Browse Prior Art Database

Self-Programmable Universal QIC Decoder

IP.com Disclosure Number: IPCOM000113071D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Medan, Y: AUTHOR

Abstract

This article describes a technique to embed control codes in a standard QIC-122 data stream which enables an enhanced compression efficiency by adopting the encoding/decoding process to variations in the properties of the information stream.

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This is the abbreviated version, containing approximately 64% of the total text.

Self-Programmable Universal QIC Decoder

      This article describes a technique to embed control codes in a
standard QIC-122 data stream which enables an enhanced compression
efficiency by adopting the encoding/decoding process to variations in
the properties of the information stream.

      QIC-122 is an industry standard for decoding compressed data
for 1/4- inch cartridge tape drives.  The standard defines, in a
concise and fixed way, the format of the encoded compressed data.  It
does not, however, imply how compression may be achieved as long as
the encoded stream follows the standard.  There exist a number of
fast hardware implementations of QIC-122.

      The QIC-122 standard assumes that a byte-oriented input stream
is to be encoded using a mixture of direct coding, stating the actual
value of the byte, and indirect coding, using offset and runlength
values to point to a previous instance of a given string.  The format
of direct and indirect encoding modes is fixed and therefore no
provisions are made in the standard to adopt its parameters according
to the context, nature and statistical properties of the data to be
encoded.

      The technique of this disclosure introduces 128 control codes
set embedded in the data stream that may allow to program the decoder
function in any desirable manner during its operation, such as to
optimize its performance and enable to achieve a better compression
gain.  These control codes comply with the existi...