Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
43
M
U
X
Σ
3D Bypass
SRC
Vol
Mute
SRC
Vol Mute
Vol
Mute
V
ol
Mute
Analog
Sources
PCM
Out
Key
PC BEEP*
MIC1
MIC2*
PHONE*
LINE
_
IN
VIDEO*
+20dB
V
ol
Mute
V
ol
Mute
Vol
Mute
Vol Mute
CD
A
UX
_
IN*
Stereo Mix
Mono Mix
Mic
Phone
Line In
CD
Au
x
Video
A/DMute
Gain
A/DMuteGain
Slots 3 & 4
Slot 6
Slots 3&4
D/A
D/A
SRC
A
nalog
Outputs
PCM
In
Σ
ΣΣ
Σ
3D
MONO
_
OU
T
LINE
_
OUT
Mono Analog
Stereo Analog
Mono Digital
Stereo Digital
Optional*
Source Function Connection
PCM Out Digital audio from the AC ’97 controller AC-link
PC_BEEP PC beep pass thru From PC beeper output
PHONE Speakerphone in From telephony subsystem
MIC1 Desktop microphone From desktop microphone jack
MIC2 Headset microphone From headset microphone jack
LINE_IN External audio source From line in jack
CD Audio from CD-ROM drive Cable from CD-ROM
VIDEO Audio from TV tuner or video camera Cable from TV or Video Capture card
AUX_IN Internal audio source Internal connector
Destination Function
Connection
LINE_OUT Analog mix and front channels To stereo mini speaker jack
LNLVL_OUT Fixed line level output To stereo mini or RCA pair
4CH_OUT Rear channels To stereo mini rear speaker jack
HP_OUT Analog mix and front channels To stereo mini headphone jack
MONO Mic or mix for speakerphone out To telephony subsystem
PCM In Digital audio input to AC ’97 controller AC-link
Output Mix Supports:
 Stereo mix of all analog sources for line out
 AUX_OUT output configurable as line level,
optional headphone, or optional 4-channel

Optional microphone or mix for mono out

Optional 3D and tone controls

PCM out can be mixed pre or post 3D
Input Mux Supports:
 Select from 1, 2, or
optionally 3 channels
 Any mono or stereo source
 Mono or stereo mix of line out
 2-channel input with output reference
(microphone + mono mix)

Optional 3
rd
channel dedicated to microphone

Optional 3-channel input with output reference
(microphone + stereo mix)
Tone
Σ
Σ
Σ
Σ
Σ
Σ
Σ
Σ
Σ
ΣΣ
Σ
Slots 7&8
Vol
Mute
Slots 3&4
Slots 7&8
Slots 6&9
S/PDIF
transmitter*
S/PDIF
out
Slots 10&11
A
UX
_
OUT
V
ol
Mute
Vol
Mute
V
ol
Mute
SRC
Mic
Configurable AUX_OUT
•
LNLVL - line level
• HP – headphone*
• 4CH – rear L & R*
Tone
3D
Figure 17. AC ‘97 Mixer Functional Diagram
5.5.1 Analog Mixer Output
The AC ‘97 mixer generates two distinct outputs:
• a stereo mix of all sources for output to the speakers, headset, and line out (LINE_OUT and HP_OUT)
• a mono “microphone only” or mix of all sources (minus PHONE and PC_BEEP) for speakerphone out
(MONO_OUT)
If analog 3D stereo enhancement is supported in AC ‘97 it is desirable that the PCM out source be mixable pre- or
post-analog 3D processing. This allows digital 3D audio (rendered with volume, pan, reverb, Doppler, HRTF, etc.)
on PCM out to bypass the analog 3D processing regardless of whether analog 3D is enabled or disabled. This
prevents “smearing” of digital 3D audio, and also enables digital 3D audio sources to be mixed with 3D stereo
enhanced analog sources (CD, AUX_IN, etc).
The default PCM out path is through volume, mute, and analog 3D stereo enhancement. However, if the AC ‘97
Controller implements digital 3D audio, and detects analog 3D stereo enhancement support in the AC ‘97 analog, it
can enable the 3D bypass path. This capability to switch to post 3D can also be exposed via API’s to support SW
which emulates or accelerates digital 3D rendering.
In either PCM out scenario, it is advantageous for the AC ‘97 Controller to use the post D/A analog volume control