Advanced Audio Coding Low Complexity (AAC LC) combined with Spectral Band Replication (SBR) and Parametric Stereo (PS) was defined as HE-AAC v2.
16–48 kbit/s and down to 14.4 kbps in xHE-AAC used in DRM) to give a good stereo impression, so while it can improve perceived quality at very low bitrates, it generally does not achieve transparency, since simulating the stereo dynamics of the audio with the technique is limited and generally deteriorates perceived quality regardless of the bitrate.
[1] Parametric Stereo was originally developed in Stockholm, Sweden by companies Philips and Coding Technologies, and was first unveiled in Naples, Italy, in 2004 during the 7th International Conference on Digital Audio Effects (DAFx'04).
[2] The implementation in MPEG-4 is based on specifying the relative amount, delay, and correlation (coherence) of left and right channels by each frequency band in the mixed mono audio.
Compared to intensity stereo coding, which does not record delay or correlation, PS can provide more ambience.