The Dreamcast is capable of matrixed multi-channel surround sound. This is achieved by piggybacking an inverted-phase signal across both left and right audio channels. Under normal stereo configuration circumstances, this results in standard stereo audio. But if the signal is sent to a device (such as a home theater receiver or dedicated outboard surround decoder) capable of decoding matrixed surround, a true multi-channel surround sound experience is achieved. There are the standard stereo left and right signals, but compatible games will be sending a limited-bandwidth inverted-phase signal across each of the two stereo RCA cables, that are decoded by the appropriate device into a Center and a Rear channel as well! This is how Dolby Surround works, and it's the same as the way it works on VHS and some LaserDiscs as well as some early DVDs and other 1990s game consoles. Unfortunately, very few official Dreamcast titles shipped with surround sound, and it was mostly limited to a handful of Sega's first party sports games. Some modern AV Receivers are quietly dropping compatibility with older surround formats, but others are holding strong. It is recommended to research the surround format capabilities of a given receiver before purchasing new.