U2Ch1L5_Lossy Compression and File Formats

Purpose: Students will understand what Lossy Compression is and When it is best to use it.

Activity: Go the Lossy Text Compression App Lab
Answer the Following Questions

• You compressed poems several classes ago. Would you consider what you are viewing on this phone screen to be Text Compression? Why or Why Not?
• Do you remember the name of the type of compression we were working with when we compressed the poems? (the poems…Lossless!)
• Can you guess the type of compression you are viewing here on the app (phone screen)? This is Lossy compression – What is the difference between it and Lossless?
• Lossless: in doing the compression, and in reconstructing the original text, nothing was lost; every character that was part of the original text could be recovered.
• Lossy compression schemes are ones in which “useless” or less-than-totally-necessary information is thrown out in order to reduce the size of the data. Problem: there’s no real way to know what the original word was. The original word is lost. Positive: human brains are good at filling the gaps when information is missing.

Video:  Lossy Video (lossy in second half – go to 00:35 -1:22)

Activity: Handout – “File Formats Rapid Research – Worksheet!”

• In pairs Fill In – Research unknown online

Review for Test: Unit 2 – Digital Information

Test: Unit 2 – Digital Information