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Method for Padding the Right and Bottom Edges of an Image for Joint Photographic Experts Group Interleaved Coding

IP.com Disclosure Number: IPCOM000113198D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Finlay, IR: AUTHOR [+4]

Abstract

An alternative method for completing the MCU (Minimum Coding Unit) as required by the JPEG (Joint Photographic Experts Group) still image compression standard when coding multiple components in an interleaved scan is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method for Padding the Right and Bottom Edges of an Image for Joint
Photographic Experts Group Interleaved Coding

      An alternative method for completing the MCU (Minimum Coding
Unit) as required by the JPEG (Joint Photographic Experts Group)
still image compression standard when coding multiple components in
an interleaved scan is disclosed.

      When compressing an image using JPEG [*]  and coding multiple
components in a single interleaved scan, it is required that the
image be padded to an Minimum Coding Unit (MCU) boundary.  The
standard recommends, but does not require, that this padding be done
by replicating the pixels along the right and/or bottom edge of the
image (section A.2.4 of [*].  For the lossy JPEG modes, this requires
that the processor performing the DCT (discrete cosine transform)
"know" whether the data is to be compressed in an interleaved or
non-interleaved scan, or alternatively that the entropy encoder
either know enough to discard padding blocks when interleaved coding
is not required or reconstruct the pixel data from the edge DCT
blocks (which in general it cannot do exactly), extend the image, and
perform a DCT on the resulting blocks when interleaved coding is
required.  These requirements may be a nuisance in certain types of
systems.  For the lossless JPEG modes, which do not use DCTs, the
requirement is simply to generate "fake" sample values.  The term
"padding units" will be used to refer to either complete 8x8 blocks
of padding samples (for the lossy modes) or individual padding
samples (for the lossless modes).  Note that since padding units are
discarded in the entropy decoder, their content is unimportant.

      This is an alternative method for creating padd...