quote:

Originally posted by PatMcGroin then why aren't we all doing it???

Well I dunno maybe it's something few people have or an old DOS program. Considering there are lots of things on the net that not everyone has

___________________
Image removed, is over max allowd file size - see your profile options for the advance sig editor - Wicked Neo

quote:

Originally posted by trance_n_dance Well I dunno maybe it's something few people have or an old DOS program. Considering there are lots of things on the net that not everyone has

if it exsited, we'd all be using it

quote:

Originally posted by trance_n_dance Well I dunno maybe it's something few people have or an old DOS program. Considering there are lots of things on the net that not everyone has

Consider this: if this program, that could cut file sizes in half no matter what file you gave it, existed, try applying it again and again, until you ended up with a file of 1 byte, say. There's 256 possible value assignments for such a file and thus only 256 representable original files. So - since there's a lot more files - several files would be compressed to the same byte and the decompression algorithm would have no way of knowing what file to decompress back into.
Consequently such a compression algorithm cannot exists.

This is called the counting argument. I've done projects on compression at the university I attend, and can assure you that it does hold.

There are basically four kind of compression algorithms in use today:
1: Enthropy-based unique prefix coding (such as Huffman codes), which replaces every symbol in the source file with a code of varying length according to the frequency with which the symbol appears. Normally you can gain about 40% reduction in filesize using this technique.
2: Run lenght encoding, which simply replaces long runs of similar symbols, with a single copy along with a counter. Reduction is about 25% for your typical file.
3: Lemple-Ziv sliding window algorithms, which searches the previously encountered part of the file for occurences of the next x symbols, and replaces them with a reference to the previously encountered occurence. Reduction is usually about the 55% mark, but it does vary a lot.
4: Lossy compression, which removes true information from the file. A lot of techniques exists for this, but they all ruthlessly exploit shortcommings in our senses, so the loss isn't noticeable to ordinary humans. Reduction can reach over 99.5% in cases such as uncompressed video.

Most standards use a variety of these techniques. Mpeg, for instance, use all but the Lemple-Ziv methods. Generally, WinRAR has very good reduction ratios, but like all other programs, files containing little redundancy cannot be compressed further.

I hope some of this made some sense and you won't spend a lot of time searching for that super-compressor.

that was all complete jibberish to me

UHARC is dos based and works better than winrar and winace, it is used for the gamez rls on the w*r*z scene... you can save a few megs with it. But 700 -> 100 it's impossible (except if there is empty sectors on your bin files... some dreamcast releases took about 40Megs compressed, then 700 uncompressed, that was only to fill the cd entirely)

___________________
Ibiza 2011: 04 sept - 13 sept
Celebrating my 11th time on the white island and my 30 years ;-)

Well games can be compressed easily, coz they usually contain wav files, and files which dont have any or little compression.

But files like mp3s are already highly compressed, so zipping doesnt make much of an effect on them, and can decrease quality.

Hope that helps a bit

___________________

notice: i stopped caring

na, just to lazy to read all that crap

quote:

Originally posted by mr_sick some dreamcast releases took about 40Megs compressed, then 700 uncompressed, that was only to fill the cd entirely)

See told you . Exactly the type of image I was talking about as well.

___________________
Image removed, is over max allowd file size - see your profile options for the advance sig editor - Wicked Neo

okay this is one of those "it depends" response...

the compression ratio depends on the type of data you are working with!

in general, the greater the redundancy (number of repeating patterns); the greater the compression ratio

example file formats:

Bitmap:
- this is an uncompressed file format, thus, there is a lot of redundancy. one could convert this file into a jpeg or gif image....in the process of the conversion a compression techinque(s) is used.
- note: this technique 'usually' uses 'lossy' compression, meaning that shit is thrown away....so thats why your pictures become grainy.

Wav:
- this is also an uncompressed file format, hence, a lot of redundancy here too. one could convert this file into either a file format that uses 'lossy' or 'lossless' compression.
- so say i want to maintain ALL sound quality...this means that when i compress the file i must not throw away anything, hence, i use 'lossless' compression.
- if we convert this to the "monkey audio" file format we can achieve about 50% compression, but maintain full sound quality
- but, if we convert this to the "mp3" file format we can achieve a much greater compression ratio because the mp3 format uses 'lossy' compression....thus, we can throw away some data such as frequency ranges that fall above or below the hearing ranges of 'normal' human-beings and also apply a compression techinque(s).

(i could talk about video (pictures & audio combined), but naw

Now, so say i have a bullshit directory on my computer that contains bmp, jpeg, wav, mp3, bin, etc...
Compressing the whole directory's contents with winrar will considerably reduce the size of ONLY the 'uncompressed' file formats. files such as mp3, gif, jpeg have already been compressed.

Thank you Intense_Sounds for explaining it to me . I didn't know how the whole thing worked exactly so thanks for explaining to me in pure english exactly how it works .

___________________
Image removed, is over max allowd file size - see your profile options for the advance sig editor - Wicked Neo