Specification for the audio sub-system of personal computers
Intel High Definition Audio (IHDA)
(also called
HD Audio
or development codename
Azalia
) is a specification for the audio sub-system of
personal computers
. It was released by
Intel
in 2004 as the successor to their
AC'97
PC
audio
standard.
[1]
Features
[
edit
]
The Intel High Definition Audio specification includes the following features:
[2]
Motherboards
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
or an external
audio interface
, as these provide additional features that are more oriented towards professional audio applications.
Operating system support
[
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]
The
Service Pack 3
update to
Windows XP
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
, Server 2003 and XP Service Pack 1/2.
[3]
macOS
provides support for Intel HD Audio with its AppleHDA driver. Several
Linux
operating systems
also support HD Audio, as well as
OpenSolaris
,
[4]
FreeBSD
,
[5]
and
OpenBSD
.
[6]
Host controller
[
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]
Like AC'97, HD Audio acts as a device driver, defining the
architecture
,
link frame format
, and
programming interfaces
used in the hardware of the
host controller
of the
PCI bus
and linking it to a codec used by a computer's software.
[7]
Configurations of the host controller (Chipset) are available from third-party suppliers, including
Nvidia
,
VIA
and
AMD
,
[7]
while codecs have also been provided by third-party suppliers including
Realtek
,
Conexant
,
IDT
,
VIA
,
SigmaTel
,
Analog Devices
,
C-Media
and
Cirrus Logic
.
[8]
[9]
AMD's
TRX40
chipset was introduced in 2019 for use with
Ryzen
"Threadripper"
CPUs
, 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.
[10]
Limitations
[
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]
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).
[
citation needed
]
Front panel connector
[
edit
]
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.
[11]
The pin assignments for the AC'97 and HD Audio connectors are:
[11]
: 21, 22
Pin
|
AC'97
|
HD Audio (HDA)
|
Signal
|
Description
|
Signal
|
Description
|
1
|
MIC
|
- 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
|
- 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 V
|
SENSE_SEND
|
Jack detection sense, resistance multiplexed
|
8
|
KEY
|
Not present, physical key
|
KEY
|
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 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.
[11]
: 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 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.
[11]
: 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
jumpers
to short these pins if no front panel audio module is connected, so audio passes to the speakers.
[11]
: 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 kΩ pull-up resistor is attached to pin 4 (
PRESENCE#
). 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
SENSE1_RETURN
(pin 6) and
SENSE2_RETURN
(pin 10) signals.
[11]
: 24
Intel warns that HDA dongles should be used with HDA motherboards:
[11]
: 19
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 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
]
See also
[
edit
]
References
[
edit
]
- ^
Smith, Tony (16 April 2004).
"Intel completes hi-def audio spec"
.
The Register
. Retrieved
14 January
2014
.
- ^
"High Definition Audio Specification 1.0a"
(PDF)
. Intel Corporation. 2010. p. 17.
- ^
"Universal Audio Architecture (UAA) High Definition Audio class driver version 1.0a available for Windows XP, Windows Server 2003, and Windows 2000"
.
Microsoft
. Retrieved
September 19,
2022
.
- ^
"Open Sound System at OpenSolaris.org"
.
OpenSolaris
. Archived from
the original
on April 26, 2008
. Retrieved
September 19,
2022
.
- ^
"Intel High Definition Audio bridge device driver"
.
FreeBSD
. January 25, 2012
. Retrieved
September 19,
2022
.
- ^
"Azalia ? Generic High Definition Audio device"
.
OpenBSD
. March 15, 2012
. Retrieved
September 19,
2022
.
- ^
a
b
"AMD SB600 Product Information Page"
.
Advanced Micro Devices
. Retrieved
September 19,
2022
.
- ^
"ALC888 | 7.1+2 Channel High Definition Audio Codec"
.
Realtek
. Archived from
the original
on April 25, 2007
. Retrieved
September 22,
2022
.
- ^
"Conexant - PC HD-Audio"
.
Conexant
. Archived from
the original
on August 19, 2013
. Retrieved
September 22,
2022
.
- ^
Bonshor, Gavin (November 28, 2019).
"The AMD TRX40 Motherboard Overview: 12 New Motherboards Analyzed"
.
AnandTech
. Retrieved
September 22,
2022
.
- ^
a
b
c
d
e
f
g
Intel Corporation (February 2005),
Front Panel I/O Connectivity Design Guide
(PDF)
, Version 1.3, pp. 19?25, archived from
the original
(PDF)
on 2011-05-11
, retrieved
2011-11-04
External links
[
edit
]
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General
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Standards
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Storage
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Peripheral
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Audio
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Portable
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Embedded
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Interfaces are listed by their speed in the (roughly) ascending order, so the interface at the end of each section should be the fastest.
Category
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Platforms
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Discontinued
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Current
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Upcoming
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IBM compatible standards
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Other standards
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Related
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