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

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?