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9-2 Section Nine

RAID Level 1

9-13

RAID Level 2

9-14

RAID Level 3

9-15

RAID Level 4

9-15

RAID Level 5

9-16

Other RAID levels

9-16

Digital Media Applications

9-17

Optimizing Digital Media Disk Performance

9-19

Thermal Calibration

9-21

SCSI and Fibre Channel

9-21

FC-AL Topology

9-22

Connectivity Considerations

9-23

Bandwidth

9-23

Remote Online Storage

9-24

Array Implementations

9-24

Server-Based Audio/Video Editing

9-24

Perspective on Storage Options

9-25

References

9-25

Bibliography

9-25

Chapter 9.2: Properties of Magnetic Materials

9-27

Introduction

9-27

Basic Principles of Magnetism

9-28

Curie Point

9-30

Magnetic Induction

9-30

Initial Magnetization B-H Curve

9-32

Hysteresis Loop

9-33

Hysteresis Losses

9-33

Initial M-H Curve and M-H Hysteresis Loop

9-34

Demagnetization

9-35

References

9-37

Chapter 9.3: Recording Fundamentals

9-39

Introduction

9-39

Fundamental Principles

9-39

Recording Signal Parameters

9-40

The Recording Process

9-41

Bias Recording

9-44

Particle Orientation

9-45

Erasure

9-45

References

9-46

Bibliography

9-46

Chapter 9.4: Magnetic Tape

9-47

Introduction

9-47

Basic Construction

9-47

Magnetic Coating

9-49

Audio Recording Systems

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Audio Recording Systems 9-3

Magnetic Materials

9-49

Binders

9-51

Miscellaneous Additives

9-52

Manufacturing Process

9-52

Dispersion

9-53

Coating

9-53

Metal Evaporation Process

9-53

Slot Die Coating

9-55

Orientation

9-56

Drying

9-56

Surface Finishing

9-56

Slitting

9-57

Testing

9-57

Assembly and Packaging

9-57

References

9-57

Bibliography

9-57

On the CD-ROM:

•

“Analog Magnetic Tape Recording and Reproduction” by E. Stanley Busby, an archive chap-
ter from the first edition of the Audio Engineering Handbook. This reference material pro-
vides considerable background information on analog audio recording technologies and
techniques.

•

“Digital Magnetic-Tape Recording and Reproduction” by W. J. van Gestel, et. al., an archive
chapter from the first edition of the Audio Engineering Handbook. This reference material
explains in detail the fundamental recording technologies applicable to digital audio systems.

•

“Analog Disk Recording and Reproduction” by Gregory Bogantz and Joseph Ruda, an
archive chapter from the first edition of the Audio Engineering Handbook. This reference
material examines analog disk recording technologies, techniques, and applications.

Reference Documents for this Section

Anderson, D: “Fibre Channel-Arbitrated Loop: The Preferred Path to Higher I/O Performance,

Flexibility in Design,” Seagate Technology Paper #MN-24, Seagate, Scotts Valley, Calif.,
1995.

Bate, G.: “Recent Developments in Magnetic Recording Materials,” J. Appl. Phvs. pg. 2447,

1981.

Bertram, H. N.: “Long Wavelength ac Bias Recording Theory,” IEEE Trans. Magnetics, vol.

MAG-10, pp. 1039–1048, 1974.

Bozorth, Richard M.: Ferromagnetism, Van Nostrand, Princeton, N.J., 1961.

Chikazumi, Soshin: Physics of Magnetism, Wiley, New York, N.Y., 1964.

Goldberg, Thomas: “New Storage Technology,” Proceedings of the Advanced Television Summit,

Intertec Publishing, Overland Park, Kan., 1996.

Audio Recording Systems

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)

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9-4 Section Nine

Grega, Joe: “Magnetic and Optical Recording Media,” in NAB Engineering Handbook, 9th ed.,

Jerry C. Whitaker (ed.), National Association of Broadcasters, Washington, D.C., pp. 893–
906, 1999.

Hawthorne, J. M., and C. J. Hefielinger: “Polyester Films,” in Encyclopedia of Polymer Science

and Technology, N. M. Bikales (ed.), vol. 11, Wiley, New York, N.Y., pg. 42, 1969.

Heyn, T.: “The RAID Advantage,” Seagate Technology Paper, Seagate, Scotts Valley, Calif.,

1995.

Jorgensen, F.: The Complete Handbook of Magnetic Recording, Tab Books, Blue Ridge Summit,

Pa., 1980.

Kalil, F. (ed): Magnetic Tape Recording for the Eighties, NASA References Publication 1975,

April 1982.

Kraus, John D.: Electromagnetics, McGraw-Hill, New York, N.Y., 1953.

Lehtinen, Rick, “Editing Systems,” Broadcast Engineering, Intertec Publishing, Overland Park.

Kan., pp. 26–36, May 1996.

Lueck, L. B. (ed): Symposium Proceedings Textbook, Symposium on Magnetic Media Manufac-

turing Methods, Honolulu, May 25–27, 1983.

McConathy, Charles F.: “A Digital Video Disk Array Primer,” SMPTE Journal, SMPTE, New

York, N.Y., pp. 220–223, April 1998.

McKnight, John G.: “Erasure of Magnetic Tape,” J. Audio Eng. Soc., Audio Engineering Society,

New York, N.Y., vol. 11, no.3, pp. 223–232, 1963.

Nylen, P., and E. Sunderland: Modern Surface Coatings, Interscience Publishers Division, Wiley,

London, 1965.

Pear, C. B.: Magnetic Recording in Science and Industry, Reinhold, New York, N.Y., 1967.

Perry, R. H., and A. A. Nishimura: “Magnetic Tape,” in Encyclopedia of Chemical Technology,

3d ed., Kirk Othmer (ed.), vol. 14, Wiley, New York, N.Y., pp. 732–753, 1981.

Plank, Bob: “Video Disk and Server Operation,” International Broadcast Engineer, September

1995.

Robin, Michael, and Michel Poulin: “Multimedia and Television,” in Digital Television Funda-

mentals, McGraw-Hill, New York, N.Y., pp. 455–488, 1997.

Sharrock, Michael P., and D. P. Stubs: “Perpendicular Magnetic Recording Technology: A

Review,” SMPTE J., SMPTE, White Plains, N.Y., vol. 93, pp. 1127–1133, December 1984.

Smit, J., and H. P. J. Wijn: Ferrite, Wiley, New York, N.Y., 1959.

Tochihara, S.: “Magnetic Coatings and Their Applications in Japan,” Prog. Organic Coatings,

vol. 10, pp. 195–204, 1982.

Tyson, H: “Barracuda and Elite: Disk Drive Storage for Professional Audio/Video,” Seagate

Technology Paper #SV-25, Seagate, Scotts Valley, Calif., 1995.

Whitaker, Jerry C.: “Data Storage Systems,” in The Electronics Handbook, Jerry C. Whitaker

(ed.), CRC Press, Boca Raton, Fla., pp. 1445–1459, 1996.

Audio Recording Systems

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9-5

Chapter

9.1

Audio/Video Server Systems

Jerry C. Whitaker, Editor-in-Chief

9.1.1

Introduction

Audio/video servers, with their unique set of features and functions, have reshaped the way pro-
gram segments are stored and played to air. These systems have emerged from the realm of lim-
ited-use, special-purpose devices to mainstream program production. Among the many attributes
of servers are:

•

They permit material from a single storage source to be used simultaneously by multiple
users

•

Provide a migration path to the all-digital facility that is not necessarily format-limited

•

Result in a reduction in lost or misplaced materials

•

Reduction in the size and space requirements relative to a tape environment

•

Complete computer-control capabilities

•

Near-instant access and playback of audio and video segments

The end-result of these attributes is an environment where multiple applications and/or services
can be generated from a single system. This reduces the amount of playback equipment required,
reduces tape consumption, and generally permits more efficient use of human resources.

9.1.2

Basic Architecture

The basic server architecture consists of three elements [1]:

•

A multiple hard disk drive system capable of fast and simultaneous data access, with suffi-
cient capacity and redundancy for the contemplated application. A disk array controller man-
ages data distribution and communications among all drives.

•

Fast data communication interfaces among disk drives and networks. Several approaches can
be used to perform fast data transfer such as very fast CPUs, multiple CPUs and buses, and
routing switchers. Interfaces may also include data compression encoding and decoding.

Source: Standard Handbook of Audio and Radio Engineering

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9-6 Audio Recording Systems

•

An operating system capable of handling multiple digital audio and/or video data streams in
any combination of record and playback modes, while ensuring correct file management and
easy access.

The design and performance of the server involves trade-offs between the quality of com-

pressed signals, storage capacity, data speed, play time, number of channels, access speed, and
reliability. Table 9.1.1 shows the storage space requirements for different audio and video sig-
nals.

All servers have in common a large storage capacity and multiple channel capability; differ-

ences involve the basic architecture and performance targets, because different systems may be
designed to meet specific requirements. The most common application groups for broadcasting
include the following:

•

Transmission. High compression ratios can be used for server-to-air applications, typically
commercial and short-length program replay. The resulting bit rates and number of channels
are usually low, therefore, with relatively low bandwidth requirements.

•

Data cache. A caching system is basically a temporary random access disk buffer. It is com-
monly used in conjunction with tape library systems in on-air applications. Caches are well
suited to commercial on-air insertion applications where elements are repeated several times
a day and last-moment changes occur frequently. Bandwidth and channel requirements are
usually not critical.

•

News. For most news materials, moderate overall quality levels are acceptable. Audio/video
compression is used to reduce the data file size and increase the transfer rate. Multiple access
to multiple segments must be possible and a moderate bandwidth is necessary. Guaranteed
availability of output ports might be required for direct on-air programming of news materi-
als.

Table 9.1.1 Storage Space Requirements for Audio and Video Data Signals

 (

After [1].)

Media Signals

Specifications

Data Rate

Voice-grade audio

1 ch; 8-bit @ 8 kHz

64 kbits/s

MPEG audio Layer II

1 ch; 16-bit @ 48 kHz

128 kbits/s

MPEG audio Layer III

1 ch; 16-bit @ 48 kHz

64 kbits/s

AC-3 

5.1 ch; 16-bit @ 48 kHz

384 kbits/s

CD

2 ch; 16-bit @ 44.1 kHz

1.4 Mbits/s

AES/EBU

2 ch; 24-bit @ 48 kHz

3.07 Mbits/s

MPEG-1 (video)

352 

×

 288, 30 f/s, 8-bit

1.5 Mbits/s

MPEG-2 (MP@ML)

720 

×

 576, 30 f/s, 8-bit 

15 Mbits/s, max.

MPEG-2 (4:2:2 P@ML)

720 

×

 608, 30 f/s, 8-bit

50 Mbits/s, max.

ITU-R Rec. 601

720 

×

 480, 30 f/s, 8-bit

216 Mbits/s

HDTV

1920 

×

 1080, 30 f/s, 8-bit

995 Mbits/s

Audio/Video Server Systems

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