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g.722
This is a well known 7KHz (medium fidelity) algorithm used in some VOIP telephones and codecs. It is provided for
compatibility purposes, but is not considered a superior algorithm for audio codecs.
AAC
This algorithm is a highly regarded standard for compressing audio to critical listening standards. It has been judged to
produce “near transparent” audio at a coding rate of 128 kbps stereo. The standard is a collaborative of several audio
companies best efforts, and has become popular as the default audio codec of the Apple™ iTunes™ program.
AAC
should be considered the highest quality codec in NX - Enhancements like HE-AAC and AAC-ELD attempt to maintain a
similar quality and reduced bandwidth and delay.
hE-AAC
This is a newer version of AAC defined for increased efficiency. The goal of the algorithm is to produce AAC comparable
quality at a lower bit rate. It does this by encoding lower frequencies to AAC, and higher frequencies using Spectral
Band Replication (SBR), a technique that partially synthesizes these high frequencies. HE-AAC is trademarked by other
companies as AACPlus™. HE-AAC (and close derivatives) are often used as the main audio codec for digital radio and
satellite networks.
hE-AACV2
This algorithm further increases the efficiency of HE-AAC by adding intensity stereo coding. This results in a lower bit rate
for stereo signals. We also cluster a very reduced rate HE-AAC mono into this category, although technically it does not
contain v2 coding.
AAC-ld
This algorithm is an extension of AAC developed by the FhG IIS, who are the contributors to AAC and primary inventors of
the MP3 algorithm. It’s quality is superior to MP3 at similar bitrates (64-128 kbps) but it exhibits very low delay (100mS).
This choice is best when reasonable network throughput is assured, near-transparent audio is required and interactivity
is needed.
AAC-Eld
This latest algorithm is a combination of the LD and HE-AAC variants. It provides the network conserving benefits of SBR
along with the dramatically reduced delay time of LD. For low delay applications, it’s usually the best choice.
