Two - to - Five Channel Sound Processing *

Since the introduction of the digital versatile disk (DVD) and the super audio CD (SACD), a revival of mul-tichannel audio has appeared in sound systems for consumer use today. It is, however, desirable to maintain compatibility with the existing two-channel stereo recordings and/or broadcasting. Therefore the conversion of two-channel stereo to the multichannel format has been studied extensively over the decades, and a considerable number of publications exist [1]–[8]. Among these, Gerzon and Barton's is particularly notable, in which many schemes have been proposed (see [6] and references therein). Although many authors have introduced multichannel sound systems with a large number of channels, we restrict ourselves to a home cinema setup for which it has been shown that five channels is sufficient for creating ambience effects [9]. Hence in this paper we focus on signal format conversion from two-channel stereo to the five-channel (two-to-five) sound processing algorithm. The desired setup is shown in Fig. 1, in which the channels are labeled L (left), C (center), R (right), S L (left surround), and S R (right surround) according to convention. This setting is adopted from the ITU multichannel configuration [10], with three loudspeakers placed in front of the listener, and the other two at the back. The front channels are used to provide a high degree of directional accuracy over a wide listening area for front-stage sounds, particularly dialogues, and the rear channels produce diffuse surround sounds, providing ambience and environment affects. An additional loudspeaker (sub-woofer) may be used to augment bass reproduction, which is often called 5.1 system, with .1 referring to the low-frequency enhancement (LFE) channel. In this paper, however, we do not use a subwoofer, since the system can easily be extended when necessary without affecting the algorithm. The algorithm presented in this paper offers two improvements above the existing two-to-five channel sound systems. First a problem associated with channel crosstalk is reduced, and therefore sound localization is better. Listening tests have confirmed that good sound localization without the need to listen at the sweet spot gives more space to the listener to enjoy the program offered rather than restricting the listener to the sweet spot. Second a better sound distribution to the surround channels is achieved by using a cross-correlation technique. Surround channels are crucial in creating the ambience effects, which is one of the main goals of multichannel audio. At the same time, the energy preservation …