Compression Methods

I've got a ton of very large files (4-7gb each) that I want to compress, for storing. I believe I can shrink these file sizes considerably, and wondering what my options are, and which ones can give best compression. Speed doesn't matter.

I hear a lot about .rar and 7zip. Are they basically my best bet?

thanks!

 

7zip is the best.

 

I'm a fan of 7zip as well. Be sure to put it into a .7z archive rather than zip.

http://www.7-zip.org/ : (note that this comparison looks a bit old)

 

ok thanks, ill be sure to check it out.

Now I'm wondering, if I try to zip/rar a video file or iso image file, will there be any compression? or will the compression ratio be poor?

 

I also use 7zip on this computer. But another one I have used and like is called ExtractNow. Not sure if it works on Vista/W7 as I used it on XP.

 

Video file is usually incompressible.

 

You're unlikely to get much compression out of any sort of an image file. For the most part, those files are already compressed, and even for those that aren't already compressed, there generally is not a lot of spare room to squeeze out using a generalized compression technique (as opposed to the carefully tailored image-compression techniques a lot of image formats use).

 

ISOs and other image 'files' aren't really files as such. An ISO is kind of like an envelope or a bucket, it's merely the container. As such it is compressible to about the same extent as its contents.

 

I tested compressing an ISO of Office 2007:

Uncompressed: 450MB
7z Compression (mode "Ultra"): 392MB
WinRAR Compression (mode "Best"): 394MB

 

Might as well use WinRAR, it's free, even though it says the trial version lasts 3-days it never stops working.

 

You might really want to ask if compression is worth it nowadays as you generally only see real gains on text files.

The key advatage I see in a "compressed file folder" is that you can upload it somewhere and share the files - e.g. upload a zip to the SkyDrive - if you just upload JPEGs they loose quality for some reason.

If you have a library of DVDs, or Music, or Photographs - it might be better to get an external HDD or another one.

 

Pretty good results! It's interesting to see that there's only about 2MB's worth of difference between the two.

 

I think you should read this, it's just a few days old, fresh review of compression software.


Four Compression And Archiving Solutions Compared

 

Yeah I noticed almost no compression in the files I tested (h264 video file and ISO image file). Is there nothing I can do about it? no other method or program that can farther compress these files?

 

You can use magic iso to compress it to .uif file. Sometimes, you get over 60% reduction in file sizes for disk images.

 

You could always try KGB Archiver, it may compress files down to 20% (80% compression rate) of their original size, the con being, it requires a strong computer (minimal requirements are low, however) to compress files in a shorter time.

KGB Archiver uses the AES-256 algorithm to encrypt the files.

For maximum compression, it took some time on the laptop computer listed on my spec, so it is, indeed, processor-heavy.

 

Its a Beta so I'd not recommend it for active storage.

 

You are quite right, I missed that detail, KGB Archiver was the first thing that passed through my mind when thinking about data compressors.

In any case, I guess that 7-Zip will do, pretty stable, reliable and has a good compression rate.

 

Nope. EXE files don't compress much either (at least one's that don't contain a lot of text such as prompts and help files). The reason is lossless compression depends on there being wasted space in the original file. A simple example would be: 'xxxxxxxxxxxxxxxxxxxxxxxxxx' could be stored as '26(x)' and you see I've saved 21 characters. EXE files are mostly computer instructions and as such are pretty much random (as in no set pattern). Compressed media files usually have all the 'duplicate' stuff already squoze out of them and also don't compress any further. If the ISOs you've tried contain compressed media files then they too won't compress. On the other hand, if you have an ISO that has a lot of text in it it can be compressed significantly. An example is on this page: Ultimate Boot CD. Look at the size difference between downloading the ISO -vs- the ZIP version.