The Helix Fixed-point HE-AAC decoder provides an optimized 32-bit fixed-point implementation, which will be dual-licensed under RCSL/RPSL. No extra copyright license is required beyond the standard Helix license terms, although patent licenses are not included and must be acquired from the appropriate AAC licensors.

The Helix AAC decoder is highly optimized for ARM processors and meets or exceeds the performance of other commercial implementations. It also features one of the first widely available fixed-point implementations of SBR.

The following features are currently supported:
· MPEG-2 and MPEG-4 low complexity decoding (intensity stereo, MS, TNS, PNS)
· spectral band replication (SBR), high-quality mode
· mono, stereo, and multichannel modes
· ADTS, ADIF, and raw data block decoding
· MP4, RM, and other file formats supported via Helix client

Great contribution for the evidence to prove the more effiective complexity design  of AAC than any other codec. From the statistical number, we can see the ARM enhanced instruction cannot bring a significant improvemnent as in speech codec. It also tell us that the comparable computation power annouced by coding technology beteewn conventional AAC decoder and HE-AAC decoder is questionable.

However, from my knowledgement base, the fastest commercial AAC ARMv2 decoder in the world can reach 18 MHZ 44.1KHz stereo. But this decoder may devote much effort between memory usage and speed.
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Hi Karl!  This is really awesome contribution to the open source community.  But is the RCSL/RPSL license compatible with GPL?  I ask because the it would be really nice to use this code in the iPodLinux project.
EDIT: Nevermind, according to this it is .
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