Is it possible to encode a 22.05 kHz stereo PCM input file into HE-AAC?

I try the following with Nero:
C:\temp>\bin\neroAacEnc.exe -if <ifile> -of <ofile> -he

*************************************************************
* *
* Nero Digital Audio Reference MPEG-4 & 3GPP Audio Encoder *
* Copyright © 2006 Nero AG *
* All Rights Reserved Worldwide *
* *
* Package build date: May 1 2006 *
* *
* See -help for a complete list of available parameters. *
* *
*************************************************************
ERROR: Unsupported encoding configuration


It works fine without the -he option. Is -he unsupported for 22 kHz audio? In general, is there a restriction on the input samples for encoding aacPlus and aacPlusV2?

It is possible.. just not with neroaacenc...

It can be done with dimzon's super old frontend for winamp's enc_aacplus.dll (can probably be done with the winamp transcoder too). But even to do it with that one, you would have to resample to greater than 32khz then resample with the encoder back down.
try this link.. might still work http://www.crapshack.com/aacenc.zip

There is no reason to encode 22khz audio with aacPlus as aacPlus has enhancement on upper frequencies and use LC-AAC to encode lower frequencies.