------------- Original Message -------------- Aseem aseem@ports.cmc.net.in wrote:

On Fri, 29 Jun 2001, N. Shrikant wrote:

Are *.gz files really compressed into smaller sizes?

try yourself. on linux note the file size before compression. and then then compress it with gzip, bzip2, winzip. and you will find that all these utilities do compress the files. compression you get depends on file format. i found that gzip compresses more for text files while bzip2 was good for binary file compression. i found both gzip and bzip2 better than winzip when it comes to maximum amount of compression. ---------------------- End ---------------

Yep, you are right, compression results do depend on the file format. Compression basically reduces redundancies in data. Some file formats are already in compressed form. Like JPEG, MP3 etc. An MP3 file is just a compressed WAV file. So compressing these file formats won't give you very high compression ratio, since most of the redundancies have already been eliminated.

Try saving a (fairly large) BMP as a JPEG file. Notice the reduction in size, which is a result of compression.

If, interested in compression techniques, you'll find loads of reading material on the Net. If you know someone from the engineering fraternity, try getting hold of books like 'Computer Networks' by Tanenbaum, or 'Principles of Comm. Systems' by Taub & Schilling. Look for Information Theory in the latter. These are the books I came accross. There are many more.

Regards, Nikhil.

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