Consider first the case of audio. The desired quality of sound determines the bandwidth required. For example, each channel of CD quality sound requires that 16 bits be transferred at a rate of 44,100 times per second, or 44.1 KHz. This amounts to a bandwidth requirement of 176 Kbps, or 10.4 MB per minute. An audio CD with 60 minutes of music on it thus stores approximately 650 MB of data.
Video places much higher demands on the system than does audio.
It is easy to see that without some sort of compression scheme, the demands of digital video are far too great to be practical. Each frame has 640 X 480 pixels, or about 300,000 pixels. Each frame thus requires about 900,000 bytes, or 0.9 MB of data. This is still a large amount of data, however, and a CD ROM disk with a capacity of 650 MB can only store about 10 minutes of uncompressed video. The need for data compression is obvious.