GCSE Computing/the differences between lossy and lossless compression

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Lossless versus lossy compression[edit]

Summary[edit]

It is often necessary to compress a file to make it small enough to be used - for example making a music file small enough so that enough can be stored on an iPod. There are two main possibilities:

  • Lossless
    • These are used to make a file a smaller size but without losing any of the information. Using this method you can always get back to the original file
  • Lossy
    • Sometimes some loss of quality is acceptable. For example the human ear cannot hear all frequencies, so a file format that throws away parts that people can't hear may end up with a smaller file, but it is not possible to get back to how exactly the original music sounded.

Which format to choose?[edit]

The only real reason for choosing a lossy format is because the file would be too big if you used a lossless one. For example, a lossless picture may too big to download in a sensible amount of time, or you could store many less tracks on an iPod if you used a lossless format instead of AAC or MP3.

Examples[edit]

Lossless Compression[edit]

  • [[1]] – Portable Network Graphics
  • [[2]] – Tagged Image File Format
  • [| flac ] - Free Lossless Audio Codec

Lossy Compression[edit]