Tuesday, February 19, 2013

Data Compression

Data compression is a method of reducing the file size for conserving drive space or easier transfer. Data compression comes in three forms:

  • Archival
    • A lossless method of packing a file into a smaller space.
    • The file will need to be unpacked before using.
    • Also useful for collecting multiple files into one package for transfer.
    • Examples include zip, rar, tar, gz.
  • Lossless
    • A method of reducing the size of a file by removing statistical redundancies.
    • When the file is decompressed, the result should be identical to the original.
    • The file is decompressed by the decoder in real-time for consumption.
    • Examples include flac, alac.
  • Lossy
    • A method of reducing the size of a file by removing irrelevant information.
      • The information is gone forever.
    • Irrelevancy of information is determined by the codec used.
      • The codec determines irrelevant information based on psychovisual or psychoacoustic models.
    • Benefits include reduced disk space and bandwidth use.
    • Examples include jpeg, mp3.