Itunes, Mpeg surround, 1 itunes – Sonnox Fraunhofer Pro-Codec User Manual
Page 9: 2 mpeg surround

4.1 iTunes+
4 SUMMARY OF CODEC FEATURES AND APPLICATIONS
4.1 AppleAAC –iTunesPlus(MasteredforiTunes)(Maconly)
The addition of this Apple AAC codec allows real-time audition of files produced under
the Mastered for iTunes initiative that are destined for the iTunes store.
This codec is available for Mac computers only. It uses the same Apple codecs and
resamplers that are used for the current iTunes Catalogue. It very specifically resamples
to 44.1 kHz if necessary, and encodes as AAC-LC, 256 kbps, variable bit rate and highest
quality, which are the settings used for the iTunes catalogue. For online audition, the
signal is then resampled back to the host DAW sample rate if necessary.
This option is available only for stereo configuration. There are no options to change the
Apple codec settings because this would not be representative of the iTunes Plus
standard. The Apple codecs and re-samplers are components of the Mac OSX operating
system, so can be upgraded during an OSX update.
Note:
On Windows computers, the closest approximation to the iTunes Plus codec is the
Fraunhofer AAC-LC codec set to highest quality VBR at 256 kbps.
4.2 MPEG Surround(Fraunhofer)
MPEG Surround is a feature-rich open standard compression technique for multi-channel
audio signals. Operating on top of any core audio codec — including AAC, HE-AAC and
MPEG Layer 2 – the system provides a comprehensive feature set, including highest
surround and stereo audio quality, multi-channel support at stereo bit rates and virtualised
binaural multi-channel sound reproduction capability for stereo headphones.