Parametric Stereo

Parametric Stereo (English Parametric Stereo, abbreviated: PS ) is a method of parametric audio coding for lossy audio data compression of stereo signals.

A parametric stereo encoder created from a stereo input signal is a mono signal. To the encoder for each time point is still storing the main stereo parameters (for example, phase differences, pan information, surround ) the two input channels. The stereo parameters are embedded with a bit rate of S 2-3 kbit / as a parametric representation of the stereo information in the data stream. Using these parametric information, the decoder later tried as much as possible to restore the stereo signal from the stored mono signal. So the realistic illusion of a true stereo signal is generated for the listener.

Parametric stereo is used among other things as an extension to Advanced Audio Coding in MPEG -4 High Efficiency Advanced Audio Coding ( HE- AAC, so-called " aacPlus v2 ", " AAC v2" or " enhancedAAC ", " eAAC "). It allows an acceptable stereo quality at very low bitrates ( 16-40 kbit / s). Above this very low bit rates (ie, from about 48 kbit / s ) PS is not used for reasons of quality. PS is limited backward compatible: No PS -capable decoder provide for a parametric stereo information stream containing only a mono signal.