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Question gzip Maven Jean-loup Gailly
Posted by
Roblimo
on Mon Mar 06, 2000 11:00 AM
from the picking-the-experts'-brains dept.
from the picking-the-experts'-brains dept.
Jean-loup Gailly is the author of gzip and, now, CTO for Mandrakesoft, purveyors of Linux-Mandrake. Jean-loup's home page tells you quite a bit about him, including some interesting peeks into his life beyond Linux and open source software. Please try to keep it down to one question per post. Submitted questions will be chosen from the highest-moderated. Answers will appear within the next week.
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Question gzip Maven Jean-loup Gailly
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Why do you force the use of TAR? (Score:3)
Using tar makes things unnecessarily complicated. There is less support for tar around on non-UNIX platforms, and 'embedded compression/archiving' seems to cause great trouble for newbies who can just about handle WinZip and nothing more.
If gzip is to become a truly viable alternative to patented zip, I think the .tar.gz should become a thing of the past.
Remove the old legacy tape archive!
Alternate Algorithms within GZIP (Score:3)
Would you think it wise to roll alternatives to the Lempel-Ziv algorithms into gzip to make other compression utilities less attractive?
It seems that this approach is adopted by other applications (ssh uses multiple encryption engines, and TIFF has allowed several compression techniques for quite a long time).
Would you support an effort to implement bzip2 within gzip? Do you think such a thing could be done while maintaining gzip's stability?
Go! (Score:3)
I notice you are a keen Go player... the GNOME version of Go (Iagno) seems much more attractive to me than the KDE version (kgo). I was wondering what software you use to play games, or are you not really interested in the interface at your level of play?
Regards,
Denny
# Using Linux in the UK? Check out Linux UK [linuxuk.co.uk]
Astronomical! :) (Score:3)
On your website, in the history section, you have a link to some information about pulsars...
Were you an astronomy student, and if so how did you go from studying pulsars to CTO of a major Linux distributor?!?
Regards,
Denny
# Using Linux in the UK? Check out Linux UK [linuxuk.co.uk]
LinuxOne (Score:3)
Nasty Code (Score:3)
z = (z = g - w) > (unsigned)l ? l : z;
It makes your code almost impossible to read. Do you even know what this line does anymore?
Re:Nasty Code (Score:3)
I hate to sound like I'm flaming you, but this is the standard idiom in C for addition with saturation. When (g-w) is larger than a certain constant l, z is assigned to that constant l, otherwise, z will retain its value.
This code can also be written less efficiently (well, at least if your compiler doesn't have common sub-expression elimination) as:
if((g-w) > (unsigned) l){
z=l;
} else {
z=g-w;
}
Re:Improved compression? (Score:3)
A much more intuitive argument is the "pigeonhole principle." Let's assume that there are 16 holes in a wall, to which each is associated with a message. It is impossible for 17 messages to each be uniquely associated with a hole because there are not enough holes avalible. A 4-bit file can only represent 16 different messages, regardless of what algorithm is used to compress the message...unless, that is, you don't care about the compression being reversible!
a new question - the guy above asked mine :-( (Score:3)
patents in software design (Score:3)
Why is Mandrake better than Redhat? (Score:4)
I guess that you have at least a little something to say about this.
Is the 586 optimization enough to justify Mandrake's position? Are you especially proud of any of the architectural differences between the distributions (from what I have been told, the Apache-PHP layout is quite a bit different).
How do feel about the steps that Red Hat has taken to change their distribution in reaction to yours?
What about wavelets? (Score:4)
The Data Compression Book was an excellent reference when it came out, but there are some hot topics in compression that it doesn't cover - frequency-domain lossy audio techniques (MP3), video techniques (MPEG2 and especially MPEG4), wavelets (Sorenson video uses these, I believe, and JPEG2000 will), and the Burrows-Wheeler transform from bzip.
Do you have any plans for a new edition of the book, or good Web references for these techniques? BZip is covered well by a Digital research note, but documentation for MPEG2 seems only to exist as source code and I can't find anything concrete about using wavelets for compression. The data is all there on the comp.compression FAQ, but the excellent exposition of the book is sorely lacking.
Go and Compression (Score:4)
Inquiring minds want to know.
bzip2 Support (Score:5)
Will BW be an algorithm option within the gzip file format itself ever?
Compression software (Score:5)
However, much of the software you've written has started gathering a few grey hairs. Gzip, for example, has been at 1.2.4 for many, many moons, and looks about ready to collect it's gold watch.
Is compression software in a category that inherently plateus quickly, so that significant further work simply isn't possible? Or is there some other reason, such as Real Life(tm) intruding and preventing any substantial development?
(I noticed, for example, a patch for >4Gb files for gzip, which could have been rolled into the master sources to make a 1.2.5. This hasn't happened.)
Winzip (Score:5)
Just out of curiosity, (tell me it's none of my business if you want to and I'll be OK with that) did you receive a licensure fee from the company that makes Winzip for the code?
Proprietary algorithms (Score:5)
What do you think of the expansion of trade-secret algorithms (MP3 quantisation tables, Sorensen, RealAudio and RealVideo, Microsoft Streaming Media) where the format of the data stream is not documented anywhere?
Tom
Compression patents (Score:5)
The Data Compression Book (Score:5)
Should software authors continue to write their own compression routines, or simply trust the versions available to them in library form?
I can see some definite advantages to library code, i.e. the ability to upgrade routines, and having standardized algorithms which can be read by any program which utilizes the library.
Doug
A question about Mandrake... (Score:5)
Brad Johnson
--We are the Music Makers, and we
are the Dreamers of Dreams