From: praetzel@marconi.waterloo.edu (Eric Praetzel)
Subject: Re: Fast DCT algorithm
Keywords: DCT
Organization: University of Waterloo
Date: Tue, 28 Jul 1992 11:49:23 GMT

In article <1992Jul25.083953.28947@iti.gov.sg> taiwei@iti.gov.sg (Chua Tai Wei) writes:
>
>I am looking for efficient  Fast DCT algorithm to  implement Video
>compression on a Sun workstation...
  That sounds like something Tom Lane at the Independant JPEG Group has been
playing with.  We just implemented a new algorithm (after much searching)
that is twice as fast as the previous one.  I took the C version and rewrote
it in 386 assembler and the result was 4 times faster than the C source code
that was compiled for the 286 (16 bit) microprocessor.
  I will drop Tom a note (I am sure he would love to talk about it after many
hours of research).  Here is a bit of the readme file from the JPEG S/W:
  I am sorry about the length but I believe that some of you will find varios
parts of interest.
  - Eric 

The Independent JPEG Group's JPEG software
==========================================

README for release 3 of  17-Mar-92
==================================

This distribution contains the third official release of the Independent JPEG
Group's free JPEG software.  You are welcome to redistribute this software and
to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.

If you intend to become a serious user of this software, please contact
jpeg-info@uunet.uu.net to be added to our electronic mailing list.  Then
you'll be notified of updates and have a chance to participate in discussions,
etc.

This software is the work of Tom Lane, Philip Gladstone, Luis Ortiz,
Lee Crocker, Ge' Weijers, and other members of the Independent JPEG Group.

WHAT'S HERE
===========

This distribution contains C software to implement JPEG image compression and
decompression.  JPEG (pronounced "jay-peg") is a standardized compression
method for full-color and gray-scale images.  JPEG is intended for
"real-world" scenes; cartoons and other non-realistic images are not its
strong suit.  JPEG is lossy, meaning that the output image is not necessarily
identical to the input image.  Hence you should not use JPEG if you have to
have identical output bits.  However, on typical images of real-world scenes,
very good compression levels can be obtained with no visible change, and
amazingly high compression levels can be obtained if you can tolerate a
low-quality image.  For more details, see the references, or just experiment
with various compression settings.

The software implements JPEG baseline and extended-sequential compression
processes.  Provision is made for supporting all variants of these processes,
although some uncommon parameter settings aren't implemented yet.  For legal
reasons, we are not distributing code for the arithmetic-coding process; see
LEGAL ISSUES.  At present we have made no provision for supporting the
progressive, hierarchical, or lossless processes defined in the standard.

The present software is not far beyond the prototype stage.  It does not
support all possible variants of the JPEG standard, and some functions have
rather slow and/or crude implementations.  However, it is useful already.

The emphasis in designing this software has been on achieving portability and
flexibility, while also making it fast enough to be useful.  We have not yet
undertaken serious performance measurement or tuning; we intend to do so in
the future.


ARCHIVE LOCATIONS
=================

The "official" archive site for this software is ftp.uu.net (Internet
address 137.39.1.9 or 192.48.96.9).  The most recent released version can
always be found there in directory graphics/jpeg.  This particular version
will be archived as jpegsrc.v3.tar.Z.  If you are on the Internet, you can
retrieve files from UUNET by anonymous FTP.  If you don't have FTP access,
UUNET's archives are also available via UUCP; contact postmaster@uunet.uu.net
for information on retrieving files that way.

Various other Internet sites maintain copies of the UUNET file, which may or
may not be up-to-date.  In Europe, try nic.funet.fi (128.214.6.100; look in
directory pub/graphics/programs/jpeg).

You can also obtain this software from CompuServe, in the GRAPHSUPPORT forum
(GO PICS), library 10; this version will be file jpsrc3.zip.

If you are not reasonably handy at configuring and installing portable C
programs, you may have some difficulty installing this package.  You may
prefer to obtain a pre-built executable version.  A collection of pre-built
executables for various machines is currently available for anonymous FTP at
procyon.cis.ksu.edu (129.130.10.80 --- this number is due to change soon);
look under /pub/JPEG.  The administrators of this system ask that FTP traffic
be limited to non-prime hours.  For more information on this archive, please
contact Steve Davis (strat@cis.ksu.edu).  This collection is not maintained by
the Independent JPEG Group, and programs in it may not be the latest version.


REFERENCES
==========

The best and most readily available introduction to the JPEG compression
algorithm is Wallace's article in the April '91 CACM:
	Wallace, Gregory K.  "The JPEG Still Picture Compression Standard",
	Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
(Adjacent articles in that issue discuss MPEG motion picture compression,
applications of JPEG, and related topics.)  We highly recommend reading that
article before trying to understand the innards of any JPEG software.
If you don't have the CACM issue handy, a PostScript file containing a revised
version of the article is available at ftp.uu.net, graphics/jpeg/wallace.ps.Z.
The file (actually a preprint for an article to appear in IEEE Trans. Consumer
Electronics) omits the sample images that appeared in CACM, but it includes
corrections and some added material.  Note: the Wallace article is copyright
ACM and IEEE, and it may not be used for commercial purposes.

For more detail about the JPEG standard you pretty much have to go to the
draft standard (which is not nearly as intelligible as Wallace's article).
The standard is not now available electronically; you must order a paper copy
through ISO.  In the US, copies may be ordered from ANSI Sales at (212)
642-4900.  The standard is divided into two parts: Part 1 is the actual
specification, and Part 2 covers compliance testing methods.  The current
"committee draft" version of Part 1 is titled "Digital Compression and Coding
of Continuous-tone Still Images, Part 1: Requirements and guidelines" and has
document number ISO/IEC CD 10918-1.  (The alternate number SC2 N2215 should
also be mentioned when ordering.)  This draft is expected to be superseded by
the Draft International Standard version around the end of November 1991.
Ordering info will be the same as above, but replace "CD" with "DIS" in the
document number (alternate number not yet known).  The committee draft of
Part 2 is expected to be available around the end of December 1991.  It will
be titled "Digital Compression and Coding of Continuous-tone Still Images,
Part 2: Compliance testing" and will have document number ISO/IEC CD 10918-2
(alternate number not yet known).

The JPEG standard does not specify all details of an interchangeable file
format.  For the omitted details we follow the "JFIF" conventions, revision
1.01.  A copy of the JFIF spec is available from:
	Literature Department
	C-Cube Microsystems, Inc.
	399A West Trimble Road
	San Jose, CA  95131
	(408) 944-6300
The same source can supply copies of the draft JPEG-in-TIFF documents
(Appendixes O and P to the TIFF spec).  PostScript versions of these
documents can also be obtained by e-mail from the C-Cube mail server,
netlib@c3.pla.ca.us.  Send the message "send jfif_ps from jpeg" to obtain the
JFIF document; "send app_o_ps from jpeg" and "send app_p_ps from jpeg" will
produce the TIFF documents.  Send the message "help" if you have trouble.


Please send bug reports, offers of help, etc. to jpeg-info@uunet.uu.net.