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Psyko12 · 30/01/2010 05:04 PM

So... today I -obtained- a PSP mini game. It was only 6mb so I was like "yay praise the creator for making a supr small gaem!!!11one"
So I extracted the .rar and got a 131mb ISO. I was stunned. I had no idea you could compress ISO's that far.

My question is: How can I compress files this much, and will it work with all files, or ISO's only?

Silvertie · 30/01/2010 06:07 PM

I've seen some games rar'd to about 25% compression. If you're willing to give it a shot, UHARC does some pretty gnarly compression, too. (No idea how you use it, though. It's all command prompt stuff, but it can get up to 10% compression ratio.)

Assassinator · 30/01/2010 06:17 PM

It would depend a lot on the file in question, some stuff are extremely compressible (eg. certain data files), some stuff just don't compress at all (eg. video).

Take this simplified example....
1). 0000000000001111111111111112222222222299999999999000000000000
2). :Oim&(^$0o[jalaohiPIHUGsfoa)_(*5432"?>:'.'?"{})(12uhfapihgaPOAFMU78

The first one would obviously compress a whole lot better than the second one. How much you can compress stuff all depends on how compressible the file is.

Btw... 7z > rar.

ProperBritish · 30/01/2010 06:22 PM

Assassinator Wrote:It would depend a lot on the file in question, some stuff are extremely compressible (eg. certain data files), some stuff just don't compress at all (eg. video).

Take this simplified example....
1). 0000000000001111111111111112222222222299999999999000000000000
2). :Oim&(^$0o[jalaohiPIHUGsfoa)_(*5432"?>:'.'?"{})(12uhfapihgaPOAFMU78

The first one would obviously compress a whole lot better than the second one. How much you can compress stuff all depends on how compressible the file is.

Btw... 7z > rar.

the first one could compress to 01290, amirite?

hypothetically speaking

Psyko12 · 30/01/2010 06:27 PM

well... I asked joo-muh-lah about it and he said something about batch/command stuff. that's all he knew. Google wasn't wanting to help.

edit: 7z doesn't compress better than winrar. I googled some benchmarks, and it turns out that winrar beats 7z, winzip etc...

diego · 30/01/2010 06:34 PM

Theres that KGB archiver that would take hours to compress and decompress.
But it did shrink stuff by a lot.
http://kgbarchiver.net/

Psyko12 · 30/01/2010 06:40 PM

diego Wrote:Theres that KGB archiver that would take hours to compress and decompress.
But it did shrink stuff by a lot.
http://kgbarchiver.net/

worth a try.

thanks

Assassinator · 30/01/2010 06:45 PM

Psyko12 Wrote:edit: 7z doesn't compress better than winrar. I googled some benchmarks, and it turns out that winrar beats 7z, winzip etc...

Depends on what stuff. But on most things, 7z > winrar.

And a lot of these benchmarks are retarded (either retarded settings or retarded test files). Here's a non-retarded benchmark, as you can see, each are better at different stuff.

diego Wrote:Theres that KGB archiver that would take hours to compress and decompress.
But it did shrink stuff by a lot.
http://kgbarchiver.net/

PAQ compression is like SLOWWWW, and practically unusable in normal circumstances because of how SLOOWWW it is.

diego · 30/01/2010 06:51 PM

Assassinator Wrote:
Psyko12 Wrote:edit: 7z doesn't compress better than winrar. I googled some benchmarks, and it turns out that winrar beats 7z, winzip etc...

Depends on what stuff. But on most things, 7z > winrar.

And a lot of these benchmarks are retarded (either retarded settings or retarded test files). Here's a non-retarded benchmark, as you can see, each are better at different stuff.

diego Wrote:Theres that KGB archiver that would take hours to compress and decompress.
But it did shrink stuff by a lot.
http://kgbarchiver.net/

PAQ compression is like SLOWWWW, and practically unusable in normal circumstances because of how SLOOWWW it is.

I agree. I just wanted to show it to him.

ZiNgA BuRgA · 30/01/2010 08:19 PM

As said, depends on compressability, but 131MB to 6MB is quite astounding for a general PSP ISO, especially since media (music/FMVs) generally takes up the most space and are often compressed. Perhaps the game has a fair bit of padding.

ProperBritish Wrote:the first one could compress to 01290, amirite?

hypothetically speaking

Depends what scheme you're using.  For deflate (most popular compression algo, used in ZIP/zlib/gzip and I believe RAR is based on it) there's two stages - a dictionary compress and then an entropy encode.
You'd get something like what you said above with the dictionary phase (it just detects duplicate stuff).  The entropy encode phase would then reduce the above to a few bits.

From what I've read, 7-zip with LZMA2 (v9.xx) generally beats RAR consistently.  Previously, I think RAR was slightly better at handling uncompressed media (eg WAV, BMP etc) than LZMA.
I think PAQ8px is generally considered the best compressor.  KGB is based off PAQ6 or something like that, right?

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