MPEG-1 - MPEG-1 enables video on CD-ROMs. MPEG-1 is a standard for coding of moving pictures and associated audio for digital storage media up to about 1.5 Mbps.  Its quality is comparable to VHS video. This standard is designed to work at 1.2 Mbps, which is the data rate of CD-ROMs, thus the video could be played from CDs. The quality however is not sufficient for TV broadcast. It may be used by interactive TV content developers for TV stills (shots with no motion.)
http://en.wikipedia.org/wiki/MPEG-1
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MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular audio encoding format. It is the primary audio format used in iPODs.
http://electronics.howstuffworks.com/ipod.htm