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I want to learn how to highly compress a file. I have downloaded files whose compressed size was 4 GB, and after extracting they became 10 GB.

  • Which software do I need to use for such high compression?
  • Will I lose quality of the data by compression?
  • If you direct me to WinRAR or 7-Zip, please tell me how can I highly compress a file because I have tried compression with it, but the size was reduced just by only a few MBs.

I am compressing games like .exe files.

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What operating system are you using? What type of file or files are you compressing. Will it be one file of one type or multiple files of the same type or mixed type? What programs have you tried so far and why did they not work for you? –  Dave Rook Aug 14 '12 at 8:57
    
Are you actually downloading 4gb of .exe though or installation files which results in an .exe? Because the installation is probably not just one compressed file but multiple compressed files, the installation process will un-compress as it installs. –  Dave Rook Aug 14 '12 at 10:48
    
First, you start with highly compressible data. –  Fiasco Labs Nov 8 '13 at 3:39
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4 Answers

Some basic background information on compression:

Truly random data is not losslessly compressible at all. This is something of a basic tenet of a field of study known as Information Theory (closely related to Computer Science). For a file to be losslessly compressible, its data must be repetitive or predictable.

One rule of thumb is that arbitrary computer files are typically around 50% compressible using a decent lossless algorithm. Text files are often dramatically compressible.

If you have pictures, audio, or video files, they may be able to be dramatically compressed while still remaining reasonable fidelity to the original if you can accept lossy compression. The lossy compression algorithms vary based on the medium (still photos, audio, video, etc.), and even by the sub-category; a photo from a camera might be best compressed with JPEG, whereas a computer graphic might be best compressed with a different codec. Music does best with codecs like MP3 or AAC at bitrates of 256kbps or higher, but voice recordings can be compressed to just 9.6kbps and still be perfectly intelligible.

The H.264 AVC codec can compress HD video by two or almost three orders of magnitude (that is, to less than 1% of its original size) while still retaining reasonable quality. Uncompressed full HD is 1920 pixels wide * 1080 pixels high * 24 bits/pixel * 30 frames per second = about 1.5 gigabits per second, but it's not uncommon to see H.264 AVC compressed HD at 15 megabits per second or less with reasonable image quality.

If you compress a file once (lossy or lossless), and then try to do a lossless compression of that, it tends to not be capable of much further compression. That's because any good compression algorithm should have gotten rid of all the wasted space (repetitive or unnecessary data), so there shouldn't be anything left to compress.

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So can I compress computer games. If yes than by which percentage the size will reduce –  Alfred James Aug 14 '12 at 8:52
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@Alfred, again - if you have something in mind you need to update your question for it. People are taking time to help you and your question does not mention what type of file you are trying to compress. A game could be an MSI, an EXE (if for Windows at all?). As for what % it's not predicable - read Spiff's excellent answer again (+1). –  Dave Rook Aug 14 '12 at 8:56
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The level of awesomeness in your answer is in such stark contrast with that in the question, I'm just speechless... –  Mehrdad Aug 14 '12 at 9:36
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This is a very old topic, don't know if my input will be helpful at this point but I think he wants to repack an already installed game,

If that is the case then a combination of 7z, srep and precomp will be able to reduce a 2.2gb game to 680mb. See this tutorial on youtube.

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You could try Winrar. There are many compression options. If this is not enough then try 7-ZIP

EDIT

It depends on what type of files you are trying to compress. 7z's LZMA algorithm has a higher compression ratio than RAR, except for "multimedia" files like .wav and .bmp files, for which RAR uses specialized routines that outperform LZMA.

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It can't higly compress a file –  Alfred James Aug 14 '12 at 8:03
    
tried that too. –  Alfred James Aug 14 '12 at 8:06
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Since 7-ZIP is a valid answer, I think you need to update your question to list what you have tried please. –  Dave Rook Aug 14 '12 at 8:07
    
What type of files do you want to compress? The ones you downloaded - what compression scheme had been used? File extension? –  DaveP Aug 14 '12 at 8:31
    
@AlfredJames saying that "Rar/7zip" can't "highly compress" is false. –  Sathya Aug 14 '12 at 10:42
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KGB Archiver is known for having a very high compression ratio.

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...and it is no longer available! –  Dave Rook Aug 14 '12 at 10:45
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