Compression

Question 1

Purpose of compression

Answer 1

To reduce the size of files, as ISP (Internet service providers) and mobile phone networks impose limits and charges on bandwidth.

Question 2

Compression on images

Answer 2

Images on websites need to be in a compressed format to enable a web page to load quickly - even on a fast connection.

Question 3

How is music & videos streaming compressed? And is it recognizable?

Answer 3

Takes advantage of compression in order to reduce buffering.

Question 4

Lossy compression

Answer 4

Works by removing non-essential information.

Question 5

How are images compressed? And is it recognizable?

Answer 5

When images are compressed the subjects are still identifiable but at the cost of quality of the images.

Question 6

How is sound & videos compressed? And is it recognizable?

Answer 6

When sound and videos works via removing frequencies too high for most of us to hear and remove quieter sounds that are played at the same time as louder sounds.
The resulting file is about 10% of original size.

Question 7

How voice is compressed? And is it recognizable?

Answer 7

Transmitted over the Internet or mobile telephone networks using lossy compression and although we have no problem understanding it the difference can be recognized, this difference is the data that has been removed.

Question 8

Lossless compression

Answer 8

Works by recording patterns in data rather than the actual data. Through these patterns and a set of instructions on how to use them, the computer can reverse the procedure and reassemble an image, sound or text file with exact accuracy and no data is lost.

This is most important with the compression of program files, e.g. a single lost character will result in an error in the program code.

Lossless compression has a lower compression ratio than lossy compression.