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AS Level Computer Science > Information representation and multimedia > Flashcards

Information representation and multimedia Flashcards

1
Q

Bit-map images are made up of ________

A

Pixels

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2
Q

Colour depths

A

The number of bits used to represent a pixel

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3
Q

Bit depths

A

It determines the Color depth of that pixel

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4
Q

An increase in bit depth, increases _________

A

The number of possible colors

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5
Q

Image resolution

A

The number of pixels that make up an image.

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6
Q

Screen resolution

A

The number of horizontal & vertical pixels that make up a screen display.

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7
Q

Pixel density

A

The number of pixels per square inch

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8
Q

How do you calculate the pixel density?

A

1) add together the squares of the resolution size
2) find the square root
3) divide by the screen size

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9
Q

What are the drawbacks of using high resolution images?

A
  • Increase in file size
  • increase in download time
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10
Q

What are 2 things that must be considered when the file size needed to store a bit-map image?

A

-image resolution
-bit depth

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11
Q

What are vector images?

A

Images that use mathematical formulas to draw lines and curves that can be combined to create an image

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12
Q

Vector graphics contains a drawing list which are a _______

A

set of commands used to define a vector image

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13
Q

Vector images tend to be ______ than bitmap images because a bitmap image has to _________ for each individual pixel that forms the image

A
  • smaller
  • store color information
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14
Q

A vector image only has to store mathematical formulas that make up the image, which _______

A
  • takes up less space
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15
Q

The 3 most popular image formats used on the web are _________, and are all bitmap formats

A
  • PNG
  • JPEG
  • GIF
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16
Q

What are vector graphics?

A

a graphic consisting of components defined by geometric formulae and associated properties, such as line color and style

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17
Q

Sound is an _______ value

A

analogue

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18
Q

An ______ is used to digitise sound into files

A

ADC converter

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19
Q

If the sound is going to be used as a sound file, it gets __________

A

filtered first to remove higher and lower frequencies

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20
Q

_________ is the number of bits used to represent each sample

A

Sampling resolution

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21
Q

The higher the sample resolution, the better the audio quality.
Because if more bits are available for each sample, ________

A

then more levels of the signals can be captured, improving the detail of the recording

22
Q

________ is the number of sound samples taken per second.
The higher the sampling rate and/or sampling resolution, the greater the file size

A

Sampling rate

23
Q

How is sampling used to record a sound clip?
1. ________ of the soundwave is _______ at ________
2. (this gives an approx. representation of the sound wave,)
3. Sound wave is then encoded as a series of binary digits

A
  • amplitude
  • determined
  • set time intervals
24
Q

how does a microphone digitise sound?

A
  • microphone measures change in air pressure
  • microphone translates air pressure into electrical voltage
  • ADC digitizes electrical voltage to bytes of info
  • computer displays the digitized sound for manipulation
25
Q

________ is the amount of data that can be transmitted in a fixed amount of time.

A
  • bandwidth
    Digital devices express them in bits per second (bps). Analog devices express them in cycles per second (Hz)
26
Q

What are the factors that affect the digital audio quality?

A
  • sample rate
  • sample resolution/bit depth
27
Q

__________ the number of bits used to store one second of sound

A

bit rate

28
Q

File size formula (for sound)

A

sample rate x sample resolution x sound length

29
Q

Bit rate formula

A

frequency x bit depth x channels

30
Q

file size formula (for screen and pictures)

A

total pixels x colour depth

31
Q

coloured images need at least __________ to code them

A

8 bits or 1 byte for 1 pixel

32
Q

Monochrome images need _______ to represent the color

A

1 bit for 1 pixel

33
Q

A common audio sample rate for music is _________

A

44,100 samples per second

34
Q

___________ are the number of frames recorded per second

A

frame rate

35
Q

_________ are the smallest picture element which can be drawn

A

pixels

36
Q

_______ is a type of compression where all data from the original file can be reconstructed when the file is uncompressed again

A

lossless

37
Q

______ is a type of compression where the file compression algorithm gets rid of unnecessary data

A

Lossy

38
Q

________ uses audio compression to convert sounds into an MP3 format

A

MPEG-3 (MP3)

39
Q

audio compression with an MPEG-3 reduces the file size by __________

A

90%

40
Q

____________ allows an original music file to be reduced by 90% while keeping most of the music quality

A

perpetual music shaping

41
Q

MP3 files uses a _______ format

A

lossy

42
Q

Quality of mp3 files can differ depending on the _______

A

bit rate

43
Q

_______ gives a sound quality close to CDs

A

200 kilobits and higher

44
Q

__________ format allows the storage of multimedia files rather than sound

A

MPEG-4 (MP4)

45
Q

photographic (bit-map) images when compressed, both _________ is reduced

A
  • file size
  • image quality
46
Q

_______ is a common file format for images that uses lossy compression

A

JPEG

47
Q

A JPEG reduced the image by a factor between _______, depending on the quality

A

5 and 15

48
Q

Run Length Encoding (RLE) is a form of ___________ that reduces the size of _______

A
  • lossless compression
  • identical data
49
Q

A repeated string is encoded into 2 values.
- the first value represent the ______
- the second value represent the ________

A
  • no. of identical data items
  • code of the data item (such as ASCII code)
50
Q

Methods of compressing movie files.
- reduce the ________
- reduce the ____
- reduce the _______

A
  • sampling rate used
  • sampling resolution
  • frame rate
51
Q

Methods of compressing image files.
- ______ the image
- _____ the colour/bit depth
- _______ the image resolution

A
  • crop
  • decrease
  • reduce

AS Level Computer Science (2 decks)

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