Intel High Definition Audio (also called HD Audio or Azalia) refers to the specification released by Intel in 2004[1] for delivering high-definition audio that is capable of playing back more channels at higher quality than previous integrated audio codecs like AC'97. During development it had the codename Azalia.
Hardware based on Intel HD Audio specifications is capable of delivering 192-kHz 32-bit quality for two channels, and 96-kHz 32-bit for up to eight channels. However, as of 2008[update], most audio hardware manufacturers do not implement the full high-end specification, especially 32-bit sampling resolution.
Microsoft Windows XP SP3 and later Windows versions[2] include a Universal Audio Architecture (UAA) class driver which supports audio devices built to the HD Audio specification. There are UAA drivers for Windows 2000 and Windows XP SP2 as well. Mac OS X has full support with its AppleHDA driver. Linux also supports Intel HDA controllers, as do the OpenSolaris,[3] FreeBSD,[4] NetBSD and OpenBSD[5] operating systems.
Like AC'97, HD Audio is a specification that defines the architecture, link frame format, and programming interfaces used by the controller on the PCI bus and by the codec on the other side of the link. Implementations of the host controller are available from at least Intel, Nvidia, and AMD.[6] Codecs which can be used with such controllers are available from many companies, including Realtek,[7] Conexant, Analog Devices (SoundMAX),[8] Integrated Device Technology (IDT) (acquired from SigmaTel), VIA, Wolfson Microelectronics, and formerly C-Media.
Computer motherboards often provide a connector to bring microphone and headphone signals to the computer's front panel. Intel provides a specification for that header; the signal assignments are different for AC'97 and HD Audio headers.[9]
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