Now, assume that there was an error in the final bit.
1
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2
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3
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4
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5
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6
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7
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8
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P1
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P2
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P3
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P4
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1
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1
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0
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1
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0
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0
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0
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1
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1
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0
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0
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1
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x
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x
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x
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x
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1
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|
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x
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x
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x
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x
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1
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|
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x
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x
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|
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x
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x
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|
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0
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|
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x
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x
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x
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x
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1
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Parity bit P1 would agree with the parity bit in the transmitted word, P2 would NOT agree, P3 and P4 would agree. Since P2 is the only parity bit not agreeing with the transmitted word -- then the error must be in the 8th bit.
Unfortunately, the majority of error-detection and correction algorithms used in CD players are not as simple as the binary check code discussed above.
Simple interleaving: Interleaving is a very simple and powerful idea. To illustrate interleaving, assume that you have a frame consisting of several characters of information,
U N I V E R S I T Y O F W A S H I N G T O N
Assume that you spit on the disk and destroy several of the characters.
R S I T Y O F W A S H I N G T O N
The first word is then very hard to reconstruct! However, you can take the original frame and scramble it as,
U N I V E R S I T Y O F W A S H I N G T O N
O N S T H U G R F S I I O T W N N v E I Y A
Then you can damage it,
U G R F S I I O T W N N V E I Y A
Then you can unscramble it,
U N I V E R I Y O F W A S I G T N
It is much easier to "interpolate" or "guess" the missing letters.
Concealment: In practice some errors are so large that they cannot be corrected by the error-detection and correction algorithms. Unless these errors are handled by some other means, they can result in audible clicks in the audio output. In order to avoid these clicks, several methods are used to conceal uncorrectable errors:
Interpolation: In this technique, some average is constructed using the valid data around an error. This average is then substituted in for the erroneous data. Since most music (with the possible exception of heavy metal!) is continuous -- this method works well for concealing relatively short errors.
Muting: Muting is a last ditch technique -- as it effectively creates a brief period of silence in the audio train. However, it is not effective to simply set all the binary digits to zero --as this produces exactly the click that we are trying to avoid! Instead, the volume is faded out and then back in again to conceal the error.
In theory, the combination of parity and interleaving in a CD player can detect and correct a burst error of up to 4000 bad bits -- or a physical defect 2.47 mm long. Interpolation can conceal errors up to 13,700 or physical defects up to 8.5 mm long.
Ex. 2. Which of the following statements are true and which are false?
Parity bits in parity checks may represent either odd or even total numbers. T/F
Data errors may be corrected by a parity check based on one parity bit. T/F
Error-correction algorithms used in CD players are quite simple. T/F
It’s easier to guess the missing letters in a damaged frame if it was interleaved. T/F
Uncorrectable errors cannot be concealed. T/F
Valid data areas before and after the error help reconstruct the damaged frame. T/F
Music in the genre of heavy metal is usually continuous. T/F
Muting is used when nothing else helps. T/F
Setting all digits to zero will mute the music volume. T/F
Interpolation can correct larger defects than parity and interleaving combined. T/F
Ex. 3. Translate from Russian into English.
Некоторые ошибки так велики, что не могут быть исправлены алгоритмами.
Ошибки могут проявиться в слышимых щелчках при воспроизведении.
Усредненные данные подставляются вместо ошибочных.
Уровень громкости постепенно снижется, а затем постепенно увеличивается.
Пакетная ошибка величиной до 4000 бит может быть исправлена комбинацией контроля четности с чередованием.
Table of Contents
№
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Title
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Page
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BASIC VOCABULARY
|
3
|
1
|
The computer
|
4
|
2
|
The desktop
|
5
|
3
|
Using a word processor
|
5
|
4
|
Word processing: for and against
|
6
|
5
|
Storing data
|
6
|
6
|
Creating a folder
|
7
|
7
|
Saving files
|
8
|
8
|
The Internet
|
9
|
9
|
Research on the Internet
|
10
|
10
|
E-mail, telephones and the post
|
10
|
11
|
Mobile phones
|
11
|
12
|
Writing e-mails
|
12
|
13
|
E-mail addresses and servers
|
13
|
14
|
Sending files over the Internet
|
14
|
15
|
Viewing and downloading files
|
15
|
16
|
Music on the Internet
|
15
|
17
|
Desktop publishing (DTP)
|
16
|
18
|
Image editing
|
17
|
19
|
Reviewing websites
|
18
|
20
|
Designing Web pages
|
19
|
21
|
Multimedia
|
20
|
22
|
E-commerce
|
20
|
23
|
Chat rooms
|
21
|
24
|
Netiquette
|
22
|
25
|
Computer programming
|
22
|
26
|
Videoconferencing
|
24
|
27
|
Men, women and IT
|
25
|
28
|
Careers in IT
|
25
|
|
Glossary revision
|
26
|
ADITIONAL TEXTS AND VOCABULARY
|
|
1 TEXT
|
What is the difference between DVD-R/DVD-RW, DVD+R/DVD+RW and DVD-RAM discs?
|
29
|
2
|
The Real E-mail System
|
31
|
3
|
POP3 and IMAP Servers
|
34
|
4
|
File Compression: Finding redundancy and looking for patterns
|
35
|
5
|
File Compression: The file-reduction ratio. Lossy and Lossless
|
37
|
6
|
AGP graphics card: Getting Off the Bus
|
40
|
7
|
AGP graphics card: Saving RAM
|
42
|
8
|
3-D Graphics: Making It Look Like the Real Thing by Shapes, Surface Textures, Lighting.
|
43
|
9
|
3-D Graphics: Making It Look Like the Real Thing by Perspective, Depth of Field and Anti-aliasing
|
46
|
10
|
The future of PC: EUVL Chipmaking
|
48
|
11
|
The future of PC: DNA and Quantum
|
50
|
12
|
What BIOS Does
|
52
|
13
|
Storing Data on a DVD
|
54
|
14
|
Keyboard Technologies
|
56
|
15
|
Types of Infection: E-mail viruses
|
58
|
16
|
Flash Basics
|
60
|
17
|
Removable Flash Memory Cards
|
62
|
18
|
How Telephones Work
|
64
|
19
|
The Telephone Network: Wires and Cables. Digitizing and Delivering
|
66
|
20
|
Calling Someone by Phone. Tones
|
68
|
21
|
How Digital Cameras Work: CMOS and CCD sensors
|
70
|
22
|
How Digital Cameras Work: Resolution
|
72
|
23
|
How Digital Cameras Work: Capturing Color
|
73
|
24
|
Printer technologies
|
75
|
25
|
Inkjet technologies
|
77
|
26
|
A Hierarchy of Networks. Routers. Backbones
|
79
|
27
|
CD Encoding Issues
|
81
|
28
|
Encoding data on optical discs: Binary parity checks. Interleaving. Interpolation
|
82
|
|
Список использованной литературы
|
86
|
Список использованной литературы:
1. Dinos Demetriades Information technology:Workshop.- Oxford, Oxford UP. 2003. - 40 p.
2.
http://www.howstuffworks.com;
http://www.computer.howstuffworks.com, etc.
3. Пройдаков Э.М., Теплицкий Л.А. Англо-русский толковый словарь по вычислительной технике, Интернету и программированию- М.: Издательско-торговый дом «Русская редакция», 2003.- 640 с.
4. ABBY Lingvo 10. Многоязычный электронный словарь. Выпуск 10.0.0.13. Copyrigh 2004 ABBYY Software Ltd.
