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

I try the following:
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?

Isn't HE used to reconstuct the frequencies above 11KHz?

Mike,
No, it's not that simple.

HE is basen on SBR (Spectral Band Replication). If sampling frequency is 22.05 kHz, why couldn't you 'replicate' some bands from 0-5 kHz to somewhere between 5-10 kHz? It's just that Nero doesn't support 22.05 kHz.

There are a few bitstream parameters (see the graph titles below) that tell decoder what-and-where to replicate. It is up to encoder to decide.

Here are two examples.

First example shows how two bands are replicated: 1-6.5 to 6.5-12, and 3.7-6.5 to 12-14.8 in this case. With a slight variation of encoding parameters in the second example, we get different replication - with tree patches frequency range after decoding is wider. The parameters depend on the bitrate, of course - again, it is up to encoder to decide. The higher the bitrate, the more lower frequencies core AAC encoder can take, etc...

Ex. 1


Ex. 2


Hope this helped.
Daniel