Parametric coding

Parametric coding is a compression technology used for audio and speech whereby the audio or speech signal is represented by means of different parameters. These parameters are coded into a bitstream format. The decoder rebuilts the signal from these parameters.

The parameters that are used to describe the signal are a little bit different for audio and speech. Parameters that are used for audio are:

• sinusoids,
  the tones that are in the signal,
• transients,
  behaviour in time,
• noise and,
• stereo image

Parameters that are used for speech are:

• pitch,
  the fundamental tones,
• transient,
  the harmonics,
• noise,

A parametric code is especially useful for low bit-rate audio and speech coding demanding medium to good quality. Parametric coding is used in low bit-rate audio and speech codecs like MPEG-4 HVCX.