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Helix Fixed-point open source HE-AAC decoder, open source optimized fixed point HE-AAC
karl_lillevold
post Mar 3 2005, 20:05
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RealNetworks Sr. Codec Engineer


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

QUOTE
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


https://datatype.helixcommunity.org/2005/aacfixptdec


--------------------
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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yanchen
post Mar 6 2005, 08:27
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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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chelgrian
post Mar 6 2005, 21:09
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QUOTE (yanchen @ Mar 6 2005, 08:27 AM)
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.
*


Hum they only tested it on a ARM9TDMI (v4T), ARM9E (V5TE), StrongARM (v4) and Xscale (V5TE). They didn't test on anything like a ARM1136 (v6) which has various media and SIMD extensions.

They also compiled it with ADS 1.2 rather than the latest ARM compiler RVCT 2.2 which produces significantly faster code.

The fastest ARM ACC codec was handcrafted in assembler by some guys down the corridor from me but we no longer license it commercially.
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