Xbox:Audio Information

Surround Sound
The Xbox is the first home video game console natively capable of discrete Dolby Digital 5.1 surround sound, which consists of five separate channels of audio, and an additional sixth, or ".1" channel of low frequencies that are routed to a subwoofer. Unlike Pro Logic II, Dolby Digital is a fully digital signal with separate channels of audio for each speaker, with no need to piggyback limited-bandwidth signals across stereo channels. Most Xbox games take advantage of Dolby Digital surround, though to take advantage of it, the user needs the correct AV output method for the console, as it does not have a built-in optical audio port like the PS2 does. Things like the official Xbox HD AV Pack, the official Xbox Advanced AV Pack or the Monster-brand composite, S-Video, or component cables with accompanying SPDIF adapter include a TOSLINK port for optical audio. Those were common solutions for a long time, but more recently such projects as the Xbox HDMI mod and the Chimeric Systems Xbox HDMI converter pass the Xbox's native Dolby Digital audio signal alongside the video signal via HDMI, which is especially helpful for modern home theater configurations.

The Xbox will output digital audio regardless of which video mode the A/V cable is set to, but it will only output Surround, Dolby Digital 5.1 or DTS if the cable is set to Advanced AV Pack or HD AV Pack video mode.