The MPEG Surround standard describes a highly efficient method of transmitting surround sound through bandwidth limited channels. Rather than coding all of the channels in a multi-channel audio signal, MPEG Surround utilizes parametric descriptions of key signal characteristics in order to deliver multi-channel audio at only slightly higher bit-rates than stereo.
MPEG Surround offers three distinct modes of operation, all of which are compatible with a stereo-only decoder for playback over legacy hardware. This makes MPEG Surround the perfect vehicle to introduce multi-channel audio into existing stereo formats or distribution services. In each of the three modes a multi-channel signal is represented as a downmix signal (either algorithmically or artistically produced) with a set of parameters describing the spatial characteristics. A multi-channel rendering is then produced by an MPEG Surround decoder utilizing one of the three operating modes: discrete multi-channel output (e.g. 5.1), a matrix compatible downmix for use with existing matrix surround systems, or a binaural mode which produces an effective impression of surround sound over standard stereo headphones.
In combination with MPEG-4 HE AAC, high quality surround sound can be achieved at bit-rates of 64 kbps, or lower.
MPEG Surround operates independently of the underlying audio codec and can be used with, for example, AAC, HE AAC (aacPlus) Layer-2, or even PCM.
Additional information about MPEG Surround is available at www.mpegsurround.com. A copy of the standard (ISO/IEC 23003-1) as well as the MPEG reference software can be obtained from the at ISO online store (search for 23003-1).