1.3. Compression

Question 1

Compression

Answer 1

• The process of reducing file size without a
  significant loss in quality which results in:
• Reducing the time needed to search for data.
• Faster transfer of compressed files, which uses less
  bandwidth than uncompressed files.

Question 2

Lossless Compression

Answer 2

• Type of compression that allows original data to
  perfectly reconstructed from compressed file when
  the file is opened by utilizing some form of
  replacement.
• E.g. bitmap (.bmp), vector graphic (.svg) and .png
  images, text file compression, database records

Question 3

Run-length Encoding (RLE)

Answer 3

• Form of lossless compression which is used for
  compressing text files and bitmap images.
• Reduces file size of a sequence of elements which
  has adjacent, identical elements (characters in text
  file and pixels in bitmap images).
• Repeating sequence of elements encoded in two
  values: run count and run value.

Question 4

Lossy Compression

Answer 4

• Type of compression which irreversibly eliminates
  unnecessary data
• File accuracy/quality lower than that of lossless but
  file size is lower (~10% of lossless).
• E.g. Sound files (.mp3), .jpeg images
• Sound files compression (.mp3) utilizes Perceptual
  Coding to remove certain parts of sound that are less
  audible/discernible to human hearing