DVD Formats and Details

The advantage of DVD’s over CD’s are…

5 to 6 times the capacity
longer shelf life
faster retrieval

Both CD’s and DVD’s store data in microscopic grooves running in a spiral around the disc. Reflective bumps (lands) and non-reflective highs (pits) aligned along the grooves represent the zeros and ones of digital information.

DVD technology writes in smaller pits by reducing the laser’s wavelength from 780mm to 625-650mm, resulting in higher capacity. In addition, the DVD tracks are closer together.

DVD’s access data faster than CD and users more error correction. A DVD 1x is faster than 8x CD.

Most DVD’s can read CD’s and CD-R’s, so the transition from CD to DVD is simple. It is important to understand thedifferent types of DVD drives (here we go with more abbreviations, sorry)…

DVD Types

DVD-RAM- Random Access Memory (Read and Write)
DVD-R or DVD+R Recordable (Only write one time)
DVD-RW or DVD+RW Re-recordable or Rewritable (Read and Write)
DVD-ROM Read Only Memory (Read Only)

Random versus Sequential

DVD-RAM uses random access technology
DVD-R, +R, -RW, +RW or ROM use a sequential technology.

Random Access: DVD-RAM (Read & Write)

Can be used as the ideal technology for backup or storage. Unlike tape storage that can only read data sequentially, DVD-RAM can access data randomly just like a normal hard drive. This makes a selective recovery process much easier and faster.
Can be overwritten up to 100,000 times.
Provides 4.7GB (Type 2) per side storage capacity or 9.4GB (Type 4) two-sided.
Life expectancy of 100 years.
Can only be written and read with DVD-R/RAM drives.
Since first introduced in 1998, the price for has dropped from $2,000 to less than $500.

Sequential: DVD-R, +R, -RW, +RW or ROM

This group of DVD’s are intended for the hi-tech graphics, video for movies and audio for music. They provide better quality for graphics and sound along with higher capacity of4.7GB.

Writable: One Time

DVD-R
- Can only be written with -R type drives.
- Can be read with -R or +R type drives.
- DVD+R
  - 2 hours of video in SP mode or 4 hours in EP mode
  - Can only be written with +R type drives.
  - Can be read with -R or +R type drives.

Writable: Re-writable up to 1000 Times

DVD-RW
- Contains protection technology that prevents copying of CSS-protected discs.
- Can only be written with -R type drives.
- Can be read with -R or +R type drives.
- DVD+RW
  - Can hold 2 hours of MPEG2.
  - Can only be written with +R type drives.
  - Can be read with -R or +R type drives.