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Helix Fixed-point open source HE-AAC decoder, open source optimized fixed point HE-AAC
post Mar 3 2005, 20:05
Post #1

RealNetworks Sr. Codec Engineer

Group: Developer (Donating)
Posts: 89
Joined: 12-June 03
From: Seattle
Member No.: 7151

Yesterday, the RealNetworks Codec Team released an open source optimized High-Efficiency AAC (aacPlus) decoder to the Helix Community.

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


Sr. Codec Engineer (video) | RealNetworks Codec Group | helixcommunity.org
This information is provided "AS IS" with no warranties, grants no rights, and reflects my personal opinion.
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post Mar 6 2005, 08:27
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Group: Members
Posts: 19
Joined: 5-March 02
From: Taipei
Member No.: 1449

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.

This post has been edited by yanchen: Mar 6 2005, 08:34
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