Text, Images, Video and Sound - PowerPoint PPT Presentation

Loading...

PPT – Text, Images, Video and Sound PowerPoint presentation | free to download - id: 6d2d1f-MGY1M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Text, Images, Video and Sound

Description:

Text, Images, Video and Sound CS 1 Introduction to Computers and Computer Technology Rick Graziani Spring 2015 ... – PowerPoint PPT presentation

Number of Views:15
Avg rating:3.0/5.0
Slides: 93
Provided by: RickG176
Learn more at: http://www.cabrillo.edu
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Text, Images, Video and Sound


1
Text, Images, Video and Sound
  • CS 1 Introduction to Computers and Computer
    Technology
  • Rick Graziani
  • Spring 2015

2
Digitizing Text
  • Earliest uses of PandA (Presence and Absence) was
    to digitize text (keyboard characters).
  • We will look at digitizing images and video
    later.
  • Assigning Symbols in United States
  • 26 upper case letters
  • 26 lower case letters
  • 10 numerals
  • 20 punctuation characters
  • 10 typical arithmetic characters
  • 3 non-printable characters (enter, tab,
    backspace)
  • 95 symbols needed

3
ASCII-7
  • In the early days, a 7 bit code was used, with
    128 combinations of 0s and 1s, enough for a
    typical keyboard.
  • The standard was developed by ASCII (American
    Standard Code for Information Interchange)
  • Each group of 7 bits was mapped to a single
    keyboard character.
  • 0 0000000
  • 1 0000001
  • 2 0000010
  • 3 0000011
  • 127 1111111

4
Byte
  • Byte A collection of bits (usually 7 or 8 bits)
    which represents a character, a number, or other
    information.
  • More common 8 bits 1 byte
  • Abbreviation B

5
Bytes
  • 1 byte (B)
  • Kilobyte (KB) 1,024 bytes (210)
  • one thousand bytes
  • 1,024 2 2 2 2 2 2 2 2 2 2
  • Megabyte (MB) 1,048,576 bytes (220)
  • one million bytes
  • Gigabyte (GB) 1,073,741,824 bytes (230)
  • one billion bytes

6
Wikipedia
7
ASCII-8
  • IBM later extended the standard, using 8 bits per
    byte.
  • This was known as Extended ASCII or ASCII-8
  • This gave 256 unique combinations of 0s and 1s.
  • 0 00000000
  • 1 00000001
  • 2 00000010
  • 3 00000011
  • 255 11111111

1
8
ASCII-8
9
Try it!
1
  • Write out Cabrillo College (Upper and Lower case)
    in bits (binary) using the chart above.
  • 0100 0011 0110 0001
  • C a

10
The answer!
1
  • 0100 0011 0110 0001 0110 0010 0111 0010
    0110 1001 0110 1100
  • C a b
    r i
    l
  • 0110 1100 0110 1111 0010 0000 0100 0011
    0110 1111 0110 1100
  • l o
    space C o
    l
  • 0110 1100 0110 0101 0110 0111 0110 0101
  • l e
    g e

11
Unicode
  • Although ASCII works fine for English, many other
    languages need more than 256 characters,
    including numbers and punctuation.
  • Unicode uses a 16 bit representation, with 65,536
    possible symbols.
  • Unicode can handle all languages.
  • www.unicode.org

12
Non-text Files Representing Images and Sound
13
(No Transcript)
14
(No Transcript)
15
Pixels
  • A monitors screen is divided into a grid of small
    unit called picture elements or pixels.
  • The more pixels per inch the better the
    resolution, the sharper the image.
  • All colors on the screen are a combination of
    red, green and blue (RGB), just at various
    intensities.

16
(No Transcript)
17
  • Each Color intensity of red, green and blue
    represented as a quantity from 0 through 255.
  • Higher the number the more intense the color.
  • Black has no intensity or no color and has the
    value (0, 0, 0)
  • White is full intensity and has the value (255,
    255, 255)
  • Between these extremes is a whole range of colors
    and intensities.
  • Grey is somewhere in between (127, 127, 127)

18
RGB Colors and Binary Representation
  • You can use your favorite program that allows you
    to choose colors to view these various red, green
    and blue values.

19
RGB Colors and Binary Representation
  • Lets convert these colors from Decimal to
    Binary!
  • Red Green Blue
  • Purple 172 73 185
  • Gold 253 249 88

20
RGB Colors and Binary Representation
  • Red Green Blue
  • Purple 172 73 185
  • Gold 253 249 88
  • Number of
  • 27 26 25 24 23 22 21
    20
  • 128s 64s 32s 16s 8s 4s 2s 1s
  • Dec.
  • 172
  • 73
  • 185
  • 253
  • 249
  • 88

21
RGB Colors and Binary Representation
  • Red Green Blue
  • Purple 172 73 185
  • Gold 253 249 88
  • Number of
  • 27 26 25 24 23 22 21
    20
  • 128s 64s 32s 16s 8s 4s 2s 1s
  • Dec.
  • 172 1 0 1 0 1 1 0 0
  • 73 0 1 0 0 1 0 0 1
  • 185 1 0 1 1 1 0 0 1
  • 253 1 1 1 1 1 1 0 1
  • 249 1 1 1 1 1 0 0 1
  • 88 0 1 0 1 1 0 0 0

22
RGB Colors and Binary Representation
  • We have now converted these colors from Decimal
    to Binary!
  • Red Green Blue
  • Purple 172 73 185
  • 10101100 01001001 10111001
  • Gold 253 249 88
  • 11111101 11111001 01011000
  • Why does this matter?

23
First a word about Pixels Per Inch
1600 pixels
1600 pixels /300 ppi 5.3 inches
1200 pixels
1200 pixels/300 ppi 4 inches
  • graphicssoft.about.com
  • PPI stands for pixels per inch.
  • PPI is a measurement of image resolution that
    defines the size an image will print.
  • The higher the PPI value, the better quality
    print you will get--but only up to a point.
  • 300ppi is generally considered the point of
    diminishing returns when it comes to ink jet
    printing of digital photos.

24
First a word about Pixels Per Inch
  • The higher the PPI value, the better quality
    print you will get--but only up to a point.

25
RGB Colors and Binary Representation
  • Red Green Blue
  • Purple 172 73 185
  • 10101100 01001001 10111001
  • 24 bits for
    one pixel!
  • True color systems require 3 bytes or 24 bits
    per pixel.
  • There is 8 bit and 16 bit color, which gives you
    less of a color palette.

26
RGB Colors and Binary Representation
10 inches or 3,000 pixels
8 inches or 2,400 pixels
  • Red Green Blue
  • Purple 172 73 185
  • 10101100 01001001 10101111 24 bits per
    pixel
  • An 8 inch by 10 inch image scanned in at 300
    pixels per inch
  • 8 x 300 2,400 pixels 10 x 300 3,000 pixels
  • 2,400 pixels by 3,000 pixels 7,200,000 pixels
    or 7.2 megapixels
  • At 24 bits per pixel (7,200,000 x 24)
  • 172,800,000 bits or 21,600,000 bytes (21.6
    megabytes)
  • RAM memory, video memory, disk space, bandwidth,

27
File Compression
  • Typical computer screen only has about 100 pixels
    per inch, not 300.
  • Images still require a lot of memory and disk
    space, not to mention transferring images over
    the network or Internet.
  • Compression A means to change the
    representation to use fewer bits to store or
    transmit information.
  • Information sent via a fax is either black or
    white, long strings of 0s or long strings of
    1s.

28
Run-length encoding
  • Many fax machines use run-length encoding.
  • Run-length encoding uses binary numbers to
    specify how long the first sequence (run) of 0s
    is, then how long the following sequence of 1s
    is, then how long the following sequence of 0s
    is, and so on.
  • Fewer bits needed than sending 100 0s, then 373
    1s etc.
  • Run-length encoding is a lossless compression
    scheme, meaning that the original representation
    of 0s and 1s can be reconstructed exactly.

29
JPEG Compression
  • JPEG Joint Photographic Experts Group
  • JPEG is a common standard for compressing and
    storing still images.
  • Our eyes are not very sensitive to small changes
    in hue (chrominance), but we are sensitive to
    brightness (luminance).
  • This means we can store less accurate description
    of the hue of the picture (fewer bits) and our
    eyes will not notice it.
  • This is a lossy compression scheme, because we
    have lost some the original representation of the
    image and it cannot be reconstructed exactly.

30
JPEG Compression Scheme
  • With JPEG we can get 201 compression ratio or
    more, without being able to see a difference.
  • There are large areas of similar hues in pictures
    that can be lumped together without our noticing.
  • Because of this, when Run-length compression is
    used there is more compression because there is
    less variations in the hue.

31
MPEG Compression Scheme
  • MPEG (Motion Pictures Experts Group)
  • MPEG compression is similar to JPEG, but applied
    to movies.
  • JPEG compression is applied to each frame.
  • Then interframe coherency is used, which only
    records and transmits the differences between
    frames.

32
Hexadecimal Number System
lttrgt lttd rowspan"2" bgcolor"cccc99"gtnbsplt
/tdgt lttd height"30" bgcolor"999966"gtltdiv
id"mainnav"gt
33
(No Transcript)
34
(No Transcript)
35
Pixels
  • A monitors screen is divided into a grid of small
    unit called picture elements or pixels.
  • The more pixels per inch the better the
    resolution, the sharper the image.
  • All colors on the screen are a combination of
    red, green and blue (RGB), just at various
    intensities.

36
(No Transcript)
37
Dreamweaver
38
lttrgt lttd rowspan"2" bgcolor"cccc99"gtnbsplt
/tdgt lttd height"30" bgcolor"999966"gtltdiv
id"mainnav"gt
Hexadecimal Number
  • With web applications like HTML (Hypertext Markup
    Language), colors are sometime described using
    their RGB color specification in hexadecimal.

39
Hexadecimal RED GREEN BLUE
  • lttd rowspan"2" bgcolor"cccc99"gtnbsplt/tdgt
  • Red Green Blue
  • cc cc 99
  • lttd height"30" bgcolor"999966"gtltdiv
    id"mainnav"gt
  • Red Green Blue
  • 99 99 66
  • means hexadecimal in web applications

40
Hexadecimal Numbers
  • What are they?
  • Why do these people use them?
  • web designers
  • digital medial creators
  • computer scientists
  • networking professionals

41
Ricks Number System Rules
  • All digits start with 0
  • A Base-n number system has n number of digits
  • Decimal Base-10 has 10 digits
  • Binary Base-2 has 2 digits
  • Hexadecimal Base-16 has 16 digits
  • The first column is always the number of 1s
  • Each of the following columns is n times the
    previous column (n Base-n)
  • Base 10 10,000 1,000 100 10 1
  • Base 2 16 8 4 2 1
  • Base 16 65,536 4,096 256 16 1

42
Hexadecimal Digits
  • Hexadecimal 16 digits
  • Dec Hex
  • 0 0
  • 1 1
  • 2 2
  • 3 3
  • 4 4
  • 5 5
  • 6 6
  • 7 7

Dec Hex 8 8 9 9 10 A 11
B 12 C 13 D 14 E 15 F
43
0, 1, 2, 3, 4, 5, 6, 7 ,8, 9, A, B, C, D, E, F
  • Hexadecimal
  • Decimal 16s 1s
  • 8 8
  • 9 9
  • 10 A
  • 14 E
  • 15 F
  • 16 1 0

44
0, 1, 2, 3, 4, 5, 6, 7 ,8, 9, A, B, C, D, E, F
  • Hexadecimal
  • Decimal 16s 1s
  • 17 1 1
  • 20 1 4
  • 21 1 5
  • 26 1 A
  • 12 C
  • 29 1 D

45
0, 1, 2, 3, 4, 5, 6, 7 ,8, 9, A, B, C, D, E, F
  • Hexadecimal
  • Decimal 16s 1s
  • 30 1 E
  • 31 1 F
  • 32 2 0
  • 33 2 1
  • 50 3 2
  • 60 3 C

46
Question
  • Luigi went into a bar and ordered a beer. The
    bartender ask Luigi for his ID to make sure he
    was old enough to order a beer (21). After
    looking at Luigis ID the bartender told Luigi he
    was not at least 21. Luigi answered, Im sorry
    but you are wrong. I am exactly 21. My ID shows
    my age in Hexadecimal.
  • What age is on McLuigis ID in Hexadecimal?
  • Decimal 16s 1s
  • 21 1 5
  • 16 5

47
Dont forget why we are doing this!
lttrgt lttd rowspan"2" bgcolor"cccc99"gtnbsplt
/tdgt lttd height"30" bgcolor"999966"gtltdiv
id"mainnav"gt
Hexadecimal Number
48
Why Hexadecimal?
  • Hexadecimal is perfect for matching 4 bits.
  • Every combination of 4 bits can be matched with
    one hex number.
  • 4 bits can be represented by 1 Hex value
  • 8 bits can be represented by 2 Hex values

49
Hexadecimal Digits 4 bits can be represented by
1 Hex value
Dec Hex Binary 8421 8 8
1000 9 9 1001 10 A 1010 11 B
1011 12 C 1100 13 D 1101 14 E
1110 15 F 1111
  • Hexadecimal 16 digits
  • Dec Hex Binary
  • 8421
  • 0 0 0000
  • 1 1 0001
  • 2 2 0010
  • 3 3 0011
  • 4 4 0100
  • 5 5 0101
  • 6 6 0110
  • 7 7 0111

50
Hexadecimal Digits 4 bits can be represented by
1 Hex value
  • Hexadecimal is perfect for matching 4 bits.
  • Every combination of 4 bits can be matched with
    one hex number.
  • 4 bits can be represented by 1 Hex value
  • 8 bits can be represented by 2 Hex values
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111

51
Converting Decimal, Hex, and Binary
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • Dec. Hex Binary Dec. Hex Binary Dec. Hex
    Binary
  • 0 0010 10
  • F 1110 12
  • A 0000 5
  • C 0010
    1000

52
Converting Decimal, Hex, and Binary
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • Dec. Hex Binary Dec. Hex Binary Dec. Hex
    Binary
  • 0 0 0000 2 2 0010 10 A
    1010
  • 15 F 1111 14 E 1110 12 C
    1100
  • 10 A 1010 0 0 0000 5 5
    0101
  • 12 C 1100 2 2 0010 8 8
    1000

53
What about 8 bits?
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • HEX BINARY
  • 2 4 ?

54
What about 8 bits?
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • HEX BINARY
  • 2 4 0010 0100

55
Using Hex for 8 bits
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • Hex Binary Hex Binary Hex
    Binary
  • 12 0001 0010 3C 99
  • AB 1A 00
  • 02 B4 7D
  • 0111 0111 1000 1111
    1111 1111
  • 0000 0010 1100 1001
    0101 1100

56
Using Hex for 8 bits
  • Dec. Hex. Binary Dec. Hex. Binary
  • 0 0 0000 8 8 1000
  • 1 1 0001 9 9 1001
  • 2 2 0010 10 A 1010
  • 3 3 0011 11 B 1011
  • 4 4 0100 12 C 1100
  • 5 5 0101 13 D 1101
  • 6 6 0110 14 E 1110
  • 7 7 0111 15 F 1111
  • --------------------------------------------------
    ---
  • Hex Binary Hex Binary Hex
    Binary
  • 12 0001 0010 3C 0011 1100 99
    1001 1001
  • AB 1010 1011 1A 0001 1010 00
    0000 0000
  • 02 0000 0010 B4 1011 0100 7D
    0111 1101
  • 77 0111 0111 8F 1000 1111 FF
    1111 1111
  • 02 0000 0010 C9 1100 1001 5C
    0101 1100

57
So why is Rick torturing us?
lttrgt lttd rowspan"2" bgcolor"cccc99"gtnbsplt
/tdgt lttd height"30" bgcolor"999966"gtltdiv
id"mainnav"gt
Hexadecimal Number
58
How much RED GREEN BLUE ?
  • lttd rowspan"2" bgcolor"cccc99"gtnbsplt/tdgt
  • Red Green Blue
  • cc cc 99
  • lttd height"30"bgcolor"999966"gtltdividgt
  • Red Green Blue
  • 99 99 66

59
Hexadecimal RED GREEN BLUE
  • lttd rowspan"2" bgcolor"cccc99"gtnbsplt/tdgt
  • Red Green Blue
  • cc cc 99
  • Convert to Binary
  • Red Green Blue
  • Hex cc cc 99
  • Bin 1100 1100 1100 1100 1001 1001

24 bits represent a single color
60
  • Red Green Blue
  • Hex cc cc 99
  • Bin 1100 1100 1100 1100 1001 1001

24 bits represent a single color
61
  • Red Green Blue
  • Hex 00-gtFF 00-gtFF 00-gtFF
  • Bin 0000 0000 0000 0000 0000 0000
  • thru thru thru
  • 1111 1111 1111 1111 1111 1111
  • Dec 0 -gt 255 0 -gt 255 0 -gt 255

255
255
255
?
?
?
0
0
0
62
How Much? 0 to 255
255
?
0
255
?
0
255
?
0
63
  • Red Green Blue
  • Hex cc cc 99
  • Bin 1100 1100 1100 1100 1001 1001
  • Hexadecimal
  • Decimal 16s 1s
  • c c
  • or
  • 12 12
  • (12x16) (12x1)
  • 204 192 12

64
  • Red Green Blue
  • Hex cc cc 99
  • Bin 1100 1100 1100 1100 1001 1001
  • Dec 204 204 153

65
255
204
0
255
204
0
255
153
0
66
lttd rowspan"2" bgcolor"cccc99"gtnbsplt/tdgt
67
255
FF
0
0
00
255
FF
  • Red Green Blue
  • Dec 0 0 255
  • Hex 00 00 FF
  • Bin 0000 0000 0000 0000 1111 1111

0
0
00
Hexadecimal Decimal 16s 1s
255
FF
255
0
00
68
255
FF
200
0
00
255
FF
  • Red Green Blue
  • Dec 200 48 127
  • Hex c8 30 7F
  • Bin 1100 1000 0011 0000 0111 1111

48
0
00
Hexadecimal Decimal 16s 1s
255
FF
127
0
00
69
255
FF
74
0
00
255
FF
  • Red Green Blue
  • Dec 74 132 40
  • Hex 4A 84 28
  • Bin 0100 1010 1000 0100 0010 1000

132
0
00
Hexadecimal Decimal 16s 1s
255
FF
40
0
00
70
255
FF
255
0
00
255
FF
  • Red Green Blue
  • Dec 255 255 255
  • Hex FF FF FF
  • Bin 1111 1111 1111 1111 1111 1111

255
0
00
Hexadecimal Decimal 16s 1s
255
FF
255
0
00
71
255
FF
50
0
00
255
FF
  • Red Green Blue
  • Dec 50 128 60
  • Hex 32 80 3C
  • Bin 0011 0010 1000 0000 0011 1100

128
0
00
Hexadecimal Decimal 16s 1s
255
FF
60
0
00
72
CMYK - Cyan-Magenta-Yellow-Black
  • From Wikipedia
  • The CMYK color model (process color, four color)
    is used in color printing.
  • Comparisons between RGB displays and CMYK prints
    can be difficult, since the color reproduction
    technologies and properties are so different.
  • A computer monitor mixes shades of red, green,
    and blue to create color pictures.
  • There is no simple or general conversion formula
    that converts between them.
  • Conversions are generally done through color
    management systems.
  • Nevertheless, the conversions cannot be exact.

73
Color Codes
74
Digitizing Sound
75
Theme from Shaft
76
Digitizing Sound
  • Many definitions of analog.
  • (Our definition) analog wave is a wave form
    analogous to the human voice.
  • The telephone systems uses an analog wave to
    transmit your voice over the telephone line to
    their Central Office.

77
Digitizing Sound
78
Digitizing Sound
  • Many definitions of analog.
  • (Our definition) analog wave is a wave form
    analogous to the human voice.
  • The telephone systems uses an analog wave to
    transmit your voice over the telephone line to
    their Central Office.

79
Digitizing Sound
  • Two parts of the wave
  • Amplitude Height of the wave which equates to
    volume.
  • Frequency Number of waves per second, which
    equates to pitch.
  • Computers are digital devices, so the analog wave
    needs to be converted to a digital format.

80
Digitizing Sound
  • Converting Analog to Digital requires three
    steps
  • 1. Sampling
  • 2. Quantifying
  • 3. Coding

81
Digitizing Sound
  • Sampling To take measurements at regular
    intervals.
  • The more samples you take, the more accurately
    you represent the original wave, and the more
    accurately you can reproduce the original wave.

82
Digitizing Sound
1 second, 40,000 samples
  • Nyquists Theorem which states that a sampling of
    two times the highest allowable frequency is
    sufficient for reconstructing an analog wave into
    a digital data.
  • Human can hear frequencies up to about 20,000 Hz
    or 20,000 frequencies per second.
  • Using Nyquists Theorem, this means we need to
    sample each analog wave at 40,000 times per
    second of sound.
  • In other words, each one second of sound gets
    sample 40,000 times. (Actually, 44,100 times per
    second.)

83
Sampling Quantifying - Coding
  • A digital audio processor is used to sample the
    analogue audio wave 44,100 times a second.
  • This means, at every tick (44,100 times per
    second), the digital audio processor (sampling)
  • Determines the amplitude of the original very
    complex audio wave.
  • It records it as a 16 bit value (quantifying)
  • This means there are 65,536 possible values for
    this amplitude (coding)
  • 32,767 values above zero
  • 32,767 values below zero.
  • It does this sampling for the two channels of
    stereo as well.

84
(No Transcript)
85
6
If we sample at too low a rate, we may miss some
peaks and troughs in the original audio and so
the resulting waveform may sound completely
different and muddy
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
86
2
Here we've got a fairly high sample rate, but the
measurements of the amplitude are pretty coarse.
1
0
-1
-2
87
Digitizing Sound
  • Quantifying This is the process of giving a
    value to each of the samples taken.
  • The larger the range of numbers, the more
    detailed or specific you can be in your
    quantifying.

88
Digitizing Sound
  • Coding This is the process taking the value
    quantified and representing it as a binary
    number.
  • Audio CDs use 16 bits for coding.
  • 16 bits gives a range from 0 to 65,536.
  • Actually
  • 15 bits are used for the range of numbers
  • 1 bit is used for (positive) or (negative)
  • 32,768 positive values and 32,768 negative values
  • How many bits does it take to record one minute
    of digital audio?

89
Digitizing Sound
  • How many bits does it take to record one minute
    of digital audio?
  • 1 minute 60 seconds
  • 44,100 samples per second
  • This equals 2,646,000 samples.
  • Each sample requires 16 bits.
  • 2,646,000 samples times 16 bits per sample equals
    42,336,000 bits.
  • 42,336,000 bits times 2 for stereo equals
    84,672,000 bits for 1 minute of audio.
  • 84,672,000 bits divided by 8 bits per byte equals
    10,584,000 bytes for 1 minute of audio. (More
    than 10 megabytes!)
  • One hour of audio equals 635,040,000 bytes or 635
    MB (megabytes)!

90
MP3 Compression
  • Compressing digital audio means to reduce the
    number of bits needed to represent the
    information.
  • There are many sounds, frequencies, that the
    human ear cannot hear, some too high, some too
    low.
  • These waves can be removed without impacting the
    quality of the audio.
  • MP3 uses this sort of compression for a typical
    compression ratio of 101, so a one minute of MP3
    music takes 1 megabyte instead of 10 megabytes.

91
Advantage of Digitizing Information
  • A key advantage to digital representation of
    information, images and sounds, is that the it
    can be reproduced exactly without losing a bit
    of the quality.

92
Text, Images, Video and Sound
  • CS 1 Introduction to Computers and Computer
    Technology
  • Rick Graziani
About PowerShow.com