Lossy and Lossless Compression

Lossy and Lossless Compression

Lesson Objectives​

• Explain the need for compression

• Describe the difference between lossy and lossless compression

What is compression?

• Compression is the name given to algorithms which reduce file sizes

  • Decompression is the process where compressed data is  restored to its original format

• Compression is heavily used with sound, image and video files

Multiple Select

What are the two main types of compression?

• Lossy Compression

• Loss Compression

• Lossless Compression

• Compact Compression

​Why use compression?

• Compression is often used for files and data that are sent via the internet

  • Download times are reduced

  • Data allowances go further

  • It is possible to transmit video and music data streams as fast as they are playing

Lossy compression is mainly used to compress:

• images

• audio

• video

​It achieves the reduction by permenatly removing data.

​Lossy Compression

​

​Lossless compression is mainly used to compress:

• Images

• Sound

• Text​

Lossless compression uses algorithms to find repeating groups of data, and then encode them in a different way to compress the file. No Data is lost and the file can be restored to its original form.

Lossless compression

​

Open Ended

What are the benefits of compression? Provide at least 2-3 benefits

Benefits of compression

• Smaller files = fewer packets = faster transmission time

  • Quicker to complete transmission

  • Reduces traffic over the Internet

• Reduces download times of video, sound (including speech used for VOIP systems) and image files

  • Streaming is also possible as the data can be sent as fast as the rate it is played

• Images inside web pages appear faster

• Reduces space on disk / servers

Multiple Choice

What type of compression would be best for text?

• Lossy Compression

• Lossless Compression

Multiple Choice

A Music artist would like to send a version of their music to a friend over the internet. They want the file to get to their friend as quickly as possible.

Suggest a suitible type of compression.

• Lossy Compression

  .mp3

• Lossless Compression

  .wav

Multiple Choice

A Teacher would like to send a high quaility version of the schools logo to a company to make a poster for the school. Suggest a suitible file type to send the image as.

The teacher would like to keep the background transparent.

• .tig

• .mp3

• .jpg

• .png

Fill in the Blank

What type of compression permenantly removes data?

Fill in the Blank

What type of compression achieves the greatest compression results?

Open Ended

The image to left shows the representation of part of an image.

Explain if this is an example of lossy or lossless compression and why?