2.6 Compression

Question 1

What is compression?

Answer 1

Algorithms which reduce file sizes

Question 2

What is decompression?

Answer 2

The process where compressed data is returned to its original format

Question 3

What sort of media is used with compression?

Answer 3

Sound, image and video files

Question 4

What are the 2 different types of compression?

Answer 4

Lossy and Lossless

Question 5

Lossy compression

Answer 5

Permanently loses some data

Question 6

Give some lossy compression artefacts

Answer 6

• Small mistakes (digital artefacts)
• Noise
• Blocks

Question 7

Does lossless image compression lose any of the image data?

Answer 7

No

Question 8

What does the losseless image compression algorithm do?

Answer 8

Finds groups of repeating data and records data once along with the number of repetitions

Question 9

Compression advantages

Answer 9

• Download times are reduced
• Data allowances go further
• Possible to transmit video and music data streams as fast as they are playing

Question 10

Benefits compression

Answer 10

• Faster transmission time
• Reduces download times of video, sound and image files
• Images inside web pages appear faster
• Reduces space on disk/servers

Question 11

What is buffering?

Answer 11

Delayed video or music streaming.

Question 12

What can cause buffering?

Answer 12

The download speed is slower than the playback speed

Question 13

Give some Lossy file formats

Answer 13

• JPEG
• MP4
• MP3

Question 14

Give some Lossless file formats

Answer 14

• PNG
• ZIP
• GIF
• FLAC
• ALAC

Question 15

JPEG

Answer 15

Photos

Question 16

PNG

Answer 16

Images/photos may include transparency

Question 17

ZIP

Answer 17

Document compression

Question 18

GIF

Answer 18

Simple images may include animation

Question 19

MP4

Answer 19

Video file format

Question 20

MP3

Answer 20

Music format

Question 21

FLAC/ALAC

Answer 21

Lossless Music Format