Abstract: A method of image processing for conversion of an image in a sequence of images comprises the steps of associating pixels of an image with respective motion values indicative of a degree of inter-image motion for each pixel; adjusting the motion value of each pixel based upon the motion value of a secondary pixel found within a first region of a first predetermined size substantially centred upon each respective pixel, said secondary pixel being that whose associated motion value is indicative of the greatest motion of any pixel in the first region; adjusting the motion value of each pixel based upon the motion value of a secondary pixel that lies within a second region of a second predetermined size substantially centred upon each respective pixel, said secondary pixel being that whose associated motion value is indicative of the least motion of any pixel in the second region; categorising each pixel as a static pixel or a motion pixel according to its respective associated motion value, and then selecting r

Abstract: Decoders A and B decode MPEG-2 bitstreams A and B. A switch (S1) switches from decoded stream A to decoded stream B to achieve a splice. The resulting bitstream is re-encoded in an encoder 4. A new GOP is defined beginning at the splice. The new GOP is defined by picture type decision rules which may the effect of changing the GOP compared to the GOPs of streams A and B. The new GOP provides a prediction of the position in stream B where the occupancy value of stream C should coincide with that of B. A target for the new number of bits in the new GOP is calculated dependent on the difference between the occupancy value of stream C at the splice and a prediction of the occupancy of stream B at the predicted position. The occupancy value of stream C is controlled in accordance with the target so that it tends towards the occupancy value of stream B at the predicted position.

Abstract: Data compression apparatus for compressing an input data unit to produce an output data unit in accordance with a desired data quantity of the output data unit, the degree of compression being determined by a compression control variable having a range of possible values. A trial encoder compresses successive sections of the input data unit in accordance with a trial group of two or more values of the compression control variable. A data quantity detector detects the trial data quantities generated by each trial encoding of the sections of the input data unit and selects a base compression control variable applicable to the input data unit on the basis of the detected trial data quantities, in order to comply with the desired data quantity.

Abstract: Video data compression apparatus for compressing images of an input video signal on a block-by-block basis comprises a block analyser for analysing each block of an image to be compressed to detect a degree of difference between pixels within that block; a data quantity allocator for allocating target output data quantities for the compression of each block, the target data quantities being dependent on the detected degrees of pixel difference of the blocks; and a data compression encoder for compressing each block in accordance with the target output data quantity associated with that block.

Abstract: A data compression apparatus operable to perform at least one trial quantisation in order to compress input data in accordance with a predetermined target output data quantity comprises a quantisation starting point estimator for detecting, from a property of the input data, a quantisation starting point representing an approximate value for a quantisation parameter suitable for achieving the predetermined target output data quantity; one or more trial quantisers, each testing a degree of quantisation of at least part of the input data, the degree of quantisation being defined by a respective trial quantisation parameter; a parameter controller for assigning a value of the trial quantisation parameter to each of the trial quantisers in dependence upon the quantisation starting point; and a parameter selector for selecting a final level of quantisation for use in compression of the input data in accordance with results of the testing performed by the one or more trial quantisers, to ensure that the target outp

Abstract: A data compression apparatus for performing data compression on input data comprises a quantisation parameter estimation arrangement for deriving an estimated value of a quantisation parameter used in a previous compression/decompression cycle applied to the input data, by detecting rounding effects in data values of at least a subset of the input data; and a parameter selection arrangement, responsive to the quantisation parameter estimation arrangement for selecting a quantisation parameter for use in compression of the input data.

Abstract: Decoders A and B decode MPEG-2 bitstreams A0 and B0 and re-encoders 8 and 10 re-encode them as bitstreams AI and BI comprising only I frames. A switch (S1) switches from recoded stream AI to recoded stream BI to achieve a splice AI/BI. The spliced bitstream is stored in an I-frame store (12). The stored bitstream AI/BI is re-encoded in an encoder 4. A new transitional GOP is defined beginning at the splice. The new GOP is defined by picture type decision rules which may change the length of the transitional GOP compared to the GOPs of streams A and B. The transitional GOP provides a prediction of the position in stream B where the occupancy value of stream C should coincide with that of B. A target for the new number of bits in the new GOP is calculated dependent on the difference between the occupancy value of stream C at the splice and a prediction of the occupancy of stream B at the predicted position.

Abstract: Image data decompression apparatus and method for receiving data words comprising a first sub-word and a second sub-word, at least some possible values of the first sub-word specifying a run of at least m instances of a predetermined data value, corresponding second sub-words specifying a number of instances of the predetermined data value in a range from at least m instances. The apparatus includes a first decoder for decoding the first sub-words to detect whether a current first sub-word specifies a run of at least m instances of the predetermined value, and a second decoder for decoding the second sub-words to generate output decoded data.

Abstract: Video down-conversion apparatus in which lines of successive output video field are interpolated from lines of respective input video fields, the apparatus being selectively operable to interpolate each output field from an input field of either field polarity so that the successive output video fields can maintain a regular odd-even field polarity sequence even if there is a discontinuity in the field polarity sequence of the input video fields.