What's the difference between HE-AAC and HE-AAC+PS?

[FAII]

God, the AAC options just keep piling up on me. So I recently learned the difference between LC and HE. But what's this +PS thing?

[check]

instead of encoding two channels, Parametric Stereo encodes one channel and adds extra data to reproduce two channels from it. It's more efficient at the low end, but quality suffers at higher bitrates.

[FAII]

So it's basically Joint Stereo for AAC.

[shon3i]

So it's basically Joint Stereo for AAC.
No. AAC use Joint Stereo as MP3 but more complex, aslo Joint Stereo MS (which used in Nero and CT encoders) is lossless proces and not destroy stereo image. Second Joint Stereo IS (not used by any encoder for now) destroy's stereo image and it's lossy process.

Parametric Stereo is new tehnology only for AAC, an like Check, encoders encode stereo signal as mono with some extra info. This info uses decoder and reconstruct mono to stereo.

http://www.codingtechnologies.com/products/assets/PS_level1.gif

Same thing like decoder reconstructing HE-AAC