Shell Data rep recap

The website of a school allows visitors to download JPG, MP3, MPEG and PDF files.

The video clip is compressed using lossy compression.

Explain why lossy compression is suitable for a video clip, but not suitable for a text document.

• Lossy compression keeps all detail....

• Lossy compression loses some data....

• ... though the video file would still be viewable at a lower quality

• ... but if the text file were compressed in a lossy format, it would be unreadable due to missing information

• ... and the text file would be able to be restored to it's original form

Kofi uses his computer to record an audio file of himself playing his guitar.

He emails his recording to a record label. He uses lossy compression to produce the music file.

Why is using lossy compression beneficial?

• Lossy reduces the file size by more than lossless (by permanently removing information)

• The difference is unlikely to be noticed by people

• Lossy can recreate the original file again

• It is noticeably different to the original file

Organize these binary and hex values into even or odd numbers

Groups:

(a) Even

,

(b) Odd

• 11001001

• 3E

• 00100010

• 10010100

• 5A

• F3

• A7

• 0101

The security code for an alarm system is a long binary number which begins

10001111100101111011 …

The technicians prefer to use hexadecimal to enter the security code.

1. Explain why the technicians prefer to use hexadecimal.

• It uses 4 bits per hex digit, so it's straightforward to convert

• Quicker to enter than binary numbers

• It's more accurate than binary

• It means they do more work, rather than the computer

• Less susceptible to errors

What is meant by the term 'compression'?

Compression is ​ (a)   the ​ (b)   of a file.

State one advantage of compressing files before sending them over the internet.

It is ​ (c)   more ​ (d)   as there is ​ (e)  

• reducing
• size
• transmitted
• quickly
• less data
• more data
• expanding
• overlayed
• slower
• storage

Two types of compression are lossy and lossless.

State which type of compression is most appropriate for each of the following and explain why it is appropriate.

Groups:

(a) Code for a program

,

(b) Streaming a video

• Lossless compression

• The information has to be exactly as it was originally or it won't work

• Lossy Compression

• Compresses the file size by a greater amount (makes a smaller file)

• Can be used at a lower quality without the user noticing too much

Images are split up into ​ (a)   . Each one is given a ​ (b)   ​ (c)   which represents the ​ (d)   of that pixel. Each ​different colour is given a separate code. ​ (e)   stored alongside the image holds information such as the resolution, bit depth and creator of the image.

• pixels
• unique
• binary code
• colour
• Metadata
• identical
• hex value
• Megadata
• value