Mani Raj Paul - Companding

The word Companding is a combination of Compressing and Expanding, which means that it does both. This is a non-linear technique used in PCM which compresses the data at the transmitter and expands the same data at the receiver. 
There are two types of Companding techniques.

A-law Companding Technique

  • Uniform quantization is achieved at A = 1, where the characteristic curve is linear and there is no compression.
  • A-law has mid-rise at the origin. Hence, it contains a non-zero value.
  • A-law companding is used for PCM telephone systems.
  • A-law is used in many parts of the world.

µ-law Companding Technique

  • Uniform quantization is achieved at µ = 0, where the characteristic curve is linear and there is no compression.
  • µ-law has mid-tread at the origin. Hence, it contains a zero value.
  • µ-law companding is used for speech and music signals.
  • µ-law is used in North America and Japan

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