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: Video face detection apparatus in which a test image from a video sequence is compared with an image property model derived from image properties of a region detected to contain a face in a preceding image in the video sequence comprises: selecting a predetermined proportion of pixels in the region detected to contain a face in the preceding image which most closely match the image property model derived in respect of that region, thereby deriving a pixel mask; and comparing pixels in the test image defined by the pixel mask with the image property model, the mask being applied at more than one image position within the test image; a face being detected in the test image at a mask position corresponding to a lowest average difference between the image property model and pixels defined by the mask at that position.

Abstract: An encoding apparatus operable to encode video data representing successive images, each image including a plurality of pixels. The apparatus includes a differential encoder arranged to encode each image as one or more predetermined image regions. Each image is being encoded as a reference value and at least one differential pixel value. The differential pixel value(s) are derived in dependence on the reference value and/or other differential pixel value(s) in accordance with an order of encoding dependency; in which, for each image region, the differential encoder is operable in a first encoding mode for a first subset of the images to encode the image region using a first order of encoding dependency and in a second encoding mode for a second, different, subset of the images to encode the image region using a second, different, order of encoding dependency.

Abstract: A decoder 2 decodes a first compressed digital video bitstream whilst preserving the compression parameters thereof, the compression parameters including a first buffer occupancy value VBV—1 representing the occupancy by the said first bitstream of a buffer of the decoder. A signal processor 40 processes the decompressed bitstream. An encoder 6 compresses the processed bitstream to produce a second compressed bitstream having a target bit rate, optionally with reuse of the said compression parameters of the first bitstream, the second bitstream having a second occupancy value VBV—2 representing the occupancy of a downstream decoder buffer by the said second bitstream.

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 transitional GOP is defined beginning at the splice. The new GOP is defined by picture type decision rules which may have the effect of changing the GOP compared to the GOPs of streams A and B. The new GOP provides an initial 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 as the sum of the normal allocation of bits for the new GOP plus 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: Face detection apparatus generating an output indicative of the likelihood of test regions of a test image containing a face comprises: means for deriving a plurality of sets of image attribute data from the test region, each set relating to the test region scaled by a respective different scaling factor from a geometric progression of scaling factors, the progression being such that each scaling factor is related to a next scaling factor by a predetermined multiplicative factor, the factor being the same across the whole progression of scaling factors; means for comparing the derived attributes for each scaling factor with a first respective set of attributes indicative of the presence of a face to generate a first respective likelihood value; means for comparing the derived attributes for each scaling factor with a second respective set of attributes indicative of the presence of a face to generate a second respective likelihood value; means for generating a combined likelihood value in respect of at least

Abstract: Video face detection apparatus in which a test image from a video sequence is compared with an image property model derived from image properties of a region detected to contain a face in a preceding image in the video sequence comprises:

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: An encoding apparatus operable to encode video data representing successive images, each image comprising a plurality of pixels, comprises a differential encoder arranged to encode each image as one or more predetermined image regions, each image region being encoded as a reference value and at least one differential pixel value, the differential pixel value(s) being derived in dependence on the reference value and/or other differential pixel value(s) in accordance with an order of encoding dependency; in which, for each image region, the differential encoder is operable in a first encoding mode for a first subset of the images to encode the image region using a first order of encoding dependency and in a second encoding mode for a second, different, subset of the images to encode the image region using a second, different, order of encoding dependency, and in which the first and second subsets of images are arranged with respect to one another so that, from image to image, each image region is encoded in acc

Abstract: A data compression apparatus operable to compress input data, in accordance with a predetermined target output data quantity, by performing data quantisation at a degree of quantisation taken from a set of available degrees of quantisation comprises one or more trial quantisers for performing trial quantisations at respective trial degrees of quantisation, the trial degrees of quantisation being taken from a subset of the set of available degrees of quantisation; a selector for selecting a final degree of quantisation in response to the results of the trial quantisations, the final degree of quantisation being selected from the set of available degrees of quantisation such that the target output data quantity is not exceeded; and a final quantiser operable to quantise the input data at the final degree of quantisation.

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: A decoder 2 decodes a first compressed digital video bitstream whilst preserving the compression parameters thereof, the compression parameters including a first buffer occupancy value VBV—1 representing the occupancy by the said first bitstream of a buffer of the decoder. A signal processor 40 processes the decompressed bitstream. An encoder 6 compresses the processed bitstream to produce a second compressed bitstream having a target bit rate, optionally with reuse of the said compression parameters of the first bitstream, the second bitstream having a second occupancy value VBV—2 representing the occupancy of a downstream decoder buffer by the said second bitstream.

Abstract: Data are compressed on a block-by-block basis. A frequency-transformer frequency-transforms input data to generate corresponding groups of coefficient values representing different frequency components. A quantiser operates on the groups of coefficient values to map each of a contiguous plurality of ranges of coefficient values onto respective quantised data values, the extent of each range being controlled by a quantisation factor and the first non-zero range boundary being defined by a range boundary parameter.