Audio Codec; Audio Programming - HP Compaq d330 DT Technical Reference Manual

5.8.4 AUDIO CODEC

The audio codec provides pulse code modulation (PCM) coding and decoding of audio
information as well as the selection and/or mixing of analog channels. As shown in Figure 5-13,
analog audio from a microphone, tape, or CD can be selected and, if to be recorded (saved) onto a
disk drive, routed through an analog-to-digital converter (ADC). The resulting left and right PCM
record data are muxed into a time-division-multiplexed (TDM) data stream (SD IN signal) that is
routed to the audio controller. Playback (PB) audio takes the reverse path from the audio
controller to the audio codec as SD OUT data and is decoded and either routed through an
equalizer or applied directly to the digital-to-analog converter (DAC). The codec supports
simultaneous record and playback of stereo (left and right) audio. The Sample Rate Generator
may be set for sampling frequencies up to 48 KHz.
The integrated analog mixer provides the computer control-console functionality handling
multiple audio inputs.
Mic In
Line In (L)
Line In (R)
CD In (L)
CD In (R)
SPDIF
HP Out L
Analog
Output
HP Out R
Circuits
Figure 5-13. AD1981B Audio Codec Functional Block Diagram
All inputs and outputs are two-channel stereo except for the microphone input, which is inputted
as a single-channel but mixed internally onto both left and right channels. The microphone input
is the default active input. All block functions are controlled through index-addressed registers of
the codec.

5.8.5 AUDIO PROGRAMMING

S
Left
e
Audio
l
e
c
Right
t
Audio
o
r
Σ/Mixer
(L)
(L)
S
E
(R)
L
(R)
hp compaq d330 and d530 Series of Personal Computers
First Edition – June 2003
Technical Reference Guide
Audio
Format
Rec
Data (L)
Rec
ADC
Gain
Rec
Data (R)
Rec
ADC
Gain
Sample
Rate
Gen.
PB
Data (L)
PB
DAC
Gain
PB
Data (R)
PB
DAC
Gain
Featuring the Intel Pentium 4 Processor
SD IN
AC97
Link
I/F
EQ
SD Out
EQ
5-31
Audio
Controller