occupancy (B.sub.ic) is specified with a controllably varied target number of bits being used to encode a picture. The targeting produces an encoder buffer occupancy substantially equal to the predetermined buffer occupancy (B.sub.ic) at the moment the last picture of the segment has been read into the buffer.

Abstract: A transform coder wherein different segments of signal samples to be transmitted to a receiver are encoded using different coding transforms. In order to avoid problems encountered with signal samples forming the transition between successive segments an intermediate transform is used for such transition. This has conventionally required significant transmission overhead, because the selected intermediate transform matrix must be transmitted to the receiver to enable it to decode the transitional signal samples. The invention instead provides weighting factors to indicate the extent to which frequency spectra of the basis functions of the intermediate transform resemble the frequency spectra of the basis functions of the transforms used for the adjoining signal segments. The inverse of the intermediate transform can then be calculated by the receiver from the weighting factors.

Abstract: In source coding, use can be made of switching filter banks in order to adapt the filter bank to the properties of the signal to be coded. If it is not allowed that the switching introduces transient phenomena in the reconstructed signal, so-called boundary filters have to be used in the system according to the present invention, it is possible to dispose with the transition filters without introducing undesired transient phenomena. In order to obtain said property the new filter coefficients (after switching) have to be a linear combination of the original filter coefficients (before switching).

Abstract: Method and arrangement for marking a video or audio signal to assign a classification to said signal, for example, to identify that the signal is authentic and may not be copied. The signal comprises at least two components (Y, UV) according to a predetermined standard (MPEG, PAL, NTSC). According to the invention, values are assigned to said components which in combination can normally not occur. For example, in black picture portions where Y, U and V are all zero, U and/or V are now wilfully made non-zero to constitute the watermark. Television receivers still display said black portion. The watermark is not lost when the signal is re-encoded and copied on a recordable disc. A player will not reproduce the copy because the watermark no longer corresponds with the "wobble key" of the new disc.

Abstract: In accordance with the MPEG-2 standard for compression of a digital signal representative of a video image, the image is separated into groups of several different types of pictures and those of each type are encoded by respective encoders. Depending on the complexity and bitrates of each picture, the bitrates of the encoders may vary and so must be restored to a constant bitrate by respective output buffers. Also, the global sum of the contents of the individual buffers must be maintained substantially constant so as to provide a constant global bitrate. The invention provides a method and apparatus for bitrate control of each encoder based on a measure of the complexity of the picture being processed thereby and the bitrates which are required in order to maintain a substantially equivalent quality of the pictures encoded by the respective encoders.

Abstract: Method and device for estimating motion between segmented images, or partitions, composed of a number I regions R.sub.i. For performing the method, this device comprises a stage (41) for initializing parameters which describe the motion of each region R.sub.i, in which one of different motion hypotheses chosen a priori is selected after prediction, computation of the prediction error and selection of the motion hypothesis to which the smallest prediction error corresponds. This stage (41) is followed by a stage (42) for intermediate processing by filtering, and a stage (43) for refining the motion parameters and is looped to the input of the stage (42) for an iterative operation until it ends at a given criterion so as to finally obtain I motion information M.sub.i (t) corresponding to the regions R.sub.i.

Abstract: A device for the exchange of information with an electronic memory card which can be placed into a read position in the device through an insertion opening along an insertion track, in which position electrical contacts of the memory card are in contact with electrical contacts of the device provided on a carrier which is displaceable transversely to the insertion track. In the absence of the memory card, the contacts are situated in the insertion track under the influence of a pretensioning force. The carrier has an abutment surface which extends obliquely relative to the insertion track so that the carrier can be displaced out of the insertion track by the memory card against the pretensioning force during the passage of the memory card. In the read position of the memory card, accordingly, the carrier is in a position which is adapted to the thickness of the memory card, so that the device is suitable for cooperating with memory cards of various thicknesses.

Abstract: A hybrid waveform and model-based image signal encoder and decoder are described. The image signal is waveform-encoded (11) and decoded (31) so as to approximate the waveform of the original input signal as well as possible after compression. In order to compensate its loss, the noise component of the signal (or, more generally, a signal component which gets lost by the waveform encoding) is model-based encoded (12,13) and separately transmitted or stored. In the decoder, the noise is regenerated (32-34) and added (36) to the waveform-decoded image signal. The invention is particularly applicable to compression of medical X-ray angiographic images where loss of noise leads a cardiologist or radiologist to believe that the image is distorted.

Abstract: A collective address is defined at the transmitter end, not only by the contents of a field of bits, but also by a compulsory position of said field in a word which is larger than said field. Said word is full of zeros, outside said field.To recognize in a receiver whether a message received from the transmitter is concerned,a word having the same length as the word, transmitted with its zeros, is constructed by placing several fields (CA1, CA2, . . . , CA10) end to end, each field corresponding to the contents of one of the multiple addresses concerning the receiver, and being also placed in its compulsory position,this word is compared with the received collective address word, while one similar field in the two words is searched separately for each field,the message is recognized if such a similar field is found.

Abstract: A system is provided for encoding clips of video data for multiplexing into a system level stream with associated audio and control data. By deriving a relationship between encoder and decoder buffer occupancy levels, and taking into account buffer fill rate, the multiplexer targets a starting occupancy for the video system layer buffer (the MPEG STD) at that for the decoders video buffer (the MPEG VBV). With knowledge of fill rate, the decoder buffer need only be filled to a predetermined level prior to reading out clips for decoding, rather than filling the buffer completely, and seamless joining of video clips can then be simply achieved. The technique has particular application to interactive multimedia systems where continuous display is required.

Abstract: For fractal image coding optimal scaling factors for the image contents in the domain blocks are searched. Each image is divided into analysis blocks, which jointly represent the whole image. The analysis blocks are embedded in analysis regions, which contain besides the analysis blocks areas with a predetermined signal value. Also, comparison regions are formed, which contain at least parts of the image and which have the same size as the analysis regions. The analysis regions and the comparison regions are Fourier transformed. The transformed signals are converted logarithmically. The logarithmized signals are again Fourier-transformed. One of these signals is converted in its conjugate-complex form before both signals are multiplied. The product is normalized, so that it no longer contains amplitude information. Then the signal is subjected to an inverse Fourier-Transformation. If the signal has been logarithmized then it is de-logarithmized.

Abstract: The invention relates to an image sequence coding method in which images are segmented and coded with respect to their contours and textures. The texture coding step is carried out by means of a new technique relying on a wavelet decomposition of the images, called quincunx bidimensional wavelet transform and adapted to a region-based coding scheme, for applications allowing to reach very low bit rates while keeping a good image quality.

Abstract: The circuit (7, 8, 9, 10) comprises, in addition to the automatic gain control (AGC), a gain reduction means for controlling the gain of an amplifier (8), intended to avoid the desynchronization of the local oscillator (7) controlled by a phase-locked loop comparator (12). This is controlled by a peak detector of the amplified signal situated at the output of the amplifier (8).

Abstract: A frequency synthesizer SYNT intended to supply an output signal Sout having an output frequency which depends on the average frequency, referred to as symbol frequency, of an input signal Sin beset with a strong phase noise. This synthesizer SYNT includes: a phase/frequency detector PHD comparing the symbol frequency with a predetermined fraction of the output frequency, and supplying a control signal; a low-pass filter LPF filtering the control signal; and an oscillator VCO supplying a signal Sout with a frequency which is adjusted by the filtered control signal Cs. Reference pulses having the symbol frequency are generated within the synthesizer SYNT by means of pulses from an internal clock, which pulses are validated by active states of the input signal Sin.

Abstract: A method and apparatus are provided for video signal processing of sequences of digitized images originating from video (10) or film. A field grabber (12) receives the digitized images from the input and identifies the separate fields thereof. An image manipulation stage (14) combines fields as required and reduces the number of pixels per line and pixel lines in each image by applying horizontal and vertical compression; this stage also provides filtering and resizing of the image as required. Following encoding (16) of the compressed images, the encoded data stream may then be processed (18) into a form for recording onto, for example, an optical disc. By appropriate choice of the number of lines to which the image manipulation stage (14) reduces the image, discs playable on either PAL or NTSC standard equipment may be produced from a single image source.

Abstract: Disclosed are a method and arrangement for accessing interactive audiovisual programs stored on a remote server (1) by a multimedia station (2). The audiovisual program is stored in the same format as it is stored on a CDi disc, i.e. in the form of sectors. Although based on the same data compression technology, the CDi video coding standard does not comply with the MPEG coding specification. Moreover, MPEG does not cover the handling of specific CDi features. In order to allow conventional CDi decoders to access remotely stored CDi applications via interactive networks (3,4), the interactive audiovisual program is transmitted as a private MPEG2 data stream, using the concept of MPEG's transport stream. The multimedia station comprises a network interface (7) having a circuit (72) which assembles the transport packets and applies the signal sectorwise to a "stripped" CDi player (5,6).

Abstract: The invention relates to the reception of MPEG encoded television signals from a Video-On-Demand server (1) via a network (3). Non-linear playback functions such as `pause` and `resume` require a very accurate control of the bit stream, taking account of typical network aspects such as network latency. The receiver (2) comprises a latency buffer (24) for storing the signal delivered while the reproduction is stalled. The pause and resume commands from the user are not forwarded to the server until the latency buffer reaches a predetermined fullness. This allows the receiver to resume flawlessly signal reproduction after a pause.

Abstract: The invention relates to a device for decoding encoded digital signals of the MPEG-type, comprising different modules (M1, M2, M3, . . . ), provided for communicating with an external random-access memory via an arbiter (ARB) intended to control the different types of access. Storage in the memory and the method of addressing are such that the decoding operation may not only be carried out with a conventional memory (DRAM) but also with synchronous DRAM memories (SDRAM), in which the arbiter uses the same mode of communication in each case and the other modules remain unchanged.