CS Last Unit 1 Test

Question 1

Why is it necessary to reduce (compress) the size of a file?

Answer 1

1. To save storage space on devices (ex. hard disc drive)
2. to reduce time taken to stream music or video
3. to reduce the time taken to upload, download, or transfer files
4. reduced file size also reduces costs

Question 2

How is file compression enabled?

Answer 2

File compression is enabled through a file or data compression software

Question 3

File compression can either be____ or ____

Answer 3

File compression can either be lossless or lossy

Question 4

With lossless file compression..

Answer 4

with lossless file compression, all the data bits from the original file are reconstructed when the file is compressed

Question 5

when is lossless file compression important

Answer 5

lossless is important for files where loss of any data would be disastrous (like a spreadsheet)

Question 6

what are the features of lossless compression?

Answer 6

• used where code must be the same as the original
• a compression algorithm is used
• no data is removed in the process
• the number of times the word appears is stored

Question 7

With lossy file compression..

Answer 7

with lossy file compression, the file compression algorithm eliminates unnessacary bits of data

Question 8

bad sides of lossy file compression

Answer 8

with lossy file compression it is impossible to get the original file back once it has been compressed

Question 9

features of lossy compression

Answer 9

• makes the file smaller than lossless
• quality can be reduced but the file will still run
• redundant data can be removed
• used when no requirement for the file to be exactly the same as original

Question 10

MIDI stands for

Answer 10

musical instrument digital interface

Question 11

midi files….?

Answer 11

• MIDI files are not music and don’t contain sounds
• you can’t listen to it
• MIDI is a communications protocol that allows musical instruments to interact with each other
• it uses an 8-bit serial transmission

Question 12

What technology does Mp3 use?

Answer 12

It uses a technology known as audio compression to convert music and sounds into the mp3 file format

Question 13

drawbacks of Mp3

Answer 13

• it will reduce the size of normal music files by about 90%
• the quality of mp3 files can be different since it depends on the BIT RATE

Question 14

what file compression does mp3 use?

Answer 14

lossy format (because part of the original is lost)

Question 15

what technique does mp3 use?

Answer 15

a technique called PERCEPTUAL MUSIC SHARING is used to remove sounds the human ear cannot detect + when 2 sounds are played simultaneously the softer sound if removed

Question 16

differences between mp3 and MIDI

Answer 16

• mp3 is a digital recording of a sound
  -mp3 is produced by recording software
• mp3 is a compressed file format
• MIDI is instructions on how to make sound
• MIDI isn’t audio
• MIDI is produced by a synthesizer

Question 17

facts about mp4

Answer 17

• it allows the storage of multimedia files and not just sound

Question 18

what can mp4 also be called

Answer 18

MPEG-4

Question 19

what happens when a photographic files goes under file compression

Answer 19

the size of the file;e is reduced, the reduced file size means reduced quality of image

Question 20

what are the highest image qualities?

Answer 20

TIFF and BMP but unlike jpeg they aren’t in compressed format

Question 21

JPEG is..

Answer 21

• lossy file compression
• reduces photographic image file sizes
• relies on properties of the human eye
• can produce 40 million colors
• images can be split into 8x 8 pixel blocks

Question 22

what does RLE stand for

Answer 22

Run-length encoding

Question 23

RLE is…

Answer 23

• a form of lossless file compression
• reduces the size of a string of adjacent, identical data
• a repeating string is encoded into 2 values
• RLE is only effective where there is a long run of repeated units/bits

Question 24

what colors are each color made up of?

Answer 24

red, green, and blue (together main black)