Abstract: Image data compression apparatus for generating compressed output data to be handled by an output data handling channel having an output data capacity per image comprises a data compressor for compressing image data so as not to exceed a target quantity of data per image; in which the target quantity of data per image is higher than the output data capacity per image.

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: 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:

Abstract: Image data compression apparatus in which data is encoded using a variable degree of quantization selected for areas of an image so that the quantity of encoded data for each area does not exceed a predetermined maximum quantity of data comprises two or more trial encoders operable in parallel to trial encode image data using respective predetermined trial degrees of quantization; a selector for selecting one of the predetermined trial degrees of quantization in response to the quantities of data produced during the trial quantizations; and one or more further trial encoders operable to trial encode image data using degrees of quantization derived from the degree of quantization selected by the selector.

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: Image data compression apparatus comprises a data compressor for receiving data representing sub-areas of an input image and for generating respective blocks of compressed data representing those sub-areas, each block of compressed data comprising at least low spatial frequency image data and higher spatial frequency image data; a data formatter for formatting predetermined groups of said blocks of compressed data into output data blocks, said data formatter having a predetermined data capacity; a detector for detecting whether a current group of said blocks of compressed data contains more data than said data capacity of said data formatter; and a block truncator, responsive to a detection that a current group of said blocks of compressed data contains more data than said data capacity of said data formatter, for truncating one or more of said blocks of compressed data by discarding at least said higher spatial frequency image data.

Abstract: Image data compression apparatus for generating groups of encoded image data representing respective sub-areas of an image, in which the degree of data compression applied to each sub-area is specified at least in part by an attribute value associated with that sub-area, comprises selection logic for selecting the attribute value to be associated with each sub-area of an image; an attribute encoder for encoding the attribute value for each sub-area of the image according to a selected one of a plurality of predetermined sets of attribute codes, different sets of attribute codes being encoded using different respective quantities of data; a comparator for comparing attribute values for a group of the data blocks to detect whether the attribute values for the group of sub-areas could be encoded using a replacement one of said sets of attribute codes requiring a smaller quantity of data; and replacing logic responsive to a detection that the attribute values for the group of sub-areas could be encoded using a re

Abstract: Video data compression apparatus in which successive images are encoded, comprises a data quantity allocator for allocating respective quantities of output encoded data for two or more complementary areas of each image; and an encoder for encoding each area of each image of the group of images in accordance with the quantity of output encoded data allocated to that area.

Abstract: Video data compression apparatus in which successive groups of two or more images are encoded, each encoded group of images including at least one intra-image encoded image and at least one inter-image encoded image. A data quantity allocator allocates respective quantities of output encoded data for each image in the group of images according to an allocation ratio between intra-image encoded images and inter-image encoded images dependent on the quantities of encoded data generated during encoding of a preceding group of images. A scene change in the group of images is detected and the allocation of output encoded data for images in a group of images is reset to a default allocation ratio if a scene change is detected in that group of images. An encoder encodes each image of the group of images in accordance with the quantities of output encoded data allocated to that image.