DVD
A DVD (Digital Video Disc) stores and plays
digital information on a disc similar in size to a normal CD. The output
is also clearer, sharper and uses higher colour resolutions than previous
formats. Even audio is sharper. A DVD disc can store up to 9 hours of video
and multichannel surround sound audio and interactive multimedia computer
programs. Otherwise it can be used for over 30 hours of CD quality audio.
Previously impossible features with movies (or games) on tapes are now
made possible by DVD. DVD players can play from any point on the disc,
pause, play in slow motion and fast forward or freeze frames. Random new
features allow the viewer to for instance choose which ending a movie should
have. They also include first-person interactive video games and multiple
camera angles. With parental control parents can password protect programs
that they don't want their children to view. Another form of parental control
is storing different versions of a movie on the same disc. A disc can then
for instance contain an R-rated version of a movie and a PG-13 version.
Up to eight languages for one movie can also be stored on a DVD disc.
The mastering process formats data so that
it can be read by DVD players. By using MPEG-2 video encoding standard
the mastering process can manipulate the large amounts of information into
a format that the more common DVD player can understand. The discs are
made of reflective aluminium foil encased in a clear plastic. Data can
be stored on the foil as small pits arranged in a tight spiral. For a double
sided disc two halves, with their foil full of data, are bonded back to
back.