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: 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 comprises a source detection arrangement for detecting whether or not the input data is source data that has not undergone a previous compression/decompression cycle; a data quantity generator, responsive to the source detection arrangement, for setting a desired data output quantity for the compressed data, the desired data quantity having a first value for source input data and a second, higher, value for non-source input data; a target allocator for allocating a target data quantity to respective subsets of the input data in dependence upon the desired output data quantity, the target data quantities together providing a desired output data quantity; and a data compression arrangement for compressing each subset of the input data in accordance with its respective target data quantity.

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: Video signal processing apparatus in which at least two input video signals are combined in proportions determined by a pixel key signal to generate an output video signal for compression, at least one of the input video signals each having respective associated compression parameters from a data compression process applied to that video signal. The apparatus functions to estimate the quantity of data which will be produced by compression of a current image of the output video signal, compares the detected quantify of data with a target quantity of data, to determine whether a data overflow is expected, and in the event that a data overflow is expected, determine which blocks of the output video signal can be compressed by re-using compression parameters from corresponding block of one of the input video signals.

Abstract: Video data formatting apparatus and method in which an input signal is converted (transcoded) into an intermediate compressed video signal, where the intermediate compressed video signal has a GOP format in which each GOP contains fewer pictures than a GOP associated with the input video signal. A metadata signal which indicates data defining coding decisions is derived from the input video signal. A data quantity allocation is generated to control the transcoding into the intermediate video signal, whereby each picture of the intermediate video signal is transcoded so as not to exceed a respective data quantity allocation.

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: A digital video processing system and method for deriving an output compressed video signal from an input compressed video signal. The input compressed video signal represents successive input pictures. Subsets of the input pictures are derived from other input pictures according to input picture motion vectors corresponding to a repetitive GOP (Group of Pictures) structure. The output compressed video signal represents successive output pictures, subsets of the output pictures being derived from other output pictures according to output picture motion vectors corresponding to a repetitive GOP structure that is different from, or not picture-aligned with, the GOP structure of the input compressed video signal. The output picture motion vectors are derived from the input picture motion vectors.

Abstract: Video signal processing apparatus in which at least first and second input video signals are combined to generate an output compressed video signal, the first and second video signals each having respective associated motion vectors from a data compression process applied to the video signals; comprises: means for establishing a set of the motion vectors associated with the first and second video signals which can potentially be re-used in compressing the output compressed video signal; and means for testing the set of motion vectors, the testing means being operable: (c) to define, with respect to reference images referred to by the motion vectors under test, a first border region of a predetermined width surrounding those parts of the reference images derived in part from the first video signal, and a second border region of a predetermined width surrounding those parts of the reference images derived in part from the second video signal; and (d) to test whether motion vectors of the set which are assoc

Abstract: A video signal processor comprises a first input for receiving a compressed first video signal including parameters associated with the frames of the signal and relating to the compression. A decoder decodes the compressed first video signal while preserving the parameters in association with the frames. A second input receives additional video information to be combined with the first video information. A combiner superimposes the additional video information on the first video information. An encoder encodes the combined video information. The encoder reuses the preserved parameters for encoding at least parts of the combined information which are not derived from the superimposed video information.

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 data encoding apparatus operable to encode a plurality of data blocks produces encoded data in accordance with at least one of a selectable target data quantity or a selectable target data quality.

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 compression apparatus in which input data is compressed according to a target output data quantity using a stage of data quantization, the apparatus comprises: one or more trial quantizers for selecting a degree of quantization so that the target output data quantity is not exceeded; a data selector for selecting a subset of the current data to be quantized; a data store for storing the subset of data; a backsearch quantizer and dequantizer for sequentially quantizing and dequantizing the subset of data at a plurality of degrees of quantization including the degree of quantization selected by the trial quantizer(s) and one or more harsher degrees of quantization; a comparator for comparing data quantized and dequantized by the backsearch quantizer with the stored subset of data, to detect errors introduced by the quantization and dequantization by the backsearch quantizer; and a quantization selector for selecting a final degree of quantization for use in compression of the current data, the final degree

Abstract: Video data compression apparatus in which successive groups of two or more images are encoded subject to a predetermined limit on the quantity of output encoded data to be generated for each group of images, comprises a trial encoder for encoding at least a subset of images of a current group of images to generate trial-encoded data for each trial-encoded image; a data quantity allocator, responsive to the quantities of trial-encoded data generated by the trial encoder, for allocating respective quantities of output encoded data for each image in the group of images; and a final encoder for encoding each image of the group of images in accordance with the quantities of output encoded data allocated to that image by the data quantity allocator.

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.

Abstract: Video signal processing apparatus in which at least two input video signals are combined in proportions determined by a pixel key signal to generate an output video signal for compression, at least one of the input video signals each having respective associated compression parameters from a data compression process applied to that video signal; comprises:

Abstract: A data processing system comprises a data compression decoder arranged in operation to decode first and second encoded data to produce first and second uncompressed data representative of first and second source data from which the first and second encoded data were produced in accordance with a compression encoding algorithm respectively. The data compression decoder also produces first and second compression parameter data representative of encoding decisions made by the compression encoding algorithm when the first and second source data was compression encoded.

Abstract: Video data compression apparatus in which successive groups of two or more images are encoded subject to a predetermined limit on the quantity of output encoded data to be generated for each group of images, comprises a trial encoder for encoding at least a subset of images of a current group of images to generate trial-encoded data for each trial-encoded image; a data quantity allocator, responsive to the quantities of trial-encoded data generated by the trial encoder, for allocating respective quantities of output encoded data for each image in the group of images; and a final encoder for encoding each image of the group of images in accordance with the quantities of output encoded data allocated to that image by the data quantity allocator.