How does file compression work?

Posted by Phoshi on Super User See other posts from Super User or by Phoshi
Published on 2010-04-18T14:26:59Z Indexed on 2010/04/18 14:34 UTC
Read the original article Hit count: 199

Filed under:

compression

So, I realised today I take file compression for granted. The ability to bundle a few files together into one, and have it come out smaller than any of them, is something I just accept as a fact, but how does it actually work?

I have a limited knowledge of it that includes something to do with replacing all the duplicate entries with pointers, to shrink that way, but beyond that I'm fairly clueless!

As I'm always open to new knowledge, as I imagine most of us here are, I thought I'd ask. So, SuperUser, how does compression actually work?

Related posts about compression

Converting linear colors to SRGB shows banding in FFmpeg

as seen on Super User - Search for 'Super User'
When I convert an EXR file sequence with x264 using FFmpeg and convert the colorspace from linear to SRGB (with gamma 0.45454545) I get some heavy banding issues (most visible on a dark gradient). Here is the ffmpeg command I use: C:/ffmpeg.exe -y -i C:/seq_v001.%04d.exr -vf lutrgb=r=gammaval(0… >>> More
IIS7 Compression CSS files only compressed when dynamic compression is enabled

as seen on Server Fault - Search for 'Server Fault'
If anyone can help it would be appreciated. I would like to enable compression for static files within IIS7 (for the sake of simplicity I'll just refer to static css files for the time being). The problem I'm getting is that css files are only compressed when both dynamic and static compression… >>> More
Built-in GZip/Deflate Compression on IIS 7.x

as seen on West-Wind - Search for 'West-Wind'
IIS 7 improves internal compression functionality dramatically making it much easier than previous versions to take advantage of compression that’s built-in to the Web server. IIS 7 also supports dynamic compression which allows automatic compression of content created in your own applications (ASP… >>> More
Domino Document data compression and design compression

as seen on Server Fault - Search for 'Server Fault'
I was thinking of turning this on some large databases not just mail files - we have around 8 - 10GB of large databases as well as small databases of couple of hundred MB in size. But after reading this post I am not too sure: http://www-10.lotus.com/ldd/nd85forum.nsf/4b9931b774db788c85256bf0006b5e6d/1f4e67b569720e54852576c0003cb8ac… >>> More
I need to choose a compression algorithm

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to choose a compression algorithm to compress some data. I don't know the type of data I'll be compressing in advance (think of it as kinda like the WinRAR program). I've heard of the following algorithms but I don't know which one I should use. Can anyone post a short list of pros and cons… >>> More

Developer IT