HD Audio, or Intel High Definition Audio, is an audio specification which describes an audio signal with more channels at greater quality than established audio codecs such as AC'97. Released by Intel in 2004, the codename of the project was Azalia. Hardware compliant with Intel HD Audio specifications is able to produce 192 kHz/32-bit quality for a two channel signal, and for up to eight channels it can deliver 96 kHz/32-bit quality. The operating system of a computer must include drivers for audio devices built to the HD Audio specifications. Microsoft's Windows Vista and service pack three of Windows XP have a Universal Audio Architecture (UAA) class driver to accommodate HD Audio. Linux, Mac OS X, among other also support Intel HD Audio controllers. HD Audio also allows the user to play two unique audio streams through a PC at the same time, providing the option to listen to two separate audio signals at the same time.