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Have seen some highly compressed files around.(for eg: i have seen 700mb of data compressed to around 30-50mb)

But how do you get such compressed files, I have tried using softwares like Winrar and 7Zip but have never achieved such high compression.

What are the techniques/software that allow you to compress files so well?

(P.S. I'm using Windows Xp)

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Nice idea ... but where do you get such files from anyways? – Jenko Aug 22 '09 at 11:42
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I've seen 7zip compress server log files (mainly text) down to about 1% of their original size. – Umber Ferrule Oct 20 '09 at 13:07
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7 Answers

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If time taken to compress the data is not an issue, then you can optimize compressed size by using several different tools together.

Compress the data several times using different tools like 7zip, winrar (for zip) and bjwflate.

Next, run deflopt on each archive to reduce each archive a little more.

Finally, run zipmix on the collection of archives. Since different zip tools are better on different files, zipmix picks the best compressed version of each file from each of the archives and produces an output which is smaller than any that any of the zip tools could have produced individually.

You should note however that this is not guaranteed to work any kind of magic on your files. Certain types of data simply do not compress very well, like JPEGs and MP3s. These files are, to put it simply, already zipped internally.

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JPEGs and MP3s aren't zipped. They are compressed but not zipped. – KovBal Jul 21 '09 at 18:27
@davr: You're absolutely right. I suggest removing both your and my comments. – Georg Schölly Feb 27 '11 at 22:55
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up vote 9 down vote

This depends entirely on the data being compressed.

Text compresses very well, binary formats not so well and compressed data (mp3, jpg, mpeg) not at all.

Here is a good Compression Comparison Table from wikipedia.

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I am aware that compression depends upon the type of data, but are there any specific techniques that help you compress files further? – rzlines Jul 17 '09 at 10:35
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Once you have compressed something it's usually impossible to get it measurably smaller. You just have to select the appropriate compression method for your data. – Nifle Jul 17 '09 at 10:39
Text can easily be compressed up to 90%. – Georg Schölly Jun 13 '10 at 7:32
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up vote 3 down vote

Squeezechart.com contains comparisons of various compression rates. Although, as stated by Nifle's answer - you're unlikely to get such high compression rates for binary formats.

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up vote 2 down vote

Most compression tools have settings to allow you to achieve a higher compression rate at a compromise of slower compression/decompression times and more RAM usage.

For 7-Zip, search for "Add to Archive Dialog Box" in the built-in help for more detail.

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up vote 1 down vote

Your best bet here seems to be trial and error. Try all your available compression techniques on each file and pick the best to put on your website. Luckily computers do this sort of thing pretty fast and don't get bored. You could write a simple script to automate the process so it would be "relatively painless". I'd probably write the script in python but you might have a better choice available.

Just don't expect miracles - 700 mb down to 30 mb just doesn't happen that often. Log files as mentioned above - yes. "Your average file" - no way.

Hotei

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up vote 1 down vote

Just visit http://www.maximumcompression.com/

Best compression list http://www.maximumcompression.com/data/summary_mf2.php It lists complete compression benchmark, Best tool till now is FreeArc.

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up vote 0 down vote

Nanozip seems to have highest compression together with FreeArc. But it is not in final version yet. There is how good compression Nanozip achieves. It has very high compression and it does not takes too much time see http://www.maximumcompression.com/data/summary_mf.php#data, but FreeArc is faster.

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