Thread: Can someone tell me about compression?

For misc file times .gz, .zip, and .tar are pretty much the standard. I don't know of any others other than Winrar or .sit compression, but those are OS specific. All operating systems have native extractors for the three that I mentioned and .zip is pretty much the business standard. What is the file extension that are on the compressed files?

If you mean audio/video compression then the answer is that most are just legacy compression systems. H.264 video is the defacto standard in video. AAC is the best in audio compression and very widely used however MP3 came around at the right time so even though it only gets about half the compression, devices still use it.

Off the top of my head: .rar. There was a weird one I came across one day. I downloaded a file off a japanese website and had to personally search for an extracter just for it. I can't remember what it was called (I deleted both of them). Wikipedia said it was developed by a japanese man and that it was more efficent than .zip but had little popularity in the world.

there are multiple file compression formats for 2 reasons

1. probably the most obvious - there's multiple ways to compress data
some ways are better in certain circumstances
some make assumptions that may or may not be suitable in all cases
there's rarely a "one size fits all"

2. Patents
while not an issue in europe, the US allows software to be patented

so if you want to make use of a particular compression technique from a patented algorithm, you have to write your own implementation

Legal issues date back to the 80's, and the ARC format
http://en.wikipedia.org/wiki/ARC_(file_format)

Software patents are the reason behind the different Zip implementations, as well as various compressed image formats (GIF vs. PNG)

.rar is a format for the WinRar program. It is actually fairly popular, just not as much as others because you have to pay for the program on Windows. I think most linux distros have built in extractors for it.

If you continually get files in that format, then you may want to just shell out the money to buy it, it's not that much.

You have to pay for Winrar now? Man...

I just use 7-Zip, in my experience it's the best option. I love my passworded .7zip archives, for private stuff. The smallest files are generally .tar.gz, though, right? I downloaded something the other day, the .tar was around 350kb, but the .tar.gz was only a little over 200kb. Makes things go a lot quicker on dial-up.

tarballs are pretty much the standard for anyone using *nix. Like I said, files are usually compressed using .tar, then those are further compressed using .gz.

You can also screw with your friends by making a tarbomb. Those are funny