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program generated from the IJG code, this does not limit
you more than the foregoing paragraphs do.
The Unix configuration script “configure” was produced
with GNU Autoconf. It is copyright by the Free Software
Foundation but is freely distributable. The same holds for its
supporting scripts (config.guess, config.sub, ltconfig,
ltmain.sh). Another support script, install-sh, is copyright
by M.I.T. but is also freely distributable.
It appears that the arithmetic coding option of the JPEG
spec is covered by patents owned by IBM, AT&T, and
Mitsubishi. Hence arithmetic coding cannot legally be
used without obtaining one or more licenses. For this
reason, support for arithmetic coding has been removed
from the free JPEG software. (Since arithmetic coding
provides only a marginal gain over the unpatented Huffman
mode, it is unlikely that very many implementations will
support it.) So far as we are aware, there are no patent
restrictions on the remaining code.
The IJG distribution formerly included code to read and
write GIF files. To avoid entanglement with the Unisys LZW
patent, GIF reading support has been removed altogether,
and the GIF writer has been simplified to produce
uncompressed GIFs. This technique does not use the LZW
algorithm; the resulting GIF files are larger than usual, but
are readable by all standard GIF decoders.
We are required to state that
“The Graphics Interchange Format(c) is the Copyright
property of CompuServe Incorporated. GIF(sm) is a
Service Mark property of CompuServe Incorporated.”
REFERENCES
We highly recommend reading one or more of these
references before trying to understand the innards of the
JPEG software.
The best short technical introduction to the JPEG
compression algorithm is
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.) If you don’t have the CACM issue handy, a
PostScript file containing a revised version of Wallace’s
article is available at ftp://ftp.uu.net/graphics/jpeg/
wallace.ps.gz. The file (actually a preprint for an article that
appeared 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.
A somewhat less technical, more leisurely introduction to
JPEG can be found in The Data Compression Book by Mark
Nelson and Jean-loup Gailly, published by M&T Books (New
York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
good explanations and example C code for a multitude of
compression methods including JPEG. It is an excellent
source if you are comfortable reading C code but don’t
know much about data compression in general. The book’s
JPEG sample code is far from industrial-strength, but when
you are ready to look at a full implementation, you’ve got
one here...
The best full description of JPEG is the textbook “JPEG Still
Image Data Compression Standard” by William B.
Pennebaker and Joan L. Mitchell, published by Van
Nostrand Reinhold, 1993, ISBN 0-442-01272-1. Price
US$59.95, 638 pp. The book includes the complete text of
the ISO JPEG standards (DIS 10918-1 and draft DIS 10918-
2). This is by far the most complete exposition of JPEG in
existence, and we highly recommend it.
The JPEG standard itself is not available electronically; you
must order a paper copy through ISO or ITU. (Unless you
feel a need to own a certified official copy, we recommend
buying the Pennebaker and Mitchell book instead; it’s
much cheaper and includes a great deal of useful
explanatory material.) In the USA, copies of the standard
may be ordered from ANSI Sales at (212) 642-4900, or from
Global Engineering Documents at (800) 854-7179. (ANSI
doesn’t take credit card orders, but Global does.) It’s not
cheap: as of 1992, ANSI was charging $95 for Part 1 and $47
for Part 2, plus 7% shipping/handling. The standard is
divided into two parts, Part 1 being the actual specification,
while Part 2 covers compliance testing methods. Part 1 is
titled “Digital Compression and Coding of Continuous-tone
Still Images, Part 1: Requirements and guidelines” and has
document numbers ISO/IEC IS 10918-1, ITU-T T.81. Part 2 is
titled “Digital Compression and Coding of Continuous-tone
Still Images, Part 2: Compliance testing” and has
document numbers ISO/IEC IS 10918-2, ITU-T T.83.
Some extensions to the original JPEG standard are defined
in JPEG Part 3, a newer ISO standard numbered ISO/IEC IS
10918-3 and ITU-T T.84. IJG currently does not support any
Part 3 extensions.
The JPEG standard does not specify all details of an
interchangeable file format. For the omitted details we
follow the “JFIF” conventions, revision 1.02. A copy of the
JFIF spec is available from:
Literature Department
C-Cube Microsystems, Inc.
1778 McCarthy Blvd.
Milpitas, CA 95035
phone (408) 944-6300, fax (408) 944-6314
A PostScript version of this document is available by FTP at
ftp://ftp.uu.net/graphics/jpeg/jfif.ps.gz. There is also a plain
text version at ftp://ftp.uu.net/graphics/jpeg/jfif.txt.gz, but it
is missing the figures.
The TIFF 6.0 file format specification can be obtained by FTP
from ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG
incorporation scheme found in the TIFF 6.0 spec of 3-June-
92 has a number of serious problems. IJG does not
recommend use of the TIFF 6.0 design (TIFF Compression
tag 6). Instead, we recommend the JPEG design proposed
by TIFF Technical Note #2 (Compression tag 7). Copies of
this Note can be obtained from ftp.sgi.com or from ftp://
ftp.uu.net/graphics/jpeg/. It is expected that the next
revision of the TIFF spec will replace the 6.0 JPEG design
with the Note’s design. Although IJG’s own code does not
support TIFF/JPEG, the free libtiff library uses our library to
implement TIFF/JPEG per the Note. libtiff is available from
ftp://ftp.sgi.com/graphics/tiff/.
ARCHIVE LOCATIONS
The “official” archive site for this software is ftp.uu.net
(Internet address 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 ftp://
ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz. If you don’t
have direct Internet access, UUNET’s archives are also
available via UUCP; contact help@uunet.uu.net for
information on retrieving files that way.
Numerous Internet sites maintain copies of the UUNET
files. However, only ftp.uu.net is guaranteed to have the
latest official version.
You can also obtain this software in DOS-compatible “zip”
archive format from the SimTel archives (ftp://
ftp.simtel.net/pub/simtelnet/msdos/graphics/), or on
CompuServe in the Graphics Support forum (GO
CIS:GRAPHSUP), library 12 JPEG Tools. Again, these
versions may sometimes lag behind the ftp.uu.net release.
The JPEG FAQ (Frequently Asked Questions) article is a
useful source of general information about JPEG. It is
updated constantly and therefore is not included in this
distribution. The FAQ is posted every two weeks to Usenet
newsgroups comp.graphics.misc, news.answers, and
other groups. It is available on the World Wide Web at http:/
/www.faqs.org/faqs/jpeg-faq/ and other news.answers
archive sites, including the official news.answers archive at
rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/
jpeg-faq/. If you don’t have Web or FTP access, send e-mail
to mail-server@rtfm.mit.edu with body
send usenet/news.answers/jpeg-faq/part1
send usenet/news.answers/jpeg-faq/part2
RELATED SOFTWARE
Numerous viewing and image manipulation programs now
support JPEG. (Quite a few of them use this library to do so.)
The JPEG FAQ described above lists some of the more
popular free and shareware viewers, and tells where to
obtain them on Internet.
If you are on a Unix machine, we highly recommend Jef
Poskanzer’s free PBMPLUS software, which provides many
useful operations on PPM-format image files. In particular,
it can convert PPM images to and from a wide range of
other formats, thus making cjpeg/djpeg considerably more
useful. The latest version is distributed by the NetPBM
group, and is available from numerous sites, notably ftp://
wuarchive.wustl.edu/graphics/graphics/packages/
NetPBM/. Unfortunately PBMPLUS/NETPBM is not nearly
as portable as the IJG software is; you are likely to have
difficulty making it work on any non-Unix machine.
A different free JPEG implementation, written by the PVRG
group at Stanford, is available from ftp://
havefun.stanford.edu/pub/jpeg/. This program is designed
for research and experimentation rather than production
use; it is slower, harder to use, and less portable than the
IJG code, but it is easier to read and modify. Also, the PVRG
code supports lossless JPEG, which we do not. (On the
other hand, it doesn’t do progressive JPEG.)
FILE FORMAT WARS
Some JPEG programs produce files that are not compatible
with our library. The root of the problem is that the ISO
JPEG committee failed to specify a concrete file format.
Some vendors “filled in the blanks” on their own, creating
proprietary formats that no one else could read. (For
example, none of the early commercial JPEG
implementations for the Macintosh were able to exchange
compressed files.)
The file format we have adopted is called JFIF (see
REFERENCES). This format has been agreed to by a
number of major commercial JPEG vendors, and it has
become the de facto standard. JFIF is a minimal or “low
end” representation. We recommend the use of TIFF/JPEG
(TIFF revision 6.0 as modified by TIFF Technical Note #2) for
“high end” applications that need to record a lot of
additional data about an image. TIFF/JPEG is fairly new and
not yet widely supported, unfortunately.
The upcoming JPEG Part 3 standard defines a file format
called SPIFF. SPIFF is interoperable with JFIF, in the sense
that most JFIF decoders should be able to read the most
common variant of SPIFF. SPIFF has some technical
advantages over JFIF, but its major claim to fame is simply
that it is an official standard rather than an informal one. At
this point it is unclear whether SPIFF will supersede JFIF or
whether JFIF will remain the de-facto standard. IJG intends
to support SPIFF once the standard is frozen, but we have
not decided whether it should become our default output
format or not. (In any case, our decoder will remain capable
of reading JFIF indefinitely.)
Various proprietary file formats incorporating JPEG
compression also exist. We have little or no sympathy for
the existence of these formats. Indeed, one of the original
reasons for developing this free software was to help force
convergence on common, open format standards for JPEG
files. Don’t use a proprietary file format!
TO DO
The major thrust for v7 will probably be improvement of
visual quality. The current method for scaling the
quantization tables is known not to be very good at low Q
values. We also intend to investigate block boundary
smoothing, “poor man’s variable quantization”, and other
means of improving quality-vs-file-size performance
without sacrificing compatibility.
In future versions, we are considering supporting some of
the upcoming JPEG Part 3 extensions --- principally,
variable quantization and the SPIFF file format.
As always, speeding things up is of great interest.
Please send bug reports, offers of help, etc. to jpeg-
info@uunet.uu.net.
libupnp
Copyright (c) 2000-2003 Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, are permitted provided that the
following conditions are met:
* Redistributions of source code must retain the above
copyright notice, this list of conditions and the following
disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.
* Neither name of Intel Corporation nor the names of its
contributors may be used to endorse or promote
products derived from this software without specific
prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT
HOLDERS AND CONTRIBUTORS
“AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
EVENT SHALL INTEL OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.
AVC/H.264
THIS PRODUCT IS LICENSED UNDER THE AVC PATENT
PORTFOLIO LICENSE FOR THE PERSONAL AND NON-
COMMERCIAL USE OF A CONSUMER TO (i) ENCODE
VIDEO IN COMPLIANCE WITH THE AVC STANDARD (”AVC
VIDEO”) AND/OR (ii) DECODE AVC VIDEO THAT WAS
ENCODED BY A CONSUMER ENGAGED IN A PERSONAL
AND NON-COMMERCIAL ACTIVITY AND/OR WAS
OBTAINED FROM A VIDEO PROVIDER LICENSED TO
PROVIDE AVC VIDEO. No LICENSE IS GRANTED OR
SHALL BE IMPLIED FOR ANY OTHER USE. ADDITIONAL
INFORMATION MAY BE OBTAINED FROM MPEG LA, L.L.C.
SEE HTTP://MPEGLA.COM.
GNU GENERAL PUBLIC LICENSE
Version 2, June 1991
Copyright © 1989, 1991 Free Software Foundation, Inc., 51
Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim
copies of this license document, but changing it is not
allowed.
Preamble
The licenses for most software are designed to take away
your freedom to share and change it. By contrast, the GNU
General Public License is intended to guarantee your
freedom to share and change free software - to make sure
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