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 converts a stereo input signal into a mono signal . The encoder also saves the most important stereo parameters (e.g. phase differences, panorama information, surround sound) of the two input channels for each point in time. These stereo parameters are embedded in the data stream as a parametric representation of the stereo information at a bit rate of around 2-3 kbit / s . With the help of this parametric information, the decoder tries to restore the stereo signal as best as possible from the stored mono signal. This creates the realistic illusion of a real stereo signal 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 enables an acceptable stereo quality at very low bit rates (16–40 kBit / s). Above these very low bit rates (i.e. from around 48 kBit / s) PS is not used for quality reasons. PS is downwardly compatible to a limited extent: Decoders that are not PS-capable deliver only a mono signal with a data stream containing parametric stereo information.
See also
literature
- Thomas Görne: Sound engineering. Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich et al. 2006, ISBN 3-446-40198-9 .