Storage Media - VCRs, DVRs, DVDs

Overview
On this level you will face storage media, both magnetic and optical. The media types you will encounter are in the form of videos and discs. Beware: There are more to these than meet the eye. There are several types of videotapes, CDs, and DVDs, as well as new types such as Blu-Ray or Holographic Storage. Prepare yourself and examine the way media has changed over time. Imagine what the future will hold as media gets better and better.

Types of Storage__NEWSECTIONLINK__
Magnetic Storage


 * Use ferromagnetic materials that can be permanently magnetized by an external magnetic field
 * Tapes, Disks

Optical Storage


 * Use laser to read, write, and erase
 * CD, DVD

How the VCR Works

 * Use 2.2 MHz luminance
 * 230 lines of resolution
 * 3.4 MHz carrier using narrowband fm
 * Amplitude modulation
 * Play videotapes

CD and DVD Basics

 * 1) Laser reads over pits (indents in surface of CD) and lands (flat).
 * 2) When light hits a pit it is scattered, when it hits a land it reflects back and is detected.
 * 3) Stream of 0s and 1s is detected.
 * 4) Use Eight to Fourteen Modulation (EFM) to code bits.
 * 5) If disc is recordable, laser burns pits into organic layer of CD. Recordable disc uses organic dye, magneto-optical, or phase changes to write.

CD Capacity and Recording

 * 74 minutes
 * 650-700 MB
 * 6 MB/s or more
 * Recording and reading speeds.

DVD Capacity and Recording

 * 133 minutes of MPEG-2 (720X480 and 1280X720 at up to 60 fps)
 * Data transfer rate 10..08 Mbs
 * Recording speeds are now higher than ever

Difference Between CD and DVD

 * DVDs have more capacity, a smaller pit length, tighter tracks, larger surface utilization, more efficient channel bit modulation, more efficient error correction, and less overhead.
 * CDs use infrared lasers, DVDs use red lasers (shorter wavelenght to work with more intricate pits and lands).
 * DVDs have special regional coding that only allow them to be played in certain regions.

Blu-Ray

 * Blu-ray_Picture.jpgal blue laser
 * Record high definition television
 * Skip to any spot on disc
 * Access Web to download subtitles and extra features.
 * Single-layer disc: 27 GB, double-layer disc 54 GB

Holographic Storage

 * Blue-green argon laser
 * Beam splitters and mirrors
 * LCD pael with lenses to focus laser beams
 * 300 GB-1 TB per disc
 * The future?

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