Compression of files.

junii

Using winzip or winrar, which are the best files to compress for maximum compression? Im sure I have seen files before that were compressed up to and over 40%.

Has anyone else seen this and if so what kind of file was it?

blorg

RAR generally beats out ZIP but rarely so much as to be worth it given the reduced compatibility. I use WinRAR exclusively myself as it can produce ZIP files as well and I prefer the interface (simpler and less heavy than WinZIP IMHO.)

Compression will entirely depend on the file type. Jpegs and Mp3s won't compress at all while other documents will compress significantly, often _well_ beyond 40%. It depends on the amount of redundancy in the file. A general average quoted is ususally 50% (this is the figure used by the tape backup industry) although I would imagine that is slipping with the amount of already compressed media on modern computers.

Buceph

I'd use winrar if I were you. Not that the compression is any better, just that it can de-compress more files than the standard windows winzip. Also, it has the handiest option for zipped files you want to extract, right click and you get an extract here option. No messing around.

blorg

The zip file format also has a 2gb limitation which is another reason we use rar (database backups.) It's possible that WinZip has gone beyond this by bending the standard (WinRAR won't let you create a zip >2gb and tells you to use RAR instead.)

Ruu_Old

I think with rar files you can split up the archive into a few parts if you wanted, 7-Zip is also a good freeware file archiver with a high compression ratio.

Capt'n Midnight

The big question is what are you compressing ???

If compressing multimedia files (sound/vision/images) then they are already compressed so you are looking at "Save As", in a lower quality format.



If compressing multiple similar documents then http://www.7-zip.org archives with solid ticked wipes winzip, and it's free. IIRC 7-zip don't have a 2GB limit either



Re: the tape industry figure, ( apart from backups mainly consising of SQL dumps ) I've found a fairly consistant real life figure of 1.6 - 1.7 from DOS 6 doublespace through to today. Which is just another reason why I despise marketing gimps.

Kali

junii wrote:

Using winzip or winrar, which are the best files to compress for maximum compression? Im sure I have seen files before that were compressed up to and over 40%.

Has anyone else seen this and if so what kind of file was it?

You want to know what sort of files compress well? Uncompressed files... i.e. text files or uncompressed audio or images (bmp, tga, wav).

Create a new text file... paste a couple of hundred lines of random text into it. Guaranteed you'll get close to 99-100% compression.