It is insufficiently considered that 
                            men more often require to be reminded 
                            than informed.
                                                  Samuel Johnson


This file is part 1 of a set of Frequently Asked Questions (FAQ) for
the groups comp.compression and comp.compression.research.  If you
can't find part 2 or 3, see item 53 below. A copy of this FAQ is available
by ftp in ftp://rtfm.mit.edu/pub/usenet/news.answers/compression-faq/
files part1 to part3. This FAQ is also accessible in the World Wide Web at
http://www.faqs.org/faqs/compression-faq/part1/preamble.html or
http://www.cis.ohio-state.edu/hypertext/faq/usenet/compression-faq/top.html

Certain questions get asked time and again, and this is an attempt to
reduce the bandwidth taken up by these posts and their associated
replies.  If you have a question, *please* check this file before you
post.  It may save a lot of peoples time.

If you have not already read the overall Usenet introductory material
posted to "news.announce.newusers", please do. It is also available by
ftp in ftp://garbo.uwasa.fi/pc/doc-net/usenews.zip (see item 2 below
about .zip).

If you don't want to see this FAQ regularly, please add the subject
line to your kill file.  If you don't know what a kill file is, get by
ftp the file ftp://rtfm.mit.edu/pub/usenet/news.answers/killfile-faq
If you have corrections or suggestions for this FAQ, send them to
Jean-loup Gailly <jloup at gzip.org>. (Replace " at " with "@". This is
a protection against junk mail. Sorry for the inconvenience.)

Part 1 is oriented towards practical usage of compression programs.
Part 2 is more intended for people who want to know how compression works.
Part 3 is a long (but somewhat obsolete) list of image compression hardware.

Main changes relative to the previous version:

- LZO page moved [item 2]
- new url for the File Format Collection [items 2 & 54]
- new url for ACE [item 2]
- new pkzip version [item 3]
- fixed url for arithmetic coder [item 13]
- add url for DjVu, an image compression library [item 15]
- remove obsolete link [item 15]
- new url for DCT algorithms [item 15]
- add url for lossless image compression benchmarks [item 16]
- added urls for the MP3 audio compression standard, and for benchmarks
  of lossless audio compression programs [item 26]

Contents
========

General questions:

[1]  What are these newsgroups about?
[2]  What is this .xxx file type?
     Where can I find the corresponding compression program?
[3]  What is the latest pkzip version?
[4]  What is an archiver?
[5]  What is the best general purpose compression program?
[7]  Which books should I read?
[8]  What about patents on data compression algorithms?
[9]  Compression of random data (WEB, Gilbert and others)
[10] Fake compression programs (OWS, WIC)
[11] What is the V.42bis standard?
[12] I need source for the winners of the Dr Dobbs compression contest
[13] I need source for arithmetic coding

Image and audio compression:

[15] Where can I get image compression programs?
[16] What is the state of the art in lossless image compression?
[17] What is the state of fractal compression?
[18] I need specs and source for TIFF and CCITT group 4 Fax.
[19] What is JPEG?
[20] I am looking for source of an H.261/H.263 codec and MPEG
[25] Fast DCT (Discrete Cosine Transform) algorithms
[26] Are there algorithms and standards for audio compression?

Common problems:

[30] My archive is corrupted!
[31] pkunzip reports a CRC error!
[32] VMS zip is not compatible with pkzip!
[33] I have a problem with Stacker or DoubleSpace!

Questions which do not really belong to comp.compression:

[50] What is this 'tar' compression program?
[51] I need a CRC algorithm
[52] What about those people who continue to ask frequently asked questions?
[53] Where are FAQ lists archived?
[54] I need specs for graphics formats
[55] Where can I find Lenna and other images?
[56] I am looking for a message digest algorithm
[57] I have lost my password on a .zip file


Part 2: (Long) introductions to data compression techniques

[70] Introduction to data compression (long)
       Huffman and Related Compression Techniques
       Arithmetic Coding
       Substitutional Compressors
          The LZ78 family of compressors
          The LZ77 family of compressors

[71] Introduction to MPEG (long)
       What is MPEG?
       Does it have anything to do with JPEG?
       Then what's JBIG and MHEG?
       What has MPEG accomplished?
       So how does MPEG I work?
       What about the audio compression?
       So how much does it compress?
       What's phase II?
       When will all this be finished?
       How do I join MPEG?
       How do I get the documents, like the MPEG I draft?

[72] What is wavelet theory?
[73] What is the theoretical compression limit?
[74] Introduction to JBIG
[75] Introduction to JPEG
[76] What is Vector Quantization?
[77] Introduction to Fractal compression
[78] The Burrows-Wheeler block sorting algorithm


Part 3: (Long) list of image compression hardware

[85] Image compression hardware
[99] Acknowledgments


Search for "Subject: [#]" to get to question number # quickly. Some news
readers can also take advantage of the message digest format used here.

If you know very little about data compression, read question 70 in
part 2 first.