View source for Intel High Definition Audio

{{Short description|Specification for the audio sub-system of personal computers}}
{{for|the marketing term HD audio|High-resolution audio}}
[[File:Realtek ALC882 HDAudio codec.jpg|thumb|Realtek ALC 882 HD Audio Codec]]
'''Intel High Definition Audio (IHDA)''' (also called '''HD Audio''' or development codename '''Azalia''') is a specification for the audio sub-system of [[personal computer]]s. It was released by [[Intel]] in 2004 as the successor to their [[AC'97]] PC [[sound reproduction|audio]] standard,<ref name=reg1>{{cite web|last=Smith|first=Tony|url=https://www.theregister.co.uk/2004/04/16/intel_hd_audio/|title=Intel completes hi-def audio spec|work=[[The Register]]|date=16 April 2004|access-date=14 January 2014}}</ref> but it is not [[Backward compatibility|backwards-compatible]] with it.<ref>{{Citation|publisher=Intel Corporation|year=2010|chapter-url=http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/high-definition-audio-specification.pdf|title=High Definition Audio Specification|version=Revision 1.0a|page=17|chapter=1.2.1 AC'97 Compatibility}}</ref>

==Features==
The Intel High Definition Audio specification includes the following features:<ref name=spec>{{cite web|title=High Definition Audio Specification 1.0a|url=http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/high-definition-audio-specification.pdf|publisher=Intel Corporation|page=17|year=2010}}</ref>

* Up to 15 [[Input device|input]] and 15 [[Output device|output]] streams
* Up to 16 [[PCM]] audio channels per stream
* [[Sampling_(signal_processing)#Bit_depth|Sample resolutions]] of 8–32 bits
* [[Sampling (signal processing)#Sampling rate|Sample rates]] of 6–192&nbsp;kHz
* Support for audio [[codec]]s (e.g., [[Analog-to-digital converter|ADC]], [[Digital-to-analog converter|DAC]]), [[modem]] 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]]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/O]]s will typically opt for a [[sound card]] or an external [[Digital audio#Interfaces|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]] and all later versions of Windows (from [[Windows Vista|Vista]] onwards) included the [[Universal Audio Architecture]] (UAA) class [[Device driver|driver]], which supported audio devices built to HD Audio's specifications. Retrospective UAA drivers were also built for [[Windows 2000]], Server 2003 and XP Service Pack 1/2.<ref>{{cite web|url=http://support.microsoft.com/kb/888111|title=Universal Audio Architecture (UAA) High Definition Audio class driver version 1.0a available for Windows XP, Windows Server 2003, and Windows 2000|work=[[Microsoft]]|access-date=September 19, 2022}}</ref> [[macOS]] provides support for Intel HD Audio with its AppleHDA driver. Several [[Linux]] [[operating system]]s also support HD Audio, as well as [[OpenSolaris]],<ref>{{cite web|url=http://www.opensolaris.org/os/project/opensound/|title=Open Sound System at OpenSolaris.org|publisher=[[OpenSolaris]]|access-date=September 19, 2022|url-status=dead|archive-url=https://web.archive.org/web/20080426054635/http://www.opensolaris.org/os/project/opensound/|archive-date=April 26, 2008}}</ref> [[FreeBSD]],<ref>{{cite web|url=http://man.freebsd.org/snd_hda|title=Intel High Definition Audio bridge device driver|publisher=[[FreeBSD]]|date=January 25, 2012|access-date=September 19, 2022}}</ref> and [[OpenBSD]].<ref>{{cite web|url=https://man.openbsd.org/azalia.4|title=Azalia — Generic High Definition Audio device|publisher=[[OpenBSD]]|date=March 15, 2012|access-date=September 19, 2022}}</ref> In [[Microsoft Windows]], vendor-offered audio enhancement features usually required vendor drivers.

==Host controller==
Like AC'97, HD Audio acts as a device driver, defining the [[Software architecture|architecture]], [[Data link layer|link frame format]], and [[API|programming interface]]s used in the hardware of the [[Host adapter|host controller]] of the [[Conventional PCI|PCI bus]] and linking it to a codec used by a computer's software.<ref name="AMD">{{cite web|url=https://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_14603_14620,00.html|title=AMD SB600 Product Information Page|work=[[Advanced Micro Devices]]|access-date=September 19, 2022}}</ref> Configurations of the host controller (Chipset) are available from third-party suppliers, including [[Nvidia]], [[VIA Technologies|VIA]] and [[Advanced Micro Devices|AMD]],<ref name="AMD"/> while codecs have also been provided by third-party suppliers including [[Realtek]], [[Conexant]], [[Integrated Device Technology|IDT]], [[VIA Technologies|VIA]], [[SigmaTel]], [[Analog Devices]], [[C-Media]] and [[Cirrus Logic]].<ref>{{cite web|url=http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=28&Level=5&Conn=4&ProdID=135|title=ALC888 {{!}} 7.1+2 Channel High Definition Audio Codec|publisher=[[Realtek]]|access-date=September 22, 2022|archive-url=https://web.archive.org/web/20070425212211/http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=28&Level=5&Conn=4&ProdID=135|archive-date=April 25, 2007|url-status=dead}}</ref><ref>{{cite web|url=http://www.conexant.com/Product/Audio/pchdaudio/Pages/default.aspx|title=Conexant - PC HD-Audio|publisher=[[Conexant]]|access-date=September 22, 2022|archive-url=https://web.archive.org/web/20130819015410/http://www.conexant.com/Product/Audio/pchdaudio/Pages/default.aspx|archive-date=August 19, 2013|url-status=dead}}</ref> AMD's [[TRX40]] chipset was introduced in 2019 for use with [[Ryzen]] "Threadripper" [[Central processing unit|CPU]]s, which provided the Realtek ALC1220 chip instead of the HD Audio interface. As a result, a separate USB or [[PCIe]] 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).<ref>{{cite web|last=Bonshor|first=Gavin|url=https://www.anandtech.com/show/15121/the-amd-trx40-motherboard-overview-|title=The AMD TRX40 Motherboard Overview: 12 New Motherboards Analyzed|work=[[AnandTech]]|date=November 28, 2019|access-date=September 22, 2022}}</ref> 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]], [[Creative Technology|Creative]], [[Fortemedia]], [[SteelSeries|Nahimic]], [[Digital Theater Systems|DTS]] and [[Waves Audio]], 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 [[Phone connector (audio)|jack]]s (i.e., Play/Pause, Next, Previous, Volume up, Volume down).{{citation needed|date=September 2022}}

==Front panel connector==
Computer motherboards often provide a connector to bring microphone and headphone signals to the computer's [[front panel]]. Intel provides a general specification for this process, but the signal assignments are different for both AC'97 and HD Audio headers.<ref name="Intel FP">{{Citation |last=Intel Corporation |url=http://www.formfactors.org/developer/specs/A2928604-005.pdf |title=Front Panel I/O Connectivity Design Guide |date=February 2005 |version=Version 1.3 |pages=19&ndash;25 |access-date=2011-11-04 |archive-url=https://web.archive.org/web/20110511144045/http://www.formfactors.org/developer/specs/A2928604-005.pdf |archive-date=2011-05-11 |url-status=dead }}</ref>

The pin assignments for the AC'97 and HD Audio connectors are:<ref name="Intel FP"/>{{rp|21,22}}
{| class="wikitable"
|-
! rowspan=2 | Pin
! colspan=2 | AC'97
! colspan=2 | HD Audio (HDA)
|-
! Signal
! Description
! Signal
! Description
|-
| 1 || MIC || {{unbulleted list
 | Audio, mono, in (mic. level)
 | Audio, left, in (biased, mic.level)
}}
| PORT 1L || Audio, left, port 1
|-
| 2 || AUD_GND || Ground
| GND || Ground
|-
| 3 || MIC BIAS || {{unbulleted list
 | Microphone bias
 | Audio, right, in (biased, mic. level)
}}
| PORT 1R || Audio, right, port 1
|-
| 4 || AUD_GND || Ground
| PRESENCE# || HDA dongle/connector detection, active low
|-
| 5 || FP_OUT_R || Audio out, right, out (headphone-level capable), front panel
| PORT 2R || Audio, right, port 2
|-
| 6 || FP_RETURN_R || Audio, right, return (when jack is unconnected), front panel
| SENSE1_RETURN || Port 1 jack detection
|-
| 7 || AUD_5V || Power, +5&nbsp;V
| SENSE_SEND || Jack detection sense, resistance multiplexed
|-
| 8 || KEY || {{n/a|Not present, physical key}}
| KEY || {{n/a|Not present, physical key}}
|-
| 9 || FP_OUT_L || Audio, left, out (headphone-level capable), front panel
| PORT 2L || Audio, left, port 2
|-
| 10 || FP_RETURN_L || Audio, left, return (when jack is unconnected), front panel
| SENSE2_RETURN || Port 2 jack detection
|}

The HD Audio 3.5&nbsp;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&nbsp;mm audio jack, which typically has 5 pins: one pin for ground, two pins for stereo signal, and two pins for the return signal.<ref name="Intel FP"/>{{rp|20}} 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&nbsp;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.<ref name="Intel FP"/>{{rp|25}}

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 [[Jumper (computing)|jumper]]s to short these pins if no front panel audio module is connected, so audio passes to the speakers.<ref name="Intel FP"/>{{rp|21}}

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 10&nbsp;kΩ pull-up resistor is attached to pin 4 ({{mono|PRESENCE#}}). When the HDA dongle is plugged in, it pulls pin 4 to the ground with a 1&nbsp;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 {{mono|SENSE1_RETURN}} (pin 6) and {{mono|SENSE2_RETURN}} (pin 10) signals.<ref name="Intel FP"/>{{rp|24}}

Intel warns that HDA dongles should be used with HDA motherboards:<ref name="Intel FP"/>{{rp|19}}
{{blockquote |It is strongly recommended that motherboard designers only use Intel HD Audio analog front panel dongles with the Intel HD Audio analog front panel header to ensure that the jack detection and dynamic retasking capability are preserved.  Passive AC'97 analog front panel dongles (ones that leave the 5V Analog pin-7 line unconnected on the dongle) may be used with the Intel HD Audio analog front panel header.  But note that the front panel jack detection and re-tasking functionality will be lost as the AC'97 jacks cannot support connection to the SENSE line.  In addition, software must be aware that an AC'97 dongle is being used with an Intel HD Audio analog header since the software might need to dedicate codec ports that are connected to the header to meet the product's intended functionality.}}

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&nbsp;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.{{citation needed|date=September 2022}}

==See also==
* [[Sound chip]]

==References==
{{reflist|30em}}

==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
*[http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/high-definition-audio-specification.pdf High Definition Audio Specification] 1.0a (June 17, 2010)
*[http://www.intel.com/support/motherboards/desktop/sb/CS-015851.htm Motherboard/Sound-cards connectors pinout specifications]
*[http://www.intel.com/intelpress/sum_haud.htm Developer Education Resource: High Definition Audio for the Digital Home]

{{Computer bus}}
{{High-definition}}
{{Intel technology}}
{{PC sound standards}}

[[Category:Computer hardware standards]]
[[Category:Intel products|High Definition Audio]]
[[Category:Sound cards]]