------------- Original Message -------------- Q u a s i quasiabhi@yahoo.com wrote:

At 04:33 PM 6/29/01 +0000, Nikhil Karkera wrote:

An MP3 file is just a compressed WAV file.

err. IMHO WAV -> MP3 is more than just plain compression. A lot of sophisticated techniques are used to decide which data is redundant and can be removed. The resultant compression is "lossy" - original data cannot be retrieved after decompression. Ditto for BMP -> JPEG. ---------------- End ------------------------

Yes, lossy compression techniques do throw away data. In case of images, JPEG exploits the limitations of the human eye, and throws away data in such a manner so as to try make the loss of data as unnoticable as possible. (image is represented in the form of a discrete signal I(x,y); pixel intensities represented by magnitude; signal magnitude is quantised to certain number of levels; no of quantisation levels variable; lesser quantisation levels = more compression & lesser quality; quantisation throws data). So also for MPEG compression.

I guess it woldn't be right to call lossy compression a data compression technique (data = 0's and 1's), but rather an information compression technique(information = picture/sound represented by the 0's and 1's). But it is compression.

Lossless compression on the other hand is a data compression technique.

Regards, Nikhil.

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