Why data compression?
Storing or transmitting multimedia data requires large space or bandwidth
The size of one hour 44K sample/sec 16-bit stereo (two channels) audio is 3600x44000x2x2= 633.6MB, which can be recorded on one CD (650 MB). MP3 compression can reduce this number by factor of 10
The size of a 500x500 color image is 750KB without compression (JPEG can reduced this by a factor of 10 to 20)
The size of one minute real-time, full size, color video clip is 60x30x640x480x3= 1.659GB. A two-hour movie requires 200GB. MPEG2 compression can bring this number down to 4.7 GB (DVD)