6.1 Introduction

Approximately half a century after the introduction of two-channel stereophony, multi-channel sound is now on its way into consumers homes as the next step toward more realistic audio reproduction. Initially, multi-channel audio was predominantly present in the movie domain on consumer media (DVD for example). The widespread availability of movie material with multi-channel sound tracks led to a fast penetration of multi-channel playback devices in consumers homes. Recently, probably in part due to the increased popularity of multi-channel movie material, the demand for a compelling surround experience has extended to the audio-only market as well (such as SACD and DVD-audio).

In contrast, the traditional broadcast services (such as radio and television) are still operating in stereo mode due to bandwidth and compatibility constraints. In audio transmission systems, the required bandwidth (or amount of information) of a six-channel broadcast would require approximately three times as much bandwidth as a conventional stereo broadcast. In many cases, this increased amount of information is undesirable or unavailable. Even if the increased bandwidth were available, the upgrade process of a stereo service to multi-channel audio should ensure that existing stereo receivers will still operate as before. With the existing technology, this means an even larger increase in bandwidth for simulcast of stereo and multi-channel audio.

In this chapter, the recently finalized ISO/MPEG standard, ‘MPEG Surround’, is outlined. Given the complexity and the large variety of features of this standard, the focus is on describing the basic processing stages and their relations, rather than giving a detailed system description.

The MPEG Surround standard emerged from activities of the MPEG Audio standardization group. In March 2004, MPEG issued a call for proposals (CfP) requesting for technology in the field of spatial audio coding [142]. In response to this CfP various companies responded with a total of four submissions. The subjective evaluation of these submissions was concluded in October 2004. The test results revealed that there were two out of the four submissions that showed complementary performance. The proponents of both systems decided to cooperate and define a single system, to combine the best of both propositions. Beginning 2005, this resulted in Reference Model 0 (RM0), the starting point for the collaborative phase within the MPEG Audio group. Numerous core experiments have been conducted by various companies in order to improve and extend the MPEG Surround system, including a low-complexity mode and a dedicated binaural decoding mode to simulate a virtual multi-channel loudspeaker setup over stereo headphones. The standard specification of MPEG Surround [138] was finalized in July 2006.