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

Abstract: An RF active deflector is described for use with orthogonal frequency division multiplex signals. An input antenna receives an RF input signal and an output antenna transmits an RF signal on substantially the same frequency as the input signal. An amplification path between the input antenna and the output antenna provides substantially linear processing and includes a delay. Means responsive to the signal in the amplification path produce a plurality of control coefficients. A transversal filter receives the signal in the amplification path and, under control by the control coefficient, provides a modified signal. A combiner is provided for combining the modified signal with the signal in said amplification path so as to reduce the effect of the feedback.

Abstract: An MPEG bitstream is switched in the video domain in between a decoder and recoder pair which remain continuously in operation but which are transparent through re-use in the recoder of coding decision taken in the upstream coding of the MPEG bitstream and inferred in the decoder of the switch. Around the switch point, the coding decisions are modified.

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: 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 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: 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: After decoding of an MPLFG 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: 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 a subsequent advance or retard decision. In this way, the cumulative error can be kept within an acceptable tolerance.

Abstract: The feedback caused between the output (39) and the input (30) of an amplification path (54, 42, 56, 60, 62, 64) is reduced by providing a delay (60) in the amplification path, passing through the amplification path a signal having an auto-correlation function which is substantially a delta function, correlating (72) 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 (76) controlled by the said plurality of correlation coefficients, and combining (42) the modified signal with the signal in the amplification path so as to reduce the effect of the feedback. The signal having an auto-correlation function which is substantially a delta function may be an added noise signal (70) or may be constituted by the signal being processed itself.

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: 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: A switch arrangement is provided for MPEG or other bit-rate signals. An output switch (66) is arranged to switch between bitstream A; an interim bitstream developed about the switch point; and bitstream B. The interim bitstream is provided by a re-coder (64) the input to which is switched at (58) between a decoder (52) for bitstream A and a decoder (56) for bitstream B.

Abstract: In the combination of a video signal coder and a video signal decoder, synchronization is achieved by the addition of absolute time reference signals at the coder. These time reference signals are independent of the time base of the coder and are inserted after the coder buffer. At the decoder, the time reference signals are stripped out and used to set the decoder time base.

Abstract: High definition television coder/decoder a high definition coder or decoder includes a number of parallel sub-decoders or coders. The image to be coded or decoded is divided into a number of stripes, a given stripe being coded or decoded by a single sub-coder or sub-decoder. Every N.sup.th stripe is coded or decoded by the same sub-coder/sub-decoder, where N is the number of sub-coders or sub-decoders. The number of sub-coders is independent of the number of sub-decoders whereby a reduction in the number of sub-coders with increasing bit-rate capacity does not necessitate a change in decoder.