International Business Machines Corporation

Neil M Leeder

Joan LaVerne Mitchell

Nenad Rijavec

Albert Nessim Cazes

Rapid throughput of still image compressed data (e.g. JPEG) is achieved for presentation of images in rapid succession for browsing or browsing by panning within large images by using a hardware decoder adapted for presentation of moving images to reduce the processing load which must be performed in accordance with software although the still image data is incompatible with still image data in many respects; some of which necessarily lead to a loss of image fidelity. The still image data is partially decoded (e.g. entropy decoded) in software processing and re-encoded and reformatted to a form which can at least be accepted by the hardware decoder even though not compliant with any particular moving picture data standard (e.g. MPEG). Storage in the hardware decoder is reallocated to provide, in combination with a reduction of slower software processing, a throughput increase of four-fold or more. Software processing of the still image data is also allowed to proceed and the result substituted for the result of the hardware decoding if a given image is viewed for a time sufficient for the software image processing to be completed.

Browsing JPEG images using MPEG hardware chips

Huffman encoding, particularly from a packed data format, is simplified by using two different table formats depending on code length. Huffman tables are also reduced in size thereby. Decoding is performed in reduced time by testing for the length of valid Huffman codes in a compressed data stream and using an offset corresponding to a test criterion yielding a particular test result to provide a direct index into Huffman table symbol values while greatly reducing the size of look-up tables used for such a purpose.

Fast JPEG huffman encoding and decoding

JPEG (Joint Photographic Experts Group) images are encoded and decoded as fast as possible for a variety of disparate applications. A novel structure stores the 8&times;8 Discrete Cosine Transform (DCT) blocks after entropy decoding in a JPEG decoder or after the Forward Discrete Cosine Transform (FDCT) in the JPEG encoder to use as an intermediate format between transform processes. The format was chosen to speed up the entropy decode and encode processes and is based on the information needed for the JPEG Huffman entropy coding, but lends itself to fast execution of other DCT based transforms, including arithmetic entropy coding.

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Cary, NC, United States of America

Neil M Leeder