5.6 Conclusions

The parametric stereo coder has been described and its embedding in aacPlus v2 has been outlined. The coder employes analysis and synthesis of ICLD, ICPD and ICC parameters and is quite flexible in terms of parameter update rate, temporal framing and spectral resolution. The implementation of parametric stereo in the (hybrid) QMF domain enables an efficient combination of parametric stereo and SBR.

Listening tests have revealed that parametric stereo in aacPlus v2 provides a bitrate gain of about 33% over (stereo) aacPlus v1, enabling high-quality stereo audio transmission at bitrates of only 24 to 32 kb/s. This unsurpassed compression efficiency makes aacPlus v2 especially attractive for mobile applications, where bandwidth is relatively scarce and expensive.