What's the difference between DivX and MPEG2?

Q The playing time written on the front of a standard, blank DVD-R, which has a capacity of 4.7GB, is stated to be 120 minutes.

However, I find that two hours of video that is playable on both my PC and TV, requires far less space. So why can’t I fit more than 120 minutes of video on a DVD?
Dennis Callaghan

A The video on your computer is recorded in a different video format to the one used as standard on DVD.

DVDs use MPEG2, which is now an old video format. The video on your computer may be encoded with a different format, such as DivX, and while the picture quality will not be quite as good as a standard DVD, it is perfectly watchable and two hours of video requires far less space.

A video encoded in DivX will play on your computer, and many modern DVD players now play both standard DVDs as well as discs with DivX video on them. However, a disc containing a DivX video file will not play in an older DVD player.

An identical situation exists with audio CDs and MP3s. A CD can store 74 minutes of audio, or 650MB of files, but the file size of a 74-minute MP3 file is nowhere near 650MB in size. Few people notice the difference between the sound quality of CDs and MP3s, but the formats are different.

Depending on the audio quality and bit rate, you should be able to copy roughly 10 times the amount of music to a CD if it is encoded in MP3 format. These CDs will not work in standard CD players or old stereos. However, many newer stereos and CD players will play discs with music encoded in MP3 format.

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