Abstract: A diversity receiver for receiving digital signals has a soft-decision decoder in each of its receiving sections, to provide confidence values for the received decoded digital values, and combines the values from the receiving sections in dependence upon the confidence values. The receiver is especially suitable for use with COFDM, and has two sections, the outputs of which are applied to a soft-decision combiner which combines the signals in dependence upon confidence values received from the demodulators. The output is then applied to a Viterbi decoder. The combining can simply involve switching but preferably involves averaging. Synchronisation and squelching can be provided. The system can be used with frequency diversity, spatial or polarisation diversity, or with antenna pattern diversity, in which case it can constitute an automatic rotator. The system automatically switches between different types of diversity reception, e.g.

Abstract: In digital video, 3:4 down conversion and 4:3 down conversion are transparently cascaded. The up conversion filter is: Sup(n)=&Sgr;Sinput(k).g(3n−4k) and the down conversion filter is: Sdown(n)=&Sgr;Sup(k).h(4n−3k). The pair of up and down conversion filters are designed so that &Sgr;h(4n−3k).g(3k−4m) is equal to unity if n=m and is otherwise equal to zero.

Abstract: Apparatus for dubbing a film from a source language to a target language includes a replay device (1) which replays a film and a control unit (6) which generates an acoustic model of the scene. A dubbing soundtrack on the replay device (1) is fed via a line (2) to an acoustic processor (3). The acoustic processor (3) processes the dubbed soundtrack under the control of the control unit (6) to produce a dubbed soundtrack which is modified to take into account the acoustic environment of the scene. This soundtrack may be recorded on a recording device (5). The application further discloses the generation of soundtracks for computer generated scenes taking into account the virtual acoustic environment.

Abstract: To maintain lip-sync when a video signal has been edited or switched at a video frame boundary, the associated audio signal is advanced or retarded to the closest audio frame boundary. Any error introduced by this constraint is accumulated and carried forward to direct subsequent advance or retard decision. In this way, the cumulative error can be kept within an acceptable tolerance.

Abstract: A method of processing coded video, for example by inserting generated frames, or adjusting values in timing fields, or adjusting the time at which it is output, to adjust the timing of output of decoded video from a decoder receiving the coded video is disclosed, together with corresponding apparatus. The outputting apparatus may be included in a multiple-source video system, to enable multiple video sources to be synchronized. The output video can be synchronized to a studio reference clock.

Abstract: A digital audio broadcasting (DAB) receiver designed for receiving a signal with 1536 active carriers generated by an inverse fast Fourier transform (FFT) with 2048 points, includes the usual RF stage (14), an IF filter (20), and a demodulator (22) providing baseband I and Q signals. This is followed by an anti-aliasing filter (28), a sampler (30), and an FFT (32). The FFT is a 4096-point FFT, and is thus twice as long as required, and gathers twice as many points during each symbol period. However this is found to substantially simplify the construction of the IF filter (20) and, more particularly, the anti-aliasing filter (28). For use with real signals rather than quadrature demodulated signals, an 8192-point FFT is employed.

Abstract: After decoding of an MPEG bitstream to the form of a video signal, an information stream signal in the form of all or part of the MPEG bitstream, is transmitted alongside the video signal, embedded in the least significant bit. Recording may simply involve extraction of the embedded MPEG bitstream or, if only part of the bitstream has been embedded, an essentially “dumb” coding operation guided by the information stream signal.

Abstract: In compression encoding of a digital signal, such as MPEG2, transform coefficients are quantised with the lower bound of each interval being controlled by a parameter &lgr;. In the MPEG2 reference coder, for example, &lgr;=0.75. Because the quantised coefficients are variable length coded, improved quality or reduced bit rates can be achieved by controlling &lgr; so as to vary dynamically the bound of each interval with respect to the associated representation level. The parameter &lgr; can vary with coefficient amplitude, with frequency, or with quantisation step size. In a transcoding operation, &lgr; can also vary with parameters in the initial coding operation.

Abstract: An MPEG2 decoded video signal is accompanied by a representation of the coding decisions to aid downstream re-encoding. The representation is MPEG compliant bit modified to reduce the number of bits.

Abstract: An MPEG2 decoded video signal is accompanied by a representation of the coding decisions to aid downstream re-encoding. The representation is MPEG compliant bit modified to reduce the number of bits.

Abstract: If a signal is repeatedly encoded and decoded, coding noise generally accumulates as it passes through the various coding systems. The present system provides means for preventing this, by providing means for identifying, at the second coding system, which coding system was previously used. The second coding can then use the same system as the previous coding. This use of matching coding systems results in very little extra coding noise being introduced by the second coding. The input signal is coded by two different encoders 11 and 12, their outputs are decoded and compared with the input signal at 20 and 21, the differences accumulated at 22 and 23. The smaller of the differences is used by selector 13 to select the encoder which matches the previous coding of the signal. The principles can be extended to MPEG Layer II Audio Coding and similar block coding systems.

Abstract: In the preferred implementation, the position of an object, for example a studio camera is determined by means of a camera which views several markers disposed about a studio ceiling, the markers being patterened as a series of light and dark rings to encode information in binary form enabling the markers to be identified as the camera moves about the studio. Methods and apparatus of more general applicability are also disclosed.

Abstract: A plasma display device (10) is provided with circuitry (50) which modifies at least the R and B color component signals so as to compensate for the displacement of the display elements or sub-pixels for each color component relative to each other in the array. Surprisingly, this increases the ratio of wanted signal to alias spectrum. The modification is effected by an interpolator comprising transversal filters (31R, 31B). The circuitry can be combined with down-converters (52) when a high definition source is used. In this case a transversal filter (31G) is also included for the G color component signal.

Abstract: Auxiliary digital data are inserted into a main digital data stream, to be subsequently coded to produce a coded data stream, by identifying a component of the main data stream that will make substantially no contribution to the coded data stream. It is into this component that data from the auxiliary data stream is inserted. The main digital data stream may comprise MPEG coded audio data, and the component (which represents unoccupied sub-bands or being at a level at or below a quantization noise floor) identified by estimating sub-bands that are unoccupied, or estimating quantization levels.

Abstract: A system for cooling electronic equipment, especially modular electronic units mounted in racks, each having a casing with an air inlet, an air outlet and a fan for cooling the contents of the unit. The system uses a chiller unit, between adjacent racks for returning cooled air to ambient, each of which can be a piping array connected to a supply of chilled water. A baffle backing the piping array improves heat exchange and provides a more uniform transfer of heat to each array, thereby enabling optimum temperature differences to be achieved across each rack. A slidable framework supports the piping array and defines an air space on the cooled air side of the array. An auxiliary piping array extends rearwardly of racks so as to communicate with rear air spaces behind the racks and thereby cool heated air flowing in the rear air spaces.

Abstract: An MPEG-2 or other compressed video stream (CP) can be manipulated as separate information bus (IB) and coefficient (CP*) streams. The information bus stream (IB) contains motion vector information but also information derived from a previous decoding operation (14, 18) for use in a subsequent coding operation (22). Processing in the coefficient domain enables bit rate conversion without decoding to the pixel level and also simplifies the combination of MPEG layers.

Abstract: The feedback caused between the output and the input of an amplification path is reduced by providing a delay in the amplification path, passing through the amplification path a signal having an auto-correlation function which is substantially a delta function, correlating the said signal before being delayed in the delay with the signal after being delayed in the delay to produce a plurality of correlation coefficients, modifying the signal in the amplification path to provide a modified signal, the modification being provided by a transversal filter controlled by the said plurality of correlation coefficients, and combining the modified signal with the signal in the amplification path so as to reduce the effect of the feedback.

Abstract: Video line interpolator has delays for providing simultaneous access to a current field and at least two adjacent fields; shifters for shifting the adjacent fields in accordance with vertical motion vectors rounded to even numbers of picture lines and an interpolation filter taking information from at least three line of each of the current and shifted adjacent fields, the contributions from said adjacent fields summing to zero at low frequencies.

Abstract: Text to be spoken by a speaker, e.g. a newsreader, and held in a store, is displayed on a display which is seen by the speaker through a partially-reflecting mirror 16 mounted in front of a television camera. The text is scrolled up as the speaker speaks, this being achieved automatically by a controller. The controller recognizes the spoken speech picked up by a microphone, using speech recognition techniques, and matches the spoken text with the stored text to be spoken. The speed at which the text is spoken is thus determined and used by positioning circuit to adjust the rate at which the text scrolls up on the display. If the speech recognition fails, the text continues to be changed at a rate dependent upon the previous rate of change.

Abstract: Studio camera position and motion may be derived from the camera image by separating out the background and deriving from a background having a number of areas of hue and/or brightness different from adjacent areas estimates of movement from one image to the next. The initial image is used as a reference and amended with predicted motion value. The amended image is compared with incoming images and the result used to derive translation and scale change information. Once the proportion of the reference image contained in an incoming image falls below a threshold a fresh reference image is adopted.