Appeal No. 1997-2474 Page 2
Application No. 08/125,590
September 11, 1995, which was denied entry. We affirm-in-
part.
BACKGROUND
The invention at issue implements a Discrete Cosine
Transform (DCT) and an Inverse Discrete Cosine Transform
(IDCT) in software. DCTs and IDCTs are used in the field of
image processing to represent signals in a compact format.
Because of the demands that arithmetic operations,
particularly multiplication operations, place on a computer,
conventional software implementations of DCTs and IDCTs have
been slower than hardware implementations.
The invention exploits symmetries of the DCT and IDCT to
improve the speed at which software can process signals using
the Transforms. Based on the symmetries, the DCT and IDCT are
performed using a combination of look-up tables and butterfly
operations, thus employing only a few additions and
subtractions and no multiplications.
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