Information AboutHe-aac |
| CATEGORIES ABOUT HE-AAC | |
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HE-AAC version 1 was standardized in 2003 by MPEG and published as part of MPEG-4 in document ISO/IEC 14496-3, Amd.1:2003. HE AAC version 2 was standardized in 2004 by MPEG and published as part of MPEG-4 in document ISO/IEC 14496-3, Amd.2:2004 The progenitor of HE-AAC was developed by Coding Technologies under the trade name CT-aacPlus. CT-aacPlus combined MPEG-2 AAC LC with the Coding Technologies invented Spectral Band Replication (SBR). CT-aacPlus is the codec used by XM Radio for their satellite radio service. Subsequently, Coding Technologies submitted their SBR to MPEG as a basis of HE-AAC. Later, but prior to the standardization of HE AAC v2 by MPEG, Coding Technologies submitted the combination of HE-AAC v1 coupled with Parametric Stereo to 3GPP under the name Enhanced AAC+. As a result, aacPlus, aacPlus v2, AAC+, and EAAC+ are now common trade names which refer to the versions of HE-AAC. PERCEIVED QUALITY Scientific testing by the in the same testing received a score less than half that of HE-AAC and was ranked "Poor" using the MUSHRA scale. Data from this testing also indicated that some individuals confused 48 kb/s Encoded material with an Uncompressed original. Other testing indicates that material decoded from 64 kb/s HE-AAC does not have similar audio quality to material decoded from MP3 at 128 kb/shttp://www.rjamorim.com/test/64test/results.html. However, this testing was conducted in an uncontrolled manner and cannot be deemed conclusive. Further controlled testing by 3GPP during their revision 6 specification process indicates that HE-AAC and its derivative MPEG-4 HE-AAC v2 provide "Good" audio quality for music at low bit rates (e.g. 24 kb/s). MPEG-2 and MPEG-4 AAC LC decoders without SBR support will decode the AAC LC part of the audio, resulting in audio output with ony half the sampling frequency, thereby reducing the audio bandwidth. No known tests have been conducted which compare the audio quality of such decoded material. HE-AAC today competes only with Microsoft 's low-bitrate WMA Professional codec. and SUPPORT HE-AAC is supported in the Open Source FAAD/FAAD2 decoding library (and all players incorporating it), Winamp , Foobar2000 , and Sony's latest SonicStage version 4. HE-AAC is also used by AOL Radio clients to deliver high-fidelity music at low bitrates. As of 2007, neither ITunes , nor IPod supports HE-AAC. Only MPEG 2 AAC (MPEG 2 Audio - part 3) is supported so the only players for Mac OS X are VLC (without metadata/title streaming) and Songbird . Nero has released a free of charge command line HE-AAC encoder, and also support HE-AAC inside the Nero software suite. Sorenson Media ’s Squeeze Compression Suite includes an HE-AACv2 encoder and is available for Mac OS X as well as Windows . The encoder is available yet. PROMOTION ASPECTS Commercial trademarks and labeling HE-AAC is marketed under the trademark aacPlus(tm) by Coding Technologies and under the trademark Nero Digital(tm) by Nero AG. Nokia and Samsung use AAC+ to label support for HE AAC v1 and eAAC+ to label support for HE-AAC v2 on their phones. Motorola uses AAC+ to indicate HE AAC v1 and "AAC+ Enhanced" to indicate HE AAC v2. Licensing and patents Companies holding patents for HE AAC v1http://www.vialicensing.com/Licensing/MPEG4_licensors.html have formed a patent pool under Via Licensing to provide a single point of license for product makers. Patents owned by Coding Technologies and Philips covering the Parametric Stereo used in HE AAC v2 are not included in the Via Licensing pool and are licensed separately by Coding Technologies.http://www.codingtechnologies.com/licensing/aacplus.htm Patent licenses are required for end-product companies making hardware or software products which include HE AAC encoders and/or decoders.http://www.vialicensing.com/Licensing/MPEG4_FAQ.cfm?product=MPEG-4HEAACP Unlike the MP3 format 1, content owners are not required to pay license fees to distribute content in HE AAC. STANDARDS HE-AAC was first standardized in ISO/IEC 14496-3:2001/Amd.1. HE-AAC v2 (AAC with Parametric Stereo) was first specified in ISO/IEC 14496-3:2001/Amd.4. http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf The current version of the HE-AAC standard is ISO/IEC 14496-3:2005 (with 14496-3:2005/Amd.2. for HE-AAC v2ISO/IEC 14496-3:2005/Amd.2 {Link without Title} ) AacPlus v2 by Codingtechnologies is also standardized by ETSI ( European Telecommunications Standards Institute ) as TS 102005 for Satellite services to Handheld devices (DVB-SH) below 3 GHz. SEE ALSO REFERENCES EXTERNAL LINKS
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