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Posted: Mon Feb 24, 2003 4:43 pm
by Zornak
i have gone insane trying to figure out this thread...
i think they scare me more than i scare them
Posted: Mon Feb 24, 2003 5:12 pm
by Twilkitri
According to
www.filext.com, LHA is:
.LHA Compressed Archive File (LZH format; LHA.EXE)
Compressed Archive File (LHARC.EXE)
Compressed Archive File (LHARK.EXE)
Dunno what LZH is, it's probably a variant of LZ77 or LZ78.
Posted: Tue Feb 25, 2003 12:22 am
by chromus
LHA is/was an old file compression format. It doesn't compress as well as LZH or LZ77, but it's extremely easy to program, so it continues to be used.
Posted: Tue Feb 25, 2003 12:24 am
by Twilkitri
Hmm? But the site said that LHAs were in LZH compression. Are they wrong, or did you type the wrong acronym again?
Posted: Tue Feb 25, 2003 12:27 am
by chromus
Not misplaced acronyms this time. LZH, the old compression algorithm, was implemented in LHA files. It's hard to keep all these compression algorithms/formats straight, with all the acronyms, so I apologize.
Posted: Tue Feb 25, 2003 2:13 am
by Twilkitri
chromus wrote:LHA is/was an old file compression format. It doesn't compress as well as LZH or LZ77
chromus wrote:Not misplaced acronyms this time. LZH, the old compression algorithm, was implemented in LHA files
I'm confused...
Posted: Wed Feb 26, 2003 1:31 am
by chromus
DarkTwilkitri wrote:I'm confused...
Yeah, I tend to do that. Sorry about all the confusion, but compression algorithms/formats tend to have common acronyms with small differences. Here's a summary:
Algorithms:
LZH, LZW, LZ77
File formats:
LHA, GIF, GZ
Each file format corresponds to an algorithm, in order.
Posted: Wed Feb 26, 2003 1:44 am
by Twilkitri
It's just that you say that LHA is a file format, then you say that it's a type of compression. And you say that it doesn't compress as well as LZH, then you say it uses LZH.
Posted: Thu Feb 27, 2003 1:59 am
by chromus
Admittedly, I did screw things up. Most compression algorithms have very similar names, most of which start with LZ. Let me set the record straight, ignoring all previous posts:
The initial LZ is short for Lempel Ziv, named after Abraham Lempel and Jakob Ziv, the original publishers of the algorithm. There are many variants of the algorithm. Below are some of them, along with a common file extension that uses it:
LZH: LHA
LZW: GIF
LZ77: PNG
Posted: Thu Feb 27, 2003 6:32 pm
by Twilkitri
Which one is LZH based on, anyway? And do you know who the H is ?
Posted: Thu Feb 27, 2003 9:42 pm
by chromus
Well, LZ compression is a combination of run-length encoding and Huffman tree encoding. LZH, LZW, and LZ77 are all variations of the original LZ, like how to assume character frequencies and other variables. The H in LZH is named after Haruyasu, the co-creator of LZH compression. The W in LZW is named after Welch, the co-creator of LZW compression, a derivation of LZ78 compression. The problem is, LZW is patented by Unisys, so don't bother trying to use it.
LZ77 and LZ78 are named after the years they were documented.