Lossy Compression

• Lossy compression


  An easy-to-understand example is old-style telegrams, which were used to send messages over wire cables
• Telegram compression


  1. Take off some words

  2. Hoping the person receiving the message would still be able to understand the meaning

  3. Send a maximum amount of information using a minimum number of words
• Telegram compression example


  • Original message: 'Hello, I will be celebrating my graduation in Cornwall Town Hall next Friday November 12. I hope you can come with your family. Can you please let me know if you can't come?' (33 words)
  • Compressed message: 'Graduation next Friday Cornwall Town Hall. Come family. Let me know.' (11 words)
• The 22 words taken off the original telegram message would be lost and cannot be recovered - hence the name lossy compression
• Similarly, audio, image and video files can be compressed by removing some of the information that does not add much to the file or is simply redundant
• Lossy compression of audio, image and video files


  Exploits features of human perception to reduce the amount of data needed