Ordering and formatting coded image data and reconstructing partial

Abstract

Editing of information recovered from a relatively high speed communications medium such as a communications channel or magnetic tape often times allows only a portion of the information to be recovered. Storing information in complete segments from which portions of an image, called 'snatches,' may be recovered helps. An image signal is compressed in such a way that a snatch can be used during decompression to reconstruct a recognizable image from less than all the information that defines the image-thereby giving rise to the notion of a partially reconstructed image. The image information comprises several pixel data blocks with each block including sufficient pixel image data to reconstruct a portion of the image. The pixel data blocks are discrete cosine transformed ('dct') to generate a set of dct coefficient blocks. The dct coefficients for a group of dct coefficient blocks are rank ordered from highest visibility coefficient (corresponding to lowest dct frequency coefficient) to lowest visibility coefficient (corresponding to highest dct frequency coefficient), and then are quantized, entropy encoded, and formatted together with synchronization information and parity checks from the error correction encoding before being transmitted on a channel or recorded on magnetic tape. A decompression and reconstruction arrangement functions essentially as the inverse of the compression arrangement. It is during the decompression that snatches are retrieved and used to reconstruct a partial (video) image by using some but not necessarily all the dct coefficients that define the image.