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1、Chapter 5 Optical Storage Technology Categorizing Storage Devices History of CD/DVD player Optical Storage Devices DVD-ROM and DVD Formats Categorizing Storage Devices Storage devices hold data, even when the computer is turned off. The physical material that actually holds data is called a storage
2、medium. The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device. The two primary storage technologies are magnetic and optical. History of the CD/DVD player 4 1982 - First working CD player developed by Philips Philips
3、and Sony developed CD standard 12cm disk, 74 minutes on a single spiral 1983 - First CD players sold 1985 - CD-ROM introduced not popular at first. More powerful PCs lead to demand for multimedia, image processing and larger applications. Growth in sales brings prices down. 1990s - CD-R and CD-RW in
4、troduced big success. 1995 - DVD introduced 1999 - DVD becomes mainstream 3.9GB capacity allows disk to hold entire movie. DVD drives are standard on PCs today. Products Different Formats CD-DA (store digitized music ) CD-G (Graphics) (store graphics and music) CD-V (store analog television programs
5、) CD-ROM (store digitized images and voices) CD-I (Interactive) (store digitized images, voices and animations) CD-I FMV(Full Motion Video) (store digitized films and TV programs) Video CD (MPEG1) DVD (MPEG2) Optical Storage Devices How Optical Storage Works An optical disk is a high-capacity storag
6、e medium. An optical drive uses reflected light to read data. To store data, the disks metal surface is covered with tiny pits and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light can not be reflected back. This represents a
7、bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on). Optical Storage Devices How Optical Storage Works CD-ROM In PCs, the most commonly used optical storage technology is called Compact Disk Read-Only Memory (CD-ROM). A standard CD-ROM disk can store up
8、 to 650 MB of data, or about 70 minutes of audio. Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten The Structure of CD-ROM Diameter:120mm Depth:1.2mm CD Playback Pits are read by laser and converted to electrical signals Sequence of Operations in A CDROM Driv
9、e 1. Laser Diode - Emits a Laser Beam 2. Prisms - The laser beam is refined and Directed to a Mirror 3. Mirror - Reflects the Laser beam onto the Read Head 4. Read Head - Focuses the Laser beam onto the correct Physical Location on the Active Surface 5. Active Surface - Reflects the Laser Beam Back
10、onto the Read Head 6. Laser Beam Passes Through the Read Head onto the Mirror 7. Mirror Redirects the Laser onto a new set of Prisms 8. The Prisms Guide the Laser to a Photo Diode 9. The Photo Diode Recognizes the Character Sequence of Operations in A CDROM Drive CD-ROM Speeds and Uses How fast the
11、CD-ROM disc spins determines its speed Early CD-ROM drives were called single speed, and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 15 MBps). CD-ROM drives now can transfer data at speeds of at least to 7800 KBps. CD-ROM is typically used to store software programs. CDs
12、 can store audio and video data, as well as text and program instructions. CD-ROM CD-ROMs contain tracks which may be either data, audio or video tracks CD-ROMs have sectors Data track on a CD is one long, continuous spiral (b) CLV(constant linear velocity) requires MPEG-2 controller to decode compr
13、essed data Audio is stored in Dolby AC-3 compression DVD Formats Different formats Single-sided, single-layer4.7 GB DVD5 Double-sided, single-layer9.4 GB DVD10 Storage for approximately two feature length films. Single-sided, double-layer8.5 GB DVD9 Effectively two disks bonded together Upper disk h
14、as partially transmissive surface Lower disk has fully reflective surface Laser can focus on either surface Double-sided, double-layer17 GB DVD18 DVD Formats DVD Features Over 2 hours of high-quality digital video (a double-sided, dual-layer disc can hold about 8 hours of high-quality video, or 30 h
15、ours of VHS quality video). Support for widescreen movies on standard or widescreen TVs (4:3 and 16:9 aspect ratios). Up to 8 tracks of digital audio (for multiple languages, commentaries, etc.), each with as many as 8 channels. Up to 32 subtitle/karaoke tracks. DVD Features On-screen menus and simp
16、le interactive features (for games, etc.). Multilingual identifying text for title name, album name, song name, etc. Instant search to title, chapter, music track, and timecode. Not susceptible to magnetic fields. Resistant to heat. Language choice (for automatic selection of video scenes, audio tracks, subtitle tracks, and menus).* Random play and repeat play. Rec
