Intel High Definition Audio (IHDA) (also called HD Audio or development codename Azalia) is a specification for the audio sub-system of

personal computer A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...

s. It was released by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

in 2004 as the successor to their

AC'97 AC'97 (''Audio Codec '97;'' also MC'97 for ''Modem Codec '97'') is an audio codec standard developed by Intel Architecture Labs and various codec manufacturers in 1997. The standard was used in motherboards, modems, and sound cards. The specif ...

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

standard, but it is not

backwards-compatible In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with Input ...

with it.

Features

The Intel High Definition Audio specification includes the following features: * Up to 15 input and 15

output Output may refer to: * The information produced by a computer, see Input/output * An output state of a system, see state (computer science) * Output (economics), the amount of goods and services produced ** Gross output in economics, the valu ...

streams * Up to 16

PCM Pulse-code modulation (PCM) is a method used to Digital signal (signal processing), digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio application ...

audio channels per stream * Sample resolutions of 8–32 bits * Sample rates of 6–192 kHz * Support for audio

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

s (e.g., ADC, DAC),

modem The Democratic Movement (, ; MoDem ) is a centre to centre-right political party in France, whose main ideological trends are liberalism and Christian democracy, and that is characterised by a strong pro-Europeanist stance. MoDem was establis ...

codecs, and vendor-offered codecs * Discoverable codec architecture * Fine-grained codec power-control * Audio jack detection, sensing, and retasking * Vendor-offered (OEM or IHV) audio enhancement features

Motherboard A motherboard, also called a mainboard, a system board, a logic board, and informally a mobo (see #Nomenclature, "Nomenclature" section), is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It ho ...

s typically do not have any more than eight built-in output channels (7.1 surround sound) and four input channels (back and front panel microphone inputs, and a back-panel stereo line-in). Users requiring more audio I/Os will typically opt for a

sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio ...

or an external audio interface, as these provide additional features that are more oriented towards professional audio applications.

Operating system support

The Service Pack 3 update to

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

and all later versions of Windows (from Vista onwards) included the Universal Audio Architecture (UAA) class driver, which supported audio devices built to HD Audio's specifications. Retrospective UAA drivers were also built for

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...

, Server 2003 and XP Service Pack 1/2.

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

provides support for Intel HD Audio with its AppleHDA driver. Several

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s also support HD Audio, as well as

OpenSolaris OpenSolaris () is a discontinued open-source computer operating system for SPARC and x86 based systems, created by Sun Microsystems and based on Solaris. Its development began in the mid 2000s and ended in 2010. OpenSolaris was developed as ...

FreeBSD FreeBSD is a free-software Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version was released in 1993 developed from 386BSD, one of the first fully functional and free Unix clones on affordable ...

, and

OpenBSD OpenBSD is a security-focused operating system, security-focused, free software, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by fork (software development), forking NetBSD ...

. In

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

, vendor-offered audio enhancement features usually required vendor drivers.

Host controller

Like AC'97, HD Audio acts as a device driver, defining the

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...

, link frame format, and

programming interface An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build su ...

s used in the hardware of the

host controller In computer hardware a host controller, host adapter or host bus adapter (HBA) connects a computer system bus which acts as the host system to other computer network, network and computer storage, storage devices. The terms are primarily used ...

of the

PCI bus PCI may refer to: Business and economics * Payment card industry, businesses associated with debit, credit, and other payment cards ** Payment Card Industry Data Security Standard, a set of security requirements for credit card processors * Pro ...

and linking it to a codec used by a computer's software. Configurations of the host controller (Chipset) are available from third-party suppliers, including

Nvidia Nvidia Corporation ( ) is an American multinational corporation and technology company headquartered in Santa Clara, California, and incorporated in Delaware. Founded in 1993 by Jensen Huang (president and CEO), Chris Malachowsky, and Curti ...

, VIA and

AMD Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...

, while codecs have also been provided by third-party suppliers including

Realtek Realtek Semiconductor Corp. () is a Taiwanese fabless semiconductor company situated in the Hsinchu Science Park, Hsinchu, Taiwan. Realtek was founded in October 1987 and subsequently listed on the Taiwan Stock Exchange in 1998. Realtek has manu ...

, Conexant, IDT, VIA, SigmaTel,

Analog Devices Analog Devices, Inc. (ADI), also known simply as Analog, is an American multinational corporation, multinational semiconductor company specializing in data conversion, signal processing, and power management technology, headquartered in Wilming ...

, C-Media and Cirrus Logic. AMD's TRX40 chipset was introduced in 2019 for use with

Ryzen Ryzen ( ) is a brand of multi-core x86-64 microprocessors, designed and marketed by AMD for desktop, mobile, server, and embedded platforms, based on the Zen microarchitecture. It consists of central processing units (CPUs) marketed for mai ...

"Threadripper" CPUs, which provided the Realtek ALC1220 chip instead of the HD Audio interface. As a result, a separate USB or

PCIe PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe, is a high-speed standard used to connect hardware components inside computers. It is designed to replace older expansion bus standards such as Peripher ...

audio device was required to integrate HD audio codecs on TRX40 motherboards. This was a temporary measure until a new Audio bus was developed AMD named Audio CoProcessor (ACPBus). Intel has also decoupled the audio controller from its chipsets in favor of Intel Smart Sound Technology (SST) or I²S instead of the more traditional HD Audio Bus. A HD Audio controller can include vendor-offered audio enhancement features known as Audio Processing Objects (APOs), offered by companies like

Dolby Dolby Laboratories, Inc. (Dolby Labs or simply Dolby) is a British-American technology corporation specializing in audio noise reduction, audio encoding/compression, spatial audio, and high-dynamic-range television (HDR) imaging. Dolby li ...

, Creative, Fortemedia and

Waves Audio Waves Audio Ltd. is an Israeli developer and supplier of professional digital audio signal processing technologies and audio effects, used in recording, mixing, mastering, post production, broadcast, and live sound. The company's corporate headq ...

, they can be software-based and driver-based.

Limitations

As with the previous AC'97 standard, HD Audio does not specify handlers for the media buttons attached to headphone jacks (i.e., Play/Pause, Next, Previous, Volume up, Volume down).

Front panel connector

Computer motherboards often provide a connector to bring microphone and headphone signals to the computer's

front panel A front panel was used on early electronic computers to display and allow the alteration of the state of the machine's internal CPU register, registers and computer memory, memory. The front panel usually consisted of arrays of electric light, ...

. Intel provides a general specification for this process, but the signal assignments are different for both AC'97 and HD Audio headers. The pin assignments for the AC'97 and HD Audio connectors are: The HD Audio 3.5 mm subminiature audio jack differed from connectors used in the AC'97 specification and in general audio equipment. The AC'97 used a regular 3.5 mm audio jack, which typically has 5 pins: one pin for ground, two pins for stereo signal, and two pins for the return signal. When no plug is connected, the two stereo signals are connected to their return pins. When a plug is inserted, the stereo signals contact the respective channels on the plug and are disconnected from the jack's return pins. The HD Audio 3.5 mm jack does not have the two return audio signals; instead, it has an isolated switch that senses the presence of a plug in the jack. In the AC'97 design, the audio output is sent to the jack by default. When a headphone is detected, the return signal pins for the speakers are disconnected, directing the audio to the headphone. The jack redirects the audio to the speakers if no headphone connection is detected. Similarly, the return pins ground the microphone jack connection if no microphone detected. As a result, most motherboards with AC'97 audio require two jumpers to short these pins if no front panel audio module is connected, so audio passes to the speakers. In the HD Audio design, the codec sends the audio directly to the speakers if a plug is not inserted. When a plug is inserted, the isolated switch inside the jack informs the motherboard, and the codec sends audio to the headphones. A similar isolated switch is used to detect when a microphone has been plugged in. HD Audio can also sense the presence of an audio

dongle A dongle is a small piece of computer hardware that connects to a port on another device to provide it with additional functionality, or enable a pass-through to such a device that adds functionality. In computing, the term was initially synony ...

. A 10 kΩ pull-up resistor is attached to pin 4 (). When the HDA dongle is plugged in, it pulls pin 4 to the ground with a 1 kΩ resistor. The motherboard can determine if a dongle is connected by examining the logic level on pin 4. If the motherboard does not detect a HDA dongle, it should ignore the (pin 6) and (pin 10) signals. Intel warns that HDA dongles should be used with HDA motherboards: The different signal assignments can cause trouble when AC'97 front-panel dongles are used with HDA motherboards and vice versa. An AC'97 dongle returns audio on pins 6 and 10 rather than digital plug sensing signals. Consequently, a loud audio passage may cause a HDA motherboard with a AC'97 dongle believe headphones and microphones are being plugged and unplugged hundreds of times per second. An AC'97 motherboard with an HDA dongle will route the AC'97 5 V audio supply (pin 7; silence) to the speakers instead of the desired left and right audio signals. To avoid this, some motherboards allow choosing between HDA and AC'97 front panels in the BIOS. Even though the actual audio hardware is HD Audio, the BIOS can be manipulated to allow the use of an AC'97 front panel. Likewise, some modern enclosures have both an "AC'97" and an "HDA" plug at the end of the front-panel audio cable.

References

External links

* https://web.archive.org/web/20121202194339/http://www.intel.com/design/chipsets/hdaudio.htm * https://web.archive.org/web/20110310072114/http://www.intel.com/standards/hdaudio
High Definition Audio Specification
1.0a (June 17, 2010)

{{PC sound standards Computer hardware standards High Definition Audio Sound cards